The tyrosine kinase p56(lck) mediates activation of swelling-induced chloride channels in lymphocytes

Abstract

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 (I(Cl-swell)) by osmotic swelling in whole-cell patch-clamp experiments is blocked by herbimycin A and lavendustin. Osmotic activation of I(Ic-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 I(Cl-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 I(Cl- 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 I(Cl-swell) lymphocytes via the tyrosine kinase p56(lck).