Connexin37 forms high conductance gap junction channels with subconductance state activity and selective dye and ionic permeabilities.
Gap junctions are thought to mediate the direct intercellular coupling of adjacent cells by the open-closed gating of an aqueous pore permeable to ions and molecules of up to 1 kDa or 10-14 A in diameter. We symmetrically altered the ionic composition or asymmetrically added 6-carboxyfluorescein (6-CF, M(r) = 376), a fluorescent tracer, to pairs of connexin37-transfected mouse neuro2A cells to examine the ionic and dye permeability of human connexin37 channels. We demonstrate that the 300-pS channel formed by connexin37 has an effective relative anion/cation permeability ratio of 0.43, directly converts to at least one intermediate (63 pS) subconductance state, and that 6-CF dye transfer is accompanied by a 24% decrease in unitary channel conductance. These observations favor a new interpretation of the gap junction pore consistent with direct ion-channel interactions or electrostatic charge effects common to more conventional multistate ion channels. These results have distinct implications about the different forms of intercellular signaling (cationic, ionic, and/or biochemical) that can occur depending on the expression and conformation of the connexin channel proteins.
Veenstra
R D
RD
Department of Pharmacology, SUNY Health Science Center at Syracuse 13210.
Wang
H Z
HZ
Beyer
E C
EC
Ramanan
S V
SV
Brink
P R
PR
D000818:Animals; D002460:Cell Line; D017630:Connexins / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D005452:Fluoresceins; D005456:Fluorescent Dyes; D017629:Gap Junctions / Q000502:physiology*; D015640:Ion Channel Gating; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials; D051379:Mice; D008954:Models, Biological; D009447:Neuroblastoma; D011336:Probability; D013997:Time Factors; D014407:Tumor Cells, Cultured; D000097006:Gap Junction alpha-4 Protein
D017630:Connexins; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007473:Ion Channels; D000097006:Gap Junction alpha-4 Protein; C024098:6-carboxyfluorescein