Regulation of the cardiac voltage-gated Na+ channel (H1) by the ubiquitin-protein ligase Nedd4

The cardiac voltage-gated Na+ channel H1, involved in the generation of car diac action potential, contains a C-terminal PY motif (xPPxY). Since PY mot ifs are known ligands to WW domains, we investigated their role for H1 regu lation and the possible involvement of the WW domain containing ubiquitin p rotein ligase Nedd4, taking advantage of the Xenopus oocyte system. Mutatio n of the PY motif leads to higher peak currents when compared to wild-type channel. Moreover, co-expression of Nedd4 reduced the peak currents, wherea s an enzymatically inactive Nedd4 mutant increased them, likely by competin g with endogenous Nedd4, The effect of Nedd4 was not observed in the PY mot if mutated channel or in the skeletal muscle voltage-gated Na+ channel, whi ch lacks a PY motif, We conclude that H1 may be regulated by Nedd4 dependin g on WW-PY interaction, and on an active ubiquitination site. (C) 2000 Fede ration of European Biochemical Societies.