Connexin43 interacts with Barrestin: a pre-requisite for osteoblast survival induced by parathyroid hormone

NICOLETTA BIVI; VIRGINIA LEZCANO; MILENA ROMANELLO; TERESITA BELLIDO; LILIAN I. PLOTKIN

JOURNAL OF CELLULAR BIOCHEMISTRY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Año: 2011 vol. 112 p. 2920 - 2930

0730-2312

Parathyroid hormone (PTH) promotes osteoblast survival through a mechanism that depends on cAMP-mediated signaling downstream of the G protein-coupled receptor PTHR1. We present evidence herein that PTH-induced survival signaling is impaired in cells lacking connexin43 (Cx43). Thus, expression of functional Cx43 dominant negative proteins or Cx43 knock-down abolished the expression of cAMP-target genes and anti-apoptosis induced by PTH in osteoblastic cells. In contrast, cells lacking Cx43 were still responsive to the stable cAMP analog dibutyril-cAMP. PTH survival signaling was rescued by transfecting wild type Cx43 or a truncated dominant negative mutant of B-arrestin, a PTHR1-interacting molecule that limits cAMP signaling. On the other hand, Cx43 mutants lacking the cytoplasmic domain (Cx43) or unable to be phosphorylated at serine 368 (Cx43), a residue crucial for Cx43 trafficking and function, failed to restore the anti-apoptotic effect of PTH in Cx43 deficient cells. In addition, overexpression of wild type B-arrestin physically associated in vivo to wild type Cx43 and to a lesser extent to Cx43; and this association and the phosphorylation of Cx43 in serine 368 were reduced by PTH. Furthermore, induction of Cx43 phosphorylation or overexpression of wild type Cx43, but not Cx43245 or Cx43S368, reduced the interaction between B-arrestin and the PTHR1. These studies demonstrate that B-arrestin is a novel Cx43-interacting protein and suggest that, by sequestering B-arrestin, Cx43 facilitates cAMP signaling, thereby exerting a permissive role on osteoblast survival induced by PTH.