A Particle-Receptor Model for the Insulin-Induced Closure of Connexin43 Channels

From the SUNY Health Science Center (N.H., J.L.A., K.S., S.M.T., M.D.), Syracuse, NY, and the Cancer Research Center (A.F.L.), University of Hawaii at Manoa, Honolulu.

Correspondence to Mario Delmar, MD, PhD, Department of Pharmacology, SUNY Health Science Center, 750 E Adams St, Syracuse, NY 13210. E-mail delmarm{at}vax.cs.hscsyr.edu

Abstract—Connexin43(Cx43) channels can be regulated by a variety of factors, including low pH_i. Structure/function studies from this laboratory have demonstrated that pH gating follows a particle-receptor mechanism, similar to the "ball-and-chain" model of voltage-dependent inactivation of ion channels. The question whether the particle-receptor model is applicable only to pH gating or to other forms of Cx43 regulation as well remains. To address this question, we looked at the uncoupling effects of insulin and of insulin-like growth factor-1 (IGF) on Cx43 channels expressed in Xenopus oocytes. These agonists do not induce changes in pH_i. Junctional conductance (Gj) was measured by the dual 2-electrode voltage-clamp technique. Control studies showed that relative Gj did not change spontaneously as a function of time. Continuous exposure of Cx43-expressing oocytes to insulin (10 µ/L) led to a decrease in Gj. After 80 minutes, Gj was 54±5% from control (n=12). Exposure of oocytes to IGF (10 nmol/L) caused an even more pronounced change in Gj (37±4% of control, n=6). The time course of the IGF-induced uncoupling was similar to that observed after insulin exposure. The effect of insulin was abolished by truncation of the carboxyl-terminal domain of Cx43 at amino acid 257 (M257). Interestingly, as in the case of pH gating, coexpression of the carboxyl-terminal domain (amino acids 258 to 282) together with M257 rescued the ability of insulin to reduce coupling (Gj, 39±12% from control; n=6). Structure/function experiments using various deletion mutants of the carboxyl-terminal domain showed that insulin treatment does not modify Gj if amino acids 261 to 280 are missing from the Cx43 sequence. Our results suggest that a particle-receptor (or ball-and-chain) mechanism, similar to that described for pH gating, also applies to chemical regulation of Cx43 by other factors.

Key Words: connexin43 • gap junction conductance • insulin • phosphorylation • Xenopus oocyte

This article has been cited by other articles:

				N. S. Heyman, D. T. Kurjiaka, J. F. Ek Vitorin, and J. M. Burt Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43 Am J Physiol Heart Circ Physiol, July 1, 2009; 297(1): H450 - H459. [Abstract] [Full Text] [PDF]

				J. Kang, N. Kang, D. Lovatt, A. Torres, Z. Zhao, J. Lin, and M. Nedergaard Connexin 43 Hemichannels Are Permeable to ATP J. Neurosci., April 30, 2008; 28(18): 4702 - 4711. [Abstract] [Full Text] [PDF]

				M. H. de Pina-Benabou, V. Szostak, A. Kyrozis, D. Rempe, D. Uziel, M. Urban-Maldonado, S. Benabou, D. C. Spray, H. J. Federoff, P. K. Stanton, et al. Blockade of Gap Junctions In Vivo Provides Neuroprotection After Perinatal Global Ischemia Stroke, October 1, 2005; 36(10): 2232 - 2237. [Abstract] [Full Text] [PDF]

				A. F. Lau c-Src: Bridging the Gap Between Phosphorylation- and Acidification-Induced Gap Junction Channel Closure Sci. Signal., July 5, 2005; 2005(291): pe33 - pe33. [Abstract] [Full Text] [PDF]

				P. L. Sorgen, H. S. Duffy, P. Sahoo, W. Coombs, M. Delmar, and D. C. Spray Structural Changes in the Carboxyl Terminus of the Gap Junction Protein Connexin43 Indicates Signaling between Binding Domains for c-Src and Zonula Occludens-1 J. Biol. Chem., December 24, 2004; 279(52): 54695 - 54701. [Abstract] [Full Text] [PDF]

				K. Maass, A. Ghanem, J.-S. Kim, M. Saathoff, S. Urschel, G. Kirfel, R. Grummer, M. Kretz, T. Lewalter, K. Tiemann, et al. Defective Epidermal Barrier in Neonatal Mice Lacking the C-Terminal Region of Connexin43 Mol. Biol. Cell, October 1, 2004; 15(10): 4597 - 4608. [Abstract] [Full Text] [PDF]

				M. Delmar, W. Coombs, P. Sorgen, H. S Duffy, and S. M Taffet Structural bases for the chemical regulation of Connexin43 channels Cardiovasc Res, May 1, 2004; 62(2): 268 - 275. [Abstract] [Full Text] [PDF]

				A. P Moreno Biophysical properties of homomeric and heteromultimeric channels formed by cardiac connexins Cardiovasc Res, May 1, 2004; 62(2): 276 - 286. [Abstract] [Full Text] [PDF]

				G. Olbina and W. Eckhart Mutations in the Second Extracellular Region of Connexin 43 Prevent Localization to the Plasma Membrane, but Do Not Affect Its Ability to Suppress Cell Growth Mol. Cancer Res., July 1, 2003; 1(9): 690 - 700. [Abstract] [Full Text] [PDF]

				D. Lin, D. L. Boyle, and D. J. Takemoto IGF-I-Induced Phosphorylation of Connexin 43 by PKC{gamma}: Regulation of Gap Junctions in Rabbit Lens Epithelial Cells Invest. Ophthalmol. Vis. Sci., March 1, 2003; 44(3): 1160 - 1168. [Abstract] [Full Text] [PDF]

				A. P. Moreno, M. Chanson, J. Anumonwo, I. Scerri, H. Gu, S. M. Taffet, and M. Delmar Role of the Carboxyl Terminal of Connexin43 in Transjunctional Fast Voltage Gating Circ. Res., March 8, 2002; 90(4): 450 - 457. [Abstract] [Full Text] [PDF]

				L. I. Plotkin, S. C. Manolagas, and T. Bellido Transduction of Cell Survival Signals by Connexin-43 Hemichannels J. Biol. Chem., March 1, 2002; 277(10): 8648 - 8657. [Abstract] [Full Text] [PDF]

				A.-C. N. Le and L. S. Musil A novel role for FGF and extracellular signal-regulated kinase in gap junction-mediated intercellular communication in the lens J. Cell Biol., July 9, 2001; 154(1): 197 - 216. [Abstract] [Full Text] [PDF]

				X. Xu, W.E.I. Li, G.Y. Huang, R. Meyer, T. Chen, Y. Luo, M.P. Thomas, G.L. Radice, and C.W. Lo Modulation of mouse neural crest cell motility by N-cadherin and connexin 43 gap junctions J. Cell Biol., July 9, 2001; 154(1): 217 - 230. [Abstract] [Full Text] [PDF]

				H. Gu, J. F. Ek-Vitorin, S. M. Taffet, and M. Delmar Coexpression of Connexins 40 and 43 Enhances the pH Sensitivity of Gap Junctions : A Model for Synergistic Interactions Among Connexins Circ. Res., May 26, 2000; 86 (10): e98 - e103. [Abstract] [Full Text] [PDF]

				B. W. Doble, P. Ping, and E. Kardami The {epsilon} Subtype of Protein Kinase C Is Required for Cardiomyocyte Connexin-43 Phosphorylation Circ. Res., February 18, 2000; 86(3): 293 - 301. [Abstract] [Full Text] [PDF]

				Y. Omori and H. Yamasaki Gap junction proteins connexin32 and connexin43 partially acquire growth-suppressive function in HeLa cells by deletion of their C-terminal tails Carcinogenesis, October 1, 1999; 20(10): 1913 - 1918. [Abstract] [Full Text] [PDF]

				K. Stergiopoulos, J. L. Alvarado, M. Mastroianni, J. F. Ek-Vitorin, S. M. Taffet, and M. Delmar Hetero-Domain Interactions as a Mechanism for the Regulation of Connexin Channels Circ. Res., May 28, 1999; 84(10): 1144 - 1155. [Abstract] [Full Text] [PDF]

				L. Zhou, E. M. Kasperek, and B. J. Nicholson Dissection of the Molecular Basis of pp60v-src Induced Gating of Connexin 43 Gap Junction Channels J. Cell Biol., March 8, 1999; 144(5): 1033 - 1045. [Abstract] [Full Text] [PDF]

				A. P. Moreno, M. Chanson, J. Anumonwo, I. Scerri, H. Gu, S. M. Taffet, and M. Delmar Role of the Carboxyl Terminal of Connexin43 in Transjunctional Fast Voltage Gating Circ. Res., March 8, 2002; 90(4): 450 - 457. [Abstract] [Full Text] [PDF]

				J. M. B. Anumonwo, S. M. Taffet, H. Gu, M. Chanson, A. P. Moreno, and M. Delmar The Carboxyl Terminal Domain Regulates the Unitary Conductance and Voltage Dependence of Connexin40 Gap Junction Channels Circ. Res., April 13, 2001; 88(7): 666 - 673. [Abstract] [Full Text] [PDF]