ABSTRACT
Cell adhesion is essential for the formation of organs, cellular migration, and interaction with target cells and the extracellular matrix. Integrins are large protein α/ß-chain heterodimers and form a major family of cell adhesion molecules. Recent research has dramatically increased our knowledge of how integrin phosphorylations regulate integrin activity. Phosphorylations determine the signaling complexes formed on the cytoplasmic tails, regulating downstream signaling. α-Chain phosphorylation is necessary for inducing ß-chain phosphorylation in LFA-1, and the crosstalk from one integrin to another activating or inactivating its function is in part mediated by phosphorylation of ß-chains. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus receptor angiotensin-converting enzyme 2 (ACE2) and possible integrin coreceptors may crosstalk and induce a phosphorylation switch and autophagy.
Subject(s)
COVID-19 , Integrins , Cell Adhesion , Humans , Integrins/metabolism , Phosphorylation , SARS-CoV-2ABSTRACT
Integrins are large heterodimeric type 1 membrane proteins expressed in all nucleated mammalian cells. Eighteen α-chains and eight ß-chains can combine to form 24 different integrins. They are cell adhesion proteins, which bind to a large variety of cellular and extracellular ligands. Integrins are required for cell migration, hemostasis, translocation of cells out from the blood stream and further movement into tissues, but also for the immune response and tissue morphogenesis. Importantly, integrins are not usually active as such, but need activation to become adhesive. Integrins are activated by outside-in activation through integrin ligand binding, or by inside-out activation through intracellular signaling. An important question is how integrin activity is regulated, and this topic has recently drawn much attention. Changes in integrin affinity for ligand binding are due to allosteric structural alterations, but equally important are avidity changes due to integrin clustering in the plane of the plasma membrane. Recent studies have partially solved how integrin cell surface structures change during activation. The integrin cytoplasmic domains are relatively short, but by interacting with a variety of cytoplasmic proteins in a regulated manner, the integrins acquire a number of properties important not only for cell adhesion and movement, but also for cellular signaling. Recent work has shown that specific integrin phosphorylations play pivotal roles in the regulation of integrin activity. Our purpose in this review is to integrate the present knowledge to enable an understanding of how cell adhesion is dynamically regulated.
Subject(s)
Cell Adhesion , Cytoplasm/metabolism , Integrins/metabolism , Amino Acid Sequence , Animals , Humans , Integrins/chemistry , Ligands , Molecular Targeted Therapy , PhosphorylationABSTRACT
The integrin leukocyte function-associated antigen-1 (LFA-1) plays a pivotal role in leukocyte adhesion and migration, but the mechanism(s) by which this integrin is regulated has remained incompletely understood. LFA-1 integrin activity requires phosphorylation of its ß2-chain and interactions of its cytoplasmic tail with various cellular proteins. The α-chain is constitutively phosphorylated and necessary for cellular adhesion, but how the α-chain regulates adhesion has remained enigmatic. We now show that substitution of the α-chain phosphorylation site (S1140A) in T cells inhibits the phosphorylation of the functionally important Thr-758 in the ß2-chain, binding of α-actinin and 14-3-3 protein, and expression of an integrin-activating epitope after treatment with the stromal cell-derived factor-1α. The presence of this substitution resulted in a loss of cell adhesion and directional cell migration. Moreover, LFA-1 activation through the T-cell receptor in cells expressing the S1140A LFA-1 variant resulted in less Thr-758 phosphorylation, α-actinin and talin binding, and cell adhesion. The finding that the LFA-1 α-chain regulates adhesion through the ß-chain via specific phosphorylation at Ser-1140 in the α-chain has not been previously reported and emphasizes that both chains are involved in the regulation of LFA-1 integrin activity.
Subject(s)
Actinin/metabolism , Cell Adhesion , Integrin alpha Chains/metabolism , Integrin beta Chains/metabolism , Lymphocyte Function-Associated Antigen-1/metabolism , Receptors, Antigen, T-Cell/metabolism , Cell Movement , Humans , Jurkat Cells , Phosphorylation , Protein BindingABSTRACT
INTRODUCTION: Nebulin is a giant actin-binding protein in the thin filament of the skeletal muscle sarcomere. Studies of nebulin interactions are limited by the size, complexity, and poor solubility of the protein. We divided the nebulin super-repeat region into a super-repeat panel, and studied nebulin/actin interactions. METHODS: Actin binding was studied using a co-sedimentation assay with filamentous actin and 26 different nebulin super-repeats. RESULTS: The panel revealed notable differences in actin binding between the super-repeats. Both ends of the super-repeat region bound actin significantly more strongly, whereas the central part of the protein bound actin weakly. Thus, the binding between nebulin and actin formed a location-dependent pattern of strong vs. weak binding. DISCUSSION: The nebulin super-repeat panel allowed us to study the actin binding of each super-repeat individually. The panel will be a powerful tool in elucidating nebulin function in health and disease. Muscle Nerve 59:116-121, 2019.
Subject(s)
Actins/metabolism , Muscle Proteins/metabolism , Muscle, Skeletal/cytology , Muscle, Skeletal/metabolism , Sarcomeres/metabolism , Amino Acid Sequence , Animals , Humans , Muscle Proteins/chemistry , Muscle, Skeletal/ultrastructure , Protein Binding/physiology , RNA, Messenger , Repetitive Sequences, Nucleic Acid , Terminator Regions, Genetic/genetics , Terminator Regions, Genetic/physiologyABSTRACT
Binding of intercellular adhesion molecule-1 to the ß2-integrin leukocyte function associated antigen-1 (LFA-1) is known to induce cross-talk to the α4ß1 integrin. Using different LFA-1 monoclonal antibodies, we have been able to study the requirement and mechanism of action for the cross-talk in considerable detail. LFA-1-activating antibodies and those inhibitory antibodies that signal to α4ß1 induce phosphorylation of Thr-758 on the ß2-chain, which is followed by binding of 14-3-3 proteins and signaling through the G protein exchange factor Tiam1. This results in dephosphorylation of Thr-788/789 on the ß1-chain of α4ß1 and loss of binding to its ligand vascular cell adhesion molecule-1. The results show that with LFA-1 antibodies, we can activate LFA-1 and inhibit α4ß1, inhibit both LFA-1 and α4ß1, inhibit LFA-1 but not α4ß1, or not affect LFA-1 or α4ß1 These findings are important for the understanding of integrin regulation and for the interpretation of the effect of integrin antibodies and their use in clinical applications.
Subject(s)
Antibodies/pharmacology , Integrin alpha4beta1/immunology , Leukocytes/immunology , Lymphocyte Function-Associated Antigen-1/immunology , Signal Transduction/drug effects , Antibodies/immunology , Cell Adhesion/drug effects , Cell Adhesion/immunology , Cell Line , Humans , Leukocytes/cytology , Phosphorylation/drug effects , Phosphorylation/immunology , Signal Transduction/immunologyABSTRACT
The regulation of integrins expressed on leukocytes must be controlled precisely, and members of different integrin subfamilies have to act in concert to ensure the proper traffic of immune cells to sites of inflammation. The activation of ß2 family integrins through the T cell receptor or by chemokines leads to the inactivation of very late antigen 4. The mechanism(s) of this cross-talk has not been known. We have now elucidated in detail how the signals are transmitted from leukocyte function-associated antigen 1 and show that, after its activation, the signaling involves specific phosphorylations of ß2 integrin followed by interactions with cytoplasmic signaling proteins. This results in loss of ß1 phosphorylation and a decrease in very late antigen 4 binding to its ligand vascular cell adhesion molecule 1. Our results show how a member of one integrin family regulates the activity of another integrin. This is important for the understanding of integrin-mediated processes.
Subject(s)
CD18 Antigens/metabolism , Integrin alpha4beta1/metabolism , Integrin alphaXbeta2/metabolism , Integrin beta1/metabolism , Leukocytes/cytology , Lymphocyte Function-Associated Antigen-1/metabolism , Cell Adhesion , Cell Movement , Cells, Cultured , Cytoplasm/metabolism , Filamins/metabolism , Gene Expression Regulation , Humans , K562 Cells , Ligands , Phosphorylation , Signal TransductionABSTRACT
Mutations affecting skeletal muscle isoforms of the tropomyosin genes may cause nemaline myopathy, cap myopathy, core-rod myopathy, congenital fiber-type disproportion, distal arthrogryposes, and Escobar syndrome. We correlate the clinical picture of these diseases with novel (19) and previously reported (31) mutations of the TPM2 and TPM3 genes. Included are altogether 93 families: 53 with TPM2 mutations and 40 with TPM3 mutations. Thirty distinct pathogenic variants of TPM2 and 20 of TPM3 have been published or listed in the Leiden Open Variant Database (http://www.dmd.nl/). Most are heterozygous changes associated with autosomal-dominant disease. Patients with TPM2 mutations tended to present with milder symptoms than those with TPM3 mutations, DA being present only in the TPM2 group. Previous studies have shown that five of the mutations in TPM2 and one in TPM3 cause increased Ca(2+) sensitivity resulting in a hypercontractile molecular phenotype. Patients with hypercontractile phenotype more often had contractures of the limb joints (18/19) and jaw (6/19) than those with nonhypercontractile ones (2/22 and 1/22), whereas patients with the non-hypercontractile molecular phenotype more often (19/22) had axial contractures than the hypercontractile group (7/19). Our in silico predictions show that most mutations affect tropomyosin-actin association or tropomyosin head-to-tail binding.
Subject(s)
Genetic Association Studies , Muscular Diseases/congenital , Muscular Diseases/genetics , Mutation , Tropomyosin/genetics , Actins/metabolism , Adolescent , Adult , Amino Acid Sequence , Child , Child, Preschool , Databases, Genetic , Female , Humans , Infant , Male , Molecular Sequence Data , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Muscular Diseases/diagnosis , Phenotype , Phosphorylation , Protein Binding , Sequence Alignment , Tropomyosin/chemistry , Tropomyosin/metabolism , Young AdultABSTRACT
Mutations in the TPM2 gene, which encodes ß-tropomyosin, are an established cause of several congenital skeletal myopathies and distal arthrogryposis. We have identified a TPM2 mutation, p.K7del, in five unrelated families with nemaline myopathy and a consistent distinctive clinical phenotype. Patients develop large joint contractures during childhood, followed by slowly progressive skeletal muscle weakness during adulthood. The TPM2 p.K7del mutation results in the loss of a highly conserved lysine residue near the N-terminus of ß-tropomyosin, which is predicted to disrupt head-to-tail polymerization of tropomyosin. Recombinant K7del-ß-tropomyosin incorporates poorly into sarcomeres in C2C12 myotubes and has a reduced affinity for actin. Two-dimensional gel electrophoresis of patient muscle and primary patient cultured myotubes showed that mutant protein is expressed but incorporates poorly into sarcomeres and likely accumulates in nemaline rods. In vitro studies using recombinant K7del-ß-tropomyosin and force measurements from single dissected patient myofibres showed increased myofilament calcium sensitivity. Together these data indicate that p.K7del is a common recurrent TPM2 mutation associated with mild nemaline myopathy. The p.K7del mutation likely disrupts head-to-tail polymerization of tropomyosin, which impairs incorporation into sarcomeres and also affects the equilibrium of the troponin/tropomyosin-dependent calcium switch of muscle. Joint contractures may stem from chronic muscle hypercontraction due to increased myofibrillar calcium sensitivity while declining strength in adulthood likely arises from other mechanisms, such as myofibre decompensation and fatty infiltration. These results suggest that patients may benefit from therapies that reduce skeletal muscle calcium sensitivity, and we highlight late muscle decompensation as an important cause of morbidity.
Subject(s)
Calcium/metabolism , Muscle Fibers, Skeletal/metabolism , Mutation/physiology , Myopathies, Nemaline/genetics , Myopathies, Nemaline/metabolism , Tropomyosin/genetics , Adolescent , Adult , Aged , Amino Acid Sequence , Animals , Cell Line , Cells, Cultured , Chickens , Female , Genetic Association Studies/methods , Genetic Carrier Screening , Humans , Male , Middle Aged , Molecular Sequence Data , Pedigree , Rats , Secondary Prevention , SwineABSTRACT
Integrins are heterodimeric complex type I membrane proteins involved in cellular adhesion and signaling. They exist as inactive molecules in resting cells, and need activation to become adhesive. Although much is known about their structure, and a large number of interacting molecules have been described, we still only partially understand how their activities are regulated. In this review we focus on the leukocyte-specific ß2-integrins and, specifically, on the role of integrin phosphorylation in the regulation of activity. Phosphorylation reactions can be fast and reversible, thus enabling strictly directed regulatory activities both time-wise and locally in specific regions of the plasma membrane in different leukocytes.
Subject(s)
Integrins/physiology , Amino Acid Sequence , Animals , Humans , Integrins/chemistry , Molecular Sequence Data , Phosphorylation , Protein Structure, Tertiary , Talin/metabolismABSTRACT
Cancer immunotherapy requires a specific antitumor CD8+ T cell-driven immune response; however, upon genetic and epigenetic alterations of the antigen processing and presenting components, cancer cells escape the CD8+ T cell recognition. As a result, poorly immunogenic tumors are refractory to conventional immunotherapy. In this context, the use of viral cancer vaccines in combination with hypomethylating agents represents a promising strategy to prevent cancer from escaping immune system recognition. In this study, we evaluated the sensitivity of melanoma (B16-expressing ovalbumin) and metastatic triple-negative breast cancer (4T1) cell lines to FDA-approved low-dose decitabine in combination with PeptiCRAd, an adenoviral anticancer vaccine. The two models showed different sensitivity to decitabine in vitro and in vivo when combined with PeptiCRAd. In particular, mice bearing syngeneic 4T1 cancer showed higher tumor growth control when receiving the combinatorial treatment compared to single controls in association with a higher expression of MHC class I on cancer cells and reduction in Tregs within the tumor microenvironment. Furthermore, remodeling of the CD8+ T cell infiltration and cytotoxic activity toward cancer cells confirmed the effect of decitabine in enhancing anticancer vaccines in immunotherapy regimens.
ABSTRACT
BACKGROUND: Cancer immunotherapy relies on using the immune system to recognize and eradicate cancer cells. Adaptive immunity, which consists of mainly antigen-specific cytotoxic T cells, plays a pivotal role in controlling cancer progression. However, innate immunity is a necessary component of the cancer immune response to support an immunomodulatory state, enabling T-cell immunosurveillance. METHODS: Here, we elucidated and exploited innate immune cells to sustain the generation of antigen-specific T cells on the use of our cancer vaccine platform. We explored a previously developed oncolytic adenovirus (AdCab) encoding for a PD-L1 (Programmed-Death Ligand 1) checkpoint inhibitor, which consists of a PD-1 (Programmed Cell Death Protein 1) ectodomain fused to an IgG/A cross-hybrid Fc. We coated AdCab with major histocompatibility complex (MHC-I)-restricted tumor peptides, generating a vaccine platform (named PeptiCab); the latter takes advantage of viral immunogenicity, peptide cancer specificity to prime T-cell responses, and antibody-mediated effector functions. RESULTS: As proof of concept, PeptiCab was used in murine models of melanoma and colon cancer, resulting in tumor growth control and generation of systemic T-cell-mediated antitumor responses. In specific, PeptiCab was able to generate antitumor T effector memory cells able to secrete various inflammatory cytokines. Moreover, PeptiCab was able to polarize neutrophils to attain an antigen-presenting phenotype by upregulating MHC-II, CD80 and CD86 resulting in an enhanced T-cell expansion. CONCLUSION: Our data suggest that exploiting innate immunity activates T-cell antitumor responses, enhancing the efficiency of a vaccine platform based on oncolytic adenovirus coated with MHC-I-restricted tumor peptides.
Subject(s)
Neoplasms , Receptors, IgG , Humans , Animals , Mice , Adaptive Immunity , T-Lymphocytes, Cytotoxic , Cytokines/metabolism , Neoplasms/therapy , Neoplasms/pathologyABSTRACT
Immunotherapy has emerged as a promising approach for cancer treatment, with oncolytic adenoviruses showing power as immunotherapeutic agents. In this study, we investigated the immunotherapeutic potential of an adenovirus construct expressing CXCL9, CXCL10, or IL-15 in clear cell renal cell carcinoma (ccRCC) tumor models. Our results demonstrated robust cytokine secretion upon viral treatment, suggesting effective transgene expression. Subsequent analysis using resistance-based transwell migration and microfluidic chip assays demonstrated increased T-cell migration in response to chemokine secretion by infected cells in both 2D and 3D cell models. Flow cytometry analysis revealed CXCR3 receptor expression across T-cell subsets, with the highest percentage found on CD8+ T-cells, underscoring their key role in immune cell migration. Alongside T-cells, we also detected NK-cells in the tumors of immunocompromised mice treated with cytokine-encoding adenoviruses. Furthermore, we identified potential immunogenic antigens that may enhance the efficacy and specificity of our armed oncolytic adenoviruses in ccRCC. Overall, our findings using ccRCC cell line, in vivo humanized mice, physiologically relevant PDCs in 2D and patient-derived organoids (PDOs) in 3D suggest that chemokine-armed adenoviruses hold promise for enhancing T-cell migration and improving immunotherapy outcomes in ccRCC. Our study contributes to the development of more effective ccRCC treatment strategies by elucidating immune cell infiltration and activation mechanisms within the tumor microenvironment (TME) and highlights the usefulness of PDOs for predicting clinical relevance and validating novel immunotherapeutic approaches. Overall, our research offers insights into the rational design and optimization of viral-based immunotherapies for ccRCC.
Subject(s)
Adenoviridae , Carcinoma, Renal Cell , Kidney Neoplasms , Carcinoma, Renal Cell/immunology , Carcinoma, Renal Cell/therapy , Carcinoma, Renal Cell/pathology , Carcinoma, Renal Cell/genetics , Humans , Animals , Kidney Neoplasms/immunology , Kidney Neoplasms/therapy , Kidney Neoplasms/pathology , Kidney Neoplasms/genetics , Mice , Adenoviridae/genetics , Adenoviridae/immunology , Cell Line, Tumor , Xenograft Model Antitumor Assays , Oncolytic Virotherapy/methods , Immunotherapy/methods , Chemokine CXCL9/genetics , Chemokine CXCL9/metabolism , Chemokine CXCL9/immunology , Cell Movement , Chemokine CXCL10/genetics , Chemokine CXCL10/metabolism , Chemokine CXCL10/immunology , Cytokines/metabolism , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , Interleukin-15/genetics , Interleukin-15/metabolism , Interleukin-15/immunology , Receptors, CXCR3/metabolism , Receptors, CXCR3/genetics , Oncolytic Viruses/genetics , Oncolytic Viruses/immunology , CD8-Positive T-Lymphocytes/immunologyABSTRACT
Adhesion is pivotal for most leukocyte functions, and the ß(2) integrin family of adhesion molecules plays a central role. The integrins need activation to become functional, but the molecular events resulting in adhesion have remained incompletely understood. In human T cells, activation through the TCR results in specific phosphorylation of the T758 on the ß(2) chain of LFA-1. We now show that this phosphorylation leads to downstream binding of 14-3-3 proteins, followed by engagement of the guanine nucleotide exchange factor protein Tiam1 and Rac1 activation. Downregulation of the signaling molecules inhibits LFA-1 activity. Activation by the chemokine stromal cell-derived factor-1α also results in T758 phosphorylation and integrin activation. Thus, TCR and chemokine activation converges on LFA-1 phosphorylation, followed by similar downstream events affecting adhesion.
Subject(s)
Guanine Nucleotide Exchange Factors/immunology , Lymphocyte Activation/immunology , Lymphocyte Function-Associated Antigen-1/immunology , Receptors, Antigen, T-Cell/physiology , Signal Transduction/immunology , 14-3-3 Proteins/immunology , 14-3-3 Proteins/metabolism , Cell Adhesion/immunology , Cell Adhesion Molecules/immunology , Cell Adhesion Molecules/metabolism , Guanine Nucleotide Exchange Factors/metabolism , Humans , Integrins/immunology , Integrins/metabolism , Lymphocyte Function-Associated Antigen-1/metabolism , Phosphorylation , Receptors, Antigen, T-Cell/metabolism , T-Lymphoma Invasion and Metastasis-inducing Protein 1 , Transfection , rac1 GTP-Binding Protein/metabolismABSTRACT
NM (nemaline myopathy) is a rare genetic muscle disorder defined on the basis of muscle weakness and the presence of structural abnormalities in the muscle fibres, i.e. nemaline bodies. The related disorder cap myopathy is defined by cap-like structures located peripherally in the muscle fibres. Both disorders may be caused by mutations in the TPM2 gene encoding ß-Tm (tropomyosin). Tm controls muscle contraction by inhibiting actin-myosin interaction in a calcium-sensitive manner. In the present study, we have investigated the pathogenetic mechanisms underlying five disease-causing mutations in Tm. We show that four of the mutations cause changes in affinity for actin, which may cause muscle weakness in these patients, whereas two show defective Ca2+ activation of contractility. We have also mapped the amino acids altered by the mutation to regions important for actin binding and note that two of the mutations cause altered protein conformation, which could account for impaired actin affinity.
Subject(s)
Actins/metabolism , Myopathies, Nemaline/metabolism , Myopathies, Structural, Congenital/metabolism , Tropomyosin/genetics , Tropomyosin/metabolism , Animals , Humans , Myopathies, Nemaline/genetics , Myopathies, Nemaline/pathology , Myopathies, Structural, Congenital/genetics , Myopathies, Structural, Congenital/pathology , Recombinant Proteins , SpodopteraABSTRACT
Immune checkpoint inhibitors have clinical success in prolonging the life of many cancer patients. However, only a minority of patients benefit from such therapy, calling for further improvements. Currently, most PD-L1 checkpoint inhibitors in the clinic do not elicit Fc effector mechanisms that would substantially increase their efficacy. To gain potency and circumvent off-target effects, we previously designed an oncolytic adenovirus (Ad-Cab) expressing an Fc fusion peptide against PD-L1 on a cross-hybrid immunoglobulin GA (IgGA) Fc. Ad-Cab elicited antibody effector mechanisms of IgG1 and IgA, which led to higher tumor killing compared with each isotype alone and with clinically approved PD-L1 checkpoint inhibitors. In this study, we further improved the therapy to increase the IgG1 Fc effector mechanisms of the IgGA Fc fusion peptide (Ad-Cab FT) by adding four somatic mutations that increase natural killer (NK) cell activation. Ad-Cab FT was shown to work better at lower concentrations compared with Ad-Cab in vitro and in vivo and to have better tumor- and myeloid-derived suppressor cell killing, likely because of higher NK cell activation. Additionally, the biodistribution of the Fc fusion peptide demonstrated targeted release in the tumor microenvironment with minimal or no leakage to the peripheral blood and organs in mice. These data demonstrate effective and safe use of Ad-Cab FT, bidding for further clinical investigation.
ABSTRACT
Malignant pleural mesothelioma (MPM) is an aggressive tumor with a poor prognosis. As the available therapeutic options show a lack of efficacy, novel therapeutic strategies are urgently needed. Given its T-cell infiltration, we hypothesized that MPM is a suitable target for therapeutic cancer vaccination. To date, research on mesothelioma has focused on the identification of molecular signatures to better classify and characterize the disease, and little is known about therapeutic targets that engage cytotoxic (CD8+) T cells. In this study we investigate the immunopeptidomic antigen-presented landscape of MPM in both murine (AB12 cell line) and human cell lines (H28, MSTO-211H, H2452, and JL1), as well as in patients' primary tumors. Applying state-of-the-art immuno-affinity purification methodologies, we identify MHC I-restricted peptides presented on the surface of malignant cells. We characterize in vitro the immunogenicity profile of the eluted peptides using T cells from human healthy donors and cancer patients. Furthermore, we use the most promising peptides to formulate an oncolytic virus-based precision immunotherapy (PeptiCRAd) and test its efficacy in a mouse model of mesothelioma in female mice. Overall, we demonstrate that the use of immunopeptidomic analysis in combination with oncolytic immunotherapy represents a feasible and effective strategy to tackle untreatable tumors.
Subject(s)
Lung Neoplasms , Mesothelioma, Malignant , Mesothelioma , Pleural Neoplasms , Humans , Female , Animals , Mice , Pleural Neoplasms/drug therapy , Mesothelioma/drug therapy , Immunotherapy , Peptides/therapeutic use , Cell Line, Tumor , Lung Neoplasms/pathologyABSTRACT
The Neurofibromatosis 2 (NF2) gene product merlin is a tumour suppressor, which in addition to inhibiting cell proliferation regulates cell morphology. The morphogenic properties of merlin may play a role in tumour suppression, as patient-derived tumour cells demonstrate cytoskeletal abnormalities. However, it is still unclear how these functions are linked. The N-terminal FERM-domain of merlin is highly homologous to the oncogenic protein ezrin, while the C-termini are less conserved, suggesting that the opposite effect of the proteins on proliferation could be mediated by their distinct C-terminal regions. In this study we characterize the role of the most C-terminal residues of merlin in the regulation of proliferation, cytoskeletal organization, phosphorylation and intramolecular associations. In addition to the two full-length merlin isoforms and truncating mutations found in patients, we focused on the evolutionally conserved C-terminal residues 545-547, also harbouring disease-causing mutations. We demonstrate that merlin induces cell extensions, which result from impaired retraction of protrusions rather than from increased formation of filopodia. The residues 538-568 were found particularly important for this morphogenic activity. The results further show that both merlin isoforms are able to equally inhibit proliferation, whereas C-terminal mutants affecting residues 545-547 are less effective in growth suppression. This study demonstrates that the C-terminus contains distinct but overlapping functional domains important for regulation of the morphogenic activity, intramolecular associations and cell proliferation.
Subject(s)
Gene Expression Regulation , Genes, Tumor Suppressor , Neurofibromin 2/genetics , Amino Acid Sequence , Animals , COS Cells , Cell Proliferation , Chlorocebus aethiops , Cytoskeletal Proteins/genetics , Cytoskeletal Proteins/metabolism , Cytoskeleton/genetics , Cytoskeleton/metabolism , Fluorescent Antibody Technique , HEK293 Cells , Humans , Immunoblotting , Mice , Molecular Sequence Data , Neurofibromin 2/metabolism , Phenotype , Phosphorylation , Protein Isoforms , Pseudopodia/genetics , Pseudopodia/metabolism , TransfectionABSTRACT
Platelets can release a heterogeneous pool of vesicles which include plasma membrane-derived microparticles (PMPs) and multivesicular body-derived exosomes. As both vesicle types are generated upon activation and their distinction is complicated due to an overlap in their molecular properties and sizes, they are best discussed as an entity, the platelet-derived microvesicles (PMVs). PMPs can be formed through several induction pathways, which determine their different molecular profiles and facilitate tailor-made participation in intercellular communication. This dynamic variability may lie behind the multifaceted and sometimes very different observations of the PMPs in physiological and pathological settings. Currently, little is known of platelet-derived exosomes. In all, PMVs not only participate in several homeostatic multicellular processes, such as hemostasis, maintenance of vascular health, and immunity, but they also play a role in thrombotic and inflammatory diseases and cancer progression. In the past few years, the number of original articles and reviews on microvesicles has dramatically increased, but the data simultaneously raise further questions, the answers to which depend on forthcoming analytical improvements. In this article, the differential activation pathways and the molecular and functional properties of PMVs are reviewed in context with their sometimes paradoxical role in health and in disease. Also, the methodological issues of PMV detection and analysis are discussed in the light of recent advances within the field.
Subject(s)
Blood Platelets/cytology , Cell Communication/physiology , Exosomes , Humans , Microscopy, Electron, Transmission , Platelet Activation/physiologyABSTRACT
Most cells express several integrins. The integrins are able to respond to various cellular functions and needs by modifying their own activation state, but in addition by their ability to regulate each other by activation or inhibition. This crosstalk or transdominant regulation is strictly controlled. The mechanisms resulting in integrin crosstalk are incompletely understood, but they often involve intracellular signalling routes also used by other cell surface receptors. Several studies show that the integrin cytoplasmic tails bind to a number of cytoskeletal and adaptor molecules in a regulated manner. Recent work has shown that phosphorylations of integrins and key intracellular molecules are of pivotal importance in integrin-cytoplasmic interactions, and these in turn affect integrin activity and crosstalk. The integrin ß-chains play a central role in regulating crosstalk. In addition to Integrin-integrin crosstalk, crosstalk may also occur between integrins and related receptors, including other adhesion receptors, growth factor and SARS-CoV-2 receptors.
Subject(s)
COVID-19 , Integrins , Cell Adhesion , Cytoplasm/metabolism , Humans , Integrins/metabolism , SARS-CoV-2ABSTRACT
Besides the isolation and identification of major histocompatibility complex I-restricted peptides from the surface of cancer cells, one of the challenges is eliciting an effective antitumor CD8+ T-cell-mediated response as part of therapeutic cancer vaccine. Therefore, the establishment of a solid pipeline for the downstream selection of clinically relevant peptides and the subsequent creation of therapeutic cancer vaccines are of utmost importance. Indeed, the use of peptides for eliciting specific antitumor adaptive immunity is hindered by two main limitations: the efficient selection of the most optimal candidate peptides and the use of a highly immunogenic platform to combine with the peptides to induce effective tumor-specific adaptive immune responses. Here, we describe for the first time a streamlined pipeline for the generation of personalized cancer vaccines starting from the isolation and selection of the most immunogenic peptide candidates expressed on the tumor cells and ending in the generation of efficient therapeutic oncolytic cancer vaccines. This immunopeptidomics-based pipeline was carefully validated in a murine colon tumor model CT26. Specifically, we used state-of-the-art immunoprecipitation and mass spectrometric methodologies to isolate >8000 peptide targets from the CT26 tumor cell line. The selection of the target candidates was then based on two separate approaches: RNAseq analysis and HEX software. The latter is a tool previously developed by Jacopo, 2020, able to identify tumor antigens similar to pathogen antigens in order to exploit molecular mimicry and tumor pathogen cross-reactive T cells in cancer vaccine development. The generated list of candidates (26 in total) was further tested in a functional characterization assay using interferon-γ enzyme-linked immunospot (ELISpot), reducing the number of candidates to six. These peptides were then tested in our previously described oncolytic cancer vaccine platform PeptiCRAd, a vaccine platform that combines an immunogenic oncolytic adenovirus (OAd) coated with tumor antigen peptides. In our work, PeptiCRAd was successfully used for the treatment of mice bearing CT26, controlling the primary malignant lesion and most importantly a secondary, nontreated, cancer lesion. These results confirmed the feasibility of applying the described pipeline for the selection of peptide candidates and generation of therapeutic oncolytic cancer vaccine, filling a gap in the field of cancer immunotherapy, and paving the way to translate our pipeline into human therapeutic approach.