DT40 cells lacking the Ca2+-binding protein annexin 5 are resistant to Ca2+-dependent apoptosis.
Annexins are widely expressed Ca(2+)-dependent phospholipid-binding proteins with poorly understood physiological roles. Proposed functions include Ca(2+) channel activity and vesicle trafficking, but neither have been proven in vivo. Here we used targeted gene disruption to generate B-lymphocytes lacking annexin 5 (Anx5) expression and show that this results in reduced susceptibility to a range of apoptotic stimuli. By comparison B-lymphocytes lacking annexin 2 (Anx2) showed no such resistance, providing evidence that this effect is specific to loss of Anx5. The defect in the ANX5(-/-) cells occurs early in the apoptotic program before nuclear condensation, caspase 3 activation, and cell shrinkage, but downstream of an initial Ca(2+) influx. Only UVA/B irradiation induced similar levels of apoptosis in wild-type and ANX5(-/-) cells. Unexpectedly, ANX5(-/-) cells permeabilized in vitro also failed to release mitochondrial cytochrome C, suggesting a possible mechanism for their resistance to apoptosis. These findings demonstrate a role for Anx5 in determining the susceptibility of B-lymphocytes to apoptosis.
Hawkins
Timothy E
TE
Department of Physiology and Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Das
Debipriya
D
Young
Barry
B
Moss
Stephen E
SE
D000818:Animals; D017304:Annexin A5 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D048429:Cell Size; D002645:Chickens; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers; D005434:Flow Cytometry; D007425:Intracellular Membranes / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D016133:Polymerase Chain Reaction; D012995:Solubility
D017304:Annexin A5; D017931:DNA Primers; D002118:Calcium