Association of αB-Crystallin, a Small Heat Shock Protein, with Actin: Role in Modulating Actin Filament Dynamics in Vivo

Bhairab N. Singh, K. Sridhar Rao, Tangirala Ramakrishna, Nandini Rangaraj, Ch Mohan Rao

Research output: Contribution to journalArticlepeer-review

96 Scopus citations

Abstract

Disruption of cytoskeletal assembly is one of the early effects of any stress that can ultimately lead to cell death. Stabilization of cytoskeletal assembly, therefore, is a critical event that regulates cell survival under stress. αB-crystallin, a small heat shock protein, has been shown to associate with cytoskeletal proteins under normal and stress conditions. Earlier reports suggest that αB-crystallin could prevent stress-induced aggregation of actin in vitro. However, the molecular mechanisms by which αB-crystallin stabilizes actin filaments in vivo are not known. Using the H9C2 rat cardiomyoblast cell line as a model system, we show that upon heat stress, αB-crystallin preferentially partitions from the soluble cytosolic fraction to the insoluble cytoskeletal protein-rich fraction. Confocal microscopic analysis shows that αB-crystallin associates with actin filaments during heat stress and the extent of association increases with time. Further, immunoprecipitation experiments show that αB-crystallin interacts directly with actin. Treatment of heat-stressed H9C2 cells with the actin depolymerzing agent, cytochalasin B, failed to disorganize actin. We show that this association of αB-crystallin with actin is dependent on its phosphorylation status, as treatment of cells with MAPK inhibitors SB202190 or PD98059 results in abrogation of this association. Our results indicate that αB-crystallin regulates actin filament dynamics in vivo and protects cells from stress-induced death. Further, our studies suggest that the association of αB-crystallin with actin helps maintenance of pinocytosis, a physiological function essential for survival of cells.

Original languageEnglish (US)
Pages (from-to)756-767
Number of pages12
JournalJournal of Molecular Biology
Volume366
Issue number3
DOIs
StatePublished - Feb 23 2007
Externally publishedYes

Bibliographical note

Funding Information:
We thank Dr C. C. Glembotski, San Diego State University, USA, for kindly providing us the plasmid for the 3A-αB-crystallin mutant. B.N.S. acknowledges the Council of Scientific and Industrial Research, New Delhi, India for the grant of a Senior Research Fellowship.

Keywords

  • actin
  • cytoskeletal stabilization
  • heat stress
  • pinocytosis
  • αB-crystallin

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