Differential regulation of connexin43 and connexin37 in endothelial
cells by cell density, growth and tgf-[beta]1.
Larson, D. M., M. J. Wrobleski, G. D. V. Sagar, E. M. Westphale, and
E. C. Beyer.
Mallory Institute of Pathology, Boston University School of
Medicine, Boston, MA 02118 and Department of Pediatrics, Washington
University School of Medicine, St. Louis, MO 63110
APStracts 3:0279C, 1996.
We studied the growth related expression of the gap junction proteins
Connexin43 (Cx43) and Connexin37 (Cx37) to characterize mechanisms of
their differential regulation in cultured bovine aortic endothelial
cells. During growth to confluency, Cx43 mRNA levels were high in
subconfluent cells and decreased at confluency; Cx37 mRNA was weakly
detectable until the cultures become confluent when levels became
similar to those of Cx43. Immunoprecipitation, immunoblots and
immunostaining demonstrated that Cx43 synthesis and content
paralleled the changes in mRNA levels. These data suggested
regulation of connexin expression related to growth status or cell
density. We tested this hypothesis by inhibiting growth with TGF
-[beta]1. TGF-b1 treatment caused an upregulation of Cx43 synthesis,
content, and apparent half-life, and mRNA, independent of changes in
cell density. Increases in Cx43 synthesis preceded increases in mRNA
suggesting both translational and transcriptional regulation, while
the increased half-life suggested post-translational regulation as
well. Immunostaining revealed the development of intense vesicular
staining in the treated cells which may explain the increased half
-life. TGF-b1 treatment also suppressed the upregulation of Cx37
expression. These alterations in connexin expression may have
implications for endothelial communication under conditions of
elevated vascular TGF-b1 concentrations such as in wound healing.
Received 7 May 1996; accepted in final form 23 August 1996.
APS Manuscript Number C245-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996