Identification and characterization of Harc, a novel Hsp90-associating relative of Cdc37 - PubMed (original) (raw)

. 2001 Aug 17;276(33):30971-9.

doi: 10.1074/jbc.M103889200. Epub 2001 Jun 18.

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Identification and characterization of Harc, a novel Hsp90-associating relative of Cdc37

G M Scholz et al. J Biol Chem. 2001.

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Abstract

Although little is known about the precise mechanisms by which the molecular chaperone Hsp90 recognizes its client proteins, Cdc37 has been shown to play a critical role in the targeting of Hsp90 to client protein kinases. Described here is the identification and characterization of a novel 35-kDa human protein that is 31% identical to Cdc37. We have named this novel protein Harc (Hsp90-associating relative of Cdc37). Northern blot analysis revealed the presence of Harc mRNA in several human tissues, including liver, skeletal muscle, and kidney. Biochemical fractionation and immunofluorescent localization of epitope-tagged Harc (i.e. FLAG-Harc) indicated that it is present in the cytoplasm of cells. FLAG-Harc binds Hsp90 but unlike Cdc37 does not bind Src family kinases or Raf-1. Mapping experiments indicate that the central 120 amino acids of both Harc and Cdc37 constitute a Hsp90-binding domain not described previously. FLAG-Harc is basally serine-phosphorylated and hyperphosphorylated when co-expressed with an activated mutant of the Src family kinase Hck. Notably, FLAG-Harc forms complexes with Hsp90, Hsp70, p60Hop, immunophilins, and an unidentified p22 protein but not with the Hsp90 co-chaperone p23. Thus Harc likely represents a novel participant in Hsp90-mediated protein folding, potentially targeting Hsp90 to Hsp70-client protein heterocomplexes.

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