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 ce ll-cell and cell-extracellular matrix interactions, Each integrin is a heterodimeric glycoprotein composed of an alpha and a beta subunit, W e now report the cDNA sequence and distribution of a new human integri n alpha subunit. This sequence is 78% identical to the previously repo rted chicken alpha(8) integrin sequence, Thus, we have designated this subunit as human alpha(8). By northern blot analysis, an alpha(8) pro be detects two mRNA species of approximately 6.5 and 4.0 kb in neurogl ioma H4 cells, An anti-alpha(8) polyclonal antibody precipitates a pro tein complex containing the beta(1) subunit associated with the putati ve alpha(8) subunit, which has an apparent molecular mass of 180 kDa ( non-reduced) or 155 kDa and 25 kDa (reduced), Immunohistochemistry wit h anti-alpha(8) polyclonal antibody in adult rat tissues shows promine nt staining in vascular and visceral smooth muscle, In addition, the a ntibody strongly stained kidney mesangial cells and a cell type in the alveolar wall of the lungs, most likely corresponding to alveolar myo fibroblasts, These results suggest that in adult mammalian tissues, al pha(8) is predominantly expressed in smooth muscle and smooth muscle-l ike contractile cells.