An H+-ATPase in opposite plasma membrane domains in kidney epithelial cell subpopulations

D Brown, S Hirscht, S Gluck - Nature, 1988 - nature.com
D Brown, S Hirscht, S Gluck
Nature, 1988nature.com
Vectorial solute transport by epithelia requires the polarized insertion of transport proteins
into apical or basolateral plasmalemmal domains. In the specialized intercalated cells of the
kidney collecting duct, the selective placement of an apical plasma membrane proton-
pumping ATPase (H+-ATPase) and of a basolateral membrane anion-exchange protein
results in transepithelial proton secretion1. It is currently believed that amino-acid
sequences of membrane proteins contain critical signalling regions involved in sorting these …
Abstract
Vectorial solute transport by epithelia requires the polarized insertion of transport proteins into apical or basolateral plasmalemmal domains. In the specialized intercalated cells of the kidney collecting duct, the selective placement of an apical plasma membrane proton-pumping ATPase (H+-ATPase) and of a basolateral membrane anion-exchange protein results in transepithelial proton secretion1. It is currently believed that amino-acid sequences of membrane proteins contain critical signalling regions involved in sorting these proteins to specific membrane domains2. Recently, it was proposed that intercalated cells can reverse their direction of proton secretion under different acid-base conditions by redirecting proton pumps from apical to basolateral membranes, and anion exchangers from basolateral to apical membranes3. But others have found that antibodies raised against the red cell anion-exchange protein (Band 3) only labelled intercalated cells at the basolateral plasma membrane4,5, providing evidence against the model of polarity reversal. In this report, we have examined directly the distribution of proton pumps in kidney intercalated cells using specific polyclonal antibodies against subunits of a bovine kidney medullary H+-ATPase. We find that some cortical collecting duct intercalated cells have apical plasma membrane proton pumps, whereas others have basolateral pumps. This is the first direct demonstration of neighbouring epithelial cells maintaining opposite polarities of a transport protein. Thus, either subtle structural differences exist between proton pumps located at opposite poles of the cell, or factors other than protein sequence determine the polarity of H+-ATPase insertion.
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