A TRPM4-dependent current in murine renal primary cilia.

A TRPM4-dependent current in murine renal primary cilia. Am J Physiol Renal Physiol. 2015 Aug 19;:ajprenal.00294.2015 Authors: Flannery RJ, Kleene NK, Kleene SJ Abstract Defects in primary cilia lead to a variety of human diseases. One of these, polycystic kidney disease, can be caused by defects in a Ca(2+)-gated ion channel (TRPP2) found on the cilium. Other ciliary functions also contribute to cystogenesis, and defects in apical Ca(2+) homeostasis have been implicated. By recording directly from the native cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin, we have identified a second Ca(2+)-gated channel in the ciliary membrane: the transient receptor potential cation channel, subfamily M, member 4 (TRPM4). In excised primary cilia, TRPM4 was found to have a low sensitivity to Ca(2+), with an EC50 of 646 μM at +100 mV. It was inhibited by MgATP and by 9-phenanthrol. The channel was not permeable to Ca(2+) or Cl(-) and had a permeability ratio PK/PNa of 1.42. Reducing the expression of Trpm4 mRNA with shRNA reduced the TRPM4 current by 87% and shortened primary cilia by 43%. When phospholipase C was inhibited, the sensitivity to cytoplasmic Ca(2+) greatly increased (EC50 = 26 μM at +100 mV), which is consistent with previous reports that PIP2 modulates the channel. MgATP did not restore the channel to a pre-inactivation state, suggesting that the enzyme or substrate necessary for making PIP2 is not abundant in...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research