Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Integrin alpha6”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2004

Analysis of gene expressions of T cells from children with acute exacerbations of asthma.

BACKGROUND: Little is known about airway inflammation in childhood asthma. The aims of this study were to analyze the expression of a wide range of mediators of airway inflammation in childhood asthma. METHODS: Eight asthmatic children with acute exacerbations were recruited for the study. Peripheral blood was drawn from the patients at the time of exacerbation and after improvement. Total RNA was extracted from the isolated T lymphocytes. The differential display (DD) RT-PCR method was used to detect expressed genes, and the quantification of candidate gene expression was performed using real-time quantitative RT-PCR. RESULTS: The only gene for which significant expression differences were detected in both DD analysis and quantitative RT-PCR was lipocortin II (annexin II) (exacerbation > remission, p < 0.05). In quantitative RT-PCR of interleukin-4 (IL-4), IL-5, interferon-gamma, IL-12 receptor-beta and integrin alpha6, a significant difference was found only in the expression of IL-4 mRNA (exacerbation > remission, p < 0.05). The IL-4 plasma concentration tended to be higher in exacerbation than in remission. CONCLUSIONS: Our findings suggest activation of T cells and IL-4 production may be involved not only in the basic pathogenesis of childhood asthma but also in its acute exacerbation, and that lipocortin II may be a marker or contribute to asthma exacerbation.

Acute Disease↗
PubMed2006

Parathyroid hormone-related protein regulates tumor-relevant genes in breast cancer cells.

The effect of endogenous parathyroid hormone-related protein (PTHrP) on gene expression in breast cancer cells was studied. We suppressed PTHrP expression in MDA-MB-231 cells by RNA interference and analyzed changes in gene expression by microarray analysis. More than 200 genes showed altered expression in response to a PTHrP-specific small interfering (si) RNA (siPTHrP). Cell cycle-regulating gene CDC2 and genes (CDC25B and Tome-1) that control CDC2 activity showed increased expression in the presence of siPTHrP. CDC2 activity was also found to be higher in siPTHrP-treated cells. Studies with PTHrP peptides 1-34 and 67-86, forskolin, and a PTH1 receptor (PTH1R)-specific siRNA showed that PTHrP regulates CDC2 and CDC25B, at least in part, via PTH1R in a cAMP-independent manner. Other siPTHrP-responsive genes included integrin alpha6 (ITGA6), KISS-1, and PAI-1. When combined, siRNAs against ITGA6, PAI-1, and KISS-1 could mimic the negative effect of siPTHrP on migration, whereas siKISS-1 and siPTHrP similarly reduced the proliferative activity of the cells. Comparative expression analyses with 50 primary breast carcinomas revealed that the RNA level of ITGA6 correlates with that of PTHrP, and higher CDC2 and CDC25B values are found at low PTHrP expression. Our data suggest that PTHrP has a profound effect on gene expression in breast cancer cells and, as a consequence, contributes to the regulation of important cellular activities, such as migration and proliferation.

Biopsy↗
PubMed2000

Residual type 1 immunity in patients genetically deficient for interleukin 12 receptor beta1 (IL-12Rbeta1): evidence for an IL-12Rbeta1-independent pathway of IL-12 responsiveness in human T cells.

Genetic lack of interleukin 12 receptor beta1 (IL-12Rbeta1) surface expression predisposes to severe infections by poorly pathogenic mycobacteria or Salmonella and causes strongly decreased, but not completely abrogated, interferon (IFN)-gamma production. To study IL-12Rbeta1-independent residual IFN-gamma production, we have generated mycobacterium-specific T cell clones (TCCs) from IL-12Rbeta1-deficient individuals. All TCCs displayed a T helper type 1 phenotype and the majority responded to IL-12 by increased IFN-gamma production and proliferative responses upon activation. This response to IL-12 could be further augmented by exogenous IL-18. IL-12Rbeta2 was found to be normally expressed in the absence of IL-12Rbeta1, and could be upregulated by IFN-alpha. Expression of IL-12Rbeta2 alone, however, was insufficient to induce signal transducer and activator of transcription (Stat)4 activation in response to IL-12, whereas IFN-alpha/IFN-alphaR ligation resulted in Stat4 activation in both control and IL-12Rbeta1-deficient cells. IL-12 failed to upregulate cell surface expression of IL-18R, integrin alpha6, and IL-12Rbeta2 on IL-12Rbeta1-deficient cells, whereas this was normal on control cells. IL-12-induced IFN-gamma production in IL-12Rbeta1-deficient T cells could be inhibited by the p38 mitogen-activated protein kinase (MAP) kinase inhibitor SB203580 and the MAP kinase kinase (MEK) 1/2 inhibitor U0126, suggesting involvement of MAP kinases in this alternative, Stat4-independent, IL-12 signaling pathway.Collectively, these results indicate that IL-12 acts as a partial agonist in the absence of IL-12Rbeta1. Moreover, the results reveal the presence of a novel IL-12Rbeta1/Stat4-independent pathway of IL-12 responsiveness in activated human T cells involving MAP kinases. This pathway is likely to play a role in the residual type 1 immunity in IL-12Rbeta1 deficiency.

Adolescent↗
PubMed1999

Evidence that distinct states of the integrin alpha6beta1 interact with laminin and an ADAM.

Integrins can exist in different functional states with low or high binding capacity for particular ligands. We previously provided evidence that the integrin alpha6beta1, on mouse eggs and on alpha6-transfected cells, interacted with the disintegrin domain of the sperm surface protein ADAM 2 (fertilin beta). In the present study we tested the hypothesis that different states of alpha6beta1 interact with fertilin and laminin, an extracellular matrix ligand for alpha6beta1. Using alpha6-transfected cells we found that treatments (e.g., with phorbol myristate acetate or MnCl2) that increased adhesion to laminin inhibited sperm binding. Conversely, treatments that inhibited laminin adhesion increased sperm binding. Next, we compared the ability of fluorescent beads coated with either fertilin beta or with the laminin E8 fragment to bind to eggs. In Ca2+-containing media, fertilin beta beads bound to eggs via an interaction mediated by the disintegrin loop of fertilin beta and by the alpha6 integrin subunit. In Ca2+-containing media, laminin E8 beads did not bind to eggs. Treatment of eggs with phorbol myristate acetate or with the actin disrupting agent, latrunculin A, inhibited fertilin bead binding, but did not induce laminin E8 bead binding. Treatment of eggs with Mn2+ dramatically increased laminin E8 bead binding, and inhibited fertilin bead binding. Our results provide the first evidence that different states of an integrin (alpha6beta1) can interact with an extracellular matrix ligand (laminin) or a membrane-anchored cell surface ligand (ADAM 2).

ADAM Proteins↗
PubMed2004

Laminin isoforms differentially regulate adhesion, spreading, proliferation, and ERK activation of beta1 integrin-null cells.

The presence of many laminin receptors of the beta1 integrin family on most cells makes it difficult to define the biological functions of other major laminin receptors such as integrin alpha6beta4 and dystroglycan. We therefore tested the binding of a beta1 integrin-null cell line GD25 to four different laminin variants. The cells were shown to produce dystroglycan, which based on affinity chromatography bound to laminin-1, -2/4, and -10/11, but not to laminin-5. The cells also expressed the integrin alpha6Abeta4A variant. GD25 beta1 integrin-null cells are known to bind poorly to laminin-1, but we demonstrate here that these cells bind avidly to laminin-2/4, -5, and -10/11. The initial binding at 20 min to each of these laminins could be inhibited by an integrin alpha6 antibody, but not by a dystroglycan antibody. Hence, integrin alpha6Abeta4A of GD25 cells was identified as a major receptor for initial GD25 cell adhesion to three out of four tested laminin isoforms. Remarkably, cell adhesion to laminin-5 failed to promote cell spreading, proliferation, and extracellular signal-regulated kinase (ERK) activation, whereas all these responses occurred in response to adhesion to laminin-2/4 or -10/11. The data establish GD25 cells as useful tools to define the role integrin alpha6Abeta4A and suggest that laminin isoforms have distinctly different capacities to promote cell adhesion and signaling via integrin alpha6Abeta4A.

Animals↗
PubMed1998

Expression of alpha6 and beta4 integrin subunits on human endometrium throughout the menstrual cycle and during early pregnancy.

OBJECTIVE: To evaluate the expression of alpha6 and beta4 integrin subunits on surface and glandular endometrium throughout the menstrual cycle and during early pregnancy. SETTING: Second Department of Obstetrics and Gynecology, University of Catania, Catania, Italy. PATIENT(S): Thirty-two women. Nineteen of the women regularly menstruated in different phases of the cycle, and 13 were in the sixth to ninth week of gestation and required voluntary abortion. INTERVENTION(S): Endometrial specimens collected during endometrial biopsy, hysterectomy, or voluntary abortion. MAIN OUTCOME MEASURE(S): Immunohistochemical staining for alpha6 and beta4 integrin subunits in endometrial tissues. RESULT(S): Both subunits (poorly expressed in preimplantation days) reached a significant peak on the endometrial surface during the implantation window, which tended to disappear in the postimplantation phase. On glandular endometrium they exhibited an opposite trend, showing high levels in the preimplantation and postimplantation days, whereas their expression decreased during the implantation window. The two subunits tended to disappear in early pregnancy. CONCLUSION(S): alpha6 and beta4 integrin subunits are uniformly distributed and highly expressed on the endometrial surface during the implantation window; they decreased dramatically in the postimplantation phase. These results could suggest involvement of integrin-extracellular matrix components in blastocyst-endometrium interaction during the early stages of implantation.

Adult↗
PubMed2003

Alpha6beta1 integrin induces proteasome-mediated cleavage of erbB2 in breast cancer cells.

ErbB2 and alpha6 integrin have been implicated in malignancy of breast cancer cells. Here we have determined the influence of alpha6beta1 integrin on erbB2 signaling in anchorage-independent growth, using MDA-MB435 breast cancer cells. Firstly, we transfected the cells with erbB2 cDNA, and isolated cells with high or low levels of alpha6beta1 integrin by cell sorting (alpha6H-ErbB and alpha6L-ErbB). We found that an erbB ligand, heregulin beta1, enhanced growth activity of alpha6L-ErbB cells, but not alpha6H-ErbB cells. Secondly, we established cells expressing a beta4 integrin deletion mutant (beta4-deltacyt), which selectively inhibited alpha6beta1 integrin expression and adhesion to laminin-1. Again, heregulin beta1 enhanced the growth of erbB2 cDNA-transfected beta4-deltacyt cells, but not mock cells. Western blot analysis revealed that heregulin beta1 stimulated phosphorylation of Akt and its downstream molecules, GSK3beta and p70S6kinase, and that the extent of phosphorylation was greater in ErbB2/beta4-deltacyt cells than ErbB2/mock cells. Furthermore, we found that the erbB2 cytoplasmic domain was truncated in ErbB2/mock cells, which was independent of ligand stimulation and adhesion, and was suppressed by proteasome inhibitors. These results suggest that alpha6beta1 integrin inhibits erbB2 signals by inducing proteasome-dependent proteolytic cleavage of the erbB2 cytoplasmic domain, and may thereby contribute to the regulation of tumor growth.

Breast Neoplasms↗
PubMed2000

The role of extracellular and cytoplasmic splice domains of alpha7-integrin in cell adhesion and migration on laminins.

The major laminin-binding integrin of skeletal, smooth, and heart muscle is alpha7beta1-integrin, which is structurally related to alpha6beta1. It occurs in three cytoplasmic splice variants (alpha7A, -B, and -C) and two extracellular forms (X1 and X2) which are developmentally regulated and differentially expressed in skeletal muscle. Previously, we have shown that ectopic expression of the alpha7beta-integrin splice variant in nonmotile HEK293 cells specifically induced cell locomotion on laminin-1 but not on fibronectin. To investigate the specificity and the mechanism of the alpha7-mediated cell motility, we expressed the three alpha7-chain cytoplasmic splice variants, as well as alpha6A- and alpha6B-integrin subunits in HEK293 cells. Here we show that all three alpha7 splice variants (containing the X2 domain), as well as alpha6A and alpha6B, promote cell attachment and stimulate cell motility on laminin-1 and its E8 fragment. Deletion of the cytoplasmic domain (excluding the GFFKR consensus sequence) from alpha7B resulted in a loss of the motility-enhancing effect. On laminin-2/4 (merosin), the predominant isoform in mature skeletal muscle, only alpha7-expressing cells showed enhanced motility, whereas cells transfected with alpha6A and alpha6B neither attached nor migrated on laminin-2. Adhesion of alpha7-expressing cells to both laminin-1 and laminin-2 was specifically inhibited by a new monoclonal antibody (6A11) specific for alpha7. Expression of the two extracellular splice variants alpha7X1 and alpha7X2 in HEK293 cells conferred different motilities on laminin isoforms: Whereas alpha7X2B promoted cell migration on both laminin-1 and laminin-2, alpha7X1B supported motility only on laminin-2 and not on laminin-1, although both X1 and X2 splice variants revealed similar adhesion rates to laminin-1 and -2. Fluorescence-activated cell sorter analysis revealed a dramatic reduction of surface expression of alpha6-integrin subunits after alpha7A or -B transfection; also, surface expression of alpha1-, alpha3-, and alpha5-integrins was significantly reduced. These results demonstrate selective responses of alpha6- and alpha7-integrins and of the alpha7 splice variants to laminin-1 and -2 and indicate differential roles in laminin-controlled cell adhesion and migration.

Antigens, CD↗
PubMed1996

Identification of receptors binding fibronectin and laminin on fetal rat lung cells.

Fibronectin and laminin have been implicated in regulating lung morphogenesis. In the present study, the cell surface receptors involved in fetal lung cell binding to laminin and fibronectin were identified. Messages for alpha5- and beta1-integrin subunits were detected in both fetal lung epithelial cells and fibroblasts. The presence of alpha5 beta1 -integrin on both cell types was demonstrated by immunocytochemistry and confirmed by cell adhesion experiments with fibronectin and RGD-containing peptides. Epithelial cells adhered more readily to laminin than fibroblasts. The alpha4 beta1-integrin, and RGD-independent fibronectin receptor, was weakly expressed on either cell type. Both cell types expressed alpha6-integrin subunit mRNA and stained immunopositive for the alpha6-subunit. Although either cell type expressed nonintegrin 67-kDa laminin-elastin receptor mRNA, no positive immunoreactivity for this laminin-elastin binding protein was detected. None of these findings explain the enhanced attachment of distal fetal lung epithelial cells to laminin compared with fibroblasts. Previously, we have reported that epithelial cells were enriched in alpha3-integrin subunit mRNA and protein expression. Herein, we found that epithelial cell attachment to laminin was nearly completely inhibited by alpha3- but only partially by alpha6 -monoclonal antibodies. A peptide near the globular region at the long arm of the laminin A-chain, which contained the IKVAV sequence, and the laminin A-chain amino acid sequence representing the alpha3 beta1 -integrin binding site, inhibited the adherence of epithelial cells to laminin. Fetal lung epithelial cells attached to substrata coated with the alpha3 beta1-integrin binding site peptide and the peptide containing the IKVAV sequence. These data suggest that both fetal lung cell types bind to fibronectin via the fibronectin receptor, alpha5 beta1, and fetal lung epithelial cells interact with laminin via alpha3 beta1 and proteins that recognize the IKVAV-containing sequence on the laminin A-chain.

Amino Acid Sequence↗
PubMed2005

Cytoskeleton reorganization mediates alpha6beta1 integrin-associated actions of laminin on proliferation and survival, but not on steroidogenesis of ovine granulosa cells.

BACKGROUND: Laminin (LN) is one of the most abundant extracellular matrix components of the basal lamina and granulosa cell layers of ovarian follicles. Culture of ovine granulosa cells (GC) on LN substratum induces cell spreading, enhances cell survival and proliferation, and promotes luteinization. Previous investigations have shown that these effects are mostly mediated by the alpha6beta1 integrin, but its signalization pathways have not been investigated. This study aimed to assess the importance of the cytoskeleton in the alpha6beta1 integrin-mediated actions of laminin on survival, proliferation and steroidogenesis of ovine GC. METHODS: The relationships between morphology and functions of ovine GC cultured on substrata containing LN or/and RGD peptides were investigated. The effects of (1) cytochalasin D, an actin cytoskeleton-disrupting drug, (2) a specific function-blocking antibody raised against alpha6 integrin subunit (anti-alpha6 IgG), and (3) an inhibitor of the ERK1/2 signalization pathway (PD98059) were assessed for GC shape, pyknosis and proliferation rates, oestradiol and progesterone secretions. RESULTS: Cytoskeleton disruption by cytochalasin D induced cell rounding, inhibited proliferation, promoted pyknosis, inhibited progesterone secretion and enhanced oestradiol secretion by GC cultured on LN. When GC were cultured on various substrata containing LN and/or RGD peptides in the presence or absence of anti-alpha6 IgG, both the existence of close correlations between the percentage of round cells, and the GC proliferation rate (r = -0.87) and pyknotic rate (r = 0.76) were established, but no relationship was found between cell shape and steroidogenesis. Inhibition of the ERK1/2 signalization pathway by PD98059 had no effect on GC shape, proliferation or pyknotic rates. However, it dramatically reduced progesterone secretion, expression of cytochrome P450 cholesterol side-chain cleavage and 3beta-hydroxysteroid deshydrogenase enzymes, and enhanced oestradiol secretion, thereby reproducing all the effects of the anti-alpha6 IgG on steroidogenesis of GC cultured on LN. CONCLUSION: LN may participate in the paracrine control of follicular development through different mechanisms. It could enhance proliferation and survival of GC through its alpha6beta1 integrin-mediated actions on cytoskeleton. In contrast, its stimulating action on GC luteinization could be partly mediated by the ERK1/2 pathway, irrespective of cell shape.

Animals↗
PubMed1997

Characterization of the binding of recombinant mouse sperm fertilin beta subunit to mouse eggs: evidence for adhesive activity via an egg beta1 integrin-mediated interaction.

The sperm protein fertilin (also known as PH-30) is a candidate for mediating the interactions between sperm and egg plasma membranes. Fertilin is a heterodimer. The beta subunit, which has a region with homology to the family of integrin ligands known as disintegrins, has been hypothesized to be involved in the binding of sperm to the egg surface. To investigate this hypothesis and determine what role fertilin beta plays in fertilization, we have expressed the putative extracellular domain of mouse fertilin beta in bacteria as a fusion protein with maltose-binding protein (hereafter referred to as recombinant fertilin beta-EC) and used two assays to characterize its binding to mouse eggs. Immunocytochemistry was used to examine the localization of recombinant fertilin beta-EC binding. A luminometric assay was also developed to quantify levels of binding of recombinant fertilin beta-EC to single eggs. We find that recombinant fertilin beta-EC binds to the region of the plasma membrane of the egg to which sperm bind, thus providing the first direct evidence that fertilin beta has adhesive properties. Peptides corresponding to the disintegrin domain of fertilin beta reduce its binding to eggs, suggesting that this domain is at least partially involved in the recognition of fertilin beta by binding sites on the egg. Treatment of zona pellucida-free eggs with chymotrypsin reduces the ability of the eggs to support the binding of recombinant fertilin beta-EC, implicating an egg surface protein as a binding site for recombinant fertilin beta-EC. Binding of recombinant fertilin beta-EC to eggs is also reduced in the absence of divalent cations and is supported by 2.0 mM Ca2+, Mg2+, or Mn2+. Furthermore, eggs incubated in recombinant fertilin beta-EC prior to in vitro fertilization show reduced levels of sperm binding. Finally, we have examined the possible role of integrins on eggs as receptors for fertilin beta, since an anti-alpha6 integrin subunit monoclonal antibody, GoH3, has been shown to inhibit sperm binding (E. A. C. Almeida et al. (1995) Cell 81, 1095-1104). We find that: (a) an increased amount of GoH3 epitope on the egg surface does not correlate with an increased ability of the eggs to bind sperm or recombinant fertilin beta-EC; (b) the GoH3 antibody has virtually no inhibitory effect on recombinant fertilin beta-EC binding; and (c) recombinant fertilin beta-EC binding is reduced in the presence of anti-beta1 integrin antibodies. These results suggest that a beta1-containing integrin participates in the binding of recombinant fertilin beta-EC to mouse eggs.

ADAM Proteins↗
PubMed2002

Complex interactions between the laminin alpha 4 subunit and integrins regulate endothelial cell behavior in vitro and angiogenesis in vivo.

The alpha4 laminin subunit is a component of the basement membrane of blood vessels where it codistributes with the integrins alphavbeta3, alpha3beta1, and alpha6beta1. An antibody against the G domain (residues 919-1207; G(919-1207)) of the alpha4 laminin subunit inhibits angiogenesis in a mouse-human chimeric model, indicating the functional importance of this domain. Additional support for the latter derives from the ability of recombinant G(919-1207) to support endothelial cell adhesion. In particular, endothelial cell adhesion to G(919-1207) is half-maximal at 1.4 nM, whereas residues 919-1018 and 1016-1207 of the G domain are poor cellular ligands. Function blocking antibodies against integrins alphavbeta3 and beta1 and a combination of antibodies against alpha3 and alpha6 integrin subunits inhibit endothelial cell attachment to G(919-1207). Moreover, both alphavbeta3 and alpha3beta1 integrin bind with high affinity to G(919-1207). Together, our studies demonstrate that the G domain of laminin alpha4 chain is a specific, high affinity ligand for the alphavbeta3 and alpha3beta1 integrin heterodimers and that these integrins, together with alpha6beta1, function cooperatively to mediate endothelial cell-alpha4 laminin interaction and hence blood vessel development. We propose a model based on these data that reconcile apparent discrepancies in the recent literature with regard to the role of the alphavbeta3 integrin in angiogenesis.

Antibodies, Monoclonal↗
PubMed1999

Human corneal epithelial cell adhesion to laminins.

PURPOSE: To analyze alpha-integrin mediated adhesion of human corneal epithelial cells to placental and EHS laminin isoforms. METHODS: Western blot analysis was used to partially characterize commercially available preparations of laminin isolated from the mouse EHS sarcoma and from human placenta. Using the human corneal epithelial cell line HCE-T, adhesion to laminin isoforms and fibronectin was determined using a colorimetric adhesion assay. alpha-integrin sub-unit modulation of corneal epithelial cell interaction with laminin isoforms was analyzed using immunofluorescence microscopy and adhesion assays incorporating functional blocking antibodies. RESULTS: In short-term adhesion assays, the preferred substrate for HCE-T attachment is placental laminin. Immunofluorescence microscopy reveals that alpha-integrin protein localization patterns are not significantly different in HCE-T interacting with EHS or placental laminin. However, in short-term assays alpha3 integrin plays a major role, and alpha2 integrin a minor role, in mediating HCE-T adhesion to laminin. alpha6 integrin does not appear to mediate adhesion to either substrate. CONCLUSIONS: These studies demonstrate that human corneal epithelial cells are capable of rapid adhesion to, and enhanced spreading on, laminin isoforms not characteristically resident in the adult corneal basement membrane. This characteristic of human corneal epithelium may explain, at least in part, why amniotic membrane transplantation is proving to be clinically useful for human ocular surface reconstruction.

Animals↗
PubMed1999

Myelin formation by Schwann cells in the absence of beta4 integrin.

The interaction of the Schwann cell with its basal lamina has been hypothesized to be an important prerequisite for the formation of a myelin sheath in the peripheral nervous system. One possible player in this interaction is beta4 integrin; it is up-regulated during myelin formation and, in association with alpha6 integrin, can interact with particular components of the Schwann cell basal lamina. In order to characterize the functional roles of beta4 integrin during myelination, we investigated myelination in the absence of beta4 integrin, i.e., in peripheral nerve tissue from beta4 integrin-deficient mice. Because the mutants die within several hours after birth, we cultured dorsal root ganglia from neonatal mutants under conditions that promote myelination, quantified the myelin segments by immunofluorescence, and investigated the ultrastructure of the cultured myelin sheaths. In another approach, we quantified the few myelin sheaths that are detectable in femoral nerves of newborn animals. Based on both approaches, we conclude that myelination by Schwann cells can occur in the absence of beta4 integrin demonstrating that this Schwann cell component is dispensable for myelin formation in peripheral nerves.

Animals↗
PubMed1999

Characterization of mouse integrin alpha3 subunit gene.

Integrin alpha3beta1 (VLA-3) is an adhesion receptor for extracellular matrix proteins including various isoforms of laminin. We have isolated mouse genomic clones encoding the integrin alpha3 subunit and deduced the exon/intron organization. The mouse integrin alpha3 subunit gene is encoded by 26 exons spanning 40 kb. The exon/intron structure of the integrin alpha3 subunit gene resembles that of the integrin alpha6 subunit gene, but differs somewhat from those of other members of the integrin family. We have demonstrated that the cytoplasmic domain splicing variants of the alpha3 subunits (alpha3A and alpha3B) are generated by alternative exon usage. We also cloned the 5'-flanking region and performed a preliminary analysis of its promoter activity in various tumor cell lines with different degrees of integrin alpha3 expression. Following transfection, activity in the luciferase assay was found to be roughly correlated with the expression level of integrin alpha3 as measured by flow cytometry. Furthermore, the luciferase assay was performed with normal and SV-40- or polyoma virus-transformed fibroblasts. In mouse, human, and hamster fibroblasts, higher levels of luciferase expression were observed in transformed cells than in normal cells. This result is consistent with our previous finding that integrin alpha3 expression at both the protein and mRNA levels is enhanced upon oncogenic transformation of fibroblasts by tumor viruses.

Alternative Splicing↗
PubMed1999

Role of very late adhesion integrins in mediating repair of human airway epithelial cell monolayers after mechanical injury.

Repair of the airway epithelium after injury requires that processes such as adhesion and cell migration occur in a defined order. Both of these processes depend on interactions between extracellular matrix (ECM) proteins and appropriate integrins. To study these interactions, we examined monolayer wound repair in a cultured human airway epithelial cell line, 16HBE14o-. Wounds created in confluent monolayers grown on either collagen-IV, laminin-1, or laminin-2 matrix closed quickly in response to 15 ng/ml epidermal growth factor (EGF). Concurrent treatment of cells grown on each matrix protein with EGF and a monoclonal antibody (mAb) to beta1-integrin inhibited wound closure. Treatment with a mAb to alpha2-, alpha3-, and alpha6-integrin blocked wound repair in monolayers grown on collagen-IV but did not do so in monolayers grown either on laminin-1 or laminin-2. Inhibition was not due to cell detachment or apoptosis. These data demonstrate that integrins expressed by airway epithelial cells mediate wound closure on different constitutive ECM proteins. These data suggest that beta1-integrin subunit function is required to permit migration and spreading of epithelial cells, and that alpha-integrin subunits alone do not mediate migration of epithelial cells grown on either laminin-1 or laminin-2. These differences may become important if the matrix protein composition of airway basement membrane changes in disease states such as asthma.

Antibodies, Monoclonal↗
PubMed2005

Low-molecular-weight fucoidan enhances the proangiogenic phenotype of endothelial progenitor cells.

Endothelial progenitor cell (EPC) transplantation is a potential means of inducing neovascularization in vivo. However, the number of circulating EPC is relatively small, it may thus be necessary to enhance their proangiogenic properties ex vivo prior to injection in vivo. Fucoidan has previously been shown to potentiate in vitro tube formation by mature endothelial cells in the presence of basic fibroblast growth factor (FGF-2). We therefore examined whether fucoidan, alone or combined with FGF-2, could increase EPC proangiogenic potency in vitro. EPC exposure to 10 microg/ml fucoidan induced a proangiogenic phenotype, including cell proliferation (p < 0.01) and migration (p < 0.01); moreover, differentiation into vascular cords occurred in the presence of FGF-2 (p < 0.01). This latter effect correlated with upregulation of the cell-surface #alpha6 integrin subunit of the laminin receptor (p < 0.05). Compared to untreated HUVEC, untreated EPC #alpha6 expression and adhesion to laminin were enhanced two-fold. Fucoidan treatment further enhanced HUVEC but not EPC adhesion to laminin. These results show that fucoidan enhances the proangiogenic properties of EPC and suggest that ex vivo fucoidan preconditioning of EPC might lead to increased neovascularization when injected into ischemic tissues.

Cell Proliferation↗
PubMed1999

CD9 is expressed on the cell surface of human granulosa cells and associated with integrin alpha6beta1.

The CD9 molecule is a 24-27 kDa cell surface glycoprotein which is reported to be involved in cell adhesion and migration. Recently, CD9 was shown to be associated with beta1-related integrins. We have previously found that integrin alpha6beta1 is expressed on human granulosa cells (GC) and regulates luteinization of GC in concert with its ligand laminin. In this study, we examined the expression of CD9 in human ovary and the relationship between CD9 and integrin alpha6beta1 in GC. By immunohistochemistry, CD9 was detected on GC in a small antral follicle of <1 mm in diameter. In growing follicles, CD9 was moderately expressed on both GC and theca interna cells (TI). The expression intensity of CD9 on GC increased in preovulatory follicles. In the early luteal phase, CD9 was expressed in both luteinizing GC and TI. The expression intensity on large luteal cells decreased in the mid-luteal phase. In the corpus luteum (CL) of pregnancy, CD9 continued to be expressed on large luteal cells, but not on small luteal cells. By flow cytometry, CD9 was detected on the cell surface in approximately 90% of the isolated GC from patients undergoing in vitro fertilization. The molecular weight of CD9 in the isolated GC was shown to be 26.5 kDa by Western blotting. CD9 mRNA was also detected in the isolated GC and CL by reverse transcription-polymerase chain reaction (RT-PCR). The proteins purified from GC by immunoaffinity chromatography using anti-integrin alpha6 monoclonal antibodies were shown by Western blotting to include CD9 as well as integrin beta1. These findings suggest that CD9 is a differentiation-related molecule of GC and TI and that it is associated with integrin alpha6beta1 on the cell surface of GC, suggesting that CD9 is implicated in the function of human GC in cooperation with integrin alpha6beta1.

Adult↗