The DIAPH3 linker specifies a ß-actin network that maintains RhoA and Myosin-II at the cytokinetic furrow.

Cytokinesis is the final step of the cell division cycle that leads to the formation of two new cells. Successful cytokinesis requires significant remodelling of the plasma membrane by spatially distinct ß- and γ-actin networks. These networks are generated by the formin family of actin nucleators, DIAPH3 and DIAPH1 respectively. Here we show that ß- and γ-actin perform specialized and non-redundant roles in cytokinesis and cannot substitute for one another. Expression of hybrid DIAPH1 and DIAPH3 proteins with altered actin isoform specificity relocalized cytokinetic actin isoform networks within the cell, causing cytokinetic failure. Consistent with this we show that ß-actin networks, but not γ-actin networks, are required for the maintenance of non-muscle myosin II and RhoA at the cytokinetic furrow. These data suggest that independent and spatially distinct actin isoform networks form scaffolds of unique interactors that facilitate localized biochemical activities to ensure successful cell division.

TRPV4 mediates IL-1-induced Ca2+ signaling, ERK activation and MMP expression.

Ca2+ permeation through TRPV4 in fibroblasts is associated with pathological matrix degradation. In human gingival fibroblasts, IL-1ß binding to its signaling receptor (IL-1R1) induces activation of extracellular regulated kinase (ERK) and MMP1 expression, processes that require Ca2+ flux across the plasma membrane. It is not known how IL-1R1, which does not conduct Ca2+, generates Ca2+ signals in response to IL-1. We examined whether TRPV4 mediates the Ca2+ fluxes required for ERK signaling in IL-1 stimulated gingival fibroblasts. TRPV4 was immunostained in fibroblasts of human gingival connective tissue and in focal adhesions of cultured mouse gingival fibroblasts. Human gingival fibroblasts treated with IL-1ß showed no change of TRPV4 expression but there was increased MMP1 expression. In mouse, gingival fibroblasts expressing TRPV4, IL-1 strongly increased [Ca2+]i. Pre-incubation of cells with IL-1 Receptor Antagonist blocked Ca2+ entry induced by IL-1 or the TRPV4 agonist GSK101. Knockout of TRPV4 or expression of a non-Ca2+-conducting TRPV4 pore-mutant or pre-incubation with the TRPV4 inhibitor RN1734, blocked IL-1-induced Ca2+ transients and expression of the mouse interstitial collagenase, MMP13. Treatment of mouse gingival fibroblasts with GSK101 phenocopied Ca2+ and ERK responses induced by IL-1; these responses were absent in TRPV4-null cells or cells expressing a non-conducting TRPV4 pore-mutant. Immunostained IL-1R1 localized with TRPV4 in adhesions within cell extensions. While TRPV4 immunoprecipitates analyzed by mass spectrometry showed no association with IL-1R1, TRPV4 associated with Src-related proteins and Src co-immunoprecipitated with TRPV4. Src inhibition reduced IL-1-induced Ca2+ responses. The functional linkage of TRPV4 with IL-1R1 expands its repertoire of innate immune signaling processes by mediating IL-1-driven Ca2+ responses that drive matrix remodeling in fibroblasts. Thus, inhibiting TRPV4 activity may provide a new pharmacological approach for blunting matrix degradation in inflammatory diseases.

Impact of TRP Channels on Extracellular Matrix Remodeling: Focus on TRPV4 and Collagen.

Disturbed remodeling of the extracellular matrix (ECM) is frequently observed in several high-prevalence pathologies that include fibrotic diseases of organs such as the heart, lung, periodontium, liver, and the stiffening of the ECM surrounding invasive cancers. In many of these lesions, matrix remodeling mediated by fibroblasts is dysregulated, in part by alterations to the regulatory and effector systems that synthesize and degrade collagen, and by alterations to the functions of the integrin-based adhesions that normally mediate mechanical remodeling of collagen fibrils. Cell-matrix adhesions containing collagen-binding integrins are enriched with regulatory and effector systems that initiate localized remodeling of pericellular collagen fibrils to maintain ECM homeostasis. A large cadre of regulatory molecules is enriched in cell-matrix adhesions that affect ECM remodeling through synthesis, degradation, and contraction of collagen fibrils. One of these regulatory molecules is Transient Receptor Potential Vanilloid-type 4 (TRPV4), a mechanically sensitive, Ca2+-permeable plasma membrane channel that regulates collagen remodeling. The gating of Ca2+ across the plasma membrane by TRPV4 and the consequent generation of intracellular Ca2+ signals affect several processes that determine the structural and mechanical properties of collagen-rich ECM. These processes include the synthesis of new collagen fibrils, tractional remodeling by contractile forces, and collagenolysis. While the specific mechanisms by which TRPV4 contributes to matrix remodeling are not well-defined, it is known that TRPV4 is activated by mechanical forces transmitted through collagen adhesion receptors. Here, we consider how TRPV4 expression and function contribute to physiological and pathological collagen remodeling and are associated with collagen adhesions. Over the long-term, an improved understanding of how TRPV4 regulates collagen remodeling could pave the way for new approaches to manage fibrotic lesions.

Vimentin-mediated myosin 10 aggregation at tips of cell extensions drives MT1-MMP-dependent collagen degradation in colorectal cancer.

Colorectal cancer (CRC) is a high prevalence adenocarcinoma with progressive increases in metastasis-related mortality, but the mechanisms governing the extracellular matrix (ECM) degradation important for metastasis in CRC are not well-defined. We investigated a functional relationship between vimentin (Vim) and myosin 10 (Myo10), and whether this relationship is associated with cancer progression. We tested the hypothesis that Vim regulates the aggregation of Myo10 at the tips of cell extensions, which increases membrane-type 1 matrix metalloproteinase (MT1-MMP)-associated local collagen proteolysis and ECM degradation. Analysis of CRC samples revealed colocalization of Vim with Myo10 and MT1-MMP in cell extensions adjacent to sites of collagen degradation, suggesting an association with local cell invasion. We analyzed cultured CRC cells and fibroblasts and found that Vim accelerates aggregation of Myo10 at cell tips, which increases the cell extension rate. Vim stabilizes the interaction of Myo10 with MT1-MMP, which in turn increases collagenolysis. Vim depletion reduced the aggregation of Myo10 at the cell extension tips and MT1-MMP-dependent collagenolysis. We propose that Vim interacts with Myo10, which in turn associates with MT1-MMP to facilitate the transport of these molecules to the termini of cell extensions and there enhance cancer invasion of soft connective tissues.

TRPV4 regulates ß1 integrin-mediated cell-matrix adhesions and collagen remodeling.

Transient Receptor Potential Vanilloid-type 4 (TRPV4) is a mechanosensitive, Ca2+ -permeable plasma membrane channel that associates with focal adhesions, influences collagen remodeling, and is associated with fibrotic processes through undefined mechanisms. While TRPV4 is known to be activated by mechanical forces transmitted through collagen adhesion receptors containing the ß1 integrin, it is not understood whether TRPV4 affects matrix remodeling by altering ß1 integrin expression and function. We tested the hypothesis that TRPV4 regulates collagen remodeling through its impact on the ß1 integrin in cell-matrix adhesions. In cultured fibroblasts derived from mouse gingival connective tissues, which exhibit very rapid collagen turnover, we found that higher TRPV4 expression is associated with reduced ß1 integrin abundance and adhesion to collagen, reduced focal adhesion size and total adhesion area, and reduced alignment and compaction of extracellular fibrillar collagen. The reduction of ß1 integrin expression mediated by TRPV4 is associated with the upregulation of miRNAs that target ß1 integrin mRNA. Our data suggest a novel mechanism by which TRPV4 modulates collagen remodeling through post-transcriptional downregulation of ß1 integrin expression and function.

DNA hydrogels for bone regeneration.

DNA-based biomaterials have been proposed for tissue engineering approaches due to their predictable assembly into complex morphologies and ease of functionalization. For bone tissue regeneration, the ability to bind Ca2+ and promote hydroxyapatite (HAP) growth along the DNA backbone combined with their degradation and release of extracellular phosphate, a known promoter of osteogenic differentiation, make DNA-based biomaterials unlike other currently used materials. However, their use as biodegradable scaffolds for bone repair remains scarce. Here, we describe the design and synthesis of DNA hydrogels, gels composed of DNA that swell in water, their interactions in vitro with the osteogenic cell lines MC3T3-E1 and mouse calvarial osteoblast, and their promotion of new bone formation in rat calvarial wounds. We found that DNA hydrogels can be readily synthesized at room temperature, and they promote HAP growth in vitro, as characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Osteogenic cells remain viable when seeded on DNA hydrogels in vitro, as characterized by fluorescence microscopy. In vivo, DNA hydrogels promote the formation of new bone in rat calvarial critical size defects, as characterized by micro-computed tomography and histology. This study uses DNA hydrogels as a potential therapeutic biomaterial for regenerating lost bone.

FLNA-filaminopathy skeletal phenotypes are not due to an osteoblast autonomous loss-of-function.

Mutations in FLNA, which encodes the cytoskeletal protein FLNA, cause a spectrum of sclerosing skeletal dysplasias. Although many of these genetic variants are recurrent and cluster within the gene, the pathogenic mechanism that underpins the development of these skeletal phenotypes is unknown. To determine if the skeletal dysplasia in FLNA-related conditions is due to a cell-autonomous loss-of-function localising to osteoblasts and/or osteocytes, we utilised mouse models to conditionally remove Flna from this cellular lineage. Flna was conditionally knocked out from mature osteocytes using the Dmp1-promoter driven Cre-recombinase expressing mouse, as well as the committed osteoblast lineage using the Osx-Cre or Col1a1-Cre expressing lines. We measured skeletal parameters with µCT and histological methods, as well as gene expression in the mineralised skeleton. We found no measureable differences between the conditional Flna knockout mice, and their control littermate counterparts. Moreover, all of the conditional Flna knockout mice, developed and aged normally. From this we concluded that the skeletal dysplasia phenotype associated with pathogenic variants in FLNA is not caused by a cell-autonomous loss-of-function in the osteoblast-osteocyte lineage, adding more evidence to the hypothesis that these phenotypes are due to gain-of-function in FLNA.

Screening of functionalized collagen membranes with a porcine periodontal regeneration model.

OBJECTIVES: Current methods for periodontal regeneration do not promote collagen fiber insertions into new bone and cementum. We used a pig wound model to screen different functionalized collagen membranes in promoting periodontal reattachment to root surfaces. METHODS: Treatment groups included (1) control with no membranes, (2) collagen-coated membranes, (3) membranes with insulin-like growth factor-1 (IGF-1), (4) membranes with amelotin, or (5) membranes attached with calcium phosphate cement (CPC), or with CPC combined with IGF-1. Flap procedures were performed on mandibular and maxillary premolars of each pig. RESULTS: Histomorphometric, micro-CT, and clinical measurements obtained at 4 and 12 weeks after surgery showed cementum formation on denuded roots and reformation of alveolar bone, indicating that the pig model can model healing responses in periodontal regeneration. Calcium phosphate cement simplified procedures by eliminating the need for sutures and improved regeneration of alveolar bone (p < 0.05) compared with other treatments. There was a reduction (p < 0.05) of PD only for the IGF group. Large observed variances between treatment groups indicated that a priori power analyses should be conducted to optimize statistical analysis. CONCLUSIONS: Pigs can model discrete elements of periodontal healing using collagen-based, functionalized membranes. Screening indicates that membrane anchorage with calcium phosphate cements improve regeneration of alveolar bone.

Streptococcus mutans Proteases Degrade Dentinal Collagen.

Here, we explored the role of S. mutans's whole cell and discrete fractions in the degradation of type I collagen and dentinal collagen. Type I collagen gels and human demineralized dentin slabs (DS) were incubated in media alone or with one of the following: overnight (O/N) or newly inoculated (NEW) cultures of S. mutans UA159; intracellular proteins, supernatant or bacterial membranes of O/N cultures. Media from all groups were analyzed for protease-mediated release of the collagen-specific imino acid hydroxyproline. Images of type I collagen and DS were analyzed, respectively. Type I collagen degradation was highest for the supernatant (p < 0.05) fractions, followed by intracellular components and O/N cultures. Collagen degradation for DS samples was highest for O/N samples, followed by supernatant, and intracellular components (p < 0.05). There was lower detectable degradation for both type I collagen and DS from NEW culture samples (p < 0.05), and there was no type I collagen or DS degradation detected for bacterial membrane samples. Structural changes to type I collagen gel and dentinal collagen were observed, respectively, following incubation with S. mutans cultures (O/N and NEW), intracellular components, and supernatant. This study demonstrates that intracellular and extracellular proteolytic activities from S. mutans enable this cariogenic bacterium to degrade type I and dentinal collagen in a growth-phase dependent manner, potentially contributing to the progression of dental caries.

Impact of Vimentin on Regulation of Cell Signaling and Matrix Remodeling.

Vimentin expression contributes to cellular mechanoprotection and is a widely recognized marker of fibroblasts and of epithelial-mesenchymal transition. But it is not understood how vimentin affects signaling that controls cell migration and extracellular matrix (ECM) remodeling. Recent data indicate that vimentin controls collagen deposition and ECM structure by regulating contractile force application to the ECM and through post-transcriptional regulation of ECM related genes. Binding of cells to the ECM promotes the association of vimentin with cytoplasmic domains of adhesion receptors such as integrins. After initial adhesion, cell-generated, myosin-dependent forces and signals that impact vimentin structure can affect cell migration. Post-translational modifications of vimentin determine its adaptor functions, including binding to cell adhesion proteins like paxillin and talin. Accordingly, vimentin regulates the growth, maturation and adhesive strength of integrin-dependent adhesions, which enables cells to tune their attachment to collagen, regulate the formation of cell extensions and control cell migration through connective tissues. Thus, vimentin tunes signaling cascades that regulate cell migration and ECM remodeling. Here we consider how specific properties of vimentin serve to control cell attachment to the underlying ECM and to regulate mesenchymal cell migration and remodeling of the ECM by resident fibroblasts.

DDR1 associates with TRPV4 in cell-matrix adhesions to enable calcium-regulated myosin activity and collagen compaction.

Tissue fibrosis manifests as excessive deposition of compacted, highly aligned collagen fibrils, which interfere with organ structure and function. Cells in collagen-rich lesions often exhibit marked overexpression of discoidin domain receptor 1 (DDR1), which is linked to increased collagen compaction through the association of DDR1 with the Ca2+ -dependent nonmuscle myosin IIA (NMIIA). We examined the functional relationship between DDR1 and the transient receptor potential vanilloid type 4 (TRPV4) channel, a Ca2+ -permeable ion channel that is implicated in collagen compaction. Fibroblasts expressing high levels of DDR1 were used to model cells in lesions with collagen compaction. In these cells, the expression of the ß1 integrin was deleted to simplify studies of DDR1 function. Compared with DDR1 wild-type cells, high DDR1 expression was associated with increased Ca2+ influx through TRPV4, enrichment of TRPV4 in collagen adhesions, and enhanced contractile activity mediated by NMIIA. At cell adhesion sites to collagen, DDR1 associated with TRPV4, which enhanced DDR1-mediated collagen alignment and compaction. We conclude that DDR1 regulates Ca2+ influx through the TRPV4 channel to promote critical, DDR1-mediated processes that are important in lesions with collagen compaction and alignment.

TNF-α regulates the composition of the basal lamina and cell-matrix adhesions in gingival epithelial cells.

Laminin 5, type 4 collagen, and α6ß4 integrin contribute to the formation of hemidesmosomes in the epithelia of periodontal tissues, which is critical for the development and maintenance of the dentogingival junction. As it is not known whether TNF-α alters the composition of the epithelial pericellular matrix, human gingival epithelial cells were cultured in the presence or absence of TNF-α. Treatment with TNF-α accelerated epithelial cell migration and closure of in vitro wounds. These data indicate unexpectedly, that TNF-α promotes the formation of the pericellular matrix around epithelial cells and enhances adhesion of epithelial cells to the underlying matrix, properties which are important for cell migration and the integrity of the dentogingival junction.

Physics and Physiology of Cell Spreading in Two and Three Dimensions.

Cells spread on surfaces and within three-dimensional (3-D) matrixes as they grow, divide, and move. Both chemical and physical signals orchestrate spreading during normal development, wound healing, and pathological states such as fibrosis and tumor growth. Diverse molecular mechanisms drive different forms of cell spreading. This article discusses mechanisms by which cells spread in 2-D and 3-D and illustrates new directions in studies of this aspect of cell function.

Gelsolin is an important mediator of Angiotensin II-induced activation of cardiac fibroblasts and fibrosis.

Myocardial fibrosis is a characteristic of various cardiomyopathies, and myocardial fibroblasts play a central role in this process. Gelsolin (GSN) is an actin severing and capping protein that regulates actin assembly and may be involved in fibroblast activation. While the role of GSN in mechanical stress-mediated cardiac fibrosis has been explored, its role in myocardial fibrosis in the absence of mechanical stress is not defined. In this study, we investigated the role of GSN in myocardial fibrosis induced by Angiotensin II (Ang II), a profibrotic hormone that is elevated in cardiovascular disease. We utilized mice lacking GSN (Gsn-/- ) and cultured primary adult cardiac fibroblasts (cFB). In vivo, Ang II infusion in mice resulted in significantly less severe myocardial fibrosis in Gsn-/- compared with Gsn+/+ mice, along with diminished activation of the TGFß1-Smad2/3 pathway, and reduced expression of cardiac extracellular matrix proteins (collagen, fibronectin, periostin). Moreover, Gsn-deficient hearts exhibited suppressed activity of the AMPK pathway and its downstream effectors, mTOR and P70S6Kinase, which could contribute to the suppressed TGFß1 activity. In vitro, the Ang II-induced activation of cFBs was reduced in Gsn-deficient fibroblasts evident from decreased expression of αSMA and periostin, diminished actin filament turnover; which also exhibited reduced activity of the AMPK-mTOR pathway, and P70S6K phosphorylation. AMPK inhibition compensated for the loss of GSN, restored the levels of G-actin in Gsn-/- cFBs and promoted activation to myofibroblasts by increasing αSMA and periostin levels. This study reveals a novel role for GSN in mediating myocardial fibrosis by regulating the AMPK-mTOR-P70S6K pathway in cFB activation independent from mechanical stress-induced factors.

Suppression of the fibrotic encapsulation of silicone implants by inhibiting the mechanical activation of pro-fibrotic TGF-ß.

The fibrotic encapsulation of implants involves the mechanical activation of myofibroblasts and of pro-fibrotic transforming growth factor beta 1 (TGF-ß1). Here, we show that both softening of the implant surfaces and inhibition of the activation of TGF-ß1 reduce the fibrotic encapsulation of subcutaneous silicone implants in mice. Conventionally stiff silicones (elastic modulus, ~2 MPa) coated with a soft silicone layer (elastic modulus, ~2 kPa) reduced collagen deposition as well as myofibroblast activation without affecting the numbers of macrophages and their polarization states. Instead, fibroblasts around stiff implants exhibited enhanced intracellular stress, increased the recruitment of αv and ß1 integrins, and activated TGF-ß1 signalling. In vitro, the recruitment of αv integrin to focal adhesions and the activation of ß1 integrin and of TGF-ß were higher in myofibroblasts grown on latency-associated peptide (LAP)-coated stiff silicones than on soft silicones. Antagonizing αv integrin binding to LAP through the small-molecule inhibitor CWHM-12 suppressed active TGF-ß signalling, myofibroblast activation and the fibrotic encapsulation of stiff subcutaneous implants in mice.

Myofibroblast Adhesome Analysis by Mass Spectrometry.

Myofibroblasts form adhesions to their underlying extracellular matrices, which is an essential step in their formation and differentiation. These adhesions comprise protein-rich aggregates of a wide variety of signaling, cytoskeletal, cell adhesion, and matrix proteins that interact with one another to enable bidirectional flow of information between the cell and the surrounding extracellular matrix. The concentrated repertoire of the proteins in matrix adhesions of myofibroblasts (i.e., over 450 different proteins) and their important role in regulating the metabolic activities of myofibroblasts, has motivated in-depth analysis of their protein complement and how this repertoire is influenced by experimental conditions.In this protocol I describe in detail: (1) the method for isolating focal adhesion-associated proteins using matrix ligand-bound magnetite beads; (2) the method for eluting the proteins from the beads and their preparation for mass spectrometry (Fig. 1). I also briefly consider the mass spectrometry methods including the use of isobaric tags to enable multifactorial experiments and the analysis of the identified proteins. I consider the advantages of these approaches, and the challenges and pitfalls that are encountered with these methods.

Vimentin regulates the assembly and function of matrix adhesions.

The intermediate filament protein vimentin is a widely used phenotypic marker for identifying cells of the mesenchymal linkage such as fibroblasts and myofibroblasts, but the full repertoire of vimentin's functional attributes has not been fully explored. Here we consider how vimentin, in addition to its contributions to mechanical stabilization of cell structure, also helps to control the assembly of cell adhesions and migration through collagen matrices. While the assembly and function of matrix adhesions are critical for the differentiation of myofibroblasts and many other types of adherent cells, a potential mechanism that explains how vimentin affects the recruitment and abundance of centrally important proteins in cell adhesions has been elusive. Here we review recent data indicating that vimentin plays a central regulatory role in the assembly of focal adhesions which form in response to the attachment to collagen. We show that in particular, vimentin is a key organizer of the ß1 integrin adhesive machinery, which affects cell migration through collagen. This review provides a comprehensive picture of the surprisingly broad array of processes and molecules with which vimentin interacts to affect cell function in the context of fibroblast and myofibroblast adhesion and migration on collagen.

Vimentin tunes cell migration on collagen by controlling ß1 integrin activation and clustering.

Vimentin is a structural protein that is required for mesenchymal cell migration and directly interacts with actin, ß1 integrin and paxillin. We examined how these interactions enable vimentin to regulate cell migration on collagen. In fibroblasts, depletion of vimentin increased talin-dependent activation of ß1 integrin by more than 2-fold. Loss of vimentin was associated with reduction of ß1 integrin clustering by 50% and inhibition of paxillin recruitment to focal adhesions by more than 60%, which was restored by vimentin expression. This reduction of paxillin was associated with 65% lower Cdc42 activation, a 60% reduction of cell extension formation and a greater than 35% decrease in cell migration on collagen. The activation of PAK1, a downstream effector of Cdc42, was required for vimentin phosphorylation and filament maturation. We propose that vimentin tunes cell migration through collagen by acting as an adaptor protein for focal adhesion proteins, thereby regulating ß1 integrin activation, resulting in well-organized, mature integrin clusters.This article has an associated First Person interview with the first author of the paper.

TRPV4 integrates matrix mechanosensing with Ca2+ signaling to regulate extracellular matrix remodeling.

In healthy connective tissues, mechanosensors trigger the generation of Ca2+ signals, which enable cells to maintain the structure of the fibrillar collagen matrix through actomyosin contractile forces. Transient receptor potential vanilloid type 4 (TRPV4) is a mechanosensitive Ca2+ -permeable channel that, when expressed in cell-matrix adhesions of the plasma membrane, regulates extracellular matrix (ECM) remodeling. In high prevalence disorders such as fibrosis and tumor metastasis, dysregulated matrix remodeling is associated with disruptions of Ca2+ homeostasis and TRPV4 function. Here, we consider that ECM polymers transmit cell-activating mechanical signals to TRPV4 in cell adhesions. When activated, TRPV4 regulates fibrillar collagen remodeling, thereby altering the mechanical properties of the ECM. In this review, we integrate functionally connected processes of matrix remodeling to highlight how TRPV4 in cell adhesions and matrix mechanics are reciprocally regulated through Ca2+ signaling.

Role of the small GTPase activating protein IQGAP1 in collagen phagocytosis.

Many adult connective tissues undergo continuous remodeling to maintain matrix homeostasis. Physiological remodeling involves the degradation of collagen fibers by the intracellular cathepsin-dependent phagocytic pathway. We considered that a multidomain, small GTPase activating protein, IQGAP1, which is involved in the generation of cell extensions, is required for collagen phagocytosis, possibly arising from its interactions with cdc42 and the actin-binding protein Flightless I (FliI). We examined the role of IQGAP1 in collagen phagocytosis by human gingival fibroblasts (HGFs) and by IQGAP1+/+ and IQGAP1-/- mouse embryonic fibroblasts. IQGAP1 was strongly expressed by HGFs, localized to vinculin-stained cell adhesions and sites where cell extensions are initiated, and colocalized with FliI. Immunoprecipitation showed that IQGAP1 associated with FliI. HGFs showed 10-fold increases of collagen binding, 6-fold higher internalization, and 3-fold higher ß1 integrin activation between 30 and 180 min after incubation with collagen. Compared with IQGAP1+/+ fibroblasts, deletion of IQGAP1 reduced collagen binding (1.4-fold), collagen internalization (3-fold), ß1 integrin activation (2-fold), and collagen degradation (1.8-fold). We conclude that IQGAP1 affects collagen remodeling through its regulation of phagocytic degradation pathways, which may involve the interaction of IQGAP1 with FliI.