title: Calreticulin associates with stress proteins: implications for chaperone function during heat stress.
abstract: Acute heat stress leads to the glycosylation of a "prompt" stress glycoprotein, P-SG67/64, identified as calreticulin. In the present study, we used immunoprecipitation to investigate the interactions of P-SG/calreticulin with other proteins during cellular recovery from heat stress. In heat-stressed CHO and M21 cells, both glycosylated and unglycosylated P-SGs interact with HSP90, GRP94, GRP78, and the other prompt stress glycoprotein, P-SG50, in an ATP-independent manner. Specificity of HSP-P-SG interactions was determined by chemical cross-linking with the homo-bifunctional agent DSP (3,3'-dithiobis[succinimidyl propionate]). Characterization of the cross-linked complexes involving calreticulin and heat shock proteins (HSPs) showed an average mass of 400-600 kDa by gel filtration chromatography. Overall, the consistent association of glycosylated and unglycosylated calreticulin with P-SG50 and unglycosylated HSPs suggests that P-SG/calreticulin is an active member of the cast of glycone/aglycone chaperones that cooperate to achieve cellular recovery from acute heat stress.
authors.affiliation: Department of Medicine, University of Arkansas for Medical Sciences, Little Rock 72205, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Jethmalani
authors.forename: K J
authors.initials: KJ
authors.lastname: Henle
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D037282:Calreticulin; D002460:Cell Line; D002850:Chromatography, Gel; D006224:Cricetinae; D003432:Cross-Linking Reagents; D019084:Fluorescent Antibody Technique, Indirect; D006031:Glycosylation; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D018832:Molecular Chaperones / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D051381:Rats; D012261:Ribonucleoproteins / Q000302:isolation & purification / Q000378:metabolism*; D013388:Succinimides
chemical_list: D002135:Calcium-Binding Proteins; D037282:Calreticulin; D003432:Cross-Linking Reagents; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D012261:Ribonucleoproteins; D013388:Succinimides; D000255:Adenosine Triphosphate; C011240:dithiobis(succinimidylpropionate)