Ponsaerts, RafDe Vuyst, ElkeRetamal, MauricioD’hondt, CatheleyneVermeire, DieterWang, NanDe Smedt, HumbertZimmermann, PascaleHimpens, BernardVereecke, JohanLeybaert, LucBultynck, Geert2021-10-202021-10-202010FASEB journal 2010 Nov;24(11):4378-95https://doi.org/10.1096/fj.09-153007http://hdl.handle.net/11447/4879Connexin-assembled gap junctions (GJs) and hemichannels coordinate intercellular signaling processes. Although the regulation of connexins in GJs has been well characterized, the molecular determinants controlling connexin-hemichannel activity are unresolved. Here we investigated the regulation of Cx43-hemichannel activity by actomyosin contractility and intracellular [Ca2 ] [Ca2 ]i ) using plasma membrane-permeable TAT peptides (100 M) designed to interfere with interactions between the cytoplasmic loop (CL) and carboxy-terminal (CT) in primary bovine corneal endothelial cells and HeLa, C6 glioma, and Xenopus oocytes ectopically expressing Cx43. Peptides corresponding to the last 10 CT aa (TAT-Cx43CT) prevented the inhibition of Cx43-hemichannel activity by contractility/high [Ca2 ]i , whereas a reverse peptide (TAT-Cx43CTrev) did not. These effects were independent of zónula occludens-1, a cytoskeletal-associated Cx43- inding protein. In contrast, peptides corresponding to CL (TAT-L2) inhibited Cx43-hemichannel responses, whereas a mutant peptide (TAT-L2H126K/I130N) did not inhibit. In these assays, TAT-Cx43CT acted as a scaffold for TAT-L2 and vice versa, a finding supported by surface plasmon resonance measurements. Loop/tail interactions appeared essential for Cx43-hemichannel activity, because TAT-Cx43CT restored the activity of nonfunctional hemichannels, consisting of either Cx43 lacking the C-terminal tail (Cx43M239) or intact Cx43 ectopically expressed in Xenopus oocytes. We conclude that intramolecular loop/tail interactions control Cx43- hemichannel activity, laying the basis for developing hemichannel-specific blockers.—Ponsaerts, R., De Vuyst, E., Retamal, M., D’hondt, C., Vermeire, D., Wang, N., De Smedt, H., Zimmermann, P., Himpens, B., Vereecke, J., Leybaert, L., Bultynck, G. Intramolecular loop/tail interactions are essential for connexin 43-hemichannel activity. FASEB J. 24, 4378–4395 (2010). www.fasebj.orgen-USintercellular communicationactomyosin contractilityintracellular calciumpurinergic signalingArticle