Expression of inositol 1,4,5-trisphosphate receptors changes the
ca2+ signal of xenopus oocytes.
Delisle, Sylvain, Olivier Blondel, Frank J. Longo, William E.
Schnabel, Graeme I. Bell, and Michael J. Welsh.
Veterans Administration Medical Center and Howard Hughes Medical
Institute, Departments of Internal Medicine, [grave]aAnatomy, and
Physiology and Biophysics, University of Iowa College of Medicine,
Iowa City, Iowa 52242, Howard Hughes Medical Institute and
Departments of Biochemistry and Molecular Biology and Medicine,
University of Chicago, Chicago Illinois 60637
APStracts 3:0036C, 1996.
The receptors for the second messenger inositol 1,4,5-trisphosphate
(Ins(1,4,5)P3) form a family of closely related proteins which play
an important role in regulating the free intracellular Ca2+
concentration. To test the hypothesis that changing the expression
level of Ins(1,4,5)P3 receptors could alter the Ins(1,4,5)P3-mediated
Ca2+ signal, we over-expressed Ins(1,4,5)P3 receptor type 1 (InsP3R
-1) or type 3 (InsP3R-3) in Xenopus oocytes. Expression of InsP3R-1
increased the velocity of the propagating waves of intracellular Ca2+
release, but did not affect the Ins(1,4,5)P3-induced entry of
extracellular Ca2+ across the plasma membrane. In contrast,
expression of InsP3R-3 did not affect Ins(1,4,5)P3-induced release of
intracellular Ca2+, but markedly increased the magnitude and duration
of Ca2+ influx. Immunolocalization studies revealed InsP3R-3 at the
endoplasmic reticulum, with a relatively stronger signal at or near
the plasma membrane. The results suggest that changing the expression
level of an InsP3R can alter the Ins(1,4,5)P3-mediated Ca2+ signal,
and that InsP3R-1 and InsP3R-3 may have a different biological
function.
Received 19 September 1995; accepted in final form 8 December
1995.
APS Manuscript Number C563-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96