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1.
J Biol Chem ; 300(5): 107234, 2024 May.
Article in English | MEDLINE | ID: mdl-38552737

ABSTRACT

Focal adhesions (FAs) form the junction between extracellular matrix (ECM)-bound integrins and the actin cytoskeleton and also transmit signals that regulate cell adhesion, cytoskeletal dynamics, and cell migration. While many of these signals are rooted in reversible tyrosine phosphorylation, phosphorylation of FA proteins on Ser/Thr residues is far more abundant yet its mechanisms and consequences are far less understood. The cAMP-dependent protein kinase (protein kinase A; PKA) has important roles in cell adhesion and cell migration and is both an effector and regulator of integrin-mediated adhesion to the ECM. Importantly, subcellular localization plays a critically important role in specifying PKA function. Here, we show that PKA is present in isolated FA-cytoskeleton complexes and active within FAs in live cells. Furthermore, using kinase-catalyzed biotinylation of isolated FA-cytoskeleton complexes, we identify 53 high-stringency candidate PKA substrates within FAs. From this list, we validate tensin-3 (Tns3)-a well-established molecular scaffold, regulator of cell migration, and a component of focal and fibrillar adhesions-as a novel direct substrate for PKA. These observations identify a new pathway for phospho-regulation of Tns3 and, importantly, establish a new and important niche for localized PKA signaling and thus provide a foundation for further investigation of the role of PKA in the regulation of FA dynamics and signaling.


Subject(s)
Cyclic AMP-Dependent Protein Kinases , Focal Adhesions , Tensins , Animals , Humans , Cell Adhesion , Cell Movement , Cyclic AMP-Dependent Protein Kinases/metabolism , Cytoskeleton/metabolism , Focal Adhesions/enzymology , Phosphorylation , Tensins/metabolism , Mice , Rats , Cell Line , Signal Transduction/genetics
2.
Biomed Pharmacother ; 133: 111055, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33378961

ABSTRACT

The AKT kinase family is a high-profile target for cancer therapy. Despite their high degree of homology the three AKT isoforms (AKT1, AKT2 and AKT3) are non-redundant and can even have opposing functions. Small-molecule AKT inhibitors affect all three isoforms which severely limits their usefulness as research tool or therapeutic. Using AKT2-specific nanobodies we examined the function of endogenous AKT2 in breast cancer cells. Two AKT2 nanobodies (Nb8 and Nb9) modulate AKT2 and reduce MDA-MB-231 cell viability/proliferation. Nb8 binds the AKT2 hydrophobic motif and reduces IGF-1-induced phosphorylation of this site. This nanobody also affects the phosphorylation and/or expression levels of a wide range of proteins downstream of AKT, resulting in a G0/G1 cell cycle arrest, the induction of autophagy, a reduction in focal adhesion count and loss of stress fibers. While cell cycle progression is likely to be regulated by more than one isoform, our results indicate that both the effects on autophagy and the cytoskeleton are specific to AKT2. By using an isoform-specific nanobody we were able to map a part of the AKT2 pathway. Our results confirm AKT2 and the hydrophobic motif as targets for cancer therapy. Nb8 can be used as a research tool to study AKT2 signalling events and aid in the design of an AKT2-specific inhibitor.


Subject(s)
Antineoplastic Agents, Immunological/pharmacology , Autophagy/drug effects , Breast Neoplasms/drug therapy , Cell Cycle Checkpoints/drug effects , Focal Adhesions/drug effects , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Single-Domain Antibodies/pharmacology , Amino Acid Motifs , Breast Neoplasms/enzymology , Breast Neoplasms/immunology , Breast Neoplasms/pathology , Cell Line, Tumor , Female , Focal Adhesions/enzymology , Focal Adhesions/immunology , Focal Adhesions/pathology , Humans , Hydrophobic and Hydrophilic Interactions , Insulin-Like Growth Factor I/metabolism , Phosphorylation , Proto-Oncogene Proteins c-akt/immunology , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction
3.
Proc Natl Acad Sci U S A ; 116(14): 6766-6774, 2019 04 02.
Article in English | MEDLINE | ID: mdl-30877242

ABSTRACT

Focal adhesion kinase (FAK) is a key signaling molecule regulating cell adhesion, migration, and survival. FAK localizes into focal adhesion complexes formed at the cytoplasmic side of cell attachment to the ECM and is activated after force generation via actomyosin fibers attached to this complex. The mechanism of translating mechanical force into a biochemical signal is not understood, and it is not clear whether FAK is activated directly by force or downstream to the force signal. We use experimental and computational single-molecule force spectroscopy to probe the mechanical properties of FAK and examine whether force can trigger activation by inducing conformational changes in FAK. By comparison with an open and active mutant of FAK, we are able to assign mechanoactivation to an initial rupture event in the low-force range. This activation event occurs before FAK unfolding at forces within the native range in focal adhesions. We are also able to assign all subsequent peaks in the force landscape to partial unfolding of FAK modules. We show that binding of ATP stabilizes the kinase domain, thereby altering the unfolding hierarchy. Using all-atom molecular dynamics simulations, we identify intermediates along the unfolding pathway, which provide buffering to allow extension of FAK in focal adhesions without compromising functionality. Our findings strongly support that forces in focal adhesions applied to FAK via known interactions can induce conformational changes, which in turn, trigger focal adhesion signaling.


Subject(s)
Adenosine Triphosphate/chemistry , Avian Proteins/chemistry , Focal Adhesion Protein-Tyrosine Kinases/chemistry , Molecular Dynamics Simulation , Protein Unfolding , Adenosine Triphosphate/metabolism , Animals , Avian Proteins/genetics , Avian Proteins/metabolism , Chickens , Enzyme Activation , Focal Adhesion Protein-Tyrosine Kinases/genetics , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Focal Adhesions/enzymology , Focal Adhesions/genetics , Mechanotransduction, Cellular/genetics , Protein Domains , Structure-Activity Relationship
4.
J Cell Physiol ; 232(9): 2447-2460, 2017 Sep.
Article in English | MEDLINE | ID: mdl-27591737

ABSTRACT

Glaucoma, a leading cause of irreversible blindness, is commonly associated with elevated intraocular pressure (IOP) due to impaired aqueous humor (AH) drainage through the trabecular meshwork (TM). Although dysregulated production and organization of extracellular matrix (ECM) is presumed to increase resistance to AH outflow and elevate IOP by altering TM cell contractile and adhesive properties, it is not known whether regulation of ECM protein phosphorylation via the secretory vertebrate lonesome kinase (VLK) influences TM cellular characteristics. Here, we tested this possibility. Experiments carried out in this study reveal that the 32 kDa protein is a prominent VLK isoform detectable in lysates and conditioned media (CM) of human TM cells. Increased levels of VLK were observed in CM of TM cells subjected to cyclic mechanical stretch, or treated with dexamethasone, TGF-ß2, and TM cells expressing constitutively active RhoA GTPase. Downregulation of VLK expression in TM cells using siRNA decreased tyrosine phosphorylation (TyrP) of ECM proteins and focal adhesions, and induced changes in cell shape in association with reduced levels of actin stress fibers and phospho-paxillin. VLK was also demonstrated to regulate TGF-ß2-induced TyrP of ECM proteins. Taken together, these results suggest that VLK secretion can be regulated by external cues, intracellular signal proteins, and mechanical stretch, and VLK can in turn regulate TyrP of ECM proteins secreted by TM cells and control cell shape, actin stress fibers, and focal adhesions. These observations indicate a potential role for VLK in homeostasis of AH outflow and IOP, and in the pathobiology of glaucoma. J. Cell. Physiol. 232: 2447-2460, 2017. © 2016 Wiley Periodicals, Inc.


Subject(s)
Cell Adhesion , Cell Shape , Extracellular Matrix Proteins/metabolism , Protein-Tyrosine Kinases/metabolism , Trabecular Meshwork/enzymology , Adult , Aged , Aqueous Humor/metabolism , Cell Adhesion/drug effects , Cell Shape/drug effects , Cells, Cultured , Culture Media, Conditioned/metabolism , Dexamethasone/pharmacology , Focal Adhesions/enzymology , Glaucoma/enzymology , Glaucoma/pathology , Glaucoma/physiopathology , Humans , Intraocular Pressure , Mechanotransduction, Cellular , Middle Aged , Mutation , Paxillin/metabolism , Phosphorylation , Protein-Tyrosine Kinases/genetics , RNA Interference , Stress Fibers/enzymology , Time Factors , Trabecular Meshwork/drug effects , Transfection , Transforming Growth Factor beta2/pharmacology , Tyrosine , Young Adult , rhoA GTP-Binding Protein/genetics , rhoA GTP-Binding Protein/metabolism
5.
Cancer Lett ; 386: 151-160, 2017 02 01.
Article in English | MEDLINE | ID: mdl-27894956

ABSTRACT

Triple-negative breast cancers (TNBC) often exhibit an aggressive phenotype. Disulfiram (DSF) is an approved drug for the treatment of alcohol dependence, but has also been shown to kill TNBC cells in a copper (Cu)-dependent manner. Exactly how this occurs has not been clearly elucidated. We sought to investigate the mechanisms responsible for DSF/Cu-dependent induction of apoptosis and suppression of lung colonization by TNBC cells. DSF/Cu induced anoikis and significantly suppressed cell migration and invasion with negative effects on focal adhesions, coinciding with vimentin breakdown and calpain activation in TNBC cells. In a xenograft tumor model, DSF suppressed tumor growth and lung nodule growth, which was also associated with calpain activation. These findings warrant further investigation of disulfiram as a potential treatment for metastatic TNBC.


Subject(s)
Anoikis/drug effects , Antineoplastic Agents/pharmacology , Calpain/metabolism , Cell Movement/drug effects , Disulfiram/pharmacology , Lung Neoplasms/prevention & control , Triple Negative Breast Neoplasms/drug therapy , Animals , Cell Line, Tumor , Cell Proliferation/drug effects , Copper/pharmacology , Cytoskeleton/drug effects , Cytoskeleton/enzymology , Cytoskeleton/pathology , Dose-Response Relationship, Drug , Enzyme Activation , Female , Focal Adhesions/drug effects , Focal Adhesions/enzymology , Focal Adhesions/pathology , Humans , Lung Neoplasms/enzymology , Lung Neoplasms/secondary , Mice, Inbred BALB C , Mice, Nude , Neoplasm Invasiveness , Proteolysis , Signal Transduction/drug effects , Time Factors , Triple Negative Breast Neoplasms/enzymology , Triple Negative Breast Neoplasms/pathology , Tumor Burden/drug effects , Vimentin/metabolism , Xenograft Model Antitumor Assays
6.
Cancer Lett ; 380(2): 505-512, 2016 10 01.
Article in English | MEDLINE | ID: mdl-27452906

ABSTRACT

Triple-negative breast cancers (TNBCs) are among the most aggressive cancers characterized by a high propensity to invade, metastasize and relapse. We previously reported that the TNBC-specific inhibitor, AMPI-109, significantly impairs the ability of TNBC cells to migrate and invade by reducing levels of the metastasis-promoting phosphatase, PRL-3. Here, we examined the mechanisms by which AMPI-109 and loss of PRL-3 impede cell migration and invasion. AMPI-109 treatment or knock down of PRL-3 expression were associated with deactivation of Src and ERK signaling and concomitant downregulation of RhoA and Rac1/2/3 GTPase protein levels. These cellular changes led to rearranged filamentous actin networks necessary for cell migration and invasion. Conversely, overexpression of PRL-3 promoted TNBC cell invasion by upregulating matrix metalloproteinase 10, which resulted in increased TNBC cell adherence to, and degradation of, the major basement membrane component laminin. Our data demonstrate that PRL-3 engages the focal adhesion pathway in TNBC cells as a key mechanism for promoting TNBC cell migration and invasion. Collectively, these data suggest that blocking PRL-3 activity may be an effective method for reducing the metastatic potential of TNBC cells.


Subject(s)
Actin Cytoskeleton/enzymology , Cell Adhesion , Cell Movement , Focal Adhesions/enzymology , Neoplasm Proteins/metabolism , Protein Tyrosine Phosphatases/metabolism , Triple Negative Breast Neoplasms/enzymology , Actin Cytoskeleton/drug effects , Actin Cytoskeleton/pathology , Antineoplastic Agents/pharmacology , Calcitriol/analogs & derivatives , Calcitriol/pharmacology , Cell Adhesion/drug effects , Cell Line, Tumor , Cell Movement/drug effects , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Focal Adhesions/drug effects , Focal Adhesions/pathology , Humans , Laminin/metabolism , Matrix Metalloproteinase 10/metabolism , Neoplasm Invasiveness , Neoplasm Metastasis , Neoplasm Proteins/genetics , Protein Tyrosine Phosphatases/genetics , RNA Interference , Signal Transduction , Time Factors , Transfection , Triple Negative Breast Neoplasms/drug therapy , Triple Negative Breast Neoplasms/genetics , Triple Negative Breast Neoplasms/pathology , rac GTP-Binding Proteins/metabolism , rhoA GTP-Binding Protein/metabolism , src-Family Kinases/metabolism
7.
J Cell Biol ; 212(3): 349-64, 2016 Feb 01.
Article in English | MEDLINE | ID: mdl-26833789

ABSTRACT

Integrin adhesion complexes (IACs) form mechanochemical connections between the extracellular matrix and actin cytoskeleton and mediate phenotypic responses via posttranslational modifications. Here, we investigate the modularity and robustness of the IAC network to pharmacological perturbation of the key IAC signaling components focal adhesion kinase (FAK) and Src. FAK inhibition using AZ13256675 blocked FAK(Y397) phosphorylation but did not alter IAC composition, as reported by mass spectrometry. IAC composition was also insensitive to Src inhibition using AZD0530 alone or in combination with FAK inhibition. In contrast, kinase inhibition substantially reduced phosphorylation within IACs, cell migration and proliferation. Furthermore using fluorescence recovery after photobleaching, we found that FAK inhibition increased the exchange rate of a phosphotyrosine (pY) reporter (dSH2) at IACs. These data demonstrate that kinase-dependent signal propagation through IACs is independent of gross changes in IAC composition. Together, these findings demonstrate a general separation between the composition of IACs and their ability to relay pY-dependent signals.


Subject(s)
Cell Adhesion/drug effects , Fibroblasts/enzymology , Focal Adhesion Kinase 1/metabolism , Focal Adhesions/enzymology , Signal Transduction/drug effects , src-Family Kinases/metabolism , Animals , Cell Movement , Cell Proliferation , Dose-Response Relationship, Drug , Fibroblasts/drug effects , Focal Adhesion Kinase 1/antagonists & inhibitors , Focal Adhesion Kinase 1/genetics , Focal Adhesions/drug effects , Focal Adhesions/genetics , HEK293 Cells , Humans , Mice , NIH 3T3 Cells , Phosphorylation , Phosphotyrosine/metabolism , Protein Binding , Protein Kinase Inhibitors/pharmacology , Time Factors , Transfection , src Homology Domains , src-Family Kinases/antagonists & inhibitors
8.
Oncotarget ; 6(31): 30516-31, 2015 Oct 13.
Article in English | MEDLINE | ID: mdl-26483365

ABSTRACT

Cells induced into senescence exhibit a marked increase in the secretion of pro-inflammatory cytokines termed senescence-associated secretory phenotype (SASP). Here we report that SASP from senescent stromal fibroblasts promote spontaneous morphological changes accompanied by an aggressive migratory behavior in originally non-motile human breast cancer cells. This phenotypic switch is coordinated, in space and time, by a dramatic reorganization of the actin and microtubule filament networks, a discrete polarization of EB1 comets, and an unconventional front-to-back inversion of nucleus-MTOC polarity. SASP-induced morphological/migratory changes are critically dependent on microtubule integrity and dynamics, and are coordinated by the inhibition of RhoA and cell contractility. RhoA/ROCK inhibition reduces focal adhesions and traction forces, while promoting a novel gliding mode of migration.


Subject(s)
Breast Neoplasms/enzymology , Cell Movement , Cellular Senescence , Fibroblasts/metabolism , Myosins/metabolism , Paracrine Communication , rho-Associated Kinases/metabolism , rhoA GTP-Binding Protein/metabolism , Actins/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Cell Movement/drug effects , Cell Polarity , Cell Shape , Female , Focal Adhesions/enzymology , Humans , MCF-7 Cells , Microtubule-Associated Proteins/genetics , Microtubule-Associated Proteins/metabolism , Microtubules/enzymology , Mutation , Phenotype , Protein Kinase Inhibitors/pharmacology , Signal Transduction , Time Factors , Transfection , rho-Associated Kinases/antagonists & inhibitors , rhoA GTP-Binding Protein/antagonists & inhibitors , rhoA GTP-Binding Protein/genetics
9.
Biochem Biophys Res Commun ; 464(1): 275-80, 2015 Aug 14.
Article in English | MEDLINE | ID: mdl-26116771

ABSTRACT

Cancer cell invasion is a critical phenomenon in cancer pathogenesis. Glycogen synthase kinase-3ß (GSK-3ß) has been reported to regulate cancer cell invasion both negatively and positively. Thus, the net effect of GSK-3ß on invasion is unclear. In this report, we showed that GSK-3ß inhibitors induced dysregulation of the actin cytoskeleton and functional insufficiency of focal adhesion, which resulted in suppressed invasion. In addition, WAVE2, an essential molecule for actin fibre branching, was down-regulated after GSK-3ß inhibition. Collectively, we propose that the WAVE2-actin cytoskeleton axis is an important target of GSK-3ß inhibitors in cancer cell invasion.


Subject(s)
Actin Cytoskeleton/drug effects , Cell Movement/drug effects , Glycogen Synthase Kinase 3/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Thiazoles/pharmacology , Urea/analogs & derivatives , Wiskott-Aldrich Syndrome Protein Family/antagonists & inhibitors , Actin Cytoskeleton/enzymology , Actin Cytoskeleton/ultrastructure , Actins/chemistry , Actins/genetics , Actins/metabolism , Cell Adhesion/drug effects , Cell Line, Tumor , Collagen/chemistry , Drug Combinations , Focal Adhesions/drug effects , Focal Adhesions/enzymology , Focal Adhesions/ultrastructure , Gene Expression , Glycogen Synthase Kinase 3/genetics , Glycogen Synthase Kinase 3/metabolism , Glycogen Synthase Kinase 3 beta , Humans , Laminin/chemistry , Proteoglycans/chemistry , Urea/pharmacology , Wiskott-Aldrich Syndrome Protein Family/genetics , Wiskott-Aldrich Syndrome Protein Family/metabolism
11.
EMBO J ; 34(4): 448-65, 2015 Feb 12.
Article in English | MEDLINE | ID: mdl-25471072

ABSTRACT

Paradoxically, the thymidine kinase (TK) encoded by Kaposi sarcoma-associated herpesvirus (KSHV) is an extremely inefficient nucleoside kinase, when compared to TKs from related herpesviruses. We now show that KSHV-TK, in contrast to HSV1-TK, associates with the actin cytoskeleton and induces extensive cell contraction followed by membrane blebbing. These dramatic changes in cell morphology depend on the auto-phosphorylation of tyrosines 65, 85 and 120 in the N-terminus of KSHV-TK. Phosphorylation of tyrosines 65/85 and 120 results in an interaction with Crk family proteins and the p85 regulatory subunit of PI3-Kinase, respectively. The interaction of Crk with KSHV-TK leads to tyrosine phoshorylation of this cellular adaptor. Auto-phosphorylation of KSHV-TK also induces a loss of FAK and paxillin from focal adhesions, resulting in activation of RhoA-ROCK signalling to myosin II and cell contraction. In the absence of FAK or paxillin, KSHV-TK has no effect on focal adhesion integrity or cell morphology. Our observations demonstrate that by acting as a tyrosine kinase, KSHV-TK modulates signalling and cell morphology.


Subject(s)
Focal Adhesions/enzymology , Focal Adhesions/metabolism , Herpesvirus 8, Human/enzymology , Protein-Tyrosine Kinases/metabolism , rho GTP-Binding Proteins/metabolism , Animals , COS Cells , Chlorocebus aethiops , HeLa Cells , Humans , Immunoblotting , Immunoprecipitation , Paxillin/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Phosphorylation , Proto-Oncogene Proteins c-crk/metabolism
12.
Am J Pathol ; 184(10): 2742-56, 2014 Oct.
Article in English | MEDLINE | ID: mdl-25239564

ABSTRACT

Aberrant focal adhesion turnover is centrally involved in podocyte actin cytoskeleton disorganization and foot process effacement. The structural and dynamic integrity of focal adhesions is orchestrated by multiple cell signaling molecules, including glycogen synthase kinase 3ß (GSK3ß), a multitasking kinase lately identified as a mediator of kidney injury. However, the role of GSK3ß in podocytopathy remains obscure. In doxorubicin (Adriamycin)-injured podocytes, lithium, a GSK3ß inhibitor and neuroprotective mood stabilizer, obliterated the accelerated focal adhesion turnover, rectified podocyte hypermotility, and restored actin cytoskeleton integrity. Mechanistically, lithium counteracted the doxorubicin-elicited GSK3ß overactivity and the hyperphosphorylation and overactivation of paxillin, a focal adhesion-associated adaptor protein. Moreover, forced expression of a dominant negative kinase dead mutant of GSK3ß highly mimicked, whereas ectopic expression of a constitutively active GSK3ß mutant abolished, the effect of lithium in doxorubicin-injured podocytes, suggesting that the effect of lithium is mediated, at least in part, through inhibition of GSK3ß. Furthermore, paxillin interacted with GSK3ß and served as its substrate. In mice with doxorubicin nephropathy, a single low dose of lithium ameliorated proteinuria and glomerulosclerosis. Consistently, lithium therapy abrogated GSK3ß overactivity, blunted paxillin hyperphosphorylation, and reinstated actin cytoskeleton integrity in glomeruli associated with an early attenuation of podocyte foot process effacement. Thus, GSK3ß-modulated focal adhesion dynamics might serve as a novel therapeutic target for podocytopathy.


Subject(s)
Focal Adhesions/enzymology , Glycogen Synthase Kinase 3/metabolism , Kidney Glomerulus/enzymology , Lithium/pharmacology , Paxillin/metabolism , Podocytes/physiology , Actin Cytoskeleton/drug effects , Amino Acid Sequence , Animals , Antibiotics, Antineoplastic/pharmacology , Cell Adhesion/drug effects , Cell Movement/drug effects , Doxorubicin/pharmacology , Focal Adhesions/drug effects , Glycogen Synthase Kinase 3/antagonists & inhibitors , Glycogen Synthase Kinase 3 beta , Humans , Kidney Glomerulus/drug effects , Male , Mice , Mice, Inbred BALB C , Molecular Sequence Data , Phosphorylation/drug effects , Podocytes/drug effects , Podocytes/enzymology , Podocytes/pathology , Signal Transduction/drug effects
13.
Sci Rep ; 4: 5756, 2014 Jul 24.
Article in English | MEDLINE | ID: mdl-25056908

ABSTRACT

Focal adhesions (FAs) are dynamic subcellular structures crucial for cell adhesion, migration and differentiation. It remains an enigma how enzymatic activities in these local complexes regulate their structural remodeling in live cells. Utilizing biosensors based on fluorescence resonance energy transfer (FRET), we developed a correlative FRET imaging microscopy (CFIM) approach to quantitatively analyze the subcellular coordination between the enzymatic Src activation and the structural FA disassembly. CFIM reveals that the Src kinase activity only within the microdomain of lipid rafts at the plasma membrane is coupled with FA dynamics. FA disassembly at cell periphery was linearly dependent on this raft-localized Src activity, although cells displayed heterogeneous levels of response to stimulation. Within lipid rafts, the time delay between Src activation and FA disassembly was 1.2 min in cells seeded on low fibronectin concentration ([FN]) and 4.3 min in cells on high [FN]. CFIM further showed that the level of Src-FA coupling, as well as the time delay, was regulated by cell-matrix interactions, as a tight enzyme-structure coupling occurred in FA populations mediated by integrin αvß3, but not in those by integrin α5ß1. Therefore, different FA subpopulations have distinctive regulation mechanisms between their local kinase activity and structural FA dynamics.


Subject(s)
Focal Adhesions/enzymology , Animals , Biosensing Techniques , Cell Adhesion , Cells, Cultured , Enzyme Activation , Fibronectins/metabolism , Fluorescence Resonance Energy Transfer , Focal Adhesions/ultrastructure , Luminescent Proteins/biosynthesis , Mice , Microscopy, Fluorescence , Platelet-Derived Growth Factor/physiology , src-Family Kinases/metabolism , Red Fluorescent Protein
14.
J Biol Chem ; 289(26): 18427-41, 2014 Jun 27.
Article in English | MEDLINE | ID: mdl-24821720

ABSTRACT

Interleukin-1 (IL-1) signaling in fibroblasts is mediated through focal adhesions, organelles that are enriched with adaptor and cytoskeletal proteins that regulate signal transduction. We examined interactions of the focal adhesion kinase (FAK) with protein-tyrosine phosphatase-α (PTP-α) in IL-1 signaling. In wild type and FAK knock-out mouse embryonic fibroblasts, we found by immunoblotting, immunoprecipitation, immunostaining, and gene silencing that FAK is required for IL-1-mediated sequestration of PTPα to focal adhesions. Immunoprecipitation and pulldown assays of purified proteins demonstrated a direct interaction between FAK and PTPα, which was dependent on the FAT domain of FAK and by an intact membrane-proximal phosphatase domain of PTPα. Recruitment of PTPα to focal adhesions, IL-1-induced Ca(2+) release from the endoplasmic reticulum, ERK activation, and IL-6, MMP-3, and MMP-9 expression were all blocked in FAK knock-out fibroblasts. These processes were restored in FAK knock-out cells transfected with wild type FAK, FAT domain, and FRNK. Our data indicate that IL-1-induced signaling through focal adhesions involves interactions between the FAT domain of FAK and PTPα.


Subject(s)
Fibroblasts/enzymology , Focal Adhesion Protein-Tyrosine Kinases/chemistry , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Focal Adhesions/enzymology , Interleukin-1/metabolism , Receptor-Like Protein Tyrosine Phosphatases, Class 4/metabolism , Animals , Calcium/metabolism , Cells, Cultured , Extracellular Signal-Regulated MAP Kinases/metabolism , Fibroblasts/metabolism , Focal Adhesion Protein-Tyrosine Kinases/genetics , Focal Adhesions/metabolism , Interleukin-1/genetics , Matrix Metalloproteinase 9/genetics , Matrix Metalloproteinase 9/metabolism , Mice , Mice, Knockout , NIH 3T3 Cells , Protein Binding , Protein Structure, Tertiary , Receptor-Like Protein Tyrosine Phosphatases, Class 4/genetics , Signal Transduction
15.
Int J Biochem Cell Biol ; 51: 131-41, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24747131

ABSTRACT

Focal contacts, large macromolecular complexes that link the extracellular matrix and the internal cell cytoskeleton, are thought to govern cell locomotion. However, the maturation process through which focal contacts control the cellular migratory machinery by changes in size and molecular composition remain unclear. Here, we fabricated cell growth substrates that contained linear ECM strips of micron- or submicron-width in order to limit the enlargement of focal contacts. We found that NBT-II cells plated on the submicron substrate possessed smaller focal complexes that exhibited a highly dynamic turnover. These cells possessed various leading edges at multiple sites of the cell periphery, which prevented the cell from advancing. In contrast, cells grown on the micron-width substrate possessed large and stable focal adhesions. Most of these cells were elongated bipolar cells that were tethered at both ends and were immobile. Further, EGF and ROCK signaling pathways can modulate the cellular migratory responses according to the substrate guidance. On the submicron-width substrate, EGF treatment increased the focal contact size and the contractile force, causing these cells to develop one leading edge and migrate along the submicron-sized ECM paths. In contrast, inhibition of ROCK signaling decreased the focal contact size for cells plated on the micron substrate. These cells became less tethered and were able to migrate along or even across the micron-sized ECM paths. Our results indicate that formation and maturation of focal contacts is controlled by both ECM cues and intracellular signaling and they play a central role in directed cell motion.


Subject(s)
Cell Movement/physiology , Epidermal Growth Factor/metabolism , Focal Adhesions/physiology , Urinary Bladder Neoplasms/pathology , rho-Associated Kinases/metabolism , Animals , Cell Line, Tumor , Focal Adhesions/enzymology , Rats , Signal Transduction , Transfection , Urinary Bladder Neoplasms/enzymology , Urinary Bladder Neoplasms/metabolism
16.
Eur J Pharm Sci ; 55: 46-57, 2014 May 13.
Article in English | MEDLINE | ID: mdl-24486483

ABSTRACT

Diacylglycerol (DAG) is a central mediator of signaling pathways that regulate cell proliferation, survival and apoptosis. Therefore, C1 domain, the DAG binding site within protein kinase C (PKC) and other DAG effector proteins, is considered a potential cancer drug target. Derivatives of 5-(hydroxymethyl)isophthalic acid are a novel group of C1 domain ligands with antiproliferative and differentiation-inducing effects. Our previous work showed that these isophthalate derivatives exhibit antiproliferative and elongation-inducing effects in HeLa human cervical cancer cells. In this study we further characterized the effects of bis(3-trifluoromethylbenzyl) 5-(hydroxymethyl)isophthalate (HMI-1a3) on HeLa cell proliferation and morphology. HMI-1a3-induced cell elongation was accompanied with loss of focal adhesions and actin stress fibers, and exposure to HMI-1a3 induced a prominent relocation of cofilin-1 into the nucleus regardless of cell phenotype. The antiproliferative and morphological responses to HMI-1a3 were not modified by pharmacological inhibition or activation of PKC, or by RNAi knock-down of specific PKC isoforms, suggesting that the effects of HMI-1a3 were not mediated by PKC. Genome-wide gene expression microarray and gene set enrichment analysis suggested that, among others, HMI-1a3 induces changes in small GTPase-mediated signaling pathways. Our experiments revealed that the isophthalates bind also to the C1 domains of ß2-chimaerin, protein kinase D (PKD) and myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK), which are potential mediators of small GTPase signaling and cytoskeletal reorganization. Pharmacological inhibition of MRCK, but not that of PKD attenuated HMI-1a3-induced cell elongation, suggesting that MRCK participates in mediating the effects of HMI-1a3 on HeLa cell morphology.


Subject(s)
Cell Shape/drug effects , Phthalic Acids/pharmacology , Protein Serine-Threonine Kinases/metabolism , Signal Transduction/drug effects , Cell Proliferation/drug effects , Cofilin 1/metabolism , Dose-Response Relationship, Drug , Focal Adhesions/drug effects , Focal Adhesions/enzymology , HeLa Cells , Humans , Myotonin-Protein Kinase , Phenotype , Phosphorylation , Protein Kinase C/antagonists & inhibitors , Protein Kinase C/genetics , Protein Kinase C/metabolism , Protein Kinase Inhibitors/pharmacology , Protein Serine-Threonine Kinases/antagonists & inhibitors , Protein Serine-Threonine Kinases/genetics , RNA Interference , Stress Fibers/drug effects , Stress Fibers/enzymology , Time Factors , Transfection
17.
J Orthop Res ; 32(3): 448-54, 2014 Mar.
Article in English | MEDLINE | ID: mdl-24249698

ABSTRACT

Focal adhesions are transmembrane protein complexes that attach chondrocytes to the pericellular cartilage matrix and in turn, are linked to intracellular organelles via cytoskeleton. We previously found that excessive compression of articular cartilage leads to cytoskeleton-dependent chondrocyte death. Here we tested the hypothesis that this process also requires integrin activation and signaling via focal adhesion kinase (FAK) and Src family kinase (SFK). Osteochondral explants were treated with FAK and SFK inhibitors (FAKi, SFKi, respectively) for 2 h and then subjected to a death-inducing impact load. Chondrocyte viability was assessed by confocal microscopy immediately and at 24 h post-impact. With no treatment immediate post-impact viability was 59%. Treatment with 10 µM SFKi, 10 µM, or 100 µM FAKi improved viability to 80%, 77%, and 82%, respectively (p < 0.05). After 24 h viability declined to 34% in controls, 48% with 10 µM SFKi, 45% with 10 µM FAKi, and 56% with 100 µM FAKi (p < 0.01) treatment. These results confirmed that most of the acute chondrocyte mortality was FAK- and SFK-dependent, which implicates integrin-cytoskeleton interactions in the death signaling pathway. Together with previous findings, these data support the hypothesis that the excessive tissue strains accompanying impact loading induce death via a pathway initiated by strain on cell adhesion receptors.


Subject(s)
Cartilage, Articular/injuries , Cell Death/physiology , Chondrocytes/enzymology , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Focal Adhesions/enzymology , src-Family Kinases/metabolism , Animals , Cartilage, Articular/enzymology , Cattle , Focal Adhesion Protein-Tyrosine Kinases/antagonists & inhibitors , Focal Adhesions/pathology , Random Allocation , src-Family Kinases/antagonists & inhibitors
18.
Mol Cells ; 36(1): 1-6, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23686429

ABSTRACT

Focal adhesion kinase (FAK) is a protein tyrosine kinase (PTK) crucial in regulation of cell migration and proliferation. In addition to its canonical roles as a cytoplasmic kinase downstream of integrin and growth factor receptor signaling, recent studies revealed new aspects of FAK action in the nucleus. Nuclear FAK promotes p53 and GATA4 degradation via ubiquitination, resulting in enhanced cell proliferation and reduced inflammatory responses. FAK can also serve as a co-transcriptional regulator that alters a gene transcriptional activity. These findings established a new paradigm of FAK signaling from cellular adhesions to the nucleus. Although physiological stimuli for controlling FAK nuclear localization have not been completely characterized, FAK shuttles from focal adhesions to the nucleus to directly convey extracellular signals. Interestingly, nuclear translocation of FAK becomes prominent in kinase-inhibited conditions such as in de-adhesion and pharmacological FAK inhibition, while a small fraction of nuclear FAK is observed a normal growth condition. In this review, roles of nuclear FAK in regulating transcription factors will be discussed. Furthermore, a potential use of a pharmacological FAK inhibitor to target nuclear FAK function in diseases such as inflammation will be emphasized.


Subject(s)
Cell Nucleus/enzymology , Focal Adhesion Protein-Tyrosine Kinases/metabolism , Gene Expression Regulation , Animals , Cell Adhesion/genetics , Focal Adhesion Protein-Tyrosine Kinases/chemistry , Focal Adhesions/enzymology , Humans , Signal Transduction/genetics
19.
Microcirculation ; 20(7): 637-49, 2013 Oct.
Article in English | MEDLINE | ID: mdl-23600470

ABSTRACT

OBJECTIVE: To determine the role of FAK in the regulation of endothelial barrier function. METHODS: Stable FAK knockdown HLEC were generated by lentiviral infection of FAK shRNA. Measurements of isometric tension and transendothelial electrical resistance were performed. RESULTS: A FAK knockdown human pulmonary endothelial cell line was generated by lentiviral infection with FAK shRNA and resulted in greater than 90% reduction in FAK protein with no change in Pyk2 protein. Loss of FAK altered cell morphology and actin distribution in both pre- and post-confluent endothelial cells. Large, polygonal shaped endothelial cells with randomly organized stress fibers were identified in pre-confluent cultures, while in confluent monolayers, endothelial cells were irregularly shaped with actin bundles present at cell margins. An increase in the number and size of vinculin plaques was detected in FAK-depleted cells. FAK knockdown monolayers generated a greater transendothelial electrical resistance than controls. Thrombin treatment induced similar changes in TER in both FAK knockdown and control cell lines. FAK-depleted endothelial cells developed a higher stable basal isometric tension compared to control monolayers, but the increase in tension stimulated by thrombin does not differ between the cell lines. Basal myosin II regulatory light chain phosphorylation was unaltered in FAK-depleted cells. In addition, loss of FAK enhanced VE-cadherin localization to the cell membrane without altering VE-cadherin protein levels. CONCLUSIONS: The loss of FAK in endothelial cells enhanced cell attachment and strengthened cell-cell contacts resulting in greater basal tension leading to formation of a tighter endothelial monolayer.


Subject(s)
Endothelial Cells/enzymology , Endothelium, Vascular/enzymology , Focal Adhesion Kinase 1/metabolism , Focal Adhesions/enzymology , Lung/enzymology , Animals , Cell Line, Transformed , Electric Impedance , Endothelial Cells/cytology , Endothelium, Vascular/cytology , Focal Adhesion Kinase 1/genetics , Focal Adhesions/genetics , Gene Knockdown Techniques , Humans , Lung/cytology , Mice , Mice, Knockout
20.
Biol Psychiatry ; 74(6): 418-26, 2013 Sep 15.
Article in English | MEDLINE | ID: mdl-23482246

ABSTRACT

BACKGROUND: Evidence from genetic association studies implicate genes involved in neural migration associated with schizophrenia risk. Neural stem/progenitor cell cultures (neurosphere-derived cells) from olfactory mucosa of schizophrenia patients have significantly dysregulated expression of genes in focal adhesion kinase (FAK) signaling, a key pathway regulating cell adhesion and migration. The aim of this study was to investigate whether olfactory neurosphere-derived cells from schizophrenia patients have altered cell adhesion, cell motility, and focal adhesion dynamics. METHODS: Olfactory neurosphere-derived cells from nine male schizophrenia patients and nine male healthy control subjects were used. Cells were assayed for cell adhesion and cell motility and analyzed for integrins and FAK proteins. Focal adhesions were counted and measured in fixed cells, and time-lapse imaging was used to assess cell motility and focal adhesion dynamics. RESULTS: Patient-derived cells were less adhesive and more motile than cells derived from healthy control subjects, and their motility was reduced to control cell levels by integrin-blocking antibodies and by inhibition of FAK. Vinculin-stained focal adhesion complexes were significantly smaller and fewer in patient cells. Time-lapse imaging of cells expressing FAK tagged with green fluorescent protein revealed that the disassembly of focal adhesions was significantly faster in patient cells. CONCLUSIONS: The evidence for altered motility and focal adhesion dynamics in patient-derived cells is consistent with dysregulated gene expression in the FAK signaling pathway in these cells. Alterations in cell adhesion dynamics and cell motility could bias the trajectory of brain development in schizophrenia.


Subject(s)
Focal Adhesions/ultrastructure , Neural Stem Cells/physiology , Schizophrenia/physiopathology , Adolescent , Adult , Cell Movement , Focal Adhesion Protein-Tyrosine Kinases/physiology , Focal Adhesions/enzymology , Humans , Male , Middle Aged , Neural Stem Cells/enzymology , Olfactory Mucosa/cytology , Olfactory Mucosa/physiology , Schizophrenia/enzymology , Schizophrenia/pathology , Young Adult
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