Distinctive Regulation of Low-Voltage-activated Calcium Channels by Neural precursor cell Expressed Developmentally Down-regulated protein 4 (NEDD4) Family E3 Ubiquitin Ligases

Dysregulation of low-voltage-activated calcium channels (CaV3.1-CaV3.3) underlies diseases including chronic pain, autism, and hypertension. As a major determinant of protein half-life, the ubiquitin-proteasome system (UPS) may not only cause abnormal CaV3 expression but also be targeted to control channel levels for therapy. There are >600 E3 ubiquitin ligases that catalyse the final step in ubiquitination. A crucial aspect of harnessing the UPS is knowing which E3 ligases regulate a given substrate, and whether their actions are redundant. We report that CaV3.1 and CaV3.2 are distinctively regulated by two NEDD4 family E3 ligases – NEDD4L and Smurf1. Reconstituted CaV3.1 currents were robustly suppressed by Smurf1 but not NEDD4L, whereas CaV3.2 was inhibited by both NEDD4L and Smurf1, concomitant with diminished channel surface density and expression. FRET experiments revealed NEDD4L and Smurf1 interact with distinct loci in CaV3.1 and CaV3.2. Nanobody-mediated targeting of NEDD4L or Smurf1, but not WWP1, HECT domains to CaV3.1 and CaV3.2 strongly suppressed currents through both channels. shRNA knockdown of either NEDD4L or Smurf1 in dorsal root ganglion (DRG) neurons substantially increased both low-voltage and high-voltage-activated calcium channel currents. The results reveal non-redundant regulation of CaV3 channels by NEDD4L and Smurf1; introduce Smurf1 as a potent determinant of ion channel expression; suggest a new mechanism for CaV3.2 up-regulation in chronic pain; and advance leveraging the UPS to control CaV3 expression for therapy.