Subconductance States of Cx30 Gap Junction Channels: Data from Transfected HeLa Cells versus Data from a Mathematical Model

AbstractHuman HeLa cells expressing mouse connexin30 were used to study the electrical properties of gap junction channel substates. Experiments were performed on cell pairs using a dual voltage-clamp method. Single-channel currents revealed discrete levels attributable to a main state, a residual state, and five substates interposed, suggesting the operation of six subgates provided by the six connexins of a gap junction hemichannel. Substate conductances, γj,substate, were unevenly distributed between the main-state and the residual-state conductance (γj,main state=141 pS, γj,residual state=21 pS). Activation of the first subgate reduced the channel conductance by ∼30%, and activation of subsequent subgates resulted in conductance decrements of 10–15% each. Current transitions between the states were fast (