title: Heat stress-induced localization of small heat shock proteins in mouse myoblasts: intranuclear lamin A/C speckles as target for alphaB-crystallin and Hsp25.
abstract: We examined the effect of heat stress on localization of two sHsps, alphaB-crystallin and Hsp25, and of Hsc70, a member of a different class of heat shock proteins (Hsps), in both undifferentiated and differentiated mouse C2C12 cells. Under normal conditions, alphaB-crystallin and Hsp25 are found in the cytoplasm; only alphaB-crystallin is also found in the nucleus, distributed in a speckled pattern. Hsc70 is found to be homogeneously distributed throughout the cell. On heat stress, all these proteins translocate almost entirely into the nucleus and upon recovery relocate to the cytoplasm. Dual staining experiments using C2C12 myoblasts show that alphaB-crystallin and Hsp25, but not Hsc70, colocalize with the intranuclear lamin A/C and the splicing factor SC-35, suggesting interactions of sHsps and intranuclear lamin A/C. Interestingly, none of these proteins are found in the myotube nuclei. Upon heat stress, only Hsc70 translocates into the myotube nuclei. This differential entry of alphaB-crystallin and Hsp25 into the nuclei of myoblasts and myotubes upon heat stress may have functional role in the development and/or in the maintenance of muscle cells. Our study therefore suggests that these sHsps may be a part of the intranuclear lamin A/C network or stabilizing this specific network.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad AP 500 007, India.
authors.forename: Amit S
authors.initials: AS
authors.lastname: Adhikari
authors.forename: K
authors.initials: K
authors.lastname: Sridhar Rao
authors.forename: Nandini
authors.initials: N
authors.lastname: Rangaraj
authors.forename: Veena K
authors.initials: VK
authors.lastname: Parnaik
authors.forename: Ch
authors.initials: Ch
authors.lastname: Mohan Rao
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018882:Heat Stress Disorders; D006360:Heat-Shock Proteins / Q000378:metabolism; D034904:Lamin Type A / Q000378:metabolism*; D051379:Mice; D018832:Molecular Chaperones; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D021381:Protein Transport; D012261:Ribonucleoproteins / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D038203:alpha-Crystallin B Chain / Q000378:metabolism*
chemical_list: D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C486113:Hsbp1 protein, mouse; C494372:Hspa8 protein, mouse; D034904:Lamin Type A; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D012261:Ribonucleoproteins; C499372:SRSF2 protein, mouse; D038203:alpha-Crystallin B Chain; C440308:lamin C; D000068103:Serine-Arginine Splicing Factors