scholarly journals The size of the intracellular β 1-integrin precursor pool regulates maturation of β 1-integrin subunit and associated α-subunits

1994 ◽  
Vol 300 (3) ◽  
pp. 771-779 ◽  
Author(s):  
L Koivisto ◽  
J Heino ◽  
L Häkkinen ◽  
H Larjava
Keyword(s):  
Cell Surface ◽  
Antisense Rna ◽  
Integrin Subunit ◽  
Integrin Receptors ◽  
Transfected Cells ◽  
Precursor Pool ◽  
Cell Clones ◽  
Beta 1 Integrin ◽  
Α Subunits

A large pool of precursor beta 1-integrin subunits is frequently found intracellularly. During malignant transformation this pool often disappears. Concomitantly, integrin-mediated cell-adhesion functions are disturbed, even though no change in the number of beta 1-integrin receptors on the cell surface can be observed. Here, we have studied the role of an intracellular pre-beta 1-integrin pool by transfecting human MG-63 osteosarcoma cells with plasmid construction producing an antisense RNA for the beta 1-integrin subunit. Stable cell clones expressing beta 1-integrin antisense RNA were shown to have a reduced intracellular pool of pre-beta 1-integrin subunits. In the antisense-transfected cells, the synthesis of the beta 1-integrin chain was reduced by 65% compared with non-transfected or vector-transfected MG-63 cells. The decreased synthesis of the beta 1-integrin chain was associated with accelerated maturation of the beta 1-integrin chain (half-maturation time about 5 h in antisense-transfected cells compared with about 10.5 h in control cells), whereas maturation of the alpha-integrin chain slowed down. The amount of beta 1-integrins on the cell surface, however, remained unaltered. Cell clones with the largest decrease in the relative amount of the pre-beta 1-integrin subunit also showed altered integrin function. They were found to synthesize fibronectin, but were unable to assemble it into a fibronectin matrix on the cell surface. Thus we conclude that the repression of biosynthesis of the beta 1-integrin chain leads to alterations in receptor maturation and may be connected with altered receptor function.

scholarly journals Altered glycosylation and cell surface expression of beta 1 integrin receptors during keratinocyte activation

1992 ◽  
Vol 103 (3) ◽  
pp. 743-753 ◽  
Author(s):  
L.T. Kim ◽  
S. Ishihara ◽  
C.C. Lee ◽  
S.K. Akiyama ◽  
K.M. Yamada ◽  
...  
Keyword(s):  
Cell Culture ◽  
Cell Surface ◽  
Fold Increase ◽  
Cell Surface Expression ◽  
Activation Process ◽  
Integrin Subunit ◽  
Integrin Receptors ◽  
Serum Factors ◽  
Keratinocyte Proliferation ◽  
Beta 1 Integrin

We studied the mechanism by which cell adhesiveness becomes activated when keratinocytes are removed from skin and placed into cell culture. Our results suggest that activation involves altered beta 1 integrin subunit glycosylation accompanied by an increase in cell surface beta 1 integrin receptors. Activated keratinocytes contained two forms of the beta 1 integrin subunit, approximately 93 kDa and approximately 113 kDa. As shown by pulse-chase experiments, the smaller represented the cytoplasmic precursor of the larger, and only the 113 kDa mature form was detected in integrin receptors expressed at the cell surface. Pre-activated keratinocytes contained beta 1 integrin subunits ranging from approximately 97 to 110 kDa. These beta 1 subunits had been processed through the Golgi, based on resistance to endoglycosidase-H treatment, and were not converted to 113 kDa subunits during subsequent cell culture. Experiments with endoglycosidase-F showed that differences in the apparent sizes of beta 1 integrin subunits observed in pre-activated and activated keratinocytes could be attributed to differences in subunit glycosylation. Smaller beta 1 subunits found in pre-activated keratinocytes, like the precursor beta 1 subunits of activated cells, appeared to be less efficient in reaching the cell surface. Overall, a approximately 10-fold increase in the level of cell surface integrin receptors occurred concomitant with the increased proportion of 113 kDa beta 1 subunits found in activated cells. Endoglycosidase-F experiments also indicated that there were changes in keratinocyte alpha subunits associated with beta 1. In related experiments, keratinocytes cultured in low Ca2+, serum-free MCDB medium for 4 days proliferated but their adhesiveness did not become activated. Therefore, keratinocyte proliferation and activation of adhesion are regulated separately. Finally, substantial activation of keratinocytes was observed when serum was added to cells cultured in MCDB with serum, indicating a role for serum factors in the activation process.

Down regulation of talin alters cell adhesion and the processing of the alpha 5 beta 1 integrin

1995 ◽  
Vol 108 (10) ◽  
pp. 3317-3329 ◽  
Author(s):  
C. Albiges-Rizo ◽  
P. Frachet ◽  
M.R. Block
Keyword(s):  
Antisense Rna ◽  
Marked Decrease ◽  
Cell Spreading ◽  
Cdna Fragment ◽  
Down Regulation ◽  
Transfected Cells ◽  
Cell Matrix ◽  
Beta 1 Integrin ◽  
Kinetics Of

The role of talin was addressed by down regulating its expression using an antisense RNA strategy. HeLa cells were transfected with a talin 5′ cDNA fragment under the control of the inducible human metallothionein promotor. Isolated clones displayed a decrease in talin level down to 10% of control. The reduction in talin expression dramatically slowed down the kinetics of cell spreading. Mock-transfected cells, spread out onto fibronectin, exhibited large peripheral adhesion plaques. In contrast, cells with reduced talin expression showed smaller focal contacts localized all over the ventral face, and displayed a marked decrease in the number of stress fibers. Immunoprecipitation experiments carried out with a polyclonal antibody on surface-labeled receptor indicated a shift in the mobility for both alpha 5 and beta 1 subunits. Surprisingly, beta 1 integrin chains could not be detected by indirect immunofluorescence using monoclonal antibodies in talin deficient clones. Western blot analysis indicated the presence of two forms of beta 1. We analyzed the processing of beta 1 in normal and talin deficient cells using pulse chase experiments. Normal cells required a minimum of 5 hours for the processing of mature beta 1, while the talin deficient AT22 clone showed that the beta 1 precursor was slowly converted into a very low molecular mass product. Our data demonstrate that talin plays a central role in the establishment of cell-matrix contacts. In addition, down regulation of talin impairs the folding and processing of beta 1 integrins.

Regulation of epithelial cell surface polarity reversal by beta 1 integrins

1994 ◽  
Vol 107 (3) ◽  
pp. 561-576 ◽  
Author(s):  
G.K. Ojakian ◽  
R. Schwimmer
Keyword(s):  
Extracellular Matrix ◽  
Cell Surface ◽  
Outer Membrane ◽  
Collagen Gel ◽  
Polarity Reversal ◽  
Integrin Subunit ◽  
Membrane Remodeling ◽  
Surface Polarity ◽  
Beta 1 Integrin

The role of extracellular matrix in the regulation of epithelial cell surface polarity development was studied using MDCK cells. Previous work has demonstrated that MDCK cells cultured in suspension form epithelial cysts having polarized cell surface distributions of several membrane proteins. When MDCK suspension cysts are incubated within collagen gel, a dynamic epithelial membrane remodeling occurs that is accompanied by the reversal of cell surface polarity (Wang et al., 1990b, J. Cell Sci. 95, 153–165), suggesting that extracellular matrix is important in the modulation of epithelial polarity development. To determine if members of the integrin receptor family were involved, MDCK cyst binding studies were done utilizing antifunctional monoclonal antibodies (AIIB2 and AJ2) against the beta 1 integrin subunit. These antibodies inhibited cyst binding to type I collagen, type IV collagen and laminin, providing evidence that functional beta 1 integrin heterodimers were present on the cyst outer membrane. Integrin localization on suspension cysts demonstrated that the alpha 2, alpha 3 and alpha 6 integrin subunits had a non-polarized cell surface distribution and were localized to both the apical and basolateral membranes. Interestingly, immunofluorescence microscopy determined that the beta 1 subunit had a polarized, basolateral membrane distribution although cyst binding studies using inhibitory monoclonal antibodies suggested that functional beta 1 subunits were present on the cyst outer membrane. After incubation of suspension cysts in collagen gel for 8 hours, the beta 1 integrin subunit was detected on the outer membrane, suggesting that the formation of additional integrin alpha/beta heterodimers could be involved in epithelial remodeling. To establish the role of beta 1 integrins in polarity reversal, experiments were done on cysts incubated in collagen gel. After 6 hours in collagen gel, considerable membrane remodeling had occurred as determined by a reduction in outer membrane microvilli. However, the presence of monoclonal antibody AIIB2 inhibited membrane remodeling by preventing both microvillar loss and the endocytosis of the apical membrane glycoprotein gp135. These results provide strong evidence that members of the beta 1 integrin family are involved in the regulation of epithelial polarity reversal, and demonstrate that MDCK cysts constitute an excellent model system for studying the role of cell-extracellular matrix interactions in the regulation of epithelial plasticity and cell surface polarity development.

Alpha 7 beta 1 integrin is a component of the myotendinous junction on skeletal muscle

1993 ◽  
Vol 106 (2) ◽  
pp. 579-589 ◽  
Author(s):  
Z.Z. Bao ◽  
M. Lakonishok ◽  
S. Kaufman ◽  
A.F. Horwitz
Keyword(s):  
Skeletal Muscle ◽  
Cytoplasmic Domain ◽  
Cross Reactivity ◽  
Myotendinous Junction ◽  
Integrin Subunit ◽  
Adult Skeletal Muscle ◽  
Beta 1 Integrin ◽  
Alpha 7 ◽  
Adhesion Plaque

Immunization against a 70 kDa band that co-purifies with skeletal muscle integrins has resulted in an antibody directed against the avain alpha 7 integrin subunit. The specificity of the antibody was established by patterns of tissue staining and cross-reactivity with antibodies directed against the cytoplasmic domain of the rat alpha 7 cytoplasmic domain. On sections of adult skeletal muscle the alpha 7 integrin was enriched in the myotendinous junction (MTJ). This localization was unique as neither the alpha 1, alpha 3, alpha 5, alpha 6 and alpha v subunit localizes in the myotendinous junction. The distribution of the alpha 7 subunit in the MTJ was examined during embryonic development. alpha 7 expression in the junction is first apparent around embryo day 14 and is almost exclusively at the developing MTJ at this stage. alpha 3 is expressed with distinctive punctate staining around the junctional area in earlier embryos (11-day). The time of appearance of the alpha 7 subunit in the MTJ correlates with the insertion of myofibrils into subsarcolemmal densities and folding of the junctional membrane, suggesting a role of the alpha 7 integrin in this process. Vinculin is present throughout development of the myotendinous junction, suggesting that the alpha 7 integrin recognizes a preformed cytoskeletal structure. The presence of the alpha 7 subunit in the myotendinous junction and the alpha 5 subunit in the adhesion plaque demonstrates a molecular difference between these two adherens junctions. It also points to possible origins of junctional specificity on muscle. Differences between these two junctions were developed further using an antibody against phosphotyrosine (PY20). Phosphotyrosine is thought to participate in the organization and stabilization of adhesions. The focal adhesion and the neuromuscular junction, but not the MTJ, contained proteins phosphorylated on tyrosine.

The alpha 2 beta 1 integrin regulates collagen-mediated MDCK epithelial membrane remodeling and tubule formation

1995 ◽  
Vol 108 (6) ◽  
pp. 2487-2498 ◽  
Author(s):  
R. Schwimmer ◽  
G.K. Ojakian
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Cell Surface ◽  
Apical Membrane ◽  
Apical Cell ◽  
Collagen Gel ◽  
Integrin Subunit ◽  
Membrane Remodeling ◽  
Tubule Formation ◽  
Beta 1 Integrin

Previous studies have demonstrated that incubation of MDCK cell epithelial cysts in collagen gel induced a reversal in cell surface polarity that was regulated by beta 1 integrins. Further experiments were done to identify the specific collagen binding integrin involved by applying collagen gel overlays to the apical membrane of subconfluent MDCK monolayers. Cell surface levels of the apical membrane glycoprotein gp135 were monitored by ELISA to quantitate the extent of collagen-mediated membrane remodeling. After an 8 hour incubation with collagen, there was a 35% reduction in gp135 while the cell surface levels of the alpha 2, alpha 3 and beta 1 integrin subunits were not affected. Immunofluorescence microscopy confirmed the loss of gp135 from selected regions of the apical cell surface while the alpha 2 and beta 1 integrin subunits were distributed in small clusters over the entire apical membrane in both control and collagen-treated monolayers. Collagen-mediated loss of gp135 was inhibited by monoclonal antibodies which recognize either the alpha 2 or beta 1 integrin subunits but not by a monoclonal antibody against the alpha 6 beta 1 integrin. These results demonstrated that remodeling of the apical membrane had occurred, allowing the selective retention of beta 1 integrins but not gp135. They were supported by the observation that collagen-mediated loss of apical membrane microvilli was inhibited by the monoclonal antibody against the alpha 2 integrin subunit. Incubation of confluent monolayers with collagen gel induced the formation of polarized epithelial tubules within 16 hours. Epithelial tubule biogenesis was completely inhibited by monoclonal antibodies against either the alpha 2 or beta 1 integrin subunits, providing strong evidence that the alpha 2 beta 1 integrin is essential for collagen-mediated epithelial membrane remodeling and tubule formation.

scholarly journals Potential role of Rab4 in the regulation of subcellular localization of Glut4 in adipocytes.

1996 ◽  
Vol 16 (12) ◽  
pp. 6879-6886 ◽  
Author(s):  
M Cormont ◽  
M N Bortoluzzi ◽  
N Gautier ◽  
M Mari ◽  
E van Obberghen ◽  
...  
Keyword(s):  
Cell Surface ◽  
Subcellular Distribution ◽  
Potential Role ◽  
Glucose Transporter ◽  
Small Gtpase ◽  
Wild Type ◽  
Transfected Cells ◽  
Isolated Adipocytes ◽  
Glucose Transporter Glut4

A role for Rab4 in the translocation of the glucose transporter Glut4 induced by insulin has been recently proposed. To study more directly the role of this small GTPase, freshly isolated adipocytes were transiently transfected with the cDNAs of both an epitope-tagged Glut4-myc and Rab4, a system which allows direct measurement of the concentration of Glut4 molecules at the cell surface. When cells were cotransfected with Glut4-myc and Rab4, the concentration of Glut4-myc at the cell surface decreased in parallel with the increased expression of Rab4, suggesting that Rab4 participates in the intracellular retention of Glut4. In parallel, the amount of Rab4 associated with the Glut4-containing vesicles increased. When Rab4 was moderately overexpressed, the number of Glut4-myc molecules recruited to the cell surface in response to insulin was similar to that observed in mock-transfected cells, and thus the insulin efficiency was increased. When Rab4 was expressed at a higher level, the amount of Glut4-myc present at the cell surface in response to insulin decreased. Since the overexpressed protein was predominantly cytosolic, this suggests that the cytosolic Rab4 might complex some factor(s) necessary for insulin action. This hypothesis was strengthened by the fact that Rab4 deltaCT, a Rab4 mutant lacking the geranylgeranylation sites, inhibited insulin-induced recruitement of Glut4-myc to the cell surface, even when moderately overexpressed. Rab3D was without effect on Glut4-myc subcellular distribution in basal or insulin-stimulated conditions. While two mutated proteins unable to bind GTP did not decrease the number of Glut4-myc molecules in basal or insulin-stimulated conditions at the plasma membrane, the behavior of a mutated Rab4 protein without GTPase activity was similar to that of the wild-type Rab4 protein, indicating that GTP binding but not its hydrolysis was required for the observed effects. Altogether, our results suggest that Rab4, but not Rab3D, participates in the molecular mechanism involved in the subcellular distribution of the Glut4 molecules both in basal and in insulin-stimulated conditions in adipocytes.

scholarly journals Cell-surface expression of RhD blood group polypeptide is posttranscriptionally regulated by the RhAG glycoprotein

Blood ◽  
2002 ◽  
Vol 100 (3) ◽  
pp. 1038-1047 ◽  
Author(s):  
Isabelle Mouro-Chanteloup ◽  
Anne Marie D'Ambrosio ◽  
Pierre Gane ◽  
Caroline Le Van Kim ◽  
Virginie Raynal ◽  
...  
Keyword(s):  
Cell Surface ◽  
K562 Cells ◽  
Surface Expression ◽  
Hek293 Cells ◽  
Expression Vectors ◽  
Cell Surface Expression ◽  
Membrane Expression ◽  
Cmv Promoter ◽  
Transfected Cells

Abstract In most cases, the lack of Rh in Rhnull red cells is associated with RHAG gene mutations. We explored the role of RhAG in the surface expression of Rh. Nonerythroid HEK293 cells, which lack Rh and RhAG, or erythroid K562 cells, which endogenously express RhAG but not Rh, were transfected with RhD and/or RhAG cDNAs using cytomegalovirus (CMV) promoter–based expression vectors. In HEK293 cells, a low but significant expression of RhD was obtained only when RhAG was expressed at a high level. In K562 cells, as expected from the opposite effects of the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA) on erythroid and CMV promoters, the levels of endogenous RhAG and recombinant RhD transcripts were substantially decreased and enhanced upon TPA treatment of RhD-transfected cells (K562/RhD), respectively. However, flow cytometry and fluorescence microscopy analysis revealed a decreased cell-surface expression of both RhAG and RhD proteins. Conversely, TPA treatment of RhAG-transfected cells increased both the transcript and surface expression levels of RhAG. When K562/RhD cells were cotransfected by the RhAG cDNA, the TPA-mediated induction of recombinant RhAG and RhD transcription was associated with an increased membrane expression of both RhAG and RhD proteins. These results demonstrate the role of RhAG as a strictly required posttranscriptional factor regulating Rh membrane expression. In addition, because the postulated 2:2 stoichiometry between Rh and RhAG observed in the native red cell membrane could not be obtained in cotransfected K562 cells, our study also suggests that as yet unidentified protein(s) might be involved for optimal membrane expression of Rh.

A novel role for alpha 3 beta 1 integrins in extracellular matrix assembly

1995 ◽  
Vol 108 (6) ◽  
pp. 2511-2523 ◽  
Author(s):  
C. Wu ◽  
A.E. Chung ◽  
J.A. McDonald
Keyword(s):  
Extracellular Matrix ◽  
Cell Adhesion ◽  
Binding Activity ◽  
Integrin Subunit ◽  
Pericellular Matrix ◽  
Matrix Assembly ◽  
Amino Terminal ◽  
Beta 1 Integrin ◽  
Fibronectin Deposition

To study the biological role of alpha 3 beta 1 integrins in cell adhesion, migration, and in the deposition of extracellular matrix, we stably expressed the human alpha 3 integrin subunit in the alpha 4, alpha 5 integrin deficient CHO cell line B2. The expression of alpha 3 beta 1 integrins enhanced cell adhesion on entactin (also known as nidogen), but not on fibronectin. Using recombinant GST-fusion proteins that span the entire length of the entactin molecule, we located cell adhesive activity to the G2 domain of entactin. These results suggest that the alpha 3 beta 1 integrin functions as an adhesion receptor interacting with the G2 domain of entactin. On the other hand, the expression of alpha 3 beta 1 integrins did not confer the ability to migrate on entactin. Strikingly, the expression of alpha 3 beta 1 dramatically increased the deposition of entactin and fibronectin into the pericellular matrix. This was accompanied by increased binding activity of the 29 kDa amino-terminal domain of fibronectin. Thus, similar to alpha 5 beta 1 integrins, alpha 3 beta 1 integrins can play an important role in modulating the assembly of pericellular matrices. However, unlike fibronectin deposition supported by alpha 5 beta 1, alpha 3 beta 1 supported fibronectin deposition into pericellular matrix was not inhibited by antibodies binding to the RGD containing cell adhesion domain of fibronectin, demonstrating that the two processes are mechanistically distinct. The role of alpha 3 beta 1 in pericellular matrix assembly potentially implicates this receptor in the assembly and/or recognition of entactin-containing pericellular matrices, an observation consistent with its apparent role in the renal glomerulus of the mammalian kidney.

Loss of MDCK cell alpha 2 beta 1 integrin expression results in reduced cyst formation, failure of hepatocyte growth factor/scatter factor-induced branching morphogenesis, and increased apoptosis

1995 ◽  
Vol 108 (11) ◽  
pp. 3531-3540 ◽  
Author(s):  
E.U. Saelman ◽  
P.J. Keely ◽  
S.A. Santoro
Keyword(s):  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Antisense Rna ◽  
Mdck Cells ◽  
Cyst Formation ◽  
Branching Morphogenesis ◽  
Integrin Subunit ◽  
Scatter Factor ◽  
Beta 1 Integrin ◽  
Hepatocyte Growth

Cellular interactions with collagen in a model of kidney tubulogenesis were investigated using Madin-Darby canine kidney (MDCK) cells in an in vitro morphogenetic system. MDCK cells adhered to collagen types I and IV in a Mg(2+)-dependent manner, typical of the alpha 2 beta 1 integrin. Collagen-Sepharose affinity chromatography and immunoblotting demonstrated the presence and collagen binding activity of the alpha 2 beta 1 integrin on MDCK cells. To assess the function of alpha 2 beta 1 integrin, MDCK cells were transfected with a plasmid pRSV alpha 2′ which allowed the expression of alpha 2-integrin subunit antisense RNA. Three G418-resistant clones showing reduced adhesion to collagen, stable genomic integration of the antisense construct, decreased alpha 2-integrin subunit mRNA and decreased alpha 2-integrin subunit protein expression were selected for analysis in morphogenetic experiments. MDCK cells and plasmid-only control transfectants, cultured in three-dimensional collagen type I gels, showed normal cyst formation, whereas the antisense RNA transfectants showed increased apoptosis and formed small rudimentary cysts. Stimulation with hepatocyte growth factor/scatter factor-containing 3T3 fibroblast-conditioned medium or recombinant hepatocyte growth factor/scatter factor resulted in extensive branching of the preformed control cysts whereas the surviving small cysts formed by antisense expressing cells increased in size but failed to elongate and branch upon stimulation. We conclude that alpha 2 beta 1 integrin collagen interactions play a crucial role in the hepatocyte growth factor/scatter factor-induced tubulogenesis and branching morphogenesis of MDCK cells in collagen gels as well as an important role in cell survival.

scholarly journals Integrin recognition of different cell-binding fragments of laminin (P1, E3, E8) and evidence that alpha 6 beta 1 but not alpha 6 beta 4 functions as a major receptor for fragment E8.

1990 ◽  
Vol 110 (6) ◽  
pp. 2145-2155 ◽  
Author(s):  
A Sonnenberg ◽  
C J Linders ◽  
P W Modderman ◽  
C H Damsky ◽  
M Aumailley ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Cell Types ◽  
Integrin Subunit ◽  
Integrin Receptors ◽  
Cell Binding ◽  
Vitronectin Receptor ◽  
Beta 1 Integrin ◽  
Integrin Alpha 6 ◽  
Alpha V Beta 3 ◽  
Integrin Family

The involvement of integrins in mediating interaction of cells to well-characterized proteolytic fragments (P1, E3, and E8) of laminin was assessed by antibody blocking studies. Cell adhesion to fragment P1 was affected by mAbs against the integrin beta 1 and beta 3 subunits and furthermore could be prevented completely by a synthetic peptide containing the Arg-Gly-Asp sequence. Because the beta 3 antibody-sensitive cell lines expressed the vitronectin receptor (alpha v beta 3) at high levels, the involvement of this receptor in cell adhesion to P1 is strongly suggested. Integrin-mediated cell adhesion to E3 is of low affinity and was inhibited by antibodies against the integrin beta 1 subunit. In contrast, adhesion of some cell types to E3 was not or only partially sensitive to inhibition by anti-integrin subunit antibodies. Cell adhesion to E8 was blocked completed by integrin alpha 6 or beta 1 antibodies. The alpha 6-specific antibody did not inhibit cell adhesion to E3 or P1. Furthermore, the antibody only blocked adhesion to laminin of those cells that adhered exclusively to the E8 fragment. In addition, expression of alpha 6 beta 1 was closely correlated with the ability of cells to bind to the E8 fragment of laminin. These results indicate that the alpha 6 beta 1 integrin is a specific receptor for the E8 fragment of laminin. Many cell types expressed, instead of or in addition to alpha 6 beta 1 the recently described integrin alpha 6 beta 4. Although the ligand of alpha 6 beta 4 was not identified, it must be different from that of alpha 6 beta 1, because cells that express alpha 6 beta 4, but not alpha 6 beta 1, do not adhere to E8, and cell adhesion to E8 was specifically blocked by beta 1 specific antibodies. In conclusion, the data indicate that distinct integrin receptors belonging to the beta 1 or beta 3 subfamily are involved in adhesion of cells to the various laminin fragments. Adhesion to E3 may also be brought about by other receptor molecules, possibly proteoglycans, not belonging to the integrin family.

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