Gap junction hemichannels in astrocytes of the CNS

Juan C. Sáez, J. E. Contreras, F. F. Bukauskas, M. A. Retamal, Michael V. L. Bennett

Research output: Contribution to journalArticle

105 Citations (Scopus)

Abstract

Connexins are protein subunits that oligomerize into hexamers called con-nexons, gap junction hemichannels or just hemichannels. Because some gap junction channels are permeable to negatively and/or positively charged molecules up to ∼1kDa in size, it was thought that hemichannels should not open to the extracellular space. A growing amount of evidence indicates that opening of hemichannels does occur under both physiological and pathological conditions in astrocytes and other cell types. Electrophysiological studies indicate that hemichannels have a low open probability under physiological conditions but may have a much higher open probability under certain pathological conditions. Some of the physiological behaviours of astrocytes that have been attributed to gap junctions may, in fact, be mediated by hemichannels. Hemichannels constituted of Cx43, the main connexin expressed by astrocytes, are permeable to small physiologically significant molecules, such as ATP, NAD+ and glutamate, and may mediate paracrine as well as autocrine signalling. Hemichannels tend to be closed by negative membrane potentials, high concentrations of extracellular Ca2+ and intracellular H+ ions, gap junction blockers and protein phosphorylation. Hemichannels tend to be opened by positive membrane potentials and low extracellular Ca2+, and possibly by as yet unidentified cytoplasmic signalling molecules. Exacerbated hemichannel opening occurs in metabolically inhibited cells, including cortical astrocytes, which contributes to the loss of chemical gradients across the plasma membrane and speeds cell death.

Original languageEnglish (US)
Pages (from-to)9-22
Number of pages14
JournalActa Physiologica Scandinavica
Volume179
Issue number1
DOIs
StatePublished - Sep 1 2003

Fingerprint

Gap Junctions
Astrocytes
Connexins
Membrane Potentials
Autocrine Communication
Paracrine Communication
Connexin 43
Protein Subunits
Extracellular Space
NAD
Glutamic Acid
Cell Death
Adenosine Triphosphate
Phosphorylation
Cell Membrane
Ions

Keywords

  • Astroglia
  • Cell signalling
  • Connexins
  • Connexons
  • Ischaemia

ASJC Scopus subject areas

  • Physiology

Cite this

Gap junction hemichannels in astrocytes of the CNS. / Sáez, Juan C.; Contreras, J. E.; Bukauskas, F. F.; Retamal, M. A.; Bennett, Michael V. L.

In: Acta Physiologica Scandinavica, Vol. 179, No. 1, 01.09.2003, p. 9-22.

Research output: Contribution to journalArticle

Sáez, Juan C. ; Contreras, J. E. ; Bukauskas, F. F. ; Retamal, M. A. ; Bennett, Michael V. L. / Gap junction hemichannels in astrocytes of the CNS. In: Acta Physiologica Scandinavica. 2003 ; Vol. 179, No. 1. pp. 9-22.
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