Nephrology & Therapeutics

Biography

Biography: Edward J. Filardo

Abstract

Estrogen promotes renoprotective effects that are linked to the G-protein-coupled estrogen receptor-1 (GPER-1). Our studies have shown that GPER-1 immunoreactivity is primarily localized in distal convoluted tubules and the Loop of Henle (stained with Tamm-Horsfall Protein-1). Lower GPER-1 expression is observed in proximal convoluted tubules marked with megalin, and GPER-1 is not readily detected in collecting ducts. Plasma membrane fractions prepared from whole kidney tissue or HEK293 cells expressing recombinant human GPER-1 (HEK-GPER-1) display high-affinity, specific [3H]-17-estradiol ([3H]-E2) binding, but no specific [3H]-aldosterone binding. In contrast, cytosolic preparations exhibit specific binding to [3H]-aldosterone but not to [3H]-E2, consistent with the subcellular distribution of GPER-1 and mineralocorticoid receptor (MR) in these preparations. Aldosterone and MR antagonists, spironolactone and eplerenone, failed to compete for specific [3H]-E2 binding to membranes of HEK-GPER-1 cells. Furthermore, aldosterone did not increase [35S]-GTP-S binding to membranes of HEK-GPER-1 cells, indicating that it is not involved in G-protein signaling mediated through GPER-1. During the follicular phases of the estrus cycle, GPER-1 is upregulated on renal cortical epithelia and localized to the basolateral surface during proestrus and redistributed intracellularly during estrus. GPER-1 is down-modulated during the luteal phases of the estrus cycle with significantly less receptor on the surface of renal epithelia, and as measured by gel electrophoretic analysis. Our results demonstrate that GPER-1 is associated with specific estrogen binding and not aldosterone binding and that GPER-1 expression is modulated during the estrus cycle which may suggest a physiological role for GPER-1 in the kidney during reproduction. Presenting author.