Membrane channel

Membrane channels are a family of biological membrane proteins which allow the passive movement of ions (ion channels), water (aquaporins) or other solutes to passively pass through the membrane down their electrochemical gradient. They are studied using a range of channelomics experimental and mathematical techniques. Insights have suggested endocannabinoids (eCBs) as molecules that can regulate the opening of these channels during diverse conditions.^[1]

Properties

Hemichannels

A hemichannel is a membrane channel made up of six subunits.^[2] A hemichannel is defined as one-half of a gap junction channel.^[3] Hemichannels consist of connexins.^[2]

Pannexin

Pannexins are involved in the process of purinergic signalling. They release adenosine triphosphate (ATP), which activate purinergic receptors. On the other hand, purinergic receptor activation can also lead to the opening of the channel, via a positive feedback loop.^[4] In addition, P2Y receptors activate inositol trisphosphate, which leads to a transient increase in intracellular calcium, and opens both connexin and pannexin channels, therefore contributing to the propagation of calcium waves across astrocytes and epithelial cells.^[4]

References

1. Labra VC, Santibáñez CA, Gajardo-Gómez R, Díaz EF, Gómez GI, Orellana JA (2018-03-20). "The Neuroglial Dialog Between Cannabinoids and Hemichannels". Frontiers in Molecular Neuroscience. 11: 79. doi:10.3389/fnmol.2018.00079. PMC 5890195. PMID 29662436.
2. Retamal MA (2014). "Connexin and Pannexin hemichannels are regulated by redox potential". Frontiers in Physiology. 5: 80. doi:10.3389/fphys.2014.00080. PMC 3933782. PMID 24611056.
3. Spray DC, Ye ZC, Ransom BR (November 2006). "Functional connexin "hemichannels": a critical appraisal". Glia. 54 (7): 758–73. CiteSeerX 10.1.1.124.4117. doi:10.1002/glia.20429. PMID 17006904. S2CID 17677517.
4. Baroja-Mazo A, Barberà-Cremades M, Pelegrín P (January 2013). "The participation of plasma membrane hemichannels to purinergic signaling". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1828 (1): 79–93. doi:10.1016/j.bbamem.2012.01.002. PMID 22266266.

Further reading

• Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2002). Molecular Biology of the Cell (4th ed.). New York and London: Garland Science. ISBN 9780815332183. See Glossary, under "membrane channels".