Integrin Β1 Subunit Research Articles

The endothelial-to-mesenchymal transition changes the focal adhesion site proteins levels and the SLRP-lumican level in HMEC-1 cell line

Scleroderma, the chronic autoimmune disease is a consequence of inflammation in the connective tissue. Prolonged duration affects formation of compact connective tissue strands (scarring) within the target organ. Endothelial cells undergoing endothelial-to-mesenchymal transition (EndMT) are the source of fibroblast phenotype-resembling cells. EndMT contributes to reorganization of the focal adhesion proteins (FA), including integrins, and intensive extracellular matrix (ECM) remodelling. However, in endothelial cells, the relationship between EndMT and the interaction of integrin receptors with lumican - a component of ECM, is still unclear. Our findings indicate that at the early stages of EndMT caused by Snail-1 transcription factor overexpression, the level of the β1 integrin subunit and its phosphorylation are elevated. Simultaneously, the changes in the level of proteins that build FAs and promote activation of integrin receptors as well as a decrease in lumican quantity were observed. These modulations contributed to increased migration of human microvascular endothelial cells, HMEC-1. Our findings were achieved by WB, ELISA and wound healing assay. Taken altogether, transfection of HMEC-1 cells with Snail-1 plasmids inducing the early stages of EndMT results in the increase of total FAK and integrin β1 phosphorylation as well as cell migration: phenomena which are modulated by interaction with lumican.

294-OR: Hepatic Integrin ß1 Subunit Is Required for Liver Insulin Resistance but Not Fatty Liver in Diet-Induced Obese Mice

Obesity can lead to liver fibrosis and a selective insulin resistance whereby insulin-stimulated lipogenesis is maintained and liver triglycerides (TG) are elevated, while insulin suppression of liver glucose production (Ra) is impaired. The hypothesis that extracellular matrix (ECM) proteins of the fibrotic liver signal via integrin receptors contributing to hepatic insulin resistance was tested. Integrins consist of an α subunit that confers ligand specificity and a β subunit that interacts with adhesion proteins that transmit signals that lead to adaptations in cell function. The integrin β1 subunit is the primary isoform in the liver. Lean and diet-induced obese (DIO) C57Bl/6J mice with hepatocyte-specific deletion of the integrin β1 subunit (hitgβ1) knockout (KO) and wild type littermates (WT) were studied. Insulin clamps were performed in hitgβ1 KO and WT mice. Ra and glucose utilization (Rd) were measured before and during clamps. Metabolism in lean mice was unaffected by hitgβ1 KO. DIO WT mice were resistant to insulin suppression of Ra and had elevated liver TG. This insulin resistance to suppression of Ra was completely alleviated in DIO hitgβ1 KO mice. However, liver TG remained elevated. Alleviation of hepatic insulin resistance in DIO hitgβ1 KO mice was reflected by a greater activation of the insulin signaling pathway in hepatocytes. In contrast, impaired response of enzymes that participate in cytoskeletal organization and mitochondrial oxidation were observed in DIO hitgβ1 KO mice. It is postulated that impaired cytoskeletal organization decreases mitochondrial oxidation through effects on mitochondrial interactions. Impaired oxidation may contribute to the elevated TG that is present despite the improvement in insulin action. In conclusion, the hitgβ1 subunit contributes to selective hepatic insulin resistance in DIO mice. These data provide a mechanistic basis for an ECM - integrin receptor - insulin resistance axis in DIO mice. Disclosure E.Trefts: None. D.H.Wasserman: None. K.Ghoshal: None. A.V.Do: None. A.Guerin: None. C.Guan: None. D.Bracy: None. L.Lantier: None. R.Zent: None. A.Pozzi: None. Funding National Institutes of Health (DK050277, DK054902, DK059637)

The Role of Integrin Receptor's α and β Subunits of Mouse Mesenchymal Stem Cells on the Interaction of Marine-Derived Blacktip Reef Shark (Carcharhinus melanopterus) Skin Collagen.

Marine collagen (MC) has recently attracted more attention in tissue engineering as a biomaterial substitute due to its significant role in cellular signaling mechanisms, especially in mesenchymal stem cells (MSCs). However, the actual signaling mechanism of MC in MSC growth, which is highly influenced by their molecular pattern, is poorly understood. Hence, we investigated the integrin receptors (α1β1, α2β1, α10β1, and α11β1) binding mechanism and proliferation of MCs (blacktip reef shark collagen (BSC) and blue shark collagen (SC)) compared to bovine collagen (BC) on MSCs behavior through functionalized collagen molecule probing for the first time. The results showed that BSC and SC had higher proliferation rates and accelerated scratch wound healing by increasing migratory rates of MSCs. Cell adhesion and spreading results demonstrated that MC had a better capacity to anchor MSCs and maintain cell morphology than controls. Living cell observations showed that BSC was gradually assembled by cells into the ECM network within 24 h. Interestingly, qRT-PCR and ELISA revealed that the proliferative effect of MC was triggered by interacting with specific integrin receptors such as α2β1, α10β1, and α11β1 of MSCs. Accordingly, BSC accelerated MSCs' growth, adhesion, shape, and spreading by interacting with specific integrin subunits (α2 and β1) and thereby triggering further signaling cascade mechanisms.

Amino Acid Substitution in the Cysteine-Rich Region of the Integrin β4 Subunit Causes Late-Onset Mild Junctional Epidermolysis Bullosa without Extracutaneous Involvement

Integrin α6β4, encoded by ITGA6 and ITGB4, is a transmembrane component of hemidesmosomes and plays an important role in connecting keratinocytes with extracellular matrix proteins. ITGB4 or ITGA6 biallelic pathogenic variants cause junctional epidermolysis bullosa (JEB) with pyloric atresia, which is associated with high lethality. Patients who survive usually develop JEB of intermediate severity and urorenal manifestations. In this study, we report a very rare subtype of late-onset, nonsyndromic JEB associated with a recurrent amino acid substitution in the highly conserved cysteine-rich tandem repeats of the integrin β4 subunit. Literature review shows that among the patients diagnosed with ITGB4 mutations, only two had no extracutaneous manifestations, and only two patients with JEB with pyloric atresia carried missense mutations located in cysteine-rich tandem repeats. We analyzed the consequences of the novel ITGB4 variant c.1642G>A, p.Gly548Arg, on the clinical phenotype, the predicted protein structure, cellular phenotype, and gene expression pattern to show its pathogenicity. The results indicated that the p.Gly548Arg amino acid substitution affected the protein structure of integrin β4 subunits and disrupted the stability of hemidesmosomes and in turn impaired the adhesion of keratinocytes. RNA-sequencing results indicated similar changes in extracellular matrix structure organization and differentiation in keratinocytes completely devoid of integrin β4 and with the amino acid substitution p.Gly548Arg, which further supports the dysregulation of the function of the integrin β4 subunit caused by p.Gly548Arg. Our results provided evidence for a late-onset, mild JEB subtype without extracutaneous manifestations and extend the ITGB4-related genotype-phenotype correlations.

Transglutaminase 2 associated with PI3K and PTEN in a membrane-bound signalosome platform blunts cell death

Atypically expressed transglutaminase 2 (TG2) has been identified as a poor prognostic factor in a variety of cancers. In this study, we evaluated the contribution of TG2 to the prolonged cell survival of differentiated acute promyelocytic leukaemia (APL) cells in response to the standard treatment with combined retinoic acid (ATRA) and arsenic trioxide (ATO). We report that one advantage of ATRA + ATO treatment compared to ATRA alone diminishes the amount of activated and non-activated CD11b/CD18 and CD11c/CD18 cell surface integrin receptors. These changes suppress ATRA-induced TG2 docking on the cytosolic part of CD18 β2-integrin subunits and reduce cell survival. In addition, TG2 overexpresses and hyperactivates the phosphatidylinositol-3-kinase (PI3K), phospho-AKT S473, and phospho-mTOR S2481 signalling axis. mTORC2 acts as a functional switch between cell survival and death by promoting the full activation of AKT. We show that TG2 presumably triggers the formation of a signalosome platform, hyperactivates downstream mTORC2-AKT signalling, which in turn phosphorylates and inhibits the activity of FOXO3, a key pro-apoptotic transcription factor. In contrast, the absence of TG2 restores basic phospho-mTOR S2481, phospho-AKT S473, PI3K, and PTEN expression and activity, thereby sensitising APL cells to ATO-induced cell death. We conclude, that atypically expressed TG2 may serve as a hub, facilitating signal transduction via signalosome formation by the CD18 subunit with both PI3K hyperactivation and PTEN inactivation through the PI3K-PTEN cycle in ATRA-treated APL cells.

MicroRNA‑155 modulation of CD8+ T‑cell activity personalizes response to disease‑modifying therapies of patients with relapsing‑remitting multiple sclerosis.

Multiple sclerosis (MS) is a chronic autoimmune disease where activated immune cells can attack oligodendrocytes causing damage to the myelin sheath. Several molecular mechanisms are responsible for the auto-activation of immune cells such as RNA interference (RNAi) through microRNAs (miRNAs or miRs). In the present study, the role of miR-155 in regulating CD8+ T-cell activity in patients with relapsing-remitting multiple sclerosis (RRMS) was investigated, in terms of its migratory functions with regard to intracellular adhesion molecule-1 (ICAM1) and integrin subunit β2 (ITGB2), and its cytotoxic proteins, perforin and granzyme B. Gene expression of miR-155, ICAM1, ITGB2, perforin and granzyme B was evaluated following epigenetic modulations using reverse transcription-quantitative polymerase chain reaction in CD8+ T-cells isolated from blood samples of patients with RRMS and compared to healthy controls. The ectopic expression of miR-155 resulted in a persistent downregulation in all genes of interest related to CD8+ T-cell activation that were positively correlated with the Expanded Disability Status Scale of patients. The present study revealed the interplay between miR-155, ICAM1, and ITGB2, shedding light on their beneficial use as possible therapeutic regulators and diagnostic biomarkers of disease. Moreover, epigenetic modulations enhancing the efficacy of disease-modifying therapies (DMTs) may be employed as personalized therapy, to decrease the side effects of DMTs and improve the outcomes of patients.

The CIS association of CD47 with integrin Mac-1 regulates macrophage responses by stabilizing the extended integrin conformation

CD47 is a ubiquitously expressed cell surface integrin-associated protein. Recently, we have demonstrated that integrin Mac-1 (αMβ2, CD11b/CD18, CR3), the major adhesion receptor on the surface of myeloid cells, can be coprecipitated with CD47. However, the molecular basis for the CD47-Mac-1 interaction and its functional consequences remain unclear. Here, we demonstrated that CD47 regulates macrophage functions directly interacting with Mac-1. In particular, adhesion, spreading, migration, phagocytosis, and fusion of CD47-deficient macrophages were significantly decreased. We validated the functional link between CD47 and Mac-1 by co-immunoprecipitation analysis using various Mac-1-expressing cells. In HEK293 cells expressing individual αM and β2 integrin subunits, CD47 was found to bind both subunits. Interestingly, a higher amount of CD47 was recovered with the free β2 subunit than in the complex with the whole integrin. Furthermore, activating Mac-1-expressing HEK293 cells with PMA, Mn2+, and activating antibody MEM48 increased the amount of CD47 in complex with Mac-1, suggesting CD47 has a greater affinity for the extended integrin conformation. Notably, on the surface of cells lacking CD47, fewer Mac-1 molecules could convert into an extended conformation in response to activation. Additionally, we identified the binding site in CD47 for Mac-1 in its constituent IgV domain. The complementary binding sites for CD47 in Mac-1 were localized in integrin epidermal growth factor-like domains 3 and 4 of the β2 and calf-1 and calf-2 domains of the α subunits. These results indicate that Mac-1 forms a lateral complex with CD47, which regulates essential macrophage functions by stabilizing the extended integrin conformation.

Role of Integrins Involved in Mn2+-Dependent Adhesion to Fibronectin Peptide of Mastocytoma P-815 Cells and Peritoneal Mast Cells

Mn2+-dependent integrin-mediated adhesion to the extracellular matrix is extensively studied, however, its implication in mast cell biology remains unexplored. This study aims to investigate the role of Mn2+ in promoting adhesion in mouse mastocytoma P-815 cells (P-815) and peritoneal mast cells (PMC) to the Arg-Gly-Asp (RGD)-enriched fibronectin peptide (RGD matrix) within the culture medium. Our findings indicate that Mn2+ induces cell adhesion, with optimal results achieved when P-815 were exposed to 2 mM Mn2+ for 30 min at 37ºC, resulting in approximately 40% cell adhesion to the RGD matrix. The Mn2+-dependent P-815 adhesion was inhibited by anti-integrin α4, β1, and β3 subunit function-blocking antibodies, and by the integrin αIIbβ3 antagonist tirofiban, indicating the involvement of integrins α4β1 and αIIbβ3. Similarly, Mn2+-dependent PMC adhesion to the RGD matrix was inhibited by anti-integrin α4, α5, β1, β3, and β7 subunit function-blocking antibodies and tirofiban, demonstrating the involvement of integrins α4β1, α4β7, α5β1, and αIIbβ3. Integrins α4β1 and αIIbβ3 were consistently involved in Mn2+-induced adhesion reactions in both P-815 and PMC, while integrins α4β7 and α5β1 were specifically implicated in the response to PMC only. The addition of the actin inhibitor cytochalasin D, glycosylphosphatidylinositol-anchored protein (GPI-AP) cleaving enzyme phosphatidylinositol-specific phospholipase C, and the PKA inhibitor H-89 significantly reduced Mn2+-dependent P-815 adhesion to the RGD matrix. However, adding the myosin II inhibitor brebbistatin and the RhoA inhibitor Y27632 did not produce the same effect. Furthermore, cellular cholesterol removal with 6-O-α-maltosyl-β cyclodextrin significantly diminished Mn2+-dependent P-815 adhesion, concomitant with a decrease in the expression of integrin α4 and β1 subunits on the cell surface.

Temperature‐induced structural change of integrin αvβ3 receptor and its interaction with the RGD peptide ligand

AbstractThe structural change of receptor protein at high temperatures is one of the factors affecting the targeting ability of ligand‐installed nanocarriers for combined therapy of hyperthermia and drug delivery. In this study, the binding behaviors and mechanisms of integrin αvβ3 receptor and the arginine‐glycine‐aspartic acid (RGD) peptide ligand at high temperatures were investigated both theoretically and experimentally. The structural parameters of integrin αvβ3 at different temperatures and the interaction forces between the RGD peptide and integrin αvβ3 at different binding sites were calculated by molecular dynamics simulation. Fourier transform infrared spectroscopy, energy dispersive spectroscopy, ultraviolet–visible absorption spectroscopy, and atomic force microscopy were used to analyze the structural changes of integrin αvβ3 and to measure the ligand‐receptor interaction. Results show that the number of hydrogen bonds decreased and the secondary structure of integrin αvβ3 changed with the increase in temperature, indicating the denaturation of integrin αvβ3. The structural stability of the integrin αv subunit was better than that of the integrin β3 subunit at high temperatures. The interaction between the RGD peptide and integrin αvβ3 weakened as the temperature increased because the structure of the integrin αvβ3 binding site became more flexible and the corresponding calcium ions were shed from the binding site. The strongest interaction force was exhibited at the binding site of the integrin β3 subunit at 310 K while it was found at the binding site of the integrin αv subunit at higher temperatures, owing to the smaller structure deformation of the integrin αv subunit.

KCNF1 promotes lung cancer by modulating ITGB4 expression

Lung cancer continues to be the leading cause of cancer death in the United States. Despite recent advances, the five-year survival rate for lung cancer compared to other cancers still remains fairly low. The discovery of molecular targets for lung cancer is key to the development of new approaches and therapies. Electrically silent voltage-gated potassium channel (KvS) subfamilies, which are unable to form functional homotetramers, are implicated in cell-cycle progression, cell proliferation and tumorigenesis. Here, we analyzed the expression of KvS subfamilies in human lung tumors and identified that potassium voltage-gated channel subfamily F member 1 (KCNF1) was up-regulated in non-small cell lung cancer (NSCLC). Silencing of KCNF1 in NSCLC cell lines reduced cell proliferation and tumor progression in mouse xenografts, re-established the integrity of the basement membrane, and enhanced cisplatin sensitivity. KCNF1 was predominately localized in the nucleoplasm and likely mediated its functions in an ion-independent manner. We identified integrin β4 subunit (ITGB4) as a downstream target for KCNF1. Our findings suggest that KCNF1 promotes lung cancer by enhancing ITGB4 signaling and implicate KCNF1 as a novel therapeutic target for lung cancer.

CD4+ T Cells Are Required for Production of Disease-Causing Antibodies in an Alloantigen-Specific Murine Model of Fetal/Neonatal Alloimmune Thrombocytopenia

Fetal/Neonatal Alloimmune Thrombocytopenia (FNAIT) occurs when maternal antibodies specific for fetal platelet alloantigens cross the placenta and clear a baby's platelets, causing thrombocytopenia that is unpredictably severe and associated with irreversible brain damage and death. Of the 37 human platelet alloantigens (HPAs) implicated in FNAIT, HPA-1a, which resides on the integrin β3 subunit, is among the most clinically significant. Indirect evidence in humans implicates CD4+ T cells in production of FNAIT-causing HPA-1a-specific antibodies; however, whether CD4+ T cells are required for disease induction, and might therefore be manipulated to prevent disease development, is not known. We employed a novel CRISPR-Cas9-generated humanized transgenic mouse expressing the HPA-1a alloantigen to examine the requirement for CD4+ T cells in development of FNAIT. CD4+ T cells and B cells were purified separately from wild-type BALB/c donor mice that had been immunized, intraperitoneally with adjuvant, with platelets from HPA-1a-transgenic mice, in which HPA-1a-specific B and CD4+ T cells are generated. Donor B cells, either alone or with CD4+ T cells, were adoptively transferred into sub-lethally irradiated Rag1-deficient BALB/c recipient mice. Recipients were immunized with HPA-1a-transgenic platelets, and HPA-1a-specific antibodies were quantified in sequential blood samples collected from recipients. Adoptive transfer of B cells alone from HPA-1a-immunized mice resulted in transient production by Rag1-deficient recipients of only very low levels of HPA-1a-specific antibodies, whereas adoptive transfer of both B and CD4+ T cells resulted in sustained production of high levels of HPA-1a-specific antibodies. These results convincingly demonstrate that, in our mouse model, CD4+ T cells are required for B cell production of the HPA-1a-specific antibodies that cause FNAIT. The phenotypes and functions of CD4+ T cells that are generated in HPA-1a-incompatible pregnancies, and that initiate and amplify production of FNAIT-causing antibodies, are under investigation.

MiR-351 promotes atherosclerosis in diabetes by inhibiting the ITGB3/PIK3R1/Akt pathway and induces endothelial cell injury and lipid accumulation

BackgroundThe miR-351 gene is significantly upregulated in diabetic mice with atherosclerosis. However, the mechanism by which its presence is important for the overall disease has not been elucidated. Therefore, this study will investigate the mechanism of miR-351 in the process of diabetes mellitus with atherosclerosis through miR-351 gene knockout mice.MethodsIn this study, miR-351−/− C57BL/6 mice were first induced to form a type 2 diabetes mellitus model with atherosclerosis by STZ injection and a high-fat diet. Pathological tests (oil red O, HE, and Masson staining) combined with biochemical indices (TC, TG, LDL-C, HDL-C, TNF-α, hs-CRP, NO, SOD, MDA, CAT, and GSH-Px) were performed to evaluate the pathological degree of atherosclerosis in each group. Mouse aortic endothelial cells were treated with oxidized low-density lipoprotein (ox-LDL) and 30 mM glucose to establish a diabetic atherosclerosis cell model. Combined with cell oil red O staining and flow cytometry, the effects of silencing miR-351 on lipid accumulation and cell apoptosis in the diabetic atherosclerosis cell model were determined. Fluorescence in situ hybridization was used to detect the localization and transcription levels of miR-351 in cells. The target genes of miR-351 were predicted by bioinformatics and verified by dual-luciferase activity reporting. Western blotting was used to detect the expression levels of phosphorylated inosine 3-kinase regulatory subunit 1 (PIK3R1)/serine/threonine kinase 1 (Akt) and apoptosis-related proteins after transfection with integrin subunit β3 (ITGB3) small interfering ribonucleic acid (siRNA).ResultsThe expression of the miR-351 gene was significantly increased in the high-fat wild-type (HWT) group, and its expression was significantly decreased in the knockout mice. Silencing miR-351 effectively alleviated atherosclerosis in mice. The levels of miR-351 expression, apoptosis, lipid accumulation, and oxidative stress in ox-LDL + high glucose-induced endothelial cells were significantly increased. These phenomena were effectively inhibited in lentivirus-infected miR-351-silenced cell lines. Bioinformatics predicted that miR-351-5p could directly target the ITGB3 gene. Transfection of ITGB3 siRNA reversed the downregulation of apoptosis, decreased oil accumulation, and decreased oxidative stress levels induced by miR-351 silencing. In addition, it inhibited the activation of the PIK3R1/Akt pathway.ConclusionSilencing miR-351 upregulates ITGB3 and activates the PIK3R1/Akt pathway, thereby exerting anti-apoptosis and protective effects on endothelial cells.

Dipeptidyl Peptidase-4 Stabilizes Integrin α4β1 Complex to Promote Thyroid Cancer Cell Metastasis by Activating Transforming Growth Factor-Beta Signaling Pathway.

Background: Metastatic disease is a major cause of thyroid cancer-related death. However, the mechanisms responsible for thyroid cancer metastasis are unclear. Dipeptidyl peptidase-4 (DPP4) is a multifunctional cell surface glycoprotein that has been reported to be a negative prognostic factor in thyroid cancer. We explored the molecular mechanism of the role of DPP4 in thyroid cancer cell metastasis. Methods: The effects of DPP4 on thyroid cancer cell migration/invasion in vitro were assessed by transwell assays. A lung metastatic mouse model was also established to determine the effect of DPP4 on tumor metastasis in vivo. DPP4 inhibitor sitagliptin was used to test its effect on thyroid cancer cell metastasis. The mechanism of which DPP4 promotes thyroid cancer cell metastasis was explored by a series of molecular and biochemical experiments. Results: We observed that DPP4 was significantly upregulated in papillary thyroid cancers compared with control subjects, and its expression was positively associated with lymph node metastasis and BRAFV600E mutation. Functional studies showed that DPP4 knockdown significantly inhibited metastatic potential of thyroid cancer cells, and vice versa. However, DPP4 inhibitor sitagliptin did not affect the metastatic ability of thyroid cancer cells, indicating that the promoting effect of DPP4 on tumor metastasis was independent of its enzymatic activity. Mechanistically, DPP4 interacted with the α4 and β1 integrin subunits, and stabilized the formation of integrin α4β1 complex. DPP4-mediated integrin signal activation promoted the nuclear localization of c-Jun through the FAK/AKT pathway, thereby inducing the transcription of transforming growth factor-beta 1 (TGFB1 coding for protein TGF-β1). TGF-β1 then facilitated tumor metastasis by inducing the epithelial-mesenchymal transition. Conclusions: DPP4 promotes thyroid cancer cell metastasis through the integrins/FAK/AKT/c-Jun/TGF-β1 signaling axis. These findings may have implications for an alternative therapeutic strategy for thyroid cancer.

Single vesicle analysis of CD47 association with integrins and tetraspanins on extracellular vesicles released by T lymphoblast and prostate carcinoma cells.

CD47 regulates the trafficking of specific coding and noncoding RNAs into extracellular vesicles (EVs), and the RNA contents of CD47+ EVs differ from that of CD63+ EVs released by the same cells. Single particle interferometric reflectance imaging sensing combined with immunofluorescent imaging was used to analyse the colocalization of tetraspanins, integrins, and CD47 on EVs produced by wild type and CD47‐deficient Jurkat T lymphoblast and PC3 prostate carcinoma cell lines. On Jurkat cell‐derived EVs, β1 and α4 integrin subunits colocalized predominantly with CD47 and CD81 but not with CD63 and CD9, conserving the known lateral interactions between these proteins in the plasma membrane. Although PC3 cell‐derived EVs lacked detectable α4 integrin, specific association of CD81 with β1 and CD47 was preserved. Loss of CD47 expression in Jurkat cells significantly reduced β1 and α4 levels on EVs produced by these cells while elevating CD9+, CD63+, and CD81+ EVs. In contrast, loss of CD47 in PC3 cells decreased the abundance of CD63+ and CD81+ EVs. These data establish that CD47+ EVs are mostly distinct from EVs bearing the tetraspanins CD63 and CD9, but CD47 also indirectly regulates the abundance of EVs bearing these non‐interacting tetraspanins via mechanisms that remain to be determined.

Adaptation of cell spreading to varying fibronectin densities and topographies is facilitated by β1 integrins.

Cells mechanical behaviour in physiological environments is mediated by interactions with the extracellular matrix (ECM). In particular, cells can adapt their shape according to the availability of ECM proteins, e.g., fibronectin (FN). Several in vitro experiments usually simulate the ECM by functionalizing the surfaces on which cells grow with FN. However, the mechanisms underlying cell spreading on non-uniformly FN-coated two-dimensional substrates are not clarified yet. In this work, we studied cell spreading on variously functionalized substrates: FN was either uniformly distributed or selectively patterned on flat surfaces, to show that A549, BRL, B16 and NIH 3T3 cell lines are able to sense the overall FN binding sites independently of their spatial arrangement. Instead, only the total amount of available FN influences cells spreading area, which positively correlates to the FN density. Immunocytochemical analysis showed that β1 integrin subunits are mainly responsible for this behaviour, as further confirmed by spreading experiments with β1-deficient cells. In the latter case, indeed, cells areas do not show a dependency on the amount of available FN on the substrates. Therefore, we envision for β1 a predominant role in cells for sensing the number of ECM ligands with respect to other focal adhesion proteins.

Ligand-independent integrin β1 signaling supports lung adenocarcinoma development.

Integrins — the principal extracellular matrix (ECM) receptors of the cell — promote cell adhesion, migration, and proliferation, which are key events for cancer growth and metastasis. To date, most integrin-targeted cancer therapeutics have disrupted integrin-ECM interactions, which are viewed as critical for integrin functions. However, such agents have failed to improve cancer patient outcomes. We show that the highly expressed integrin β1 subunit is required for lung adenocarcinoma development in a carcinogen-induced mouse model. Likewise, human lung adenocarcinoma cell lines with integrin β1 deletion failed to form colonies in soft agar and tumors in mice. Mechanistically, we demonstrate that these effects do not require integrin β1–mediated adhesion to ECM but are dependent on integrin β1 cytoplasmic tail-mediated activation of focal adhesion kinase (FAK). These studies support a critical role for integrin β1 in lung tumorigenesis that is mediated through constitutive, ECM binding–independent signaling involving the cytoplasmic tail.

The Potential Role of a Surface-Modified Additive-Manufactured Healing Abutment on the Expression of Integrins α2, β1, αv, and β6 in the Peri-Implant Mucosa: A Preliminary Human Study.

The stability of peri-implant soft tissues is essential for long-term success. Integrins play a vital role in biological processes through developing and maintaining cell interactions; however, few studies have evaluated the effects of modifications to abutment surfaces on cell adhesion across integrin expression. Therefore, this pilot study assessed the influence of different surface topographies of titanium healing abutments prepared by additive manufacturing (AM) on the gene expression levels of the integrin subunits α2, β1, αv, and β6 in the human peri-implant mucosa. Thirteen healthy adults were included. Depending on the number of required implants, the subjects were distributed in different groups as a function of healing abutment topography: group 1 (fully rough surface); group 2 (upper machined + lower rough); group 3 (rough upper surface + lower machined); group 4 (fully machined). A total of 40 samples (n = 10/group) of the peri-implant mucosa around the abutments were collected 30 days after implant placement, and subsequently, the gene expression levels were evaluated using real-time PCR. The levels of gene expression of β1-subunit integrin were upregulated for individuals receiving fully rough surface abutments compared with the other surface topographies (p < 0.05). However, the healing abutment topography did not affect the gene expression levels of the α2, αv, and β6 integrin subunits in the human peri-implant mucosa (p > 0.05). This preliminary study suggested that controlled modifications of the surface topography of titanium healing abutments produced by AM may influence the quality of the peri-implant mucosa in the early stages of the soft tissue healing process.

Association between the 5-methyl tetrahydrofolate reductase (5-MTHFR) and integrin Β3 subunit (ITGB3) genes polymorphism and major depressive disorder

Background and objectivesMajor depression disorder (MDD) is a common condition and syndromic sickness with devastating psychological, social, and economic effects. In general, it is a widespread problem, and the prevalence of MDD varies by country. The genetic contribution to MDD is estimated to be around 35%. This study was done to explore the association between 5-methyl tetrahydrofolate reductase (5-MTHFR) and integrin β3 subunit (ITGB3) genes polymorphism for development of major depressive disorder. Materials and methodsThe current study comprised thirty MDD patients, ranging in age from 18 to 52 years. All of the individuals were diagnosed using the Diagnostic and Statistical Manual of Mental Axis I Disorder in the outpatient departments of Taif Psychiatry Health Hospital (DSM-IV). The three polymorphic markers, C667T and A1298C of the 5-MTHFR gene and T1565C of the ITGB3 gene, were genotyped using the PCR-RFLP method. ResultsThe C667T single nucleotide polymorphism was found to be in heterozygous state in ten patients, while the A1298C single nucleotide polymorphism was not found in any of them. Twenty-one patients had the T1565C single nucleotide polymorphism in the ITGB3 gene, five of whom were homozygous state and 16 of whom were heterozygous state. Seven patients were discovered to have compound mutations in both genes. Interpretation & conclusionThe current findings could point to a link between MDD and the T allele of the C667T polymorphism in the 5-MTHFR gene and the C allele of the T1565C polymorphism in the ITGB3 gene.

Single‐Cell RNA‐Seq Profiling Identifies L1 Cell Adhesion Molecule (L1cam) as a Mediator in Colonic Tuft Cells ‐ Innate Lymphoid Cell (ILCs) Signaling in the Hnrnp I Knockout Mice

ObjectivesPreviously we found that ablation of heterogeneous nuclear ribonucleoprotein I, (Hnrnp I) in intestinal epithelial cells (IECs) in colon significantly upregulates inflammatory cytokines and chemokines expression and increases number of tuft cells and innate lymphoid cells (ILCs, including ILC1, ILC2 and ILC3) in colon. The objective of this current study is to investigate the cell‐cell communications and to identify the mediators involved in the colon of Hnrnp I knockout (KO) mice. We hypothesize that signal transduction between colonic tuft cells and ILCs stimulates cytokine expression in the knockout mice.MethodsSingle‐cell RNAseq libraries (n = 3) were prepared from total RNA extracted from colon using Chromium Single‐Cell Gene Expression NextGem (v3.1, 10X Genomics). Analyses from raw counts were performed using the Seurat (v3.2.0) R package using default parameters. A computational cell calling algorithm was used to identify cell types using two up‐to‐date annotated mouse cell datasets. Analyses of cell‐cell communications and identification of significant pathways were performed using CellChat (v1.1.3). Immunofluorescence staining of colon tissue was performed with anti‐DCAMKL1 antibody (Abcam, ab31704). Colon cytokine levels were examined using cytokine 32‐plex array (Eve Technologies) using total protein extracted from colon tissues.ResultsImmunofluorescence staining of DCAMKL1, a tuft cell marker, confirms that the number of Tuft cells in colon (normalized to number of crypt) is significantly increased in Hnrnp I KO mice comparing to Hnrnp I wildtype (WT). Results from CellChat suggest communications between tuft cells and immune cells (ILCs, cytotoxic T cells, helper T cells, active lymphocytes and myeloid progenitors) are mainly through L1 Cell Adhesion Molecule (L1cam) – Integrins interaction, which is KO‐specific because the ablation of Hnrnp I results in the expression of L1cam in tuft cells in KO mice. Expression of integrin αv and β3 subunits (Itgav and Itgb3) are also higher in ILCs in the KO mice. NF‐κB subunits P65, and NF‐κB pathway target genes P21 and c‐Myc, also show higher expression levels in ILCs in KO mice comparing to WT. Cytokines assay results show that IL4, IL6 and IL13 all significantly increased, while IFNγ unchanged, and IL17 decreased in colon in KO mice comparing to WT.ConclusionsOur results demonstrate an Hnrnp I KO‐specific communication in colon between tuft cells and ILCs via L1cam‐integrin αv and β3 subunits interaction. The interaction further activates NF‐κB signaling in ILCs, regulating cell cycle of ILCs. The activation of ILCs further triggers immune responses in KO mice as indicated by increased proinflammatory cytokine expressions. Our results also suggest that among ILC1, ILC2 and ILC3, ILC2 is the major cell type involved in this communication because those increased cytokines – IL4, IL6 and IL13 observed in KO mice are all effectors secreted by mature ILC2.

CRISPR-Mediated Activation of αV Integrin Subtypes Promotes Neuronal Differentiation of Neuroblastoma Neuro2a Cells.

Neuronal differentiation is a complex process whose dysfunction can lead to brain disorders. The development of new tools to target specific steps in the neuronal differentiation process is of paramount importance for a better understanding of the molecular mechanisms involved, and ultimately for developing effective therapeutic strategies for neurodevelopmental disorders. Through their interactions with extracellular matrix proteins, the cell adhesion molecules of the integrin family play essential roles in the formation of functional neuronal circuits by regulating cell migration, neurite outgrowth, dendritic spine formation and synaptic plasticity. However, how different integrin receptors contribute to the successive phases of neuronal differentiation remains to be elucidated. Here, we implemented a CRISPR activation system to enhance the endogenous expression of specific integrin subunits in an in vitro model of neuronal differentiation, the murine neuroblastoma Neuro2a cell line. By combining CRISPR activation with morphological and RT-qPCR analyses, we show that integrins of the αV family are powerful inducers of neuronal differentiation. Further, we identify a subtype-specific role for αV integrins in controlling neurite outgrowth. While αVβ3 integrin initiates neuronal differentiation of Neuro2a cells under proliferative conditions, αVβ5 integrin appears responsible for promoting a complex arborization in cells already committed to differentiation. Interestingly, primary neurons exhibit a complementary expression pattern for β3 and β5 integrin subunits during development. Our findings reveal the existence of a developmental switch between αV integrin subtypes during differentiation and suggest that a timely controlled modulation of the expression of αV integrins by CRISPRa provides a means to promote neuronal differentiation.