CALRETICULIN ASSOCIATES WITH STRESS PROTEINS - IMPLICATIONS FOR CHAPERONE FUNCTION DURING HEAT-STRESS

Acute heat stress leads to the glycosylation of a ''prompt'' stress gl ycoprotein, P-SG67/64, identified as calreticulin. In the present stud y, we used immunoprecipitation to investigate the interactions of P-SG /calreticulin with other proteins during cellular recovery from heat s tress. In hear-stressed CHO and M21 cells, both glycosylated and ungly cosylated P-SGs interact with HSP90, GRP94, GRP78, and the other promp t stress glycoprotein, P-SC50, in an ATP-independent manner. Specifici ty of HSP-P-SG interactions was determined by chemical cross-linking w ith the homo-bifunctional agent DSP (3,3'-dithiobis[succinimidyl propi onate]). Characterization of the cross-linked complexes involving calr eticulin and hear shock proteins (HSPs) showed an average mass of 400- 600 kDa by gel filtration chromatography. Overall, the consistent asso ciation of glycosylated and unglycosylated calreticulin with P-SG50 an d unglycosylated HSPs suggests that P-SG/calreticulin is an active mem ber of the cast of glycone/aglycone chaperones that cooperate to achie ve cellular recovery from acute heal stress. (C) 1998 Wiley-Liss, Inc.