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The role of the cysteine residue in the chaperone and anti‐apoptotic functions of human Hsp27
Author(s) -
Pasupuleti NagaRekha,
Gangadhariah Mahesha,
Padmanabha Smitha,
Santhoshkumar Puttur,
Nagaraj Ram H.
Publication year - 2010
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.22552
Subject(s) - hsp27 , cysteine , staurosporine , heat shock protein , chaperone (clinical) , mutant , apoptosis , biochemistry , chemistry , wild type , microbiology and biotechnology , biology , hsp70 , phosphorylation , protein kinase a , enzyme , pathology , gene , medicine
The small heat shock protein Hsp27 is a molecular chaperone and an anti‐apoptotic protein. Human Hsp27 has one cysteine residue at position 137. We investigated the role of this cysteine residue in the chaperone and anti‐apoptotic functions of Hsp27 by mutating the cysteine residue to an alanine (Hsp27 C137A ) and comparing it to wild‐type protein (Hsp27 WT ). Both proteins were multi‐subunit oligomers, but subunits of Hsp27 WT were disulfide‐linked unlike those of Hsp27 C137A , which were monomeric. Hsp27 C137A was indistinguishable from Hsp27 WT with regard to its secondary structure, surface hydrophobicity, oligomeric size and chaperone function. S‐thiolation and reductive methylation of the cysteine residue had no apparent effect on the chaperone function of Hsp27 WT . The anti‐apoptotic function of Hsp27 C137A and Hsp27 WT was studied by overexpressing them in CHO cells. No difference in the caspase‐3 or ‐9 activity was observed in staurosporine‐treated cells. The rate of apoptosis between Hsp27 C137A and Hsp27 WT overexpressing cells was similar whether the cells were treated with staurosporine or etoposide. However, the mutant protein was less protective relative to the wild‐type protein in preventing caspase‐3 and caspase‐9 activation and apoptosis induced by 1 mM H 2 O 2 in CHO and HeLa cells. These data demonstrate that in human Hsp27, disulfide formation by the lone cysteine does not affect its chaperone function and anti‐apoptotic function against chemical toxicants. However, oxidation of the lone cysteine in Hsp27 might at least partially affect the anti‐apoptotic function against oxidative stress. J. Cell. Biochem. 110: 408–419, 2010. © 2010 Wiley‐Liss, Inc.