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PubMed2001

Tumour necrosis factor-alpha provokes upregulation of alpha2beta1 and alpha5beta1 integrins, and cell migration in OST osteosarcoma cells.

OST cells enhance the induction of matrix metalloproteinase (MMP)-9 by tumour necrosis factor (TNF)-alpha and the corresponding metastasis to lungs in vivo (Kawashima et al., 1994). We focused on the adhesive and migratory properties of OST cells, and investigated the expression of integrins in OST cells stimulated by TNFalpha in vitro. OST cells potentiated not only adhesion to the extracellular matrix (ECM) but also the migration on ECM. On competitive reverse transcription-polymerase chain reaction (RT-PCR) analyses, the amounts of alpha2 (4.9-fold), alpha5 (1.2-fold) and alpha(v) (4.9-fold) were upregulated by TNFalpha at the transcriptional level. Alpha-5 showed a slight increase by flow cytometry; however, alpha2 and alphav integrins remained unchanged at the protein level. Immunofluorescence study disclosed integrins of alpha2beta1 and alpha5beta1 were much clustered at cell processes by TNFalpha stimulation, probably related to increased cell adhesion and migration. Therefore, the upregulation of alpha2beta1 and alpha5beta1 integrins seems to contribute to tumour invasion and metastatic potential.

Cell Adhesion↗
PubMed1999

Integrin engagement regulates proliferation and collagenase expression of rheumatoid synovial fibroblasts.

Growth of and metalloproteinase production by fibroblast-like synoviocytes (FLSs) in patients with rheumatoid arthritis (RA) contribute to cartilage and bone destruction associated with development of the expanding inflammatory tissue referred to as pannus. Increased levels of extracellular matrix (ECM) proteins in the pannus suggest that intracellular signals generated through integrin receptors might control these processes. We developed a cell culture system permitting accurate assessment of the effect of cell adhesion to various ECM proteins on FLS phenotype. We show that FLS proliferation to platelet-derived growth factor requires a second signal provided by adhesion to an ECM protein. Fibronectin, vitronectin, collagen, or laminin could provide the second signal and was similarly required for the proliferation of FLSs from RA or osteoarthritis patients. Adhesion to fibronectin, collagen, or Arg-Gly-Asp peptide down-regulated collagenase expression. Primarily alphav integrin receptors mediated this down-regulation upon adhesion to fibronectin. Loss of cell adhesion and TNF-alpha stimulation synergistically increased collagenase expression. Increased collagenase expression upon nonadherence was mimicked by treatment with cytochalasin B, suggesting that the loss of cytoskeletal structure associated with a change in cell shape mediates increased collagenase in nonadherent cells. Thus, although increased fibronectin in the lining layer in RA might be expected to inhibit collagenase expression, the change in cell shape associated with this multilayer structure might actually lead to increased collagenase expression.

Arthritis, Rheumatoid↗
PubMed1998

Identification of the ligand binding site for the integrin alpha9 beta1 in the third fibronectin type III repeat of tenascin-C.

The integrin alpha9 subunit forms a single heterodimer, alpha9 beta1 that mediates cell adhesion to a site within the third fibronectin type III repeat of tenascin-C (TNfn3). In contrast to at least 3 other integrins that bind to this region of tenascin-C, alpha9 beta1 does not recognize the common integrin recognition motif, Arg-Gly-Asp (RGD). In this report, we have used substitution mutagenesis to identify a unique ligand recognition sequence in TNfn3. We introduced mutations substituting alanine for each of the acidic residues in or adjacent to each of the exposed loops predicted from the solved crystal structure. Most of these mutations had little or no effect on adhesion of alpha9-transfected SW480 colon carcinoma cells, but mutations of either of two acidic residues in the B-C loop region markedly reduced attachment of these cells. In contrast, cells expressing the integrin alphav beta3, previously reported to bind to the RGD sequence in the adjacent F-G loop, attached to all mutant fragments except one in which the RGD site was mutated to RAA. The peptide, AEIDGIEL, based on the sequence of human tenascin-C in this region blocked the binding of alpha9-transfected cells, but not beta3-transfected cells to wild type TNfn3. This sequence contains a tripeptide, IDG, homologous to the sequences LDV, IDA, and LDA in fibronectin and IDS in VCAM-1 recognized by the closely related integrin alpha4 beta1. These findings support the idea that this tripeptide motif serves as a ligand binding site for the alpha4/alpha9 subfamily of integrins.

Amino Acid Sequence↗
PubMed2001

Improved gene transfer efficiency to primary and established human pancreatic carcinoma target cells via epidermal growth factor receptor and integrin-targeted adenoviral vectors.

In this study we analyzed two ways of retargeting of Ad-vectors to human pancreatic carcinoma with the aim of enhancing the gene transfer efficiency. First, we analyzed the expression of the epidermal growth factor receptor (EGFR) on primary, as well as established pancreatic carcinoma cells by flow cytometry which revealed high expression levels of EGFR on the surface of these cells. We showed that EGFR-retargeted entry pathway using a bispecific fusion protein formed by a recombinant soluble form of truncated Coxsackie and Adenovirus Receptor (sCAR) genetically fused with human EGF (sCAR-EGF) redirects them to the EGFR leading to an enhanced gene transfer efficiency to pancreatic carcinoma cells. Since flow cytometry revealed absence of CAR expression, but the presence of at least one of both alphav integrins on the pancreatic carcinoma cells, a second way of targeting was investigated using a genetically modified Ad vector which has an RGD (Arg-Gly-Asp)-containing peptide inserted into the HI-loop of the fiber knob. This RGD targeted Ad (AdlucRGD) revealed efficient CAR-independent infection by allowing binding to cellular integrins resulting in a dramatic enhancement of gene transfer. These findings have direct relevance for Ad-vector based gene therapy strategies for pancreatic carcinoma.

Adenoviridae↗
PubMed2006

Typical and atypical trafficking pathways of Ad5 penton base recombinant protein: implications for gene transfer.

The adenovirus (Ad) penton base protein facilitates viral infection by binding cell surface integrins, triggering receptor-mediated endocytosis and mediating endosomal penetration. Given these multiple functions, recombinant penton base proteins have been utilized as non-viral vehicles for gene transfer by our lab and others. Although we have previously demonstrated that penton base-derived vectors undergo integrin-specific binding and cell entry, less than desirable levels of gene expression have led us to re-evaluate the recombinant penton base as an agent for gene delivery. To do so, we have examined here the intracellular trafficking of an Ad serotype 5 (Ad5) recombinant penton base protein (PB). Here, we not only observed that PB utilizes a similar, typical trafficking pathway of whole Ad, but also found that PB entered HeLa cells through pathways not yet identified as contributing to cell entry by the whole virus. We show by high-resolution confocal microscopy and biochemical methods that binding to alphav-integrins is a requirement for cell entry, but that early internalization stages did not substantially pass through clathrin-positive and early endosomal compartments. Moreover, a subpopulation of internalized protein localized with caveolin-positive compartments and Golgi markers, suggesting that a certain percentage of proteins pass through non-clathrin-mediated pathways. Similar to the virus, trafficking toward the nucleus was affected by disruption of microtubules and dynein. The majority of penton base molecules avoided the lysosome while facilitating early vesicle release of low molecular weight dextran molecules. In further support of a vesicle escape capacity, a subpopulation of internalized penton base appeared to enter the nucleus, as observed by high-resolution confocal microscopy and cell fractionation. As a confirmation of these findings, we demonstrate that a recombinant penton base facilitated cytosolic entry of an siRNA molecule as observed by RNA interference of a marker gene. Based on our findings here, we suggest that whereas soluble penton base proteins may enter cells through clathrin- and non-clathrin-mediated pathways, vesicle escape and nuclear delivery appear to be supported by a clathrin-mediated pathway. As our previous efforts have focused on utilizing recombinant penton base proteins as delivery agents for therapeutics, these findings allow us to evaluate the use of the penton base as a cell entry and intracellular trafficking agent, and may be of interest concerning the development of vectors for efficient delivery of therapeutics to cells.

Capsid Proteins↗
PubMed2006

The ERK mitogen-activated protein kinase pathway contributes to Ebola virus glycoprotein-induced cytotoxicity.

Ebola virus is a highly lethal pathogen that causes hemorrhagic fever in humans and nonhuman primates. Among the seven known viral gene products, the envelope glycoprotein (GP) alone induces cell rounding and detachment that ultimately leads to cell death. Cellular cytoxicity is not seen with comparable levels of expression of a mutant form of GP lacking a mucin-like domain (GPDeltamuc). GP-induced cell death is nonapoptotic and is preceded by downmodulation of cell surface molecules involved in signaling pathways, including certain integrins and epidermal growth factor receptor. To investigate the mechanism of GP-induced cellular toxicity, we analyzed the activation of several signal transduction pathways involved in cell growth and survival. The active form of extracellular signal-regulated kinases types 1 and 2 (ERK1/2), phospho-ERK1/2, was reduced in cells expressing GP compared to those expressing GPDeltamuc as determined by flow cytometry, in contrast to the case for several other signaling proteins. Subsequent analysis of the activation states and kinase activities of related kinases revealed a more pronounced effect on the ERK2 kinase isoform. Disruption of ERK2 activity by a dominant negative ERK or by small interfering RNA-mediated ERK2 knockdown potentiated the decrease in alphaV integrin expression associated with toxicity. Conversely, activation of the pathway through the expression of a constitutively active form of ERK2 significantly protected against this effect. These results indicate that the ERK signaling cascade mediates GP-mediated cytotoxicity and plays a role in pathogenicity induced by this gene product.

Cell Proliferation↗
PubMed1998

c-Src is required for stimulation of gelsolin-associated phosphatidylinositol 3-kinase.

We have shown that osteopontin binding to integrin alphav beta3 in osteoclasts stimulates gelsolin-associated phosphatidylinositol (PtdIns) 3-hydroxyl kinase (PI 3-kinase), leading to increased levels of gelsolin-bound PtdIns 3,4-P2, PtdIns 4,5-P2, and PtdIns 3, 4,5-P3, uncapping of barbed end actin, and actin filament formation. Inhibition of PI 3-kinase activity by wortmannin blocks osteopontin stimulation of actin filament formation, suggesting that activation of gelsolin-associated PI 3-kinase is an important pathway in cytoskeletal regulation. To study the mechanism of gelsolin-associated PI 3-kinase activation, we analyzed anti-gelsolin immunoprecipitates for the association of protein kinases. We demonstrated that c-Src co-immunoprecipitates with gelsolin, and that osteopontin stimulates its activity. Elimination of osteopontin-stimulated Src activity associated with gelsolin through antisense oligodeoxynucleotides blocked the stimulation of PI 3-kinase activity associated with gelsolin and the gelsolin-dependent cytoskeletal reorganization induced by osteopontin, including increased F-actin levels. In addition, treatment of osteoclasts with antisense oligonucleotides to Src reduced bone resorption. Our results demonstrate that osteopontin stimulates gelsolin-associated Src, leading to increased gelsolin-associated PI 3-kinase activity and PtdIns 3,4,5-P3 levels, which facilitate actin filament formation, osteoclast motility, and bone resorption.

Actin Cytoskeleton↗
PubMed1994

Alpha v integrin subunit is predominantly located in nervous tissue and skeletal muscle during mouse development.

Alpha v integrin subunit can dimerize with different beta subunits to form receptors for several matrix proteins. The function of these receptors in vivo is still largely unknown. We examined the localization of alpha v integrin during mouse development and showed that its distribution is dynamically regulated in the glia of the central nervous system and in skeletal muscle. Immunoreactivity in the neural tube was firstly localized at embryonic day 10.5 (E10.5) around cell bodies lining the lumen and along tiny fibres extending towards the outer margin. At E12.5 alpha v distribution follows the highly defined pattern of the radial glia: fascicles of immunoreactive fibres form parallel palisades, in particular along the hindbrain and the spinal cord. At E15.5, although with weaker intensity, alpha v was still detectable in radial glia fibres, and it codistributed with glial fibrillary acidic protein positive fascicles. After birth (P8) alpha v immunoreactivity in the brain and spinal cord decreased dramatically, but remained high in the radial glia of the cerebellum. In adult mice alpha v reactivity in the central nervous system disappeared. During myogenesis alpha v appears at E10.5 in myotomal cells and from E12.5 alpha v was evident in myoblasts and in myotubes. In the developing skeletal muscle of E15.5 embryos, immunoreactivity became more concentrated in the apical portion of the myotubes. In adult striated muscle the amount of alpha v subunit dramatically declined and immunostaining was no longer detectable. During development, alpha v was weakly evident in other sites including heart and endothelia of blood vessels, mesonephric tubula, smooth muscle of the digestive tract, and bronchia. Comparative analysis of the localization of alpha v, alpha 3, and alpha 5 integrin subunits indicated that alpha v has a unique and highly regulated distribution pattern. The distribution in the nervous system is consistent with a role of alpha v in neuron-glia interaction during the organization of the neuronal layers in the brain cortex and in the cerebellum. Moreover, alpha v is likely to be involved in the myotendinous junction during embryonic life, suggesting a dual functional role of this integrin in muscle and nervous tissue.

Amino Acid Sequence↗
PubMed1996

L1 adhesion molecule on human lymphocytes and monocytes: expression and involvement in binding to alpha v beta 3 integrin.

The L1 adhesion molecule is a member of the immunoglobulin (Ig) superfamily initially identified in the nervous system which contains six Ig-like domains. Besides the known L1-L1 homotypic interaction, L1 was recently shown to bind to very late antigen (VLA)-5 in the mouse and alpha v beta 3 in the human. The sixth Ig domain is critical for this function. We now demonstrate that human CD4+ peripheral blood T lymphocytes, monocytes and B lymphocytes, but not CD8+ T lymphocytes, express L1. When compared to the expression of CD31, another ligand for alpha v beta 3 on T lymphocytes, only a small proportion of cells were CD31+L1+ double positive. L1 was also detected on the surface of human monocytic and lymphoid tumor lines and was shown to have a molecular mass of approximately 220 kDa, similar to the molecule present on neuroblastoma cells. The function of the sixth Ig domain of human L1 as an integrin ligand was also investigated. Using an RGD-containing peptide derived from the sixth Ig domain as well as a fusion protein of the sixth Ig domain of L1 and the Fc portion of human IgG1 (6.L1-Fc), we demonstrated the binding of human MED-B1 (alpha v beta 3hi, alpha 5 beta 1lo) tumor cells and this binding was blocked by alpha v-specific mAb. In contrast, human Nalm-6 cells (alpha v beta 3lo, alpha 5 beta 1hi) did not bind to the 6.L1-Fc fusion protein. MED-B1 cells could also be stained with the 6.L1-Fc fusion protein. Our results suggest that human L1 binds predominantly to alpha v beta 3 and that its presence on leukocytes could be important for adhesion and migration.

Amino Acid Sequence↗
PubMed2003

Interspecies contamination of the KM3 cell line: implications for CD63 function in melanoma metastasis.

CD63 is a member of the tetraspanin superfamily of membrane glycoproteins that has been hypothesised to provide a structural network in the organisation of large multimolecular microdomains at cell membranes. Detailed analyses of the role of CD63 in these complexes through mutagenic studies have been limited, however, by the ubiquitous cellular expression of CD63 in vivo and in vitro. In an attempt to define CD63-null cell lines, we have analysed the expression of CD63 and other tetraspanins on a panel of human cancer cell lines. Similar expression patterns were seen between cell lines from melanomas, breast cancers and prostate cancers. The melanoma cell line KM3, however, described previously as a CD63-null human cell line, was found to express none of the 7 human tetraspanins tested. KM3 was identified definitively as a rat cell line by analysis of karyotype and antigen expression. Notably, KM3 was found to express the rat homologue of CD63. Conclusions concerning the function of human CD63 drawn from studies using KM3 cells therefore require re-evaluation as does the frequently cited hypothesis that CD63 expression is linked to melanoma progression. As KM3 is the only cell line thus far identified as CD63 negative, these results highlight the necessity for the production of a CD63 null system.

Animals↗
PubMed2002

Identification of cultured progenitor cells from human marrow stroma.

The marrow stromal cells (MSC) are essential for regulation of bone remodeling and hematopoiesis. It is of prime importance to isolate MSC and to expand the proliferating cells ex vivo. In this study, we analyzed cultured MSC for various cellular parameters, including cell morphology, cell cycle, and expression of cell surface antigens by flow cytometry. MSC were divided based on cell size to small (S-cells) and large (L-cells) and were visualized by light and electron microscope. The S-cells were proliferating cells correlated with G0/G1 phase of cell cycle, and expressed cFOS. The expression of surface markers CD-34, -44, -51, -61, -62E, -62P, -62L was quantified using flow cytometry. CD-44 was ubiquitously expressed by S and L cells, CD-51 and -61 were expressed by 30%-38% of S-cells. CD-34 and -62 expressed 20% positive of the analyzed cells that were of the proliferating progenitors (S-cells). This study enables the identification of subpopulations from MSC with special attention paid to the proliferating cells from ex vivo cultures of marrow stroma.

Antigens, CD34↗
PubMed1995

Increased expression of the beta 1, alpha 5, and alpha v integrin adhesion receptor subunits occurs coincident with remodeling of stress-deprived rabbit anterior cruciate and medial collateral ligaments.

The biomechanical, biochemical, and morphological properties of the anterior cruciate and medial collateral ligaments are dramatically altered in response to deprivation of normal physical forces and joint motion. Integrin adhesion receptors are known to play important roles in the tissue remodeling that occurs in the course of normal wound repair. We propose that integrins play a similar role in the remodeling of the extracellular matrix in stress-deprived periarticular ligaments. This study tests the hypothesis that altered expression of integrins on ligament fibroblasts accompanies this remodeling. The left knees of 15 New Zealand White rabbits were surgically immobilized in acute flexion and the right knees served as controls (no operation). The anterior cruciate and medial collateral ligaments were harvested at 1, 3, 5, 9, or 12 weeks after immobilization. Sections from the ligaments were immunostained with monoclonal antibodies specific for the integrin subunits beta 1, alpha 5, alpha 6, and alpha v, as well as with a negative control antibody. Fibroblasts within both the stress-deprived anterior cruciate and medial collateral ligaments demonstrated markedly increased staining for the beta 1, alpha 5, and alpha v subunits, as compared with the controls. The increased staining was greatest at 9 weeks in the anterior cruciate ligament and at 12 weeks in the medial collateral ligament. Western blot study of ligament proteins extracted with sodium dodecyl sulfate demonstrated an increased amount of beta 1 subunit protein in both ligaments from knees that were stress deprived for 9 and 12 weeks, as compared with the control ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Differential expression of integrin subunits in canine knee ligament fibroblasts.

A method for measuring the expression of integrin subunits on the cell surface of knee ligament fibroblasts was developed with use of flow cytometry and immunofluorescence. The ligament cells exhibited uniform size and density, as shown by forward and side-scatter properties, and showed minimal nonspecific binding of isotype control antibodies compared with unstained cells. All cells expressed the alpha5 integrin subunit; lateral collateral ligament cells stained with antibody to alpha5 showed a mean fluorescence intensity 2-fold higher than that of medial collateral ligament cells, 1.5-fold higher than that of posterior cruciate ligament cells, and 3-fold higher than that of anterior cruciate ligament cells, indicating a greater expression of the alpha5 subunit by lateral collateral ligament cells than by medial collateral, posterior cruciate, and anterior cruciate ligament cells. All cells expressed the beta1 integrin subunit; the expression by posterior cruciate ligament cells was 3-fold higher than that by medial collateral ligament or lateral collateral ligament cells and 5-fold higher than that by anterior cruciate ligament cells. All cells expressed the beta3 integrin subunit; the expression by posterior cruciate ligament cells was 1.5, 3, and 4.5-fold greater than that by lateral collateral, anterior cruciate, and medial collateral ligament cells, respectively. Our data suggest there is a differential expression of integrin subunits in knee ligament fibroblasts, and this in part may explain differences in their attachment and adherence to extracellular matrix molecules.

Animals↗
PubMed1995

Upregulation of integrin expression in benign vulvar warts.

Benign anogenital warts demonstrate features both of hyperproliferation and of aberrant differentiation associated with human papillomavirus (HPV) infection. The expression of integrins has been examined in normal vulvar epithelium and benign vulvar warts to determine whether HPV infection is associated with changes in integrin expression, either during terminal differentiation or among the proliferating cell population. The expression of integrins in normal vulvar epithelium was similar to that seen in the epidermis, with little expression of alpha 1 and expression of alpha 2, alpha 3, and beta 1 at the periphery of basal cells. In vulvar wart epithelium, alpha 1 was not significantly expressed, but upregulation of alpha 2, alpha 3, and beta 1 was seen at the periphery of cells throughout the basal and spinous layers. In addition, alpha 2 staining was greater at foci along the basal layer of normal vulva, whilst such heterogeneity was not detected in wart sections. Expression of beta 4 and alpha V was confined to the basal and lateral aspects of normal basal cells, but expressed at the periphery of basal cells and to a lesser extent in epibasal and spinous layers of warts. The observed differences in integrin expression are consistent with those reported in other hyperproliferative epithelia.

Condylomata Acuminata↗
PubMed1998

Propensity for macrophage apoptosis is related to the pattern of expression and function of integrin extracellular matrix receptors.

Ligation of integrins to an extracellular matrix activates signal transduction systems which produce multiple responses in different cell types. Adhesion often provides a survival signal to cells; disruption of adhesion frequently results in apoptosis. Our laboratory has utilized apoptosis-sensitive and -resistant cell lines to investigate the role of integrin expression and function in regulation of apoptosis in macrophages. Chronic exposure of murine macrophage-like RAW264.7 cells to apoptosis-inducing agents (bacterial lipopolysaccharide and interferon-gamma) resulted in the generation of a derivative cell line (RES) resistant to apoptosis. Observation of RAW and RES cultures indicated a difference in adhesion between the two cell types. The two cell lines also exhibit significant differences in expression of integrins previously characterized to be important in apoptosis.

Animals↗
PubMed2002

Annexin-V binds to the intracellular part of the beta(5) integrin receptor subunit.

Bovine lactadherin binds to the alpha(v)beta(3) and alpha(v)beta(5) integrins in an RGD-dependent manner and also to anionic phospholipids. During the affinity purification of lactadherin binding receptors, a 35-kDa protein persistently coeluted with the alpha(v)beta(5) integrin receptor. Subsequently, peptide mapping, amino acid sequencing, and mass spectrometry analysis identified this protein as bovine annexin-V. Annexin-V accompanied the integrin receptor eluted with either RGD peptide or with EDTA suggesting that annexin-V bound specifically to the alpha(v)beta(5) integrin. To further investigate this putative interaction of annexin-V with the alpha(v)beta(5) integrin receptor, human annexin-V and intracellular domains of the human alpha(v)beta(5) integrin subunits were used in ligand blotting assays. Radiolabeled annexin-V showed weak binding to the intracellular part of beta(5) integrin subunit. However, by adding the aminophospholipid, phosphatidyl serine, the interaction with the beta(5) cytoplasmic peptide was enhanced many fold. Furthermore, the interaction was shown to be independent of phosphorylation, as annexin-V bound to unphosphorylated beta(5) peptide at a similar level to the phosphorylated peptide. Since binding of annexin-V to the alpha(v) integrin subunit tail was not detected, annexin-V was shown to associate specifically with the beta(5) cytoplasmic tail. Together these findings suggest a novel link between annexins and the integrin receptor family.

Amino Acid Sequence↗
PubMed2001

Environmental modulation of alpha(v), alpha(2) and beta(1) integrin subunit expression in human oesophageal squamous cell carcinomas.

Integrins are cell adhesion molecules pivotal in regulating normal cell behaviour. Ectopic expression of integrins, characteristic of transformed cells, is instrumental in differentiation, proliferation, apoptosis, angiogenesis, matrix degradation and migration. Oesophageal squamous cell carcinoma (SCC) has a propensity to metastasize and hence an extremely poor prognosis. It is shown here that oesophageal SCCs express alpha(v)strongly and that normal oesophageal tissue does not express alpha(v). This makes alpha(v)a significant indicator of the transformed phenotype. alpha(2)and beta(1)integrin subunits are down-regulated in oesophageal SCCs compared to normal oesophagus. Dominance of the alpha(2)beta(1)heterodimer is symptomatic of potential loss of other beta(1)binding integrins in oesophageal SCCs. These results suggest a decrease in rigid cell adhesion possibly increasing migratory potential, whilst simultaneously permitting the adhesion and migration of SCC cells on a large repertoire of ligands due to de novo alpha(v)expression.

Animals↗
PubMed1995

Integrin alpha v subunit is expressed on mesodermal cell surfaces during amphibian gastrulation.

Mesodermal cell migration during amphibian gastrulation is dependent on cellular interactions with fibronectin. One mechanism whereby cells bind fibronectin is through alpha v-containing integrin heterodimers. In order to investigate the role of alpha v in amphibian gastrulation, we have cloned the Pleurodeles homologue of the integrin alpha v subunit using homology PCR. The deduced amino acid sequence is 73 and 74% identical with the human and chick homologues, respectively. The 4.8-kb mRNA is expressed during oogenesis and persists throughout development. Messenger RNA and protein are widely expressed in oocytes and embryos while cell surface expression is spatially regulated. The protein first appears on the plasma membrane of fully grown oocytes. Fertilization results in the progressive loss of alpha v membrane localization. Before and during gastrulation, the integrin alpha v subunit is expressed on the surface of mesodermal cells. These data show that alpha v expression is developmentally regulated by a post-translational mechanism which correlates with the onset of mesodermal cell migration at gastrulation.

Amino Acid Sequence↗