A TRPM4-dependent current in murine renal primary cilia

作者：Flannery Richard J; Kleene Nancy K; Kleene Steven J

来源：American Journal of Physiology - Renal Fluid and Electrolyte Physiology, 2015, 309(8): F697-F707.

DOI：10.1152/ajprenal.00294.2015

• primary cilium
• TRPM4
• polycystic kidney disease
• TRPP2

Defects in primary cilia lead to a variety of human diseases. One of these, polycystic kidney disease, can be caused by defects in a Ca2+-gated ion channel (TRPP2) found on the cilium. Other ciliary functions also contribute to cystogenesis, and defects in apical Ca2+ 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 Ca2+-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 Ca2+, with an EC50 of 646 mu M at +100 mV. It was inhibited by MgATP and by 9-phenanthrol. The channel was not permeable to Ca2+ or Cl- and had a permeability ratio P-K/P-Na of 1.42. Reducing the expression of Trpm4 mRNA with short hairpin (sh) RNA reduced the TRPM4 current by 87% and shortened primary cilia by 43%. When phospholipase C was inhibited, the sensitivity to cytoplasmic Ca2+ greatly increased (EC50 = 26 mu M at + 100 mV), which is consistent with previous reports that phosphatidylinositol 4,5-bisphosphate (PIP2) modulates the channel. MgATP did not restore the channel to a preinactivation state, suggesting that the enzyme or substrate necessary for making PIP2 is not abundant in primary cilia of mIMCD- 3 cells. The function of TRPM4 in renal primary cilia is not yet known, but it is likely to influence the apical Ca2+ dynamics of the cell, perhaps in tandem with TRPP2.

• 出版日期2015-10-15