Journal
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
Volume 440, Issue 6, Pages 902-907Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s004240000358
Keywords
apoptosis; ATP; cell death; cell shrinkage; DNA fragmentation; Lck(56); Src-like kinase
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Mitogenic factors are known to stimulate the Na+/H+-exchanger (NHE), leading to cytosolic alkalinization and/or cell swelling. Conversely, a hallmark of apoptosis is cell shrinkage and CD95-induced apoptosis has been reported to be paralleled by cytosolic acidification. To assess whether the CD95-receptor regulates NHE activity in Jurkat T-lymphocytes, we performed conventional BCECF fluorescence measurements and SNARF flow cytometric analysis (FACS). The recoveries from acidifications following application of butyrate or a NH3 pulse were both abolished by a specific NHE-inhibitor HOE694, indicating that they fully depend on NHE activity. Thus they were taken as a measure of NHE activity. CD95-receptor stimulation caused a cytosolic acidification and blunted the recovery from acidification following application of butyrate or a NH3 pulse. Moreover, the NHE-dependent alkalinization following osmotic cell shrinkage was almost abolished by CD95-receptor stimulation. As apparent from the effect of osmotic cell shrinkage, inhibition of the NHE by CD95-receptor stimulation was absent in Lck(56)-deficient J-CaM 1.6 cells and restored by retransfection of J-CaM 1.6-cells with Lck(56) CD95-receptor stimulation led within 4 h to a decrease of cellular ATP which could contribute to NHE inhibition. Treatment of Jurkat cells with the NHE inhibitor HOE694 accelerated CD95-induced DNA fragmentation. In conclusion, CD95-receptor stimulation inhibits NHE activity through a mechanism that depends directly or indirectly on the activation of the Src-like kinase Lck(56) This effect contributes to CD95-induced cytosolic acidification, DNA fragmentation and cell shrinkage.
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