Title :
WNK3 positively regulates epithelial calcium
channels TRPV5 and
TRPV6 via a kinase-dependent pathway
Abstract :
- WNK3 , a member of the With No Lysine (K) family of protein serine/threonine kinases, was shown to regulate members of the SLC12A family of cation-chloride cotransporters and the renal outer medullary K+ channel ROMK and Cl(-) channel SLC26A9
- To evaluate the effect of WNK3 on TRPV5 , a renal epithelial Ca2 + channel that serves as a gatekeeper for active Ca2 + reabsorption, WNK3 and TRPV5 were coexpressed in Xenopus laevis oocytes and the function and expression of TRPV5 were subsequently examined
- An 82.7 +/- 7.1% increase in TRPV5-mediated Ca2 + uptake was observed when WNK3 was coexpressed
- A similar increase in TRPV5-mediated Na+ current was observed with the voltage-clamp technique
- WNK3 also enhanced Ca2 + influx and Na+ current mediated by TRPV6 , which is the closest homolog of TRPV5 that mediates active intestinal Ca2 + absorption
- The kinase domain of WNK3 alone was sufficient to increase TRPV5-mediated Ca2 + transport, and the positive regulatory effect was abolished by the kinase-inactive D294A mutation in WNK3 , indicating a kinase-dependent mechanism
- The complexly glycosylated TRPV5 that appears at the plasma membrane was increased by WNK3
- The exocytosis of TRPV5 was increased by WNK3 , and the effect of WNK3 on TRPV5 was abolished by the microtubule inhibitor colchicine
- The increased plasma membrane expression of TRPV5 was likely due to the enhanced delivery of mature TRPV5 to the plasma membrane from its intracellular pool via the secretory pathway
- These results indicate that WNK3 is a positive regulator of the transcellular Ca2 + transport pathway