Cloning of an aquaporin homolog present in water channel containing
endosomes of the toad urinary bladder.
Siner, J., A. Paredes, C. Hosselet, T. Hammond, K. Strange, and H. W.
Harris.
Division of Nephrology, Children's Hospital, Boston, MA; Div. of
Nephrology and V.A. Medical Center, University of Wisconsin, Madison,
WI.
APStracts 2:0318C, 1995.
Regulation of total body water balance in amphibians by antidiuretic
hormone (ADH) contributed to their successful colonization of
terrestrial habitats approximately 200-300 million years ago. In the
mammalian kidney, ADH modulates epithelial cell apical membrane water
permeability (Pf) by fusion and retrieval of cytoplasmic vesicles
containing water channel proteins called aquaporins (AQP). To
determine the role of AQPs in ADH elicited Pf in amphibians, we have
identified and characterized a unique AQP from Bufo marinus called
Aquaporin-toad bladder (AQP-TB). AQP-TB possesses many structural
features common to other AQPs. AQP-TB is expressed abundantly in ADH
responsive tissues including toad urinary bladder and skin as well as
lung, skeletal muscle, kidney and brain. In a manner identical to
that reported for the mammalian ADH elicited water channel AQP-2,
AQP-TB expression is increased significantly by intervals of
dehydration or chronic ADH stimulation. However, expression of AQP-TB
protein in Xenopus oocytes does not significantly increase oocyte Pf.
The lack of expression of functional AQP-TB water channels in oocytes
may result from intracellular sequestration of AQP-TB due to the
presence of a YXRF sequence motif present in its carboxyl terminal
domain.
Received 19 April 1995; accepted in final form 28 June 1995.
APS Manuscript Number C215-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.