2n8s

Publication Abstract from PubMed

Nedd4 was the first ubiquitin protein ligase identified to interact with Cx43 and its suppressed expression results in accumulation of gap junction plaques at the plasma membrane. Nedd4-mediated ubiquitination of Cx43 is required to recruit Eps15 and target Cx43 to the endocytic pathway. While the Cx43 residues that undergo ubiquitination are still unknown, in this study we address other unresolved questions pertaining to the molecular mechanisms mediating the direct interaction between Nedd4 (WW1-3 domains) and Cx43 (carboxyl terminus, CT). All three WW domains display a similar three antiparallel beta-strand structure and interact with the same Cx43CT 283PPxY286 sequence. While Y286 is essential for the interaction, MAPK phosphorylation of the preceding serine residues (pS282 and pS279) increases the binding affinity by two-fold for the WW domains (WW2>WW3>>WW1). The structure of the WW2/Cx43CTpS282,pS279 complex reveals that coordination of pS282 with the end of beta strand 3 enables pS279 to interact with the back face of beta strand 3 (Y286 is on the front face) and loop 2, forming a horseshoe-shaped structure. The close sequence identity of WW2 with WW1 and WW3 residues that interact with the Cx43CT PPxY motif and pS282/pS279 strongly suggest that the significantly lower binding affinity of WW1 is the result of a more rigid structure. This study presents the first structure illustrating how phosphorylation of the Cx43CT domain helps mediate the interaction with a molecular partner involved in gap junction regulation.

Structural Studies of the Nedd4 WW Domains and their Selectivity for the Cx43 Carboxyl-terminus.,Spagnol G, Kieken F, Kopanic JL, Li H, Zach S, Stauch KL, Grosely R, Sorgen PL J Biol Chem. 2016 Feb 3. pii: jbc.M115.701417. PMID:26841867^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.