Site-specific connexin phosphorylation is associated with reduced heterocellular communication between smooth muscle and endothelium.
OBJECTIVE
Myoendothelial junctions (MEJs) represent a specialized signaling domain between vascular smooth muscle cells (VSMC) and endothelial cells (EC). The functional consequences of phosphorylation state of the connexins (Cx) at the MEJ have not been explored.


RESULTS
Application of adenosine 3',5'-cyclic monophosphate sodium (pCPT) to mouse cremasteric arterioles reduces the detection of connexin 43 (Cx43) phosphorylated at its carboxyl terminal serine 368 site (S368) at the MEJ in vivo. After single-cell microinjection of a VSMC in mouse cremaster arterioles, only in the presence of pCPT was dye transfer to EC observed. We used a vascular cell co-culture (VCCC) and applied the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (PMA) or fibroblast growth factor-2 (FGF-2) to induce phosphorylation of Cx43 S368. This phosphorylation event was associated with a significant reduction in dye transfer and calcium communication. Using a novel method to monitor increases in intracellular calcium across the in vitro MEJ, we noted that PMA and FGF-2 both inhibited movement of inositol 1,4,5-triphosphate (IP(3)), but to a lesser extent Ca(2+).


CONCLUSIONS
These data indicate that site-specific connexin phosphorylation at the MEJ can potentially regulate the movement of solutes between EC and VSMC in the vessel wall.
Straub
Adam C
AC
Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
Johnstone
Scott R
SR
Heberlein
Katherine R
KR
Rizzo
Michael J
MJ
Best
Angela K
AK
Boitano
Scott
S
Isakson
Brant E
BE
D000818:Animals; D001160:Arterioles / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D017629:Gap Junctions / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D012694:Serine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D018031:Connexin 43; C543076:GJA1 protein, mouse; D016222:Fibroblast Growth Factor 2; D012694:Serine; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium