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Biomedical subjects

D Sheppard

Publications and source records attributed to D Sheppard.

At least 19 recordsLinked to original sources
PubMed1995

The human integrin alpha 8 beta 1 functions as a receptor for tenascin, fibronectin, and vitronectin.

The integrin family of adhesion receptors consists of at least 21 heterodimeric transmembrane proteins that differ in their tissue distribution and ligand specificity. The recently identified alpha 8 integrin subunit associates with beta 1 and is predominantly expressed in smooth muscle and other contractile cells in adult tissues, and in mesenchymal and neural cells during development. We now show that alpha 8 beta 1 specifically localizes to focal contacts in cells plated on the extracellular matrix proteins fibronectin or vitronectin. In addition we show that human embryonic kidney cells (293), transfected with alpha 8 cDNA, express alpha 8 beta 1 on their surface and use this receptor for adhesion to fibronectin and vitronectin. Furthermore, alpha 8 beta 1 binds to both fibronectin- and vitronectin-Sepharose and can be specifically eluted from either matrix protein by the arginine-glycine-aspartic acid (RGD)-containing peptide, GRGDSP. Because fibronectin and vitronectin adhesion appeared to be mediated by RGD, we examined additional RGD-containing proteins, including tenascin, fibrinogen, thrombospondin, osteopontin, and denatured collagen type I. We found that only tenascin was able to mediate adhesion of alpha 8-transfected 293 cells. By using recombinant fragments of tenascin in adhesion assays, we were able to localize the alpha 8 beta 1 binding domain of tenascin to the RGD-containing third fibronectin type III repeat. These data strongly suggest that tenascin, fibronectin, and vitronectin are ligands for alpha 8 beta 1 and that this integrin binds to the RGD site in each of these ligands through mechanisms that are distinct and separate from alpha 5- and alpha v-containing integrins.

Adult↗
PubMed1995

Differential modulation of integrin receptors and extracellular matrix laminin by transforming growth factor-beta 1 in rat alveolar epithelial cells.

The transforming growth factors-beta (TGFs-beta) family of genes plays important roles in cell growth and differentiation in many cell types. TGF beta modulates the synthesis and accumulation of extracellular matrix (ECM) components and the expression of cell surface receptors for ECM components. TGF beta is increased in alveolar lining fluid during inflammatory reactions of the lung and has been identified in alveolar epithelial cells of developing lungs and hyperplastic type II cells during repair. However, little is known about how TGF beta may regulate expression of extracellular matrix proteins and ECM receptors in lung alveolar epithelial cells. Laminin, a major glycoprotein component of epithelial basement membrane, is synthesized and secreted by alveolar epithelial cells. To study the effects of TGF beta on modulation of laminin and its integrin receptors alpha 6 beta 1 and alpha 3 beta 1 in lung alveolar epithelial cells, a rat alveolar type II cell-derived cell line, LM5, was incubated with TGF beta 1 (0-100 pg/ml) in serum-free medium for 0-16 h. We examined the expression of integrin subunits and laminin beta 2 chain (s-laminin) mRNAs and protein expression. By Northern blot analysis, TGF beta 1 induced dose-dependent increases in alpha 6 and beta 1 mRNA levels. TGF beta 1 also increased the expression of laminin beta 2 chain mRNA at 12-16 h poststimulation. In contrast, TGF beta 1 decreased alpha 3 mRNA expression. Immunoprecipitation studies of TGF beta 1-treated cells showed increased surface expression of both alpha 6 and beta 1 protein while surface expression of the alpha 3 integrin subunit was decreased. The same treatment resulted in increased laminin protein expression. These data suggest that TGF beta 1 may regulate alveolar epithelial cell differentiation in part through its modulation of integrins and laminin chains.

Animals↗
PubMed1995

Staphylococcus aureus stimulates neutrophil recruitment by stimulating interleukin-8 production in dog trachea.

The present study examined whether neutrophil recruitment in dog airways by Staphylococcus aureus is mediated by interleukin-8 (IL-8). S. aureus culture supernatant was superfused into an isolated tracheal segment in six dogs, and neutrophil recruitment and IL-8 concentrations were measured in the superfusate. Dog IL-8 was cloned, expressed in Escherichia coli, purified by chromatography, and shown to be biologically active. With the use of an enzyme-linked immunoabsorbent assay (ELISA) for the measurement of dog IL-8, we showed that S. aureus supernatant induced neutrophil recruitment and increased IL-8 concentration in the superfusate in a time-dependent manner. The chemotactic activity present in the superfusate 6 h after superfusion with S. aureus was inhibited by an anti-IL-8 antibody. S. aureus supernatant also stimulated IL-8 production and gene expression by cultured canine tracheal epithelial cells. These results provide evidence that IL-8 plays a major role in S. aureus-induced neutrophil recruitment in the airways by stimulating IL-8 production in airway cells.

Amino Acid Sequence↗
PubMed1995

Distribution of integrins alpha v beta 6 and alpha 9 beta 1 and their known ligands, fibronectin and tenascin, in human airways.

We have previously identified two integrins, alpha 9 beta 1 and alpha v beta 6, from guinea pig airway epithelium. The extracellular matrix protein tenascin is a ligand for both of these receptors, and fibronectin is also a ligand for alpha v beta 6. In the present study, we used immunohistochemistry to examine the expression and spatial distribution of the alpha 9 subunit, alpha v beta 6, tenascin, and fibronectin in the proximal airways of 10 normal nonsmoking subjects and eight patients undergoing lung resection for cancer. We also performed the same analyses on sections of peripheral lung obtained from an additional seven subjects undergoing lung resection. alpha 9 was highly expressed throughout the airway epithelium (but not on alveolar epithelium) irrespective of clinical status. In contrast, alpha v beta 6 was expressed on proximal airway epithelial cells in four of eight smokers undergoing lung resection, but in none of the normal subjects and none of the distal airways examined. On bronchial epithelial cells cultured from resected airways, alpha v beta 6 was highly expressed on cells grown from patients who did not appear to express the receptor in vivo, as well as from subjects who did, suggesting that some component of the in vitro environment can induce expression. Although both tenascin and fibronectin were present below the proximal airway epithelium of both normal nonsmoking subjects and smokers, the spatial patterns of integrin and ligand expression were not congruent, because the integrins were present diffusely on the cell surface and on some cells that were not in contact with the basement membrane, whereas the ligands were present principally in the subepithelial layer. These findings are compatible with the existence of as-yet unidentified ligands for each of these integrins--for example, ligands involved in homotypic cell-cell interactions within the epithelium.

Biopsy↗
PubMed1995

A point mutation in the integrin beta 6 subunit abolishes both alpha v beta 6 binding to fibronectin and receptor localization to focal contacts.

The integrin alpha v beta 6 was initially identified from primary cultures of airway epithelial cells. This integrin is expressed in bronchiolar and alveolar epithelium during development and in settings of injury and/or inflammation and mediates attachment of epithelial cells to fibronectin and tenascin. Like other integrins, this receptor localizes to structures called focal contacts in cells plated on appropriate ligands. In the present study, we produced a mutant beta 6 cDNA (beta 6m) containing a single substitution of Asp140 with Ala and transfected mutant (or wild-type) beta 6 cDNA into the human colon carcinoma cell line SW480. In parallel, we used cDNAs truncated just proximal to the transmembrane domain to generate secreted forms of mutant alpha v beta 6 in Chinese hamster ovary (CHO) cells. The mutant beta 6, like the wild type, formed heterodimers with human alpha v that were expressed on the cell surface of SW480 cells and secreted by CHO cells. Secreted alpha v beta 6 containing this point mutation did not bind to fibronectin-Sepharose. Furthermore, in contrast to wild-type beta 6, the mutant form did not allow SW480 cells to bind to fibronectin in the presence of beta 1-blocking antibody and did not localize to focal contacts. Our results confirm that the Asp140 of beta 6, like the corresponding residues in beta 1 (Asp130) and beta 3 (Asp119), is critical for interactions of alpha v beta 6 with ligand, and also suggest that ligand binding to alpha v beta 6 is necessary for localization of this receptor to focal contacts.

Alanine↗
PubMed1995

Vitronectin enhances internalization of crocidolite asbestos by rabbit pleural mesothelial cells via the integrin alpha v beta 5.

The mechanism by which pleural mesothelial cells, the likely progenitor cells of asbestos-induced mesothelioma, recognize and internalize crocidolite asbestos is unknown. Because incubation of asbestos fibers with serum increases their association with cells, we asked whether a protein coat on asbestos increased internalization of fibers via specific cellular receptors. Coating crocidolite with citronectin, but not with fibronectin or other proteins, increased fiber internalization by rabbit pleural mesothelial cells, as measured by a new technique using fluorescence confocal microscopy. Receptors for vitronectin, alpha v beta 3 and alpha v beta 5, were identified on mesothelial cells. Inhibiting vitronectin receptors by plating cells on a vitronectin substrate or incubating cells with excess soluble vitronectin reduced internalization of vitronectin-coated crocidolite. Inhibition of alpha v beta 5, but not alpha v beta 3, with blocking antibodies similarly reduced internalization. In addition, alpha v beta 5, but not alpha v beta 3, showed immunocytochemical colocalization with fibers. Of biologic relevance, coating crocidolite with serum also increased internalization via alpha v beta 5, an effect dependent on the vitronectin in serum. We conclude that pleural mesothelial cells recognize and internalize vitronectin- and serum-coated asbestos via the integrin alpha v beta 5. Since integrins initiate some of the same signaling pathways as does asbestos, our findings may provide insights into the mechanisms of asbestos-induced biologic effects.

Amino Acid Sequence↗
PubMed1995

Localized distribution of alpha 9 integrin in the cornea and changes in expression during corneal epithelial cell differentiation.

A recently characterized integrin alpha-chain, alpha 9, forms heterodimers with the integrin beta 1-chain and is present in the skin with a distribution similar to that of alpha 2 and alpha 3, other beta 1 integrins. To determine whether alpha 9 is expressed in the stratified squamous epithelium of the cornea, we used immunohistochemical techniques to compare the distribution of alpha 9 in the adult mouse cornea with that of alpha 3. Abundant alpha 9 was expressed in the lateral and basal membranes of the basal cells of the conjunctiva and corneal limbus, but very little alpha 9 was present in the basal cells of the central corneal epithelium. In contrast, alpha 3 was present in the membranes of basal cells of the conjunctiva, limbus, and central cornea. To determine when during postnatal maturation of the corneal epithelium alpha 9 becomes restricted to the limbus, we looked at the distribution of alpha 9 and alpha 3 in the developing mouse eye from birth to eyelid opening. At birth, the basal cells of the cornea and developing limbal region did not express alpha 9, but there was abundant alpha 9 expressed in suprabasal cells between the fused lids and in the basal cells of the skin and conjunctiva. In contrast, alpha 3, integrin was expressed uniformly in the basal cells across the surface of the conjunctiva, limbus, and cornea and was present only in the basal cells of the epithelium between the fused eyelids. In the central cornea, alpha 9 expression increased in basal cells up until Day 10 after birth. After Day 10, alpha 9 expression in the central cornea began to decrease; after the lids were open, alpha 9 expression in the central cornea became restricted to the limbus. In the basal and suprabasal cells between the fused eyelids expression of alpha 9 became increasingly restricted over time to the basal cells. Recent data suggest that alpha 9 beta 1 can interact with tenascin. Our dual labeling confocal microscopy studies indicate that localization of alpha 9 and tenascin are not coordinated in the developing mouse cornea. Many recent studies have shown an important role for beta 1 integrins in mediating epithelial cell differentiation in vitro; in vivo, changes in integrin expression have been found in wound healing, psoriasis, and in basal and squamous cell carcinomas.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1995

Sequence and tissue distribution of the human integrin alpha 8 subunit: a beta 1-associated alpha subunit expressed in smooth muscle cells.

Integrins are a major family of cell adhesion molecules involved in cell-cell and cell-extracellular matrix interactions. Each integrin is a heterodimeric glycoprotein composed of an alpha and a beta subunit. We now report the cDNA sequence and distribution of a new human integrin alpha subunit. This sequence is 78% identical to the previously reported chicken alpha 8 integrin sequence. Thus, we have designated this subunit as human alpha 8. By northern blot analysis, an alpha 8 probe detects two mRNA species of approximately 6.5 and 4.0 kb in neuroglioma H4 cells. An anti-alpha 8 polyclonal antibody precipitates a protein complex containing the beta 1 subunit associated with the putative alpha 8 subunit, which has an apparent molecular mass of 180 kDa (non-reduced) or 155 kDa and 25 kDa (reduced). Immunohistochemistry with anti-alpha 8 polyclonal antibody in adult rat tissues shows prominent staining in vascular and visceral smooth muscle. In addition, the antibody strongly stained kidney mesangial cells and a cell type in the alveolar wall of the lungs, most likely corresponding to alveolar myofibroblasts. These results suggest that in adult mammalian tissues, alpha 8 is predominantly expressed in smooth muscle and smooth muscle-like contractile cells.

Amino Acid Sequence↗
PubMed1995

Localization of the alpha v subfamily of integrins and their putative ligands in synovial lining cell layer.

OBJECTIVE: The lining cell layer of the synovium proliferates strongly in rheumatoid arthritis. It has been suggested that it has a central role in the destruction of cartilage. We have analyzed the structure of the extracellular matrix and the adhesion molecules of normal, osteoarthritic and rheumatoid lining cell layer. METHODS: We localized the alpha v integrin subunit and its 4 putative partner beta subunits in synovial samples by using indirect immunofluorescence. The specimens were also analyzed by confocal microscopy. Indirect immunofluorescence was also used to analyze the ligands of alpha v integrins, namely fibronectin and vitronectin. RESULTS: The alpha v integrin was abundant in the lining cell layer of normal and osteoarthritic synovia, whereas it was not expressed in the proliferating rheumatoid lining cell layers. A similar expression pattern was found for beta 5 subunit, suggesting that it is the major partner for alpha v. However, also some alpha v beta 1 and alpha v beta 3 heterodimers may be present. The confocal microscopy revealed the presence of both alpha v beta 5 positive and negative lining cells. The putative ligands for alpha v integrins, namely fibronectin and vitronectin were found in the lining cell layer of all the synovial specimens. CONCLUSION: In spite of the proliferation of the lining cell layer in rheumatoid inflammation, the extracellular matrix stays very similar to that in normal and osteoarthritic synovium, whereas the pattern of the adhesion receptors is completely altered.

Aged↗
PubMed1994

Integrin alpha v beta 8. Interaction with vitronectin and functional divergence of the beta 8 cytoplasmic domain.

The integrin beta 8 subunit was identified by cloning and sequencing of the cDNA and has been shown to associate with the alpha v subunit (Moyle, M., Napier, M. A., and McLean, J. W. (1991) J. Biol. Chem. 266, 19650-19658). We now present initial data on its functional properties. We produced a recombinant secreted form of alpha v beta 8 and used it to raise monoclonal antibodies that recognize the alpha v beta 8 complex or the beta 8 subunit alone on the surface of melanoma cells and on beta 8-transfected human embryonic kidney (293) cells. Affinity chromatography experiments showed that secreted alpha v beta 8 bound to vitronectin but not to fibronectin, collagen, or fibrinogen. Supporting evidence that intact full-length alpha v beta 8 could also bind to vitronectin-Sepharose was provided by performing affinity chromatography with the melanoma cell line MeWo, which normally expresses the intact beta 8 subunit. By studying the adhesive properties of melanoma cells and beta 8-transfected 293 cells, we found that alpha v beta 8 by itself does not promote cell adhesion on a vitronectin-coated substrate. To test the respective functional activities of the beta 8 extracellular and cytoplasmic domains, we analyzed chimeric beta 8/beta 3 subunit constructs. The beta 3 subunit was chosen because full-length beta 3, when transfected into 293 cells, strongly supports cell adhesion. We found that a chimeric integrin containing the beta 3 extracellular domain combined with the beta 8 transmembrane and cytoplasmic domains did not promote 293 cell adhesion. Conversely, a chimeric integrin construct combining the beta 8 extracellular domain with the beta 3 transmembrane and cytoplasmic domains did promote adhesion of transfected 293 cells. This suggests that the beta 8 cytoplasmic domain does not interact with the cytoskeleton and with cytoplasmic signaling pathways in an adhesion-promoting fashion. We conclude that the beta 8 cytoplasmic domain, which is structurally unrelated to the conserved cytoplasmic domains of other beta subunits, is functionally distinct.

Amino Acid Sequence↗
PubMed1994

The integrin alpha 9 beta 1 mediates cell attachment to a non-RGD site in the third fibronectin type III repeat of tenascin.

We have previously reported the sequence of the integrin alpha 9 subunit, a partner of the beta 1 subunit that is expressed in basal keratinocytes, hepatocytes, airway epithelial cells, and smooth and skeletal muscle. In the present study, we have stably expressed alpha 9 beta 1 on the surface of the human embryonic kidney cell line 293 and the human colon carcinoma cell line SW480 and used these transfected cells lines to identify ligand(s) for this integrin. Transfected cells did not appear to utilize alpha 9 beta 1 for attachment to the extracellular matrix proteins fibronectin, laminin, vitronectin, fibrinogen, thrombospondin, or type I or IV collagen. However, in contrast to mock transfectants, both 293 cells and SW480 cells expressing alpha 9 beta 1 adhered to intact chicken tenascin. By utilizing a variety of recombinant fragments of tenascin, we were able to localize the binding site for alpha 9 beta 1 to the third type III repeat. This repeat contains the arginine-glycine-aspartic acid (RGD) tripeptide that has been shown to serve as a binding site in tenascin for alpha v-integrins. However, the RGD site does not appear to be the binding site for alpha 9 beta 1, as the attachment of alpha 9 transfectants to this fragment was not inhibited by RGD peptide, nor by changing the RGD site to RAD or RAA.

Amino Acid Sequence↗
PubMed1994

Disruption of integrin function and induction of tyrosine phosphorylation by the autonomously expressed beta 1 integrin cytoplasmic domain.

The cytoplasmic domains of integrin beta subunits are essential for the function of integrins in cell adhesion and signaling. A chimera combining the transmembrane and cytoplasmic domains of the beta 1 integrin subunit with an irrelevant extracellular domain derived from L3T4 (murine CD4) was tested for its ability to interfere with integrin function. Expression of this construct in cultured human embryonic kidney cells under the control of the inducible metallothionein promoter resulted in cell rounding and detachment, and blocked cell adhesion mediated by the beta 1 and alpha v beta 5 integrins. Expression of the beta 1 chimera at basal levels interfered with the tyrosine phosphorylation of a 125-kDa protein induced by antibody-induced clustering of integrins. Induced expression of the chimera resulted in sustained tyrosine phosphorylation of this protein, which could be enhanced by clustering of the chimera but was insensitive to clustering of integrins. These results demonstrate that the autonomously expressed beta 1 integrin cytoplasmic domain can act as a trans-dominant inhibitor of integrin function, presumably via competitive interactions with cytoplasmic components that are required for integrin-mediated cell adhesion and tyrosine phosphorylation.

Amino Acid Sequence↗
PubMed1994

Role of the integrin alpha v beta 6 in cell attachment to fibronectin. Heterologous expression of intact and secreted forms of the receptor.

The integrin alpha v beta 6 has been shown to be a fibronectin-binding protein. To determine whether the cytoplasmic and transmembrane domains of alpha v beta 6 are necessary for binding to fibronectin, a truncated, secreted form of the integrin lacking these domains was engineered and expressed in Chinese hamster ovary cells. Fibronectin affinity chromatography demonstrated that the secreted integrin, like its full-length counterpart, was capable of binding fibronectin. Monoclonal antibodies were made to secreted alpha v beta 6 and to beta 6-transfected NIH 3T3 cells. In experiments designed to determine whether alpha v beta 6 can mediate cell attachment to fibronectin, full-length human beta 6 was expressed in Chinese hamster ovary cells and in the human colon carcinoma cell line SW480. beta 6-expressing cells were identified by alpha v beta 6-specific antibodies, and the beta 6-transfectants were used in cell-adhesion assays. In Chinese hamster ovary cells, human beta 6 associated with hamster alpha v but was incapable of mediating cell attachment to fibronectin. However, expression of beta 6 in these cells had the dominant negative effect of decreasing alpha v beta 5-dependent adhesion to vitronectin. In SW480 cells, beta 6 expression conferred the ability to bind to fibronectin even in the presence of inhibitory antibodies against beta 1 integrins. In such cells, fibronectin binding ability could be blocked by an antibody to alpha v integrins. These results constitute the first direct evidence that alpha v beta 6 mediates cell attachment to fibronectin.

3T3 Cells↗
PubMed1994

The alpha v beta 6 integrin promotes proliferation of colon carcinoma cells through a unique region of the beta 6 cytoplasmic domain.

Cell-matrix interactions are assumed to be important in regulating differentiation and tumor cell growth; however, the precise roles of individual matrix receptors in producing cellular responses are still unclear. We have previously described the alpha v beta 6 integrin, an epithelial cell fibronectin receptor expressed in many carcinoma cell lines. Here we show that heterologous expression of alpha v beta 6 in a human colon carcinoma cell line (SW480) enhances the proliferative capacity of these cells, both in vitro and in vivo in nude mice. This property of alpha v beta 6 correlates with the presence of an 11-amino acid region at the COOH terminus of the beta 6 cytoplasmic domain. This 11-amino acid sequence is required for the growth stimulatory effect, but not for other functions of the beta 6 cytoplasmic domain, such as promoting cell adhesion and focal contact localization.

Amino Acid Sequence↗
PubMed1994

Dominant negative mutants: tools for the study of protein function in vitro and in vivo.

Powerful new approaches for the identification and sequencing of novel cDNAs have produced a backlog of proteins seeking functions. Traditional approaches for characterizing protein function (e.g., blocking monoclonal antibodies and heterologous expression) have significant limitations, especially in identifying the roles specific proteins play in vivo. An alternative approach is to engineer mutations in the protein of interest that abolish its function and that also inhibit the function of simultaneously expressed wild-type protein (dominant negative mutations). This approach has wide application to the study of a number of different kinds of proteins but tends to be most effective for proteins that need to assemble into multimers to be functional. Dominant negative mutants have already provided insights into the molecular mechanisms of action of a number of protein families, including hormone receptors, oncogenes, and growth factor receptors, and have been identified as the cause of at least a few autosomal dominant diseases. Expression of dominant negative mutants under the control of highly active lung cell-specific promoters holds great promise for the study of the roles specific proteins and protein families play in lung development, health, and disease.

Animals↗
PubMed1994

Effects of beta subunit cytoplasmic domain deletions on the recruitment of the integrin alpha v beta 6 to focal contacts.

The integrin alpha v beta 6 is expressed primarily in epithelial cells and mediates attachment to the extracellular matrix protein fibronectin. We recently observed that alpha v beta 6 localizes to focal contacts when cells that express the receptor are plated on fibronectin. To determine which regions of the beta 6 cytoplasmic domain are required for recruitment to focal contacts, the wild type human beta 6 cytoplasmic domain are required for recruitment to focal contacts, the wild type human beta 6 subunit and mutants containing selective deletions within the beta 6 cytoplasmic domain were stably expressed in Chinese Hamster Ovary cells. The beta 6 cytoplasmic domain is composed of a 41 amino acid region that is highly conserved among integrin beta subunits, and a unique 11 amino acid carboxy terminal extension. The 11 amino acid extension was not required for localization to focal contacts; in fact, its removal appeared to increase receptor localization. However, removal of any of the 3 conserved regions previously identified as important for the localization of beta 1 integrins to focal contacts (Reszka, et al., 1992, J. Cell Biol. 117:1321-30) eliminated recruitment of beta 6 to focal contacts. These data suggest that, as with the integrin beta 1 subunit, multiple regions within the first 41 amino acids of the beta 6 cytoplasmic domain are necessary for recruitment of alpha v beta 6 to focal contacts. However, the unique 11 amino acid carboxy terminus of beta 6 is not required for this recruitment, and may actually play a negative regulatory role.

Actins↗
PubMed1993

Sequence and tissue distribution of the integrin alpha 9 subunit, a novel partner of beta 1 that is widely distributed in epithelia and muscle.

The integrin family of adhesion receptors consists of several heterodimeric glycoproteins, each composed of one alpha and one beta subunit. A novel integrin alpha subunit partial cDNA isolated from TGF-beta stimulated guinea pig airway epithelial cells has previously been reported (Erle, D.J., D. Sheppard, J. Bruess, C. Rüegg, and R. Pytela. 1991. Am. J. Respir. Cell Mol. Biol. 5:170-177). We have now determined cDNA and amino acid sequence for the human homolog of this subunit, named alpha 9, from a human lung cDNA library, a human small intestine cDNA library, and cDNA from the cell lines U937, HL-60 and Tera-2. This sequence is predicted to encode a 1006-amino acid mature protein that shares 39% identity with the previously identified integrin subunit alpha 4. By Northern blot analysis, alpha 9 mRNA was detected in the human carcinoma cell lines Tera-2 and Caco-2. Anti-peptide antibodies against the predicted COOH-terminal sequence of alpha 9 immunoprecipitated a heterodimer (140 kD/115 kD nonreduced; 150 kD/130 kD reduced) from Tera-2 lysates. Immunodepletion of beta 1-containing integrins with Tera-2 lysates removed alpha 9 immunoreactivity, suggesting that beta 1 is the principal beta subunit partner for alpha 9 in these cells. alpha 9 was detected by immunohistochemistry in airway epithelium, in the basal layer of squamous epithelium, and in smooth muscle, skeletal muscle, and hepatocytes.

Amino Acid Sequence↗