Received September 18, 2008
Accepted on February 26, 2009

BASIC RESEARCH

Bestrophin 1 Promotes Epithelial-to-mesenchymal Transition of Renal Collecting Duct Cells

Institut für Physiologie, Universität Regensburg, Regensburg, Germany

¹ To whom correspondence should be addressed. E-mail: uqkkunze{at}mailbox.uq.edu.au.

	Abstract

Bestrophin 1 (Best1) controls intracellular Ca²⁺ concentration, induces Ca²⁺-activated Cl^- conductance, and increases proliferation of colon carcinoma cells. Here, we show that expression of Best1 in mouse renal collecting duct (CD) cells causes i) an increase in cell proliferation, ii) a loss of amiloride-sensitive Na⁺ absorption, iii) induction of Ca²⁺-dependent Cl^- conductance (CaCC), and iv) epithelial-to-mesenchymal transition. During conditions of high proliferation or when we exposed CD cells to serum or TGF–1, we observed upregulation of Best1, increased CaCC, redistribution of the epithelial-to-mesenchymal transition marker -catenin, and upregulation of vimentin. In contrast, suppression of Best1 by RNAi inhibited proliferation, reduced CaCC, and downregulated markers of EMT. CaCC and expression of Best1 were independent of the cell cycle but clearly correlated to cell proliferation and cell density. During renal inflammation in LPS-treated mice or after unilateral ureteral obstruction, we observed transient upregulation of Best1. These data indicate that repression of cell proliferation, CaCC, and expression of Best1 occurs during mesenchymal-to-epithelial transition once CD cells polarize and terminally differentiate. These results may suggest a role for Best1 in renal fibrosis and tissue repair.