Correlative studies of gating in Cx46 and Cx50 hemichannels and gap junction channels

Miduturu Srinivas, Jack Kronengold, Feliksas F. Bukauskas, Thaddeus A. Bargiello, Vytautas Verselis

Research output: Contribution to journalArticle

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Abstract

Transjunctional voltage (Vj) gating of gap junction (GJ) channels formed of connexins has been proposed to occur by gating of the component hemichannels. We took advantage of the ability of Cx46 and Cx50 to function as unapposed hemichannels to identify gating properties intrinsic to hemichannels and how they contribute to gating of GJ channels. We show that Cx46 and Cx50 hemichannels contain two distinct gating mechanisms that generate reductions in conductance for both membrane polarities. At positive voltages, gating is similar in Cx46 and Cx50 hemichannels, primarily showing increased transitioning to long-lived substates. At negative voltages, Cx46 currents deactivate completely and the underlying single hemichannels exhibit transitions to a fully closed state. In contrast, Cx50 currents do not deactivate completely at negative voltages and the underlying single hemichannels predominantly exhibit transitions to various substates. Transitions to a fully closed state occur, but are infrequent. In the respective GJ channels, both forms of gating contribute to the reduction in conductance by Vj. However, examination of gating of mutant hemichannels and GJ channels in which the Asp at position 3 was replaced with Asn (D3N) showed that the positive hemichannel gate predominantly closes Cx50 GJs, whereas the negative hemichannel gate predominantly closes Cx46 GJs in response to Vj. We also report, for the first time, single Cx50 hemichannels in oocytes to be inwardly rectifying, high conductance channels (γ = 470 pS). The antimalarial drug mefloquine, which selectively blocks Cx50 and not Cx46 GJs, shows the same selectivity in Cx50 and Cx46 hemichannels indicating that the actions of such uncoupling agents, like voltage gating, are intrinsic hemichannel properties.

Original languageEnglish (US)
Pages (from-to)1725-1739
Number of pages15
JournalBiophysical Journal
Volume88
Issue number3
DOIs
StatePublished - Mar 2005

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Gap Junctions
Uncoupling Agents
Mefloquine
Connexins
Antimalarials
Viperidae
Oocytes
Membranes
connexin 46

ASJC Scopus subject areas

  • Biophysics

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Correlative studies of gating in Cx46 and Cx50 hemichannels and gap junction channels. / Srinivas, Miduturu; Kronengold, Jack; Bukauskas, Feliksas F.; Bargiello, Thaddeus A.; Verselis, Vytautas.

In: Biophysical Journal, Vol. 88, No. 3, 03.2005, p. 1725-1739.

Research output: Contribution to journalArticle

Srinivas, Miduturu ; Kronengold, Jack ; Bukauskas, Feliksas F. ; Bargiello, Thaddeus A. ; Verselis, Vytautas. / Correlative studies of gating in Cx46 and Cx50 hemichannels and gap junction channels. In: Biophysical Journal. 2005 ; Vol. 88, No. 3. pp. 1725-1739.
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