Microtubule assisted altered trafficking of Astrocytic Gap Junction Protein Connexin 43 is associated with depletion of Connexin 47 during Mouse Hepatitis Virus infection

Abstract

Gap junctions (GJs) are important for maintenance of central nervous system (CNS) homeostasis. GJ proteins, connexin 43 (Cx43) and connexin 47 (Cx47), play crucial role in production and maintenance of central nervous system (CNS) myelin. Cx43 is mainly expressed by astrocytes in the CNS, and forms gap junction intercellular communications (GJICs) between astrocytes (Cx43/Cx43) and astrocytes to oligodendrocytes (Cx43/Cx47). Mutations of these connexin (Cx) proteins cause dysmyelinating diseases in humans. Previously it has been shown that Cx43 localization and expression is altered due to mouse hepatitis virus (MHV)-A59 infection both in vivo and in vitro; however, its mechanism and association with loss of myelin protein was not elaborated. Thus, we explored potential mechanisms by which MHV-A59 infection alters Cx43 localization, and examined effects of viral infection on Cx47 expression and its association with loss of myelin marker proteolipid protein (PLP). Immunofluorescence and total internal reflection fluorescence (TIRF) microscopy confirmed that MHV-A59 used microtubules (MTs) as a conduit to reach the cell surface and restricted MT mediated Cx43 delivery to cell membrane. Co-immunoprecipitation experiments demonstrated that Cx43/β-tubulin molecular interaction was depleted due to protein-protein interaction between viral particles and MTs. During acute MHV-A59 infection, oligodendrocytic Cx47, which is mainly stabilized by Cx43 in vivo, was downregulated, and its characteristic staining remained disrupted even at chronic phase. The loss of Cx47 was associated with loss of PLP at the chronic stage of MHV-A59 infection.