Evidence that beta(1) integrins in keratinocyte cell-cell junctions are not in the ligand-occupied conformation

[摘要] Integrins are a family of heterodimeric cell surface molecules that function as adhesion receptors in cell-cell and cell-extracellular matrix contact, Integrins of the beta(1) family are found on keratinocytes clustered at sites of cell-cell junctions both in culture and in normal skin, The possibility that these integrins function in cell-cell adhesion has been both supported and refuted in recent conflicting publications, Rather than testing further for the presence or absence of an interaction, we present evidence to show that beta(1) integrins in keratinocyte cell-cell junctions are in the non-ligand-occupied conformation, We transfected keratinocytes with a construct that expresses a chimeric cell surface molecule containing the integrin beta(1) cytoplasmic tail, This chimera is thought to mimic the ligand-occupied receptor and has previously been shown to be actively localized to focal adhesions in fibroblasts. We find that keratinocytes are also able to localize this chimera in focal adhesions but do not localize it to areas of cell-cell junctions, A monoclonal anti-beta(1) antibody that has been previously shown to preferentially recognize ligand-occupied beta(1) receptors was used to stain keratinocytes, This antibody showed staining of focal adhesions, with little or no staining of cell-cell junctions, In contrast, four other anti-beta(1) antibodies showed strong, preferential staining at cell-cell junctions, Double staining confirmed that both the conformation-specific monoclonal antibody and a pan-beta(1) antibody were capable of recognizing the same focal adhesions, Taken together, these data indicate that integrins in cell-cell junctions of keratinocytes are in the non-ligand-occupied conformation, Although we do not directly prove the absence of an integrin-integrin interaction at this site, we show that any such interaction does not induce the ligand-occupied conformation and, therefore, is less likely to play a major role in cytoskeletal re-organization or signal transduction.

[发布日期] 1997-06-01

[关键词] focal adhesions;signal transduction;protein conformation