Effect of Acidosis on the Properties of the Glutaminase... : Journal of the American Society of Nephrology (original) (raw)
Cell and Transport Physiology
Effect of Acidosis on the Properties of the Glutaminase mRNA pH-Response Element Binding Protein
Department of Biochemistry and Molecular Biology, Colorado State University, Ft. Collins, Colorado.
Correspondence to Dr. Norman P. Curthoys, Department of Biochemistry and Molecular Biology, Colorado State University, Ft. Collins, CO 80523-1870. Phone: 970-491-5566; Fax: 970-491-0494; E-mail: [email protected]
Accepted March 6, 2000
Received January 24, 2000
Abstract
The pH-responsive stabilization of the rat renal glutaminase (GA) mRNA during metabolic acidosis is mediated by a pH-response element (pH-RE). The primary pH-RE within the GA mRNA consists of a direct repeat of an 8-base adenosine and uridine—rich sequence, which binds a specific cytosolic protein, the pH-response element binding protein (REBP). The functional analysis of this system was performed in LLC-PK1-F+ cells, a pH-responsive line of porcine proximal tubule-like cells. Cytosolic extracts of LLC-PK1-F+ cells also contain a protein that binds with high affinity to the rat GA mRNA pH-RE. The apparent binding of this protein is increased threefold in cytosolic extracts prepared from LLC-PK1-F+ cells that were grown in acidic medium (pH = 6.9, HCO3- = 10 mM). Extracts prepared from the renal cortext of rats that were made acutely acidotic also exhibit a similar increase in binding to the RNA probe that contains the direct repeat of the pH-RE. The temporal increase in binding correlates with the temporal increase in GA mRNA. Scatchard analysis indicates that the increased binding is due to an increase in both the affinity and the maximal binding of the pH-REBP. Thus, increased binding of the pH-REBP to the GA mRNA may initiate its stabilization and increased expression during acidosis.
Copyright © 2000 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
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