Molecular cloning of NHE1 from winter flounder RBCs: activation by osmotic
shrinkage, cAMP, and calyculin C.
Pedersen, Stine F., Scott A. King, Robert R. Rigor, Zhenpeng Zhuang, Jaimie M. Warren,
and Peter M. Cala.
1Department of Human Physiology, School of Medicine, University of California-
Davis, and 2USDA-ARS Western Human Nutrition Research Center, Davis, California
95616
APStracts 10:0080C, 2003.
In this report, we describe the cloning, cellular localization, and functional characteristics
of Na+/H+ exchanger 1 (NHE1) from red blood cells of the winter flounder
Pseudopleuronectes americanus (paNHE1). The paNHE1 protein localizes primarily to
the marginal band and exhibits a 74% similarity to the trout ß-NHE, and 65% to the
human NHE1 (hNHE1). Functionally, paNHE1 shares characteristics of both ß-NHE and
hNHE1 in that it is activated by manipulations that increase both cAMP and cell
shrinkage, respectively. In accordance, the paNHE1 protein exhibits both protein kinase
A consensus sites as in ß-NHE and a region of high homology to that required for
shrinkage-dependent activation of hNHE1. After shrinkage-dependent activation of
paNHE1 and resulting activation of a Cl«minus»/HCO{3?«minus»} exchanger, their
parallel operation results in net uptake of NaCl and osmotically obliged water. Activation
of paNHE1 by cAMP is at least additive to that elicited by osmotic shrinkage, suggesting
that these stimuli regulate paNHE1 by distinct mechanisms. Finally, exposure to the
serine/threonine phosphatase inhibitor calyculin A potently activates paNHE1, and this
activation is also additive to that induced by shrinkage or cAMP.
Received 3 December 2002; accepted in final form 27 January 2003
APS Manuscript Number C562-2.
Article publication pending Am J Physiol Cell Physiol
ISSN 1080-4757 Copyright 2003 The American Physiological Society.
Published in APStracts on 25 March 2003