Head-down tilt increases rat cardiac muscle eif-2a phosphorylation
.
Menon, Vandana, and Donald B. Thomason.
Department of Physiology and Biophysics, University of Tennessee
Health Science Center, Memphis
APStracts 2:0239C, 1995.
We previously demonstrated that head-down tilt in rats decreases heart
polypeptide initiation rate and proposed a mechanism whereby
redistribution of the chaperone heat-shock protein 70 (HSC/HSP 70)
facilitates the phosphorylation of initiation factor 2a (eIF-2a). In
this study, two dimensional gel electrophoretic analysis of eIF-2a
showed no phosphorylation in control hearts. At 8h of head-down tilt
there was a 45% increase in total eIF-2a; 79% was phosphorylated. At
18h eIF-2a increased to 142% of control, of which 4% was
phosphorylated. This is consistent with the previous study where at
8h there was a 78% increase in polysomal HSC/HSP 70 and a shift in
the polysome center-of-mass to lighter polysomes (indicating
decreased initiation). After 18h of suspension, polysomal HSC/HSP 70
levels were 24% relative to control and the center-of-mass returned
toward control. We conclude that the decrease in polypeptide
initiation during head-down tilt is mediated by HSC/HSP 70 via
phosphorylation of eIF-2a.
Received 12 May 1995; accepted in final form 28 June 1995.
APS Manuscript Number C266-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.