Activation of neuroendocrine L-type channels (alpha 1D subunits) in retinal pigment epithelial cells and brain neurons by pp60(c-src)

The aim of this study is to characterize the subtype of tyrosine kinase-reg ulated L-type Ca2+ channels in retinal pigment epithelial (RPE) cells. Ca2 channel alpha 1D-subunits were enriched by immunoprecipitation from membra ne proteins isolated from rat RPE cells. Western blot analysis of the preci pitates revealed coprecipitation of pp60(c-src). In addition, in precipitat es obtained with antibodies against pp60(c-src), alpha 1D-subunits were ide ntified, The same was observed in immunoprecipitations from rat brain neuro ns. Tyrosine phosphorylation of alpha 1D-subunits was confirmed using anti- phosphotyrosine antibodies. Ba2+ currents through L-type channels in cultur ed rat RPE cells were increased by intracellular application of active pp60 (c-src) (30 U/ml) (heat-inactivated pp60(c-src) had no effect). Thus, L-typ e channels of the neuroendocrine subtype can be expressed in epithelial tel ls and are activated by tyrosine kinase of the src subtype, This kind of re gulation is also suggested for brain-derived neurons. (C) 2000 Academic Pre ss.