Editorial: Single membrane channels formed by connexins or pannexins: focus on the nervous system

Citation: Orellana JA (2015) Editorial: Single membrane channels formed by connexins or pannexins: focus on the nervous system. For many years, the main function attributed to connexin hemichannels was providing the building blocks of gap junctions channels (GJCs), which allow direct but selective cytoplasmic continuity and molecular exchange between contacting cells. Nonetheless, the presence of functional connexin hemichannels in " nonjunctional " membranes has been demonstrated by several experimental approaches. These channels act like aqueous pores that are permeable to ions and small molecules and thus provide a diffusional route of exchange between the intra-and extracellular milieu. Recently, another gene family encoding a set of three membrane proteins termed pannexins (Panxs 1–3) was identified. Currently, most of evidence indicates that pannexins support the formation of single membrane channels (pannexons), similar, to connexin hemichannels; permitting paracrine/autocrine signaling among cells. Paracrine signaling mediated by connexin hemichannels and pannexons is emerging as one of the most widely distributed mechanisms of synchronization in the physiological brain parenchyma. However, it is believed that impairments of the permeability properties of connexin hemichannels and pannexons might be critical to the initiation and maintenance of the homeostatic imbalances that are observed in diverse brain diseases. In this collection, we gather a wide collection of 20 original research and review articles, providing the latest progress and insights in the field of connexin hemichannels and pannexons in the nervous system. Although, about 50% of autosomal recessive non-syndromic hearing loss occur by connexin mutations, the involvement of connexins in the etiology of acquired hearing loss remains to be fully elucidated. In this context, Figueroa and colleagues shed light on the gentamicin-induced inhibition of Cx26 hemichannels as possible cause of post-lingual hearing loss evoked by this aminoglycoside antibiotic (Figueroa et al., 2014). A puzzling aspect of connexin and pannexin field is found pharmacological tools allowing to distinguish between the function of hemichannels vs. GJCs. By employing primary cultures as well as acute hippocampal slices, Abudara and collaborators show that Gap19, a nonapeptide derived from the cytoplasmic loop of Cx43, inhibits astrocytic Cx43 hemichannels in a dose-dependent manner, without affecting GJCs (Abudara et al., 2014). This first section is closed with an article that examines the trafficking and subcellular localization of endogenous Panx2 and Panx1 proteins in astrocytes and neurons (Boassa et al., 2014), whereas the last study demonstrates that endogenous expression of Panx2 protein is not exclusively restricted to the nervous system …