TY - JOUR
T1 - Connexin Hemichannels in Astrocytes
T2 - An Assessment of Controversies Regarding Their Functional Characteristics
AU - Nielsen, Brian Skriver
AU - Hansen, Daniel Bloch
AU - Ransom, Bruce R.
AU - Nielsen, Morten Schak
AU - MacAulay, Nanna
PY - 2017/9
Y1 - 2017/9
N2 - Astrocytes in the mammalian central nervous system are interconnected by gap junctions made from connexins of the subtypes Cx30 and Cx43. These proteins may exist as hemichannels in the plasma membrane in the absence of a ‘docked’ counterpart on the neighboring cell. A variety of stimuli are reported to open the hemichannels and thereby create a permeation pathway through the plasma membrane. Cx30 and Cx43 have, in their hemichannel configuration, been proposed to act as ion channels and membrane pathways for different molecules, such as fluorescent dyes, ATP, prostaglandins, and glutamate. Published studies about astrocyte hemichannel behavior, however, have been highly variable and/or contradictory. The field of connexin hemichannel research has been complicated by great variability in the experimental preparations employed, a lack of highly specific pharmacological inhibitors and by confounding changes associated with genetically modified animal models. This review attempts to critically assess the gating, inhibition and permeability of astrocytic connexin hemichannels and proposes that connexins in their hemichannel configuration act as gated pores with isoform-specific permeant selectivity. We expect that some, or all, of the controversies discussed here will be resolved by future research and sincerely hope that this review serves to motivate such clarifying investigations.
AB - Astrocytes in the mammalian central nervous system are interconnected by gap junctions made from connexins of the subtypes Cx30 and Cx43. These proteins may exist as hemichannels in the plasma membrane in the absence of a ‘docked’ counterpart on the neighboring cell. A variety of stimuli are reported to open the hemichannels and thereby create a permeation pathway through the plasma membrane. Cx30 and Cx43 have, in their hemichannel configuration, been proposed to act as ion channels and membrane pathways for different molecules, such as fluorescent dyes, ATP, prostaglandins, and glutamate. Published studies about astrocyte hemichannel behavior, however, have been highly variable and/or contradictory. The field of connexin hemichannel research has been complicated by great variability in the experimental preparations employed, a lack of highly specific pharmacological inhibitors and by confounding changes associated with genetically modified animal models. This review attempts to critically assess the gating, inhibition and permeability of astrocytic connexin hemichannels and proposes that connexins in their hemichannel configuration act as gated pores with isoform-specific permeant selectivity. We expect that some, or all, of the controversies discussed here will be resolved by future research and sincerely hope that this review serves to motivate such clarifying investigations.
KW - Connexin
KW - Current
KW - Cx30
KW - Cx43
KW - Gating
KW - Hemichannels
KW - Isoforms
KW - Permeability
U2 - 10.1007/s11064-017-2243-7
DO - 10.1007/s11064-017-2243-7
M3 - Journal article
C2 - 28434165
AN - SCOPUS:85018824585
VL - 42
SP - 2537
EP - 2550
JO - Neurochemical Research
JF - Neurochemical Research
SN - 0364-3190
IS - 9
ER -