Biophysical evidence that connexin-36 forms functional gap junction channels between pancreatic mouse ß-cells
Por:
Moreno A.P., Berthoud V.M., Pérez-Palacios G., Pérez-Armendariz E.M.
Publicada:
1 ene 2005
Resumen:
Connexin-36 (Cx36) is the only gap junction protein that has been unambiguously identified in rodent pancreatic ?-cells. However, properties of gap junction channel unitary currents between ?-cells remain unrevealed. To address whether Cx36 forms functional channels in ?-cells, we characterized biophysical properties of macro- and microscopic junctional currents recorded from dual whole cell voltage clamp isolated pairs of dispersed mouse ?-cells. Electrical coupling was recorded in 80% of cell pairs with a junctional conductance (gj) of 355 ± 45 pS (n = 20). Transjunctional voltage dependence was identified in three of seven cell pairs with high-input membrane resistances. Normalized steady-state gj (Gj) and transjunctional-voltage relation were well described by a two-state Boltzmann equation [maximal conductance (Gmax) = 1.0, voltage-insensitive conductance (Gmin) = 0.3 and 0.28, voltage gating sensitivity (A) = 0.21 and 0.23, and voltage at which one-half of the initial voltage-dependent conductance was reached (Vo) = -85 and 87 mV for negative and positive potentials, respectively]. Halothane reversibly uncoupled ?-cell pairs, and, during recovery, unitary conductances of 5-10 pS were recorded while using patch pipettes containing mainly CsCl. Although these properties are similar to those previously described for Cx36 channels in mammalian cell systems, we found that ?-cell junctional currents were insensitive to quinine. Cx36 transcript and protein expression in islets and freshly dispersed cell preparations was confirmed by RT-PCR and immunofluorescence. In conclusion, biophysical properties of junctional channels between ?-cells are similar but not identical to those previously described for homomeric Cx36 channels. Cell type-specific mechanisms that may account for these differences are discussed. Copyright © 2005 the American Physiological Society.
Filiaciones:
Moreno A.P.:
Krannert Institute of Cardiology, Indiana School of Medicine, Indianapolis, IN, United States
Berthoud V.M.:
Section of Hematology/Oncology, Department of Pediatrics, University of Chicago, Chicago, IL, United States
Pérez-Palacios G.:
Facultad de Medicina, Departmento de Medicina Experimental, Univ. National Autonoma de Mexico, Mexico City, Mexico
Pérez-Armendariz E.M.:
Facultad de Medicina, Departmento de Medicina Experimental, Univ. National Autonoma de Mexico, Mexico City, Mexico
Depto. de Medicina Experimental, Facultad de Medicina, Hospital General de México, Dr. Balmis no. 148, Colonia Doctores Mexico, D.F., 06726, Mexico
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