title: Characterization of the interaction of Aha1 with components of the Hsp90 chaperone machine and client proteins.
abstract: The activator of Hsp90 ATPase, Aha1, is an Hsp90 co-chaperone that has been suggested to act as a general stimulator of Hsp90 function. In this report, we have characterized the interaction of Aha1 with Hsp90 and its co-chaperones in rabbit reticulocyte lysate (RRL) and in HeLa cell extracts. Complexes formed by Aha1 with Hsp90 in RRL were stabilized by molybdate and contained the co-chaperones FKBP52 and p23/Sba1, but lacked HOP/Sti1 and Cdc37. Aha1 complexes isolated from HeLa cell extracts also contained Hsp70 and DNAJA1. Over-expression of Aha1 has been reported to stimulate the activity of v-Src and steroid hormone receptors ectopically expressed in yeast, however, no interaction between Aha1 and nascent v-Src or the progesterone receptor could be detected in RRL. Contrary to expectations, over-expression of Aha1 also inhibited the rate of Hsp90-dependent refolding of denatured luciferase. A number of potential client proteins that specifically associated with Aha1 were identified by liquid chromatography/ tandem mass spectrometry (LC-MS/MS) and verified by Western blotting. The proteins identified suggest that Aha1 may play roles in modulating RNA splicing and DNA repair, in addition to other cellular processes.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Sun
authors.forename: Thomas
authors.initials: T
authors.lastname: Prince
authors.forename: Jacob R
authors.initials: JR
authors.lastname: Manjarrez
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Scroggins
authors.forename: Robert L
authors.initials: RL
authors.lastname: Matts
mesh_terms: D000818:Animals; D002457:Cell Extracts; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D011485:Protein Binding; D020673:Protein Renaturation; D011817:Rabbits; D011980:Receptors, Progesterone / Q000378:metabolism
chemical_list: C515652:AHSA1 protein, human; D002457:Cell Extracts; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D011980:Receptors, Progesterone; D008156:Luciferases; D015688:Oncogene Protein pp60(v-src)