The tyrosine kinase p56lck mediates activation of swelling-induced chloride channels in lymphocytes

Osmotic cell swelling activates Cl- channels to achieve anion efflux, In this study. we find that both the tyrosine kinase inhibitor herbimycin A and genetic knockout of p56(lck), a src-like tyrosine kinase, block regulatory volume decrease (RVD) in a human T cell line. Activation of a swelling-activated chloride current (ICl-swell) by osmotic swelling in whole-cell patch-clamp experiments is blocked by herbimycin A and lavendustin. Osmotic activation of ICl-swell is defective in p56(lck)-deficient cells, Retransfection of p56(lck) restores osmotic current activation. Furthermore, tyrosine kinase activity is sufficient for activation of ICl-swell, Addition of purified p56(lck) to excised patches activates an outwardly rectifying chloride channel with 31 pS unitary conductance. Purified p56(lck) washed into the cytoplasm activates ICl-swell in native and p56(lck)-deficient cells even when hypotonic intracellular solutions lead to cell shrinkage. When whole-cell currents are activated either by swelling or by p56(lck), slow single-channel gating events can be observed revealing a unitary conductance of 25-28 pS. In accordance with our patch-clamp data, osmotic swelling increases activity of immunoprecipitated p56(lck). We conclude that osmotic swelling activates ICl-swell in lymphocytes via the tyrosine kinase p56(lck).