2007 JASN IMPACT FACTOR 7.111	HOME   AUTHOR INFO   EDITORIAL BOARD   SUBSCRIBE   FEEDBACK   ALERTS   HELP
advanced	CURRENT ISSUE	ARCHIVES	JASN Express	ONLINE SUBMISSION

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by HAN, X. Articles by CHESNEY, R. W. Search for Related Content PubMed PubMed Citation Articles by HAN, X. Articles by CHESNEY, R. W.

Ser-322 Is a Critical Site for PKC Regulation of the MDCKCell Taurine Transporter (pNCT)

Department of Pediatrics, University of Tennessee, and the Crippled Children's Foundation Research Center at Le Bonheur Children's Medical Center, Memphis, Tennessee.

Correspondence to Dr. Russell W. Chesney, Department of Pediatrics, University of Tennessee, Memphis, 50 North Dunlap, Memphis, TN 38103. Phone: 901-572-3106; Fax: 901-572-5028; E-mail: RChesney{at}utmeml.utmem.edu

Abstract

Abstract. Previous studies have shown that the Madin—Darby canine kidney cell taurine transporter (pNCT) is downregulated by protein kinase C (PKC) activation. In this study, it is hypothesized that the highly conserved serine-322 (Ser-322) located in the fourth intracellular segment (S₄) may play an important role in the function of taurine transporter, which is modulated by PKC phosphorylation. It is demonstrated that Ser-322 is the critical site of PKC phosphorylation, as determined by site-directed mutagenesis. When Ser-322 of pNCT was changed to alanine (S322A) and this mutant was evaluated in an oocyte expression system, taurine transport activity increased threefold compared with control (wild-type pNCT). Activation of PKC by the active phorbol ester 12-myristate 13-acetate did not influence taurine transport by mutant S322A. Kinetic analysis showed that the mutation of Ser-322 essentially changed the V_max, rather than the K_m, of the transporter. Mutation of all other PKC consensus sites did not affect transporter activity when expressed in the oocyte system. Western blot analysis showed that expression of taurine transporter protein was similar in oocytes injected with either wild-type or mutant pNCT cRNA, indicating that the enhanced taurine transport activity by mutant S322A was not caused by a greater amount of transporter expressed in the oocyte. Furthermore, this study demonstrated that the taurine transporter was phosphorylated after PKC activation, and this effect was not observed in mutant S322A. In conclusion, Ser-322 is critical in PKC regulation of taurine transporter activity. The steady-state taurine transporter activity is tightly controlled by endogenous PKC phosphorylation of Ser-322, which is located in the fourth intracellular segment of the taurine transporter.

This article has been cited by other articles:

				D. D. Vadysirisack, E. S.-W. Chen, Z. Zhang, M.-D. Tsai, G.-D. Chang, and S. M. Jhiang Identification of in Vivo Phosphorylation Sites and Their Functional Significance in the Sodium Iodide Symporter J. Biol. Chem., December 21, 2007; 282(51): 36820 - 36828. [Abstract] [Full Text] [PDF]

				S. Roos, T. L. Powell, and T. Jansson Human placental taurine transporter in uncomplicated and IUGR pregnancies: cellular localization, protein expression, and regulation Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2004; 287(4): R886 - R893. [Abstract] [Full Text] [PDF]

				X. Han, A. B. Patters, and R. W. Chesney Transcriptional Repression of Taurine Transporter Gene (TauT) by p53 in Renal Cells J. Biol. Chem., October 11, 2002; 277(42): 39266 - 39273. [Abstract] [Full Text] [PDF]

Copyright © 2008 by the American Society of Nephrology. Online ISSN: 1533-3450 Print ISSN: 1046-6673