Coprecipitation of heat shock proteins with a cell surface glycoprotein

Monoclonal antibodies recognizing a mouse cell surface glycoprotein of Mr 90,000 were found to coprecipitate the Mr 70,000 and 72,000 heat shock-induced proteins of NIH/3T3 cells. These two smaller proteins were among the most abundant components of heat-treated NIH/3T3 cells. The Mr 70,000 component was not detected in normal cells whereas there was a low rate of incorporation of [35S]methionine into the Mr 72,000 polypeptide in the absence of heat shock. Tryptic peptide mapping and two-dimensional gel electrophoresis indicated that the coprecipitated and heat shock-induced polypeptides were identical and that the Mr 70,000 and 72,000 components contained homologous peptides. Also, the heat shock proteins had extensive structural homology with a cytoskeleton-associated protein of HeLa cells. The results suggest that the Mr 90,000 cell surface glycoprotein and the Mr 70,000 and 72,000 heat shock-inducible proteins mediate an association between the plasma membrane and the cell cytoskeleton.