Separate control of TRPV4 activity and trafficking in the distal nephron

Abstract

We have recently documented that Ca2+‐permeable TRPV4 channel, which is abundantly expressed in the distal nephron cells, mediates cellular Ca2+ responses to elevated luminal flow. The current research combined Fura‐2 Ca2+ imaging with immunofluorescent microscopy in split‐opened distal nephrons of C57BL/6 mice to probe molecular determinants regulating subcellular distribution and activity of TRPV4. We found that activation of PKA pathway with forskolin does not affect TRPV4‐ mediated Ca2+ responses to flow, while markedly shifting subcellular distribution of the channel towards the apical membrane. These actions are blocked with a specific PKA inhibitor H‐89. Activation of PKC pathway with PMA significantly increases Ca2+ responses to flow without affecting the subcellular distribution of TRPV4. In contrast, inhibition of PKC with BIM‐1 diminishes cellular responses to elevated flow. Concomitant activation of PKA and PKC cascades greatly increases basal Ca2+ levels indicating constitutive TRPV4 activation and this effect is precluded by a selective TRPV4 antagonist, HC‐067047. Therefore, functional status of TRPV4 channel in the distal nephron is regulated by two distinct signaling pathways. While PKA cascade appears to be responsible for TRPV4 trafficking and translocation to the apical membrane, PKC‐dependent pathway increases the activity of the channel on the plasma membrane.