PMID:23975754

Citation	Kharenko, OA, Polichuk, D, Nelson, KM, Abrams, SR and Loewen, MC (2013) Identification and characterization of interactions between abscisic acid and human heat shock protein 70 family members. J. Biochem. 154:383-391
Abstract	Abscisic acid (ABA) is a stress-inducible plant hormone comprising an inevitable component of the human diet. Recently, stress-induced accumulation of autocrine ABA was shown in humans, as well as ABA-mediated modulation of a number of disease-associated systems. Now, the application of a chemical proteomics approach to gain further insight into ABA mechanisms of action in mammalian cells is reported. An ABA mimetic photoaffinity probe was applied to intact mammalian insulinoma and embryonic cells, leading to the identification of heat shock protein 70 (HSP70) family members, (including GRP78 and HSP70-2) as putative human ABA-binding proteins. In vitro characterization of the ABA-HSP70 interactions yielded Kds in the 20-60 µM range, which decreased several fold in the presence of co-chaperone. However, ABA was found to have only variable- and co-chaperone-independent effects on the ATPase activity of these proteins. The potential implications of these ABA-HSP70 interactions are discussed with respect to the intracellular protein folding and extracellular receptor-like activities of these stress-inducible proteins. While mechanistic and functional relevance remain enigmatic, we conclude that ABA can bind to human HSP70 family members with physiologically relevant affinities and in a co-chaperone-dependent manner.
Links	PubMed Online version:10.1093/jb/mvt067
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:HSP71		GO:0016887: ATPase activity	IDA: Inferred from Direct Assay:	F	Fig. 6	complete CACAO 8862
HUMAN:DJB12		GO:0031072: heat shock protein binding	ECO:0000314:		F		Fig. 5 DnaJ activates ABA binding to HSP70-2	complete CACAO 8867
HUMAN:BIP		GO:0016887: ATPase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Fig. 6	complete CACAO 8861

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