Tyrosine kinase-dependent activation of a chloride channel in CD95-induced apoptosis in T lymphocytes

Abstract

CD95͞Fas͞APO-1 mediated apoptosis is an important mechanism in the regulation of the immune response. Here, we show that CD95 receptor triggering activates an outwardly rectifying chloride channel (ORCC) in Jurkat T lymphocytes. Ceramide, a lipid metabolite synthesized upon CD95 receptor triggering, also induces activation of ORCC in cell-attached patch clamp experiments. Activation is mediated by Src-like tyrosine kinases, because it is abolished by the tyrosine kinase inhibitor herbimycin A or by genetic deficiency of p56lck. In vitro incubation of excised patches with purified p56lck results in activation of ORCC, which is partially reversed upon addition of anti-phosphotyrosine antibody. Inhibition of ORCC by four different drugs correlates with a 30-65% inhibition of apoptosis. Intracellular acidification observed upon CD95 triggering is abolished by inhibition of either ORCC or p56lck. The results suggest that tyrosine kinase-mediated activation of ORCC may play a role in CD95-induced cell death in T lymphocytes.

The tyrosine kinase Lck is involved in regulation of mitochondrial apoptosis pathways

“…This suggests that the modulation of calcium signals might be involved in the initial apoptotic phase. In addition, other ion fluxes were shown to be regulated by Lck in response to ceramide and CD95 crosslinking apoptotic stimuli (Gulbins et al, 1997;Szabo et al, 1998). The absence of Lck interferes with both, radiation and ceramide-induced apoptosis (Belka et al, 1999;.…”

Re-expression of Detachment-inducible Chloride Channel mCLCA5 Suppresses Growth of Metastatic Breast Cancer Cells

“…For example, Maeno et al (57) showed that chloride efflux is essential for cell shrinkage early in the apoptotic cascade and that channel blockade effectively prevented shrinkage and rescued a variety of cell types from staurosporine-induced apoptosis. On the other hand, Szabo et al (58) observed an outwardly rectified 2 R. C. Elble, unpublished data.…”

Alterations of intracellular pH homeostasis in apoptosis: origins and roles

“…Concerning the death receptor pathway, pH i changes have been studied mainly during the apoptotic events initiated following activation of the tumor necrosis factor (TNF) family receptors by Fas ligand [7][8][9] and have been shown to occur downstream caspase activation. 10 Thus, application of aCD95 to Jurkat cells results in a significant pH i decrease, which has been reported as soon as 1 h after stimulation, indicating that this phenomenon might be an early event in this type of apoptosis.…”

“…As pointed out above, although poorly studied, H þ carriers other than NHE (such as the Cl À /HCO 3 À exchanger, Na þ -dependent Cl À /HCO 3 À exchanger or Na þ -HCO 3 À cotransporter), as well as membrane ion channels, might also be involved in the Fas-dependent acidification; with regard to this latter point, inhibition of an outwardly rectifying chloride channel (ORCC) activated upon CD95 receptor ligation in T lymphocytes has thus been shown to abolish the apoptosis-related acidification. 7 Clearly, the role of such transporters deserves further investigation. Moreover, it would be interesting to test the effects on pH i homeostasis of the other known ligands of the TNF family receptors, such as TNF-a and TRAIL (TNF-related apoptosis-inducing ligand).…”