HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 291/1/F129    most recent 00290.2005v1 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 ISI Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Carraro-Lacroix, L. R. Articles by Malnic, G. Search for Related Content PubMed PubMed Citation Articles by Carraro-Lacroix, L. R. Articles by Malnic, G.

Increased NHE1 expression is associated with serum deprivation-induced differentiation in immortalized rat proximal tubule cells

Departments of ¹Physiology and Biophysics and ³Cell Biology and Development, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil; and ²Biomedical Department, Faculty of Health Sciences, University of Antofagasta, Antofagasta, Chile

Submitted 15 July 2005 ; accepted in final form 10 February 2006

We studied the proton secretion mechanisms involved with pH_i regulation in immortalized rat proximal tubule cells (IRPTC), a SV40-immortalized cell line derived from rat proximal tubule, and characterized the effects of serum deprivation on them. Using pH_i measurements with the fluorescent probe BCECF, we demonstrated that the IRPTC express both Na⁺/H⁺ exchanger and H⁺-ATPase, but only NHE1 is modulated by serum deprivation. In these cells, 24 h of serum starvation increased pH_i from 7.08 ± 0.008 (n = 34) to 7.18 ± 0.018 (n = 33) as well as the pH recovery rate from intracellular acidification with NH₄Cl from 0.29 ± 0.022 pH U/min (n = 14) to 0.50 ± 0.024 pH U/min (n = 14), without modifying their buffering capacity. These effects were followed by several modifications in morphological features, indicating an increase in differentiation status. The altered activity of NHE1 was consistent with an increase of both transcription and translation of the antiporter, as the utilization of actinomycin D and cycloheximide significantly inhibited the upregulation of NHE1 induced by serum withdrawal. Inhibition of tyrosine phosphorylation by genistein blocked the serum deprivation-dependent activation of NHE. Moreover, the pharmacological inhibition of MEK1/2, the upstream activator of ERK1/2 by UO-126, significantly inhibited the stimulatory effect of serum starvation on Na⁺/H⁺ exchanger activity, whereas the putative p38 MAPK inhibitor SB-203580 failed to cause any effect on pH_i recovery rates. Our findings indicate that during IRPTC differentiation by serum deprivation, there was a net enhancement of NHE1 activity. This upregulation of NHE by serum removal was consistent with an increase of RNA and protein synthesis of the exchanger, which depends on tyrosine kinase phosphorylation and ERK pathway activation.

cell pH; tyrosine kinase; MAPK

This article has been cited by other articles:

				L. Schneider, C.-M. Stock, P. Dieterich, B. H. Jensen, L. B. Pedersen, P. Satir, A. Schwab, S. T. Christensen, and S. F. Pedersen The Na+/H+ exchanger NHE1 is required for directional migration stimulated via PDGFR-{alpha} in the primary cilium J. Cell Biol., April 6, 2009; 185(1): 163 - 176. [Abstract] [Full Text] [PDF]