Long-chain n-alkanols and arachidonic acid interfere with the V m -sensitive gating mechanism of gap junction channels

Abstract

Experiments were carried out on preformed cell pairs and induced cell pairs of an insect cell line (mosquito Aedes albopictus, clone C6/36). The coupling conductance, gj, was determined with the dual voltage-clamp method. Exposure of preformed cell pairs to lipophilic agents, such as long-chain n-alkanols (n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol) or arachidonic acid, provoked a decrease in gj. Hyperpolarization of both cells led to a recovery of gj. Systematic studies revealed that this phenomenon is caused by a shift of the sigmoidal relationship gj(ss) = f(Vm) towards more negative values of Vm (where gj(ss) = conductance at steady-state; Vm = membrane potential). The shift was dose dependent, it developed with time and was reversible. The longer the hydrocarbon chain of n-alkanols, the lower was the concentration required to produce a given shift. Besides shifting the function gj(ss) = f(Vm), arachidonic acid decreased the maximal conductance, gj(max). Single-channel records gained from induced cell pairs revealed that the lipophilic agents interfere with the Vm-sensitive slow channel gating mechanism. Application provoked slow current transitions (transition time: 5-40 ms) between an open state of the channel (i.e. main state or residual state) and the closed state; subsequently, fast channel transitions (transition time: < 2 ms) involving the main state and the residual state ceased completely. Hyperpolarization of Vm or washout of the lipophilic agents gave rise to the inverse sequence of events. The single-channel conductances gammaj(main state) and gammaj(residual state) were not affected by n-heptanol. We conclude that long-chain n-alkanols and arachidonic acid interact with the Vm-sensitive gating mechanism.

Inversion of both gating polarity and CO2 sensitivity of voltage gating with D3N mutation of Cx50

“…In the early 1990s, CO 2 application was reported to increase the V j sensitivity of Cx32 channels (38). More recently chemical gating induced by CO 2 was shown to be reversed by V j gradients positive at the mutant side of heterotypic channels between Cx32 and various Cx32 mutants (17,20), and chemical gating was reversed in insect cells by bilateral hyperpolarization (37). These observations suggest that chemical and voltage gates may be sensitive to V j and CO 2 , respectively.…”

Electrical properties of gap junction hemichannels identified in transfected HeLa cells

“…Long-chain alkanols reversibly block gap junction channels [28]. This property was used to further characterize I hc in Cx30-HeLa cells.…”

Blockade of Brain Stem Gap Junctions Increases Phrenic Burst Frequency and Reduces Phrenic Burst Synchronization in Adult Rat

“…The uncoupling agents selected included both glycyrrhetinic acid derivatives and higher-order (i.e., longchain) alcohol gap junction inhibitors as these types of agents are among those most commonly used and have all been demonstrated to rapidly reduce functional gap junction coupling in various cells (Burt and Spray 1989;Christ et al 1999;Davidson and Baumgarten 1988;Davidson et al 1986;Délèze and Hervé, 1983;Johnston et al 1980;Pappas et al 1996;Rozental et al 2001;Weingart and Bukauskas 1998;Yamane et al 2002) although the precise mechanisms of action are not known (recently reviewed by Rozental et al 2001). Although each of the uncoupling agents employed similarly modified phrenic nerve discharge (although magnitude differences were noted), it is unclear from the current experiments which respiratory-related brain stem regions were responsible for the modulation observed.…”