A new study on how a group of proteins called pannexins form communication channels between two cells demonstrates what scientists have long been struggling to confirm1. The study shows that pannexins do form 'gap junctions' in specific cell lines where these proteins are less glycosylated (or less attached to sugar molecules).
Pannexins were discovered in 2003 and are believed to be structurally similar to their better known cousins connexin. In vertebrates, cells communicate through inter-cellular channels called 'gap junctions' made out of proteins called connexins. These junctions help exchange metabolites, signalling molecules and ions. In the heart, gap junctions carry electrical impulses helping rhythmic contraction and relaxation. Interruption of junctional communication in the heart may lead to arrhythmia and heart attack. In the nervous system, gap junctions form electrical synapses and help propagate nerve impulses.
Pannexins were also shown to form gap junctions when expressed in Xenopus oocyte. However, the gap junction formation ability of pannexin was not accepted by the scientific community since a number of laboratories failed to reproduce it. Amal Kanti Bera and his group in the Department of Biotechnology of IIT Madras have now used the 'dual patch clamp' technique in combination with molecular biology and fluorescence microscopy to show that pannexin junctions are quite different from connexin junctions. Unlike most gap junctions, pannexin junctions are voltage insensitive.
Moreover, pharmacological agents like heptanol that can undo most connexin gap junctions, have no effect on pannexin junctions. The work is expected to change the present understanding of cell-cell communication in vertebrates.