Proteins interacting with the molecular chaperone hsp70/hsc70: physical associations and effects on refolding activity

Abstract

We investigated several hsp70/hsc70 interacting proteins and established by two independent techniques that hsp40 and Hop/p60 specifically interact with the 257 residue carboxy-terminal domain of hsp70 while Hap-46 and Hip/p48 bind the 383 residue amino-terminal ATP binding domain. Hap-46 and Hip/p48 competed for binding to hsc70, while Hap-46 had no effect on the binding of either Hop/p60 or hsp40 to hsc70. Hap-46 inhibited the refolding of thermally denatured firefly luciferase in an hsc70 and hsp40 dependent assay, and this effect was largely compensated by Hop/p60. These interacting proteins thus appear to cooperate in affecting the chaperoning activity of hsp70/hsc70.

Characterization of Interactions between the Anti-apoptotic Protein BAG-1 and Hsc70 Molecular Chaperones

“…The minimum region in Hsc70 required for binding BAG-1 has been localized to amino acids 186 -377, which correspond to one of the subdomains of the ATPase domain (19). Similar observations have been made for binding of the human BAG-1 isoform, RAP46/Hap-46, to Hsp70, although it was suggested that in vitro, interactions occurred between RAP46/Hap-46 and both of the ATPase subdomains (42).…”

“…A protein called Hip/p48 also binds to the ATPase domain of Hsp70 (50,51) and competes with BAG-1 for binding to this molecular chaperone (21,42). 4 Interestingly, BAG-1 and Hip regulate Hsp70 activity in opposite manners: Hip stabilizes the ADP-bound form of Hsp70, promoting formation with target peptides (50), while BAG-1 stimulates the release of ADP and peptide substrates (21).…”

“…4 Interestingly, BAG-1 and Hip regulate Hsp70 activity in opposite manners: Hip stabilizes the ADP-bound form of Hsp70, promoting formation with target peptides (50), while BAG-1 stimulates the release of ADP and peptide substrates (21). The association of Hip with Hsc70 prevents BAG-1 binding (21) and vice versa (42). Do the two compete for the same binding site to conversely regulate chaperone activity?…”

Overlapping BXSB congenic intervals, in combination with microarray gene expression, reveal novel lupus candidate genes

“…We have identified by fold change analysis four genes potentially involved in nephritis (Table 4) 21 By contrast, SAM analysis identified a more limited set of nephritis-associated genes; only the underexpression of Als2cl (11038_at, chromosome 9, 113.7 Mb) was detected.…”

Heat shock cognate protein 70 chaperone-binding site in the co-chaperone murine stress-inducible protein 1 maps to within three consecutive tetratricopeptide repeat motifs

“…TPR domains of both mSTI1\Hop and Hip mediate their interactions with hsp70 [2,3,15,19,20]. However, these cochaperones do not share a common TPR acceptor site on hsp70 [21,22]. The proposed TPR acceptor sites for Hip and Hop are the N-terminal ATPase domain and C-terminal domain of hsp70 respectively, suggesting that their mechanism of protein recognition differs.…”