Changes in cytosolic Ca2+ levels regulate Bcl-xS and Bcl-xL expression in spermatogenic cells during apoptotic death

J Biol Chem. 2006 Jan 27;281(4):2133-43. doi: 10.1074/jbc.M508648200. Epub 2005 Nov 21.

Abstract

Bcl-x exists in two isoforms, the anti-apoptotic form Bcl-xL and the proapoptotic form Bcl-xS. The critical balance between the two forms appears to be important for cell survival; however, it is still not clear exactly how the vital balance is maintained. Using an in vitro spermatogenic cell apoptosis model, this study provides a new insight into the possible role of Ca2+ in regulating the Bcl-xS and Bcl-xL expression. 2,5-Hexanedione, a metabolite of the common industrial solvent n-hexane, caused a significant increase in reactive oxygen species followed by an enhancement of intracellular Ca2+ through the T-type Ca2+ channels. Consequent to the above changes, expression of Bcl-xS increased with a concomitant drop in Bcl-xL expression, thus altering the ratio of the two proteins. Impediment of Ca2+ influx by using a T-type Ca2+ channel blocker pimozide resulted in a decrease in Bcl-xS and an increase in Bcl-xL expression. This caused prevention of mitochondrial potential loss, reduction of caspase-3 activity, inhibition of DNA fragmentation, and increase in cell survival. Alternatively, Ca2+ ionophores caused an increase of Bcl-xS encoding isoform over the Bcl-xL-encoding isoform. Therefore, this study proposes a role for Ca2+ in regulation of Bcl-xS and Bcl-xL expression and ultimately cell fate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Alternative Splicing
  • Animals
  • Annexin A5 / chemistry
  • Apoptosis*
  • Blotting, Western
  • Calcium / chemistry
  • Calcium / metabolism
  • Calcium Channels / chemistry
  • Caspase 3
  • Caspase 9
  • Caspases / metabolism
  • Cell Survival
  • Cytosol / metabolism*
  • DNA Fragmentation
  • Electrophoresis, Polyacrylamide Gel
  • Flow Cytometry
  • Hexanes / chemistry
  • Hexanones / chemistry
  • Hexanones / pharmacology
  • Immunohistochemistry
  • In Situ Nick-End Labeling
  • Ionophores / chemistry
  • Male
  • Membrane Potentials
  • Mitochondria / metabolism
  • Phosphatidylserines / chemistry
  • Pimozide / pharmacology
  • Protein Isoforms
  • Rats
  • Rats, Wistar
  • Reactive Oxygen Species
  • Solvents / chemistry
  • Spermatogenesis
  • Spermatozoa / metabolism*
  • Time Factors
  • bcl-X Protein / chemistry*
  • bcl-X Protein / metabolism

Substances

  • Annexin A5
  • Calcium Channels
  • Hexanes
  • Hexanones
  • Ionophores
  • Phosphatidylserines
  • Protein Isoforms
  • Reactive Oxygen Species
  • Solvents
  • bcl-X Protein
  • Pimozide
  • Adenosine Triphosphate
  • 2,5-hexanedione
  • Casp3 protein, rat
  • Casp9 protein, rat
  • Caspase 3
  • Caspase 9
  • Caspases
  • Calcium