Distribution, phosphorylation, and activities of Hsp25 in heat-stressed H9c2 myoblasts: a functional link to cytoprotection

The behavior of the endogenous heat shock protein 25 (Hsp25) in heat-stressed rat H9c2 myoblasts was studied. After mild or severe heating, this protein became less extractable with Triton X-100 and displayed characteristic immunofluorescence patterns, namely (1) granules in the nucleus, and (2) ass...

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Published in:	Cell stress & chaperones Vol. 7; no. 2; pp. 146 - 155
Main Authors:	Bryantsev, Anton L., Loktionova, Svetlana A., Ilyinskaya, Olga P., Tararak, Eduard M., Kampinga, Harm H., Kabakov, Alexander E.
Format:	Journal Article
Language:	English
Published:	Netherlands Cell Stress Society International 01-04-2002
Subjects:	Actins Animals Cell lines Cell nucleus Cell Nucleus - metabolism Cell Survival Cytochalasins Cytoskeleton - metabolism Endothelial cells Heat shock proteins Hot Temperature HSP27 Heat-Shock Proteins Imidazoles - metabolism Microfilaments Mitogen-Activated Protein Kinases - antagonists & inhibitors Mitogen-Activated Protein Kinases - metabolism Myoblasts - metabolism Neoplasm Proteins - metabolism Original Original s p38 Mitogen-Activated Protein Kinases Phosphorylation Protein isoforms Pyridines - metabolism Rats Shock heating
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Summary:	The behavior of the endogenous heat shock protein 25 (Hsp25) in heat-stressed rat H9c2 myoblasts was studied. After mild or severe heating, this protein became less extractable with Triton X-100 and displayed characteristic immunofluorescence patterns, namely (1) granules in the nucleus, and (2) association with F-actin bundles in the cytoplasm. The intranuclear granulation of Hsp25 and its association with F-actin were sensitive to drugs affecting Hsp25 phosphorylation (cantharidin, sodium orthovanadate, SB203580, SB202190). Isoform analysis of Hsp25 translocated to the nucleus-free cytoskeletal fraction revealed only mono- and biphosphorylated Hsp25 and no unphosphorylated Hsp25. Transfected luciferase with initial localization in the nucleosol became colocalized with the Hsp25-containing granules after a heat shock treatment that denatured the enzyme in the cells. The association of Hsp25 with actin filaments after a mild heat stress conferred protection from subsequent F-actin–damaging treatments with cytochalasins (D and B) or severe heat stress. We hypothesize that (1) the binding of heat-denatured nucleosolic proteins to the Hsp25 contained in specific granular structures may serve for the subsequent chaperoning or degradation of the bound proteins, and (2) the actin cytoskeleton is stabilized by the direct targeting of phosphorylated Hsp25 to microfilament bundles.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Correspondence to: Anton L. Bryantsev, Tel: 7 095 414-6778; Fax: 7 095 414-6659; cardiocell@cardio.ru
ISSN:	1355-8145 1466-1268
DOI:	10.1379/1466-1268(2002)007<0146:DPAAOH>2.0.CO;2