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Author: search.filters.author.Guillermo A. AltenbergSubject: search.filters.subject.gap junction protein

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    Extracellular Cysteines Are Critical to Form Functional Cx46 Hemichannels
    (2022)
    Ainoa Fernández-Olivares
    ;
    Eduardo Durán-Jara
    ;
    Daniel A. Verdugo
    ;
    Mariana C. Fiori
    ;
    Guillermo A. Altenberg
    <jats:p>Connexin (Cxs) hemichannels participate in several physiological and pathological processes, but the molecular mechanisms that control their gating remain elusive. We aimed at determining the role of extracellular cysteines (Cys) in the gating and function of Cx46 hemichannels. We studied Cx46 and mutated all of its extracellular Cys to alanine (Ala) (one at a time) and studied the effects of the Cys mutations on Cx46 expression, localization, and hemichannel activity. Wild-type Cx46 and Cys mutants were expressed at comparable levels, with similar cellular localization. However, functional experiments showed that hemichannels formed by the Cys mutants did not open either in response to membrane depolarization or removal of extracellular divalent cations. Molecular-dynamics simulations showed that Cys mutants may show a possible alteration in the electrostatic potential of the hemichannel pore and an altered disposition of important residues that could contribute to the selectivity and voltage dependency in the hemichannels. Replacement of extracellular Cys resulted in “permanently closed hemichannels”, which is congruent with the inhibition of the Cx46 hemichannel by lipid peroxides, through the oxidation of extracellular Cys. These results point to the modification of extracellular Cys as potential targets for the treatment of Cx46-hemichannel associated pathologies, such as cataracts and cancer, and may shed light into the gating mechanisms of other Cx hemichannels.</jats:p>
      2Scopus© Citations 6
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      17  1Scopus© Citations 12
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    4-Hydroxynonenal induces Cx46 hemichannel inhibition through its carbonylation
    (2020)
    Mauricio A. Retamal  
    ;
    Mariana C. Fiori
    ;
    Ainoa Fernandez-Olivares
    ;
    Sergio Linsambarth
    ;
    Francisca Peña
    Scopus© Citations 17  5
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    Role and Posttranslational Regulation of Cx46 Hemichannels and Gap Junction Channels in the Eye Lens
    (2022)
    Mauricio A. Retamal  
    ;
    Guillermo A. Altenberg
    <jats:p>Connexins are a family of proteins that can form two distinct types of channels: hemichannels and gap junction channels. Hemichannels are composed of six connexin subunits and when open allow for exchanges between the cytoplasm and the extracellular milieu. Gap junction channels are formed by head-to-head docking of two hemichannels in series, each one from one of two adjacent cells. These channels allow for exchanges between the cytoplasms of contacting cells. The lens is a transparent structure located in the eye that focuses light on the retina. The transparency of the lens depends on its lack of blood irrigation and the absence of organelles in its cells. To survive such complex metabolic scenario, lens cells express Cx43, Cx46 and Cx50, three connexins isoforms that form hemichannels and gap junction channels that allow for metabolic cooperation between lens cells. This review focuses on the roles of Cx46 hemichannels and gap junction channels in the lens under physiological conditions and in the formation of cataracts, with emphasis on the modulation by posttranslational modifications.</jats:p>
      6Scopus© Citations 8
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      8Scopus© Citations 15