Critical role of the first transmembrane domain of Cx26 in regulating oligomerization and function

Oscar Jara, Rodrigo Acuña, Isaac E. García, Jaime Maripillán, Vania Figueroa, Juan C. Sáez, Raúl Araya-Secchi, Carlos F. Lagos, Tomas Pérez-Acle, Viviana M. Berthoud, Eric C. Beyer, Agustín D. Martínez

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25 Citations (Scopus)

Abstract

To identify motifs involved in oligomerization of the gap junction protein Cx26, we studied individual transmembrane (TM) domains and the full-length protein. Using the TOXCAT assay for interactions of isolated TM α-helices, we found that TM1, a Cx26 pore domain, had a strong propensity to homodimerize. We identified amino acids Val-37-Ala-40 (VVAA) as the TM1 motif required for homodimerization. Two deafness-associated Cx26 mutations localized in this region, Cx26V37I and Cx26A40G, differentially affected dimerization. TM1-V37I dimerized only weakly, whereas TM1-A40G did not dimerize. When the full-length mutants were expressed in HeLa cells, both Cx26V37I and Cx26A40G formed oligomers less efficiently than wild-type Cx26. A Cx26 cysteine substitution mutant, Cx26V37C formed dithiothreitol-sensitive dimers. Substitution mutants of Val-37 formed intercellular channels with reduced function, while mutants of Ala-40 did not form functional gap junction channels. Unlike wild-type Cx26, neither Cx26V37I nor Cx26A40G formed functional hemichannels in low extracellular calcium. Thus the VVAA motif of Cx26 is critical for TM1 dimerization, hexamer formation, and channel function. The differential effects of VVAA mutants on hemichannels and gap junction channels imply that inter-TM interactions can differ in unapposed and docked hemichannels. Moreover, Cx26 oligomerization appears dependent on transient TM1 dimerization as an intermediate step.

Original languageEnglish
Pages (from-to)3299-3311
Number of pages13
JournalMolecular Biology of the Cell
Volume23
Issue number17
DOIs
Publication statusPublished - 1 Sep 2012

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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    Jara, O., Acuña, R., García, I. E., Maripillán, J., Figueroa, V., Sáez, J. C., Araya-Secchi, R., Lagos, C. F., Pérez-Acle, T., Berthoud, V. M., Beyer, E. C., & Martínez, A. D. (2012). Critical role of the first transmembrane domain of Cx26 in regulating oligomerization and function. Molecular Biology of the Cell, 23(17), 3299-3311. https://doi.org/10.1091/mbc.E11-12-1058