Dimer-monomer equilibrium of human HSP27 is influenced by the in-cell macromolecular crowding environment and is controlled by fatty acids and heat

Publication date: Available online 7 April 2018 Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics Author(s): Satoshi B. Sato, Miwa Sugiura, Tatsuo Kurihara Small heat shock protein 27 (HSP27) is an essential element of the proteostasis network in human cells. The HSP27 monomer coexists with the dimer, which can bind unfolded client proteins. Here, we evaluated the in-cell dimer-monomer equilibrium and its relevance to the binding of client proteins in a normal human vascular endothelial cell line. When cells were treated with a membrane-permeable crosslinker, the protein existed primarily as a free monomer (27 kDa) with a markedly smaller percentage of dimer (54 kDa), hetero-conjugates, and minor smear-like bands. When the protein was crosslinked in a cell-free lysate, two of the hetero-conjugates that were crosslinked in live cells were also detected, but the dimer and other complexes were absent. However, when cells were pretreated with fatty acid (FA) and/or heat (42.5 °C), dissociation of the dimer was selectively prevented and two types of covalently linked dimers were increased. These changes occurred most prominently in cells treated with docosahexaenoic acid (DHA) and heat, which appeared to intensify the heat resistance of the cell. Both the formation of covalently linked dimers and heat resistance were prevented by N-acetylcysteine. By contrast, nearly all of the free monomers in the lysate converted to disulfide bond-linked dimers by ...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research