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PubMed2005

Membrane type 1-matrix metalloproteinase is involved in migration of human monocytes and is regulated through their interaction with fibronectin or endothelium.

Membrane type 1-matrix metalloproteinase (MT1-MMP) is involved in endothelial and tumor-cell migration, but its putative role in leukocyte migration has not been characterized yet. Here, we demonstrate that anti-MT1-MMP monoclonal antibody (mAb) impaired monocyte chemotactic protein-1 (MCP-1)-stimulated monocyte migration on fibronectin (FN), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1). In addition, monocyte transmigration through tumor necrosis factor-alpha (TNF-alpha)-activated endothelium is also inhibited by anti-MT1-MMP mAb. Therefore, regulation of MT1-MMP in human peripheral blood monocytes was investigated. First, MT1-MMP clustering was observed at motility-associated membrane protrusions of MCP-1-stimulated monocytes migrating on FN, VCAM-1, or ICAM-1 and at the leading edge, together with profilin, of monocytes transmigrating through activated endothelial cells. In addition, up-regulation of MT1-MMP expression was induced in human monocytes upon attachment to FN in a manner dependent on alpha4beta1 and alpha5beta1 integrins. Binding of monocytes to TNF-alpha-activated human endothelial cells as well as to VCAM-1 or ICAM-1 also resulted in an increase of MT1-MMP expression. These findings correlated with an enhancement of MT1-MMP fibrinolytic activity in monocytes bound to FN, VCAM-1, or ICAM-1. Our data show that MT1-MMP is required during human monocyte migration and endothelial transmigration and that MT1-MMP localization, expression, and activity are regulated in monocytes upon contact with FN or endothelial ligands, pointing to a key role of MT1-MMP in monocyte recruitment during inflammation.

Cell Movement↗
PubMed2004

Expression and function of homing-essential molecules and enhanced in vivo homing ability of human peripheral blood-derived hematopoietic progenitor cells after stimulation with stem cell factor.

Hematopoietic stem cell (HSC) homing from blood to bone marrow is a multistep process involving rolling, extravasation, migration, and finally adhesion in the correct microenvironment. With view to the hematopoietic recovery after clinical stem cell transplantation, we investigated the effect of stem cell factor (SCF) on the expression and the adhesive function of the alpha4beta1 and alpha5beta1 integrins very-late antigen (VLA)-4 and VLA-5 on peripheral blood-derived hematopoietic progenitor cells. After SCF stimulation, the expression of VLA-4 and VLA-5 on CD34+/c-kit+ cells obtained from healthy donors increased from 54% to 90% and from 3% to 82%, respectively. For patient-derived cells, the increase was 67% to 90% and 12% to 46%. The proportion of mononuclear cells adhering to the fibronectin fragment CH296 increased by stimulation with SCF from 14% to 23%. Accordingly, functional studies showed an approximate 30% increase of adherent long-term culture-initiating cell. The improvement of the homing abilities of SCF-stimulated HSC was confirmed by transplantation into sublethally irradiated nonobese diabetic-scid/scid mice. Six weeks after the transplantation, in eight of eight animals receiving human HSC with the addition of SCF, a profound multilineage hematopoietic engraftment was detected, whereas in the control group receiving only HSC, none of eight animals engrafted. Our data provide the first in vivo evidence that stimulation with cytokines improves the homing ability of transplanted human hematopoietic progenitor cells.

Antigens, CD↗
PubMed2001

A comparison of ocular melanocyte and uveal melanoma cell invasion and the implication of alpha1beta1, alpha4beta1 and alpha6beta1 integrins.

BACKGROUND/AIMS: Posterior uveal melanoma is the most common intraocular tumour in adults, responsible for the death of approximately 35% of patients. Hepatic metastases are most frequent, and once diagnosed survival is usually less than 1 year. The beta1 family of integrins, alphavbeta3 and MMP-2 and MMP-9 have been implicated in the metastasis of several types of tumour. To study their involvement in uveal melanoma we analysed the expression of the beta1 integrins, alphavbeta3, MMP-2, and MMP-9 in 10 primary posterior uveal melanomas, and correlated expression with invasive potential in vitro. Comparable studies were undertaken on cultures of melanocytes. METHODS: Expression of integrins was studied by immunohistochemistry, secretion of MMP-2 and MMP-9 by zymography, and the invasive potential was assessed using a transwell model. RESULTS: MMP-2 was secreted by all uveal melanomas and seven of 10 secreted MMP-9. Among uveal melanoma, invasion levels of 4-25% were observed and the major integrins expressed were alpha1beta1, alpha2beta1, alpha3beta1, alpha5beta1, and avbeta3. Melanocytes did not express alpha1beta1, alpha4beta1, and alpha6beta1. CONCLUSION: The laminin binding alpha6beta1 integrin was not expressed by either melanocytes or tumours with spindle morphology, which are considered to have a better prognosis. It is possible that expression of the alpha6beta1 integrin may prove useful as a prognostic indicator.

Adult↗
PubMed2004

alpha4beta1- and alpha6beta1-integrins are functional receptors for midkine, a heparin-binding growth factor.

Midkine is a heparin-binding growth factor that promotes the growth, survival, migration and differentiation of various target cells. So far, receptor-type protein tyrosine phosphatase zeta, low-density-lipoprotein-receptor-related protein and anaplastic lymphoma kinase have been identified as receptors for midkine. We found beta1 integrin in midkine-binding proteins from 13-day-old mouse embryos. beta1-Integrin bound to a midkine-agarose column and was eluted mostly with EDTA. Further study revealed that the alpha-subunits capable of binding to midkine were alpha4 and alpha6. Purified alpha4beta1- and alpha6beta1-integrins bound midkine. Anti-alpha4 antibody inhibited the midkine-dependent migration of osteoblastic cells, and anti-alpha6 antibody inhibited the midkine-dependent neurite outgrowth of embryonic neurons. After midkine treatment, tyrosine phosphorylation of paxillin, an integrin-associated molecule, was transiently increased in osteoblastic cells. Therefore, we concluded that alpha4beta1- and alpha6beta1-integrins are functional receptors for midkine. We observed that the low-density-lipoprotein-receptor-related-protein-6 ectodomain was immunoprecipitated with alpha6beta1-integrin and alpha4beta1-integrin. The low-density-lipoprotein-receptor-related-protein-6 ectodomain was also immunoprecipitated with receptor-type protein tyrosine phosphatase zeta. alpha4beta1- and alpha6beta1-Integrins are expected to co-operate with other midkine receptors, possibly in a multimolecular complex that contains other midkine receptors.

Alleles↗
PubMed2001

Endometrial receptivity: expression of alpha3beta1, alpha4beta1 and alphaVbeta1 endometrial integrins in women with impaired fertility.

Advances in immunohistochemical methods with the specificity of poly- and monoclonal antibodies allow the description of the endometrial receptivity, which is characterized by the ability of secretion of phase specific proteins and glikoproteins by epithelial and stromal cells. We studied the differences in the expression of alpha3beta1, alpha4beta1 and alphaVbeta1 integrins in endometrium of women with recurrent miscarriages and women with unexplained infertility. The endometrial tissue was collected during hysteroscopy performed between 7th and 9th day after ovulation. The immunohistochemical evaluation of alpha3beta1, alpha4beta1 and alphaVbeta1 integrin expression was determined in all endometrial biopsies. Staining intensity of alpha3beta1 in glandular epithelium and endometrial stroma was similar in both groups. In women with recurrent miscarriages we noted a lower concentrations of the alpha4beta1 and alphaVbeta1 integrins during the midluteal phase than in women with unexplained infertility. Moreover, integrins alpha4beta1 and alphaVbeta1 were expressed more frequently in glandular epithelium and endometrial stroma of women with unexplained infertility than those of women with recurrent miscarriages. However, alphaV(2)1 staining in endometrial stroma was stronger than that of alpha4beta1. It can be concluded, that these integrins may play an important role in the implantation process.

Abortion, Habitual↗
PubMed2004

Natalizumab: AN 100226, anti-4alpha integrin monoclonal antibody.

Natalizumab [AN 100226, anti-alpha4 integrin monoclonal antibody, Antegren] is a humanised monoclonal antibody that blocks alpha4beta1 integrin-mediated leukocyte migration. Natalizumab is in phase III trials for the treatment of multiple sclerosis in North America and the UK, and for the treatment of Crohn's disease also in the UK. It may have potential in the treatment of other immune-related inflammatory disease. Elan Corporation intends to examine the potential of natalizumab in rheumatoid arthritis and ulcerative colitis. 4beta1 integrin on circulating leukocytes binds to vascular cell adhesion molecule-1, which is expressed at high levels in the blood vessels in the CNS during exacerbations of multiple sclerosis. This allows leukocytes expressing alpha4beta1 integrin (very late antigen-4) to move from the peripheral blood into the CNS. Inflammatory proteins and other factors released from lymphocytes in the brain lead to the progression of symptoms. A limitation of natalizumab is that it must be injected and cannot be administered orally. Scientists have transformed the large anti-alpha4 monoclonal antibody into much smaller, drug-like molecules suitable for oral administration. Protein Design Labs has granted a worldwide nonexclusive licence under its antibody humanisation patents to Elan Pharmaceuticals for natalizumab. Biogen Inc. has entered into an agreement with Elan for a worldwide exclusive collaboration to develop, manufacture and commercialise natalizumab for multiple sclerosis and Crohn's disease and rheumatoid arthritis. Development of natalizumab is also being funded, in part, by Axogen (acquired by Elan in 1999). In November 2003, Biogen and IDEC Pharmaceuticals merged to form Biogen Idec. Elan repurchased royalty rights on a package of products, including natalizumab, from Autoimmune Disease Research Company. Elan and Genzyme Transgenics Corporation signed an agreement to produce natalizumab in GTC's genetically engineered goats, which will express the compound in their milk. Genzyme Transgenics Corporation changed its name to GTC Biotherapeutics in June 2002; it is no longer a subsidiary of Genzyme Corporation. Following discussions with the US FDA, Elan completed enrolment in a second phase III trial, involving approximately 420 patients with Crohn's disease. This Evaluation of Natalizumab as Continuous Therapy-2 (ENACT-2) trial evaluated the effect of natalizumab on duration of response and remission in patients with Crohn's disease. In January 2004, Elan Corporation and Biogen Idec announced that the phase III, ENACT-2 maintenance trial of natalizumab in Crohn's disease met the primary endpoint of maintenance of response. Elan and Biogen Idec will discuss these data with regulatory authorities in both the US and Europe and determine the appropriate path forward for natalizumab in Crohn's disease. An NDA for Antegren in Crohn's disease was expected to be filed at the end of 2003; however, due to failing to meet the primary endpoint in the induction trial, Elan is unable to predict when and if a regulatory filing will be made. Earlier, on 23 January 2001, the Wall Street Journal reported that the Biogen CEO expects Antegren to become a blockbuster drug, with sales of at least $US1 billion. He also predicted that Antegren could be on the market as early as 2003 for the indication of Crohn's disease and in 2004 for multiple sclerosis. The Journal stated that Biogen is under pressure to develop new drugs since its flagship product Avonex will be losing its US Orphan Drug Act protection in 2003. Antegren has a different mechanism to that of Avonex and could be used either alone or as a combination therapy.

Animals↗
PubMed2003

Spatial restriction of alpha4 integrin phosphorylation regulates lamellipodial stability and alpha4beta1-dependent cell migration.

Integrins coordinate spatial signaling events essential for cell polarity and directed migration. Such signals from alpha4 integrins regulate cell migration in development and in leukocyte trafficking. Here, we report that efficient alpha4-mediated migration requires spatial control of alpha4 phosphorylation by protein kinase A, and hence localized inhibition of binding of the signaling adaptor, paxillin, to the integrin. In migrating cells, phosphorylated alpha4 accumulated along the leading edge. Blocking alpha4 phosphorylation by mutagenesis or by inhibition of protein kinase A drastically reduced alpha4-dependent migration and lamellipodial stability. alpha4 phosphorylation blocks paxillin binding in vitro; we now find that paxillin and phospho-alpha4 were in distinct clusters at the leading edge of migrating cells, whereas unphosphorylated alpha4 and paxillin colocalized along the lateral edges of those cells. Furthermore, enforced paxillin association with alpha4 inhibits migration and reduced lamellipodial stability. These results show that topographically specific integrin phosphorylation can control cell migration and polarization by spatial segregation of adaptor protein binding.

Animals↗
PubMed1999

Differences in phosphatase modulation of alpha4beta1 and alpha5beta1 integrin-mediated adhesion and migration of B16F1 cells.

It is well established that a biphasic relationship exists between the adhesive strength of beta1 integrins and their ability to mediate cell movement. Thus, cell movement increases progressively with adhesive strength, but beyond a certain point of optimal interaction, cell movement is reduced with further increases in adhesive function. The interplay between the various kinase and phosphatase activities provides the balance in beta1 integrin-mediated cell adhesion and migration. In the present study, the significance of protein tyrosine phosphatases (PTP) and ser/thr protein phosphatases (PP) in alpha4beta1 and alpha5beta1 integrin-mediated mouse melanoma B16F1 cell anchorage and migration on fibronectin was characterized using phosphatase inhibitors. At low fibronectin concentration, alpha5beta1 functioned as the predominant receptor for cell movement; a role for alpha4beta1 in B16F1 cell migration increased progressively with fibronectin concentration. Treatment of B16F1 cells with PTP inhibitors, sodium orthovanadate (Na3VO4) and phenylarsine oxide (PAO), or PP-1/2A inhibitor, okadaic acid (OA), abolished cell movement. Inhibition of cell movement by PAO and OA was associated by a reduction in the adhesive strength of alpha4beta1 and alpha5beta1. In contrast, treatment of B16F1 cells with Na3VO4 resulted in selective stimulation of the adhesive function of alpha5beta1, but not alpha4beta1. Therefore, our results demonstrate that (i) both PTP and PP-1/2A have roles in cell movement, (ii) modulation of cell movement by PTP and PP-1/2A may involve either a stimulation or reduction of beta1 integrin adhesive strength, and (iii) distinct phosphatase-mediated signaling pathways for differential regulation of the various beta1 integrins exist.

Animals↗
PubMed2006

Adult murine hematopoiesis can proceed without beta1 and beta7 integrins.

The function of alpha4beta1 and alpha4beta7 integrins in hematopoiesis is controversial. While some experimental evidence suggests a crucial role for these integrins in retention and expansion of progenitor cells and lymphopoiesis, others report a less important role in hematopoiesis. Using mice with a deletion of the beta1 and the beta7 integrin genes restricted to the hematopoietic system we show here that alpha4beta1 and alpha4beta7 integrins are not essential for differentiation of lymphocytes or myelocytes. However, beta1beta7 mutant mice displayed a transient increase of colony-forming unit (CFU-C) progenitors in the bone marrow and, after phenylhydrazine-induced anemia, a decreased number of splenic erythroid colony-forming units in culture (CFUe's). Array gene expression analysis of CD4(+)CD8(+) double-positive (DP) and CD4(-)CD8(-) double-negative (DN) thymocytes and CD19(+) and CD4(+) splenocytes did not provide any evidence for a compensatory mechanism explaining the mild phenotype. These data show that alpha4beta1 and alpha4beta7 are not required for blood cell differentiation, although in their absence alterations in numbers and distribution of progenitor cells were observed.

Anemia, Hemolytic↗
PubMed2001

Identification of a novel heparin-binding site in the alternatively spliced IIICS region of fibronectin: roles of integrins and proteoglycans in cell adhesion to fibronectin splice variants.

The extracellular matrix molecule fibronectin (FN) is a glycoprotein whose major functional property is to support cell adhesion. FN contains at least two distinct cell-binding domains: the central cell-binding domain and the HepII/IIICS region. The HepII region comprises type III repeats 12-14 and contains proteoglycan-binding sites, while the alternatively spliced IIICS segment possesses the major alpha4beta1 integrin-binding sites. Both cell surface proteoglycans and integrins are important for mediating the adhesion of cells to this region of FN. By comparing heparin binding to different recombinant splice variants of the HepII/IIICS region, evidence was obtained for the existence of a novel heparin-binding site in the centre of the IIICS. Site-directed mutagenesis of basic amino acid sequences in this region reduced heparin binding to recombinant HepII/IIICS proteins and, in conjunction with mutations in the HepII region, caused a synergistic loss of activity. Using the H/120 variant of FN, which contains type III repeats 12-15 and the full-length IIICS region, and the H/95 variant of FN, which contains type III repeats 12-15 but lacks the high affinity integrin-binding LDV sequence, the relative roles played by cell-surface proteoglycans and integrins in mediating cell adhesion have been investigated. This was achieved by studying the effects of anti-integrin antibodies and exogenous heparin on A375 melanoma cell attachment to the wild-type and three different mutants of H/120 and H/95 in which the potential proteoglycan-binding sites were partially or completely removed. A375 cell adhesion to H/120 and its mutants was found to involve the co-operative action of both integrin and cell-surface proteoglycan binding, although integrin made a dominant contribution. Anti-integrin antibodies and exogenous heparin were capable of inhibiting melanoma cell adhesion to H/95 and in this case adhesion was due primarily to cell-surface proteoglycan and not integrin binding.

Alternative Splicing↗
PubMed2000

Endometrial dating and determination of the window of implantation in healthy fertile women.

OBJECTIVE: To reassess endometrial morphological criteria of normality identifying the best morphological and molecular "implantation window" indicators in normal women. DESIGN: Prospective clinical study. SETTING: Assisted reproductive unit. PATIENT(S): Fourteen healthy volunteers. INTERVENTION(S): Blood sampling for LH, E(2), and progesterone (P4) determinations. Daily vaginal ultrasounds. Two endometrial biopsies per volunteer, 7 days apart, during luteal phase. MAIN OUTCOME MEASURE(S): Endometrial dating, pinopodes formation, immunohistochemical determination of integrins (alphavbeta3, alpha4beta1), leukemia inhibitory factor (LIF), interleukin-1 receptor type I (IL-1R tI), mouse ascites Golgi (MAG), the transmembrane mucin (MUC-1), and P4 receptor expression. RESULT(S): In 26 of 28 biopsies observers agreed; in two biopsies there was a discrepancy (difference of 72 hours). With use of LH peak, 24 of 26 samples were in phase, and 2 were 3 days behind. Pinopodes appeared on days 20-21 and persisted through day 28 in small groups or larger areas. beta3 Integrin was highly expressed in luminal and glandular epithelium from day 22 through 28; 48 hours thereafter pinopodes appeared. alpha4 Subunit exhibited luminal epithelium reaction positivity on days 22-23 and glands on days 18-23. LIF and IL-1R tI showed weak, erratic expression. MAG antibodies showed luminal epithelium expression up to day 22 and glands up to day 25. MUC-1 showed positivity during the whole luteal phase. P4 receptors were positive through day 20 and at the end of the luteal phase. CONCLUSION(S): The three most cited markers that frame the window of implantation do not correlate in our material. Pinopodes are present from day 20 on; beta3 and alpha4 integrin subunits indicate a window opening on days 22-23.

Adult↗
PubMed1999

Tenascin-C inhibits beta1 integrin-dependent T lymphocyte adhesion to fibronectin through the binding of its fnIII 1-5 repeats to fibronectin.

The extracellular matrix consists of different proteins interacting to form a meshwork-like structure. T lymphocyte adhesion to individual matrix proteins is mainly regulated at the adhesion receptor level, but it is conceivable that the composition of the matrix itself may affect T lymphocyte adhesion to individual proteins. We have addressed the latter point by studying the effect of the matrix protein tenascin-C (TN-C) on T lymphocyte adhesion to fibronectin. Here we report that TN-C inhibits adhesion of T lymphocytes and MOLT-4 lymphoma cells to fibronectin. We demonstrate that a TN-C fragment consisting of fibronectin type III repeats 1-5 (TNfnIII 1-5) but not TNfnIII A-D and TNfnIII 6-8 inhibited alpha5beta1 and alpha4beta1 integrin-mediated T lymphocyte and MOLT-4 adhesion to fibronectin. At concentrations that did not inhibit adhesion, TNfnIII 1-5 still prevented MOLT-4 cells from spreading on fibronectin. Preincubation and co-immobilization of TNfnIII 1-5 with fibronectin was more effective in inhibiting MOLT-4 adhesion to fibronectin than soluble TNfnIII 1-5 present during the adhesion test. Using an enzyme-linked immunosorbent assay we could demonstrate binding of TNfnIII 1-5 to fibronectin and fibronectin fragments. Taken together, these data demonstrate that the TNfnIII 1-5 domain is implicated in the inhibition of T lymphocyte adhesion to fibronectin caused by TN-C, and indicate that this effect involves the binding of TN-C repeats TNfnIII 1-5 to fibronectin.

Binding Sites↗
PubMed1998

Interferon regulatory factor-2 is a transcriptional activator in muscle where It regulates expression of vascular cell adhesion molecule-1.

Previously, we have suggested that vascular cell adhesion molecule-1 (VCAM-1) and its integrin receptor alpha4beta1 mediate cell-cell interactions important for skeletal myogenesis. Expression of the receptors subsequently subsides in muscle after birth. Here, we examine the mechanism regulating VCAM-1 gene expression in muscle. An enhancer located between the TATA box and the transcriptional start site is responsible for VCAM-1 gene expression in muscle-this element is inactive in endothelial cells where VCAM-1 expression is dependent on nuclear factor kappaB sites and inflammatory cytokines. We identify interferon regulatory factor-2 (IRF-2), a member of the interferon regulatory factor family, as the enhancer-binding transcription factor and show that expression of IRF-2 parallels that of VCAM-1 during mouse skeletal myogenesis. IRF-2 is not dependent upon cytokines for expression or activity, and it has been shown to act as a repressor in other nonmuscle cell types. We show that the basic repressor motif located near the COOH-terminal of IRF-2 is not active in muscle cells, but instead an acidic region in the center of the molecule functions as a transactivating domain. Although IRF-2 and VCAM-1 expression diminishes on adult muscle fiber, they are retained on myogenic stem cells (satellite cells). These satellite cells proliferate and fuse to regenerate muscle fiber after injury or disease. We present evidence that VCAM-1 on satellite cells mediates their interaction with alpha4beta1(+) leukocytes that invade the muscle after injury or disease. We propose that VCAM-1 on endothelium generally recruits leukocytes to muscle after injury, whereas subsequent interaction with VCAM-1 on regenerating muscle cells focuses the invading leukocytes specifically to the sites of regeneration.

Animals↗
PubMed1998

CD49d expression and function on allergen-stimulated T cells from blood and airway.

The alpha4 chain (CD49d), which constitutes one of the chains of alpha4beta1 (very late activating antigen-4 [VLA-4]) and alpha4beta7 integrins, mediates migration of T cells to extravascular spaces. The interaction between VLA-4 and vascular cell adhesion molecule-1 (VCAM-1) has been shown to be the critical pathway for the selective accumulation of eosinophils and basophils at sites of allergic inflammation. T lymphocytes are also specifically recruited into allergic sites, including the allergic asthmatic airway. Increased numbers of activated CD4+ cells expressing the DR antigen subset of the human leukocyte antigens (HLA-DR) appear in the allergic lung 48 h after allergen inhalation. The mechanisms by which these cells localize into the lung are still unknown. We report that stimulation of allergen-specific T cells with allergen in vitro resulted in enhanced expression of alpha4 chain (CD49d) as measured by receptor density on allergen-specific T-cell lines and T-cell clones. Kinetic studies showed that CD49d density was enhanced over a 24- to 48-h period in a time-dependent fashion, and was coordinately upregulated with HLA-DR expression. We also demonstrated that increased expression of CD49d on T-cell lines 24 h and 48 h after stimulation correlated with increased adhesion to the CS-1 fragment of fibronectin. In contrast, lymphocyte function-associated antigen-1b (LFA-1b) (CD11b), LFA-3 (CD58), and intercellular adhesion molecule-1 (ICAM-1) (CD54) expression did not change with allergen stimulation. We also showed that CD49d receptor density on T cells obtained by bronchoalveolar lavage (BAL) of allergic patients before and 48 h after allergen challenge was significantly higher than that on T cells taken from BAL of normal subjects and from controls with other inflammatory lung diseases. Taken together, these findings indicate that allergen stimulation activates allergen-specific T cells and coordinately induces increased CD49d receptor expression and binding to counterligands. We postulate that allergen-driven upregulation of CD49d, which together with the beta1 chain constitutes VLA-4 integrin, may be responsible for the selective accumulation of T cells in the allergic asthmatic lung.

Adult↗
PubMed1999

Selective tetraspan-integrin complexes (CD81/alpha4beta1, CD151/alpha3beta1, CD151/alpha6beta1) under conditions disrupting tetraspan interactions.

The tetraspans are molecules with four transmembrane domains which are engaged in multimolecular complexes (the tetraspan web) containing a subset of beta1 integrins (in particular alpha3beta1, alpha4beta1 and alpha6beta1), MHC antigens and several unidentified molecules. The molecules associated with tetraspans are readily detected after immunoprecipitation performed in mild detergents such as Brij 97 or CHAPS. In this study we show that another classical mild detergent, digitonin, dissociated most of these associated molecules, including integrins, from the tetraspans CD9, CD37, CD53, CD63, CD82, Co-029, Talla-1 and NAG-2. In contrast, reciprocal immunoprecipitations from various cell lines demonstrated that two other tetraspans, CD81 and CD151, formed complexes with integrins not disrupted by digitonin. These complexes were CD81/alpha4beta1, CD151/alpha3beta1 and CD151/alpha6beta1. Furthermore, a new anti-CD151 monoclonal antibody (mAb), TS151r, was shown to have a restricted pattern of expression, inversely related to the sum of the levels of expression of alpha6beta1 and alpha3beta1. This mAb was unable to co-precipitate integrins in digitonin, suggesting that its epitope is blocked by the association with integrins. Indeed, the binding of TS151r to the cell surface was quantitatively diminished following alpha3beta1 overexpression. Altogether, these data suggest that, among tetraspans, CD81 interacts directly with the integrin alpha4beta1, and CD151 interacts directly with integrins alpha3beta1 and alpha6beta1. Because all tetraspan-tetraspan associations are disrupted by digitonin, it is likely that the other tetraspans interact indirectly with integrins, through interactions with CD81 or CD151.

Animals↗
PubMed2005

Evaluation of specificity and effects of monoclonal antibodies submitted to the Eighth Human Leucocyte Differentiation Antigen Workshop on rotavirus-cell attachment and entry.

Rotavirus infection of permissive cells is a multi-step process that requires interaction with several cell surface receptors. Integrins alpha2beta1, alpha4beta1, alphaXbeta2, and alphavbeta3 are involved in the attachment and entry into permissive cells for many rotavirus strains. However, possible roles of known partners of these integrins in this process have not been studied. Here, the specificities of new monoclonal antibodies directed to beta1 and beta2 integrins were determined using integrin-transfected cells. The ability of monoclonal antibodies to integrin partners CD82, CD151, CD321, and CD322 to bind rotavirus-permissive cell lines (MA104, Caco-2, and RD) and K562 cells expressing or lacking alpha4beta1 also was investigated. CD82 and CD151 were expressed on K562, alpha4-K562, and RD cells. CD321-specific antibodies bound K562, alpha4-K562, MA104, and Caco-2 cells. CD322 expression was detected on MA104 but not Caco-2 cells. Antibodies to CD82, CD151, CD321, and CD322 that bound these cells were investigated for their ability to inhibit cellular attachment and entry by rotaviruses. Antibody blockade of these integrin-associated proteins did not affect cell attachment or entry of the integrin-using rhesus rotavirus RRV or porcine rotavirus CRW-8, which uses alpha4beta1 integrin for infection. Antibody blockade of CD322 did not alter cell attachment or infectivity by human rotavirus strain RV-3, so RV-3 infection was independent of CD322. Overall, these studies indicate that CD82, CD151, CD321, and CD322 are unlikely to play a role in rotavirus-cell binding or entry.

Antibodies, Monoclonal↗
PubMed2003

Role of multiple beta1 integrins in cell adhesion to the disintegrin domains of ADAMs 2 and 3.

ADAM disintegrin domains can support integrin-mediated cell adhesion. However, the profile of which integrins are employed for adhesion to a given disintegrin domain remains unclear. For example, we suggested that the disintegrin domains of mouse sperm ADAMs 2 and 3 can interact with the alpha6beta1 integrin on mouse eggs. Others concluded that these disintegrin domains interact instead with the alpha9beta1 integrin. To address these differing results, we first studied adhesion of mouse F9 embryonal carcinoma cells and human G361 melanoma cells to the disintegrin domains of mouse ADAMs 2 and 3. Both cell lines express alpha6beta1 and alpha9beta1 integrins at their surfaces. Antibodies to the alpha6 integrin subunit inhibited adhesion of both cell lines. An antibody that recognizes human alpha9 integrin inhibited adhesion of G361 cells. VLO5, a snake disintegrin that antagonizes alpha4beta1 and alpha9beta1 integrins, potently inhibited adhesion of both cell lines. We next explored expression of the alpha9 integrin subunit in mouse eggs. In contrast to our ability to detect alpha6beta1, we were unable to convincingly detect alpha9beta1 integrin on the surface of mouse eggs. Moreover, treatment of mouse eggs with 250 nm VLO5, which is 250 fold over its approximately IC(50) for inhibition of somatic cell adhesion, had minimal effect on sperm-egg binding or fusion. We did detect alpha9 integrin protein on epithelial cells of the oviduct. Additional studies showed that antibodies to the alpha6 and alpha7 integrins additively inhibited adhesion of mouse trophoblast stem cells and that an antibody to the alpha4 integrin inhibited adhesion of MOLT-3 cells to these disintegrin domains: Our data suggest that multiple integrins (on the same cell) can participate in adhesion to a given ADAM disintegrin domain and that interactions between ADAMs and integrins may be important for sperm transit through the oviduct.

ADAM Proteins↗
PubMed2002

JAM2 interacts with alpha4beta1. Facilitation by JAM3.

We have previously reported that junctional adhesion molecule 2 (JAM2) adheres to T cells through heterotypic interactions with JAM3. An examination of the cation dependence of JAM2 adhesion to HSB cells revealed a Mn(2+)-enhanced binding component indicative of integrin involvement. Using neutralizing integrin antibodies, we have defined an interaction between JAM2 and alpha(4)beta(1) in T cells. The interaction is readily amenable to drug intervention as demonstrated by the ability of TBC 772, an alpha(4)-specific inhibitor, to attenuate the Mn(2+)-enhanced component. Intriguingly, the engagement of alpha(4)beta(1) by JAM2 is only enabled following prior adhesion of JAM2 with JAM3 and is not detectable in cells where JAM3 expression is absent. Supporting this observation, we show that neutralizing JAM3 serum and soluble JAM3 ectodomain inhibit not only JAM2 binding to JAM3 but also prevent JAM2/alpha(4)beta(1) interactions in T cells. We further define the first Ig-like fold of JAM2 as being competent in binding both JAM3 and alpha(4)beta(1) counter-receptors. Mutagenesis of the only acidic residue in the C-D loop of this Ig fold, namely Asp-82, has no bearing on alpha(4)beta(1) interactions, and thus JAM2 deviates somewhat from the mechanism used by other immunoglobulin superfamily cell adhesion molecules to engage integrin.

Cell Adhesion↗