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Research Article

PTH-Induced Internalization of Apical Membrane NaPi2a: Role of Actin and Myosin VI

¹University of Colorado Denver

Submitted 17 June 2009 ; revised 15 September 2009 ; accepted in final form 15 September 2009

Parathyroid hormone (PTH) plays a critical role in the regulation of renal phosphorous homeostasis by altering the levels of the sodium phosphate cotransporter NaPi2a in the brush border membrane (BBM) of renal proximal tubular cells. While details of the molecular events of PTH-induced internalization of NaPi2a are emerging, the precise events governing NaPi2a removal from brush border microvilli in response to PTH remain to be fully determined. Here we use a novel application of total internal reflection fluorescence microscopy (TIR-FM) to examine how PTH induces movement of NaPi2a out of brush border microvill in living cells in real time. We show that a dynamic actin cytoskeleton is required for NaPi2a removal from the BBM in response to PTH. In addition, we demonstrate that a myosin motor that has previously been shown to be coregulated with NaPi2a, myosin VI, is necessary for PTH-induced removal of NaPi2a from BBM microvilli..

apical TIR-FM; NaPi2a; PTH; actin