Expression of αB-crystallin overrides the anti-apoptotic activity of XIAP

Neuro Oncol. 2012 Nov;14(11):1332-45. doi: 10.1093/neuonc/nos247. Epub 2012 Oct 16.


Although crystallins are major structural proteins in the lens, α-crystallins perform non-lens functions, and αB-crystallin has been shown to act as an anti-apoptotic mediator in various cells. The present study was undertaken to examine whether αB-crystallin expressed in human malignant glioma cells exerts anti-apoptotic activity. In addition, we sought to elucidate the mechanism underlying any observed anti-apoptotic function of αB-crystallin in these cells. Three glioma cell lines, U373MG, U118MG, and T98G, were used. We observed that only the U373MG cell line expresses αB-crystallin, whereas the other 2 glioma cell lines, U118MG and T98G, demonstrated no endogenous expression of αB-crystallin. We next observed that the silencing of αB-crystallin sensitized U373MG cells to suberoylanilide hydroxamic acid (SAHA)-induced apoptosis and that αB-crystallin associates with caspase-3 and XIAP. Because XIAP is the most potent suppressor of mammalian apoptosis through the direct binding with caspases, we assessed whether XIAP also plays an anti-apoptotic role in SAHA-induced apoptosis in αB-crystallin-expressing U373MG cells. Of note, the silencing of XIAP did not alter the amount of cell death induced by SAHA, indicating that XIAP does not exert an anti-apoptotic activity in U373MG cells. We then determined whether the ectopic expression of αB-crystallin in glioma cells caused a loss of the anti-apoptotic activity of XIAP. Accordingly, we established 2 αB-crystallin over-expressing glioma cell lines, U118MG and T98G, and found that the silencing of XIAP did not sensitize these cells to SAHA-induced apoptosis. These findings suggest that αB-crystallin expressed in glioma cells overrides the anti-apoptotic activity exerted by XIAP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / physiology*
  • Blotting, Western
  • Cell Line, Tumor
  • Flow Cytometry
  • Glioma / metabolism*
  • Humans
  • Immunohistochemistry
  • Immunoprecipitation
  • Microscopy, Confocal
  • RNA, Small Interfering
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection
  • X-Linked Inhibitor of Apoptosis Protein / metabolism*
  • alpha-Crystallin B Chain / metabolism*


  • CRYAB protein, human
  • RNA, Small Interfering
  • X-Linked Inhibitor of Apoptosis Protein
  • alpha-Crystallin B Chain