Transient loss of alphaB-crystallin: an early cellular response to mechanical stretch

Biochem Biophys Res Commun. 1997 Jun 9;235(1):69-73. doi: 10.1006/bbrc.1997.6737.


Human trabecular meshwork (HTM) is distended and stretched with increases in intraocular pressure. During this stretching, there is a rearrangement of actin filaments. The HTM cells express alpha B-crystallin, a small heat shock protein that may have a role in the stabilization and regulation of the cytoskeleton in mammalian cells. The levels of alpha B-crystallin were examined in trabecular meshwork cells after mechanical stretch. Human TM primary cell cultures, plated onto silicone sheets, were subjected to a single 10% linear stretch and samples were prepared at various times after stretch for immunoblotting or Northern blotting. Immunoblots of total protein extracts with antibody specific for alpha B-crystallin detected a 26% decrease of cellular alpha B-crystallin levels within 2 minutes. After 1 hour alpha B-crystallin levels had decreased 90% compared to control cells. The levels of alpha B-crystallin began to recover in cells stretched for 2 hours and returned to initial levels by 24 hours. Northern blots probed with alpha B-crystallin exon III cDNA detected a transcript of 0.65 kb in human TM cells and the levels of the alpha B mRNA remained constant during alpha B-crystallin protein decrease. Later, levels of the 0.65 kb transcript of alpha B-crystallin increased during the cellular recovery. These results suggest that decreased levels of alpha B-crystallin after mechanical stretch were probably not due to transcriptional changes but rather to increased degradation of alpha B-crystallin protein. An increase in mRNA levels may play a role in the recovery of alpha B-crystallin during reorganization of the cytoskeleton and attachment to the substratum. These data raise the possibility of a specific proteolysis of alpha B-crystallin protein in cells after a physiological challenge.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Blotting, Northern
  • Blotting, Western
  • Cells, Cultured
  • Crystallins / genetics
  • Crystallins / metabolism*
  • Cytoskeleton / metabolism
  • Electrophoresis, Gel, Two-Dimensional
  • Gene Expression Regulation
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Humans
  • Isoelectric Focusing
  • Phosphorylation
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Stress, Mechanical
  • Trabecular Meshwork / cytology
  • Trabecular Meshwork / metabolism*
  • Transcription, Genetic


  • Crystallins
  • Heat-Shock Proteins
  • RNA, Messenger