a1 The Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, NY, USA
a2 Department of Physiology and Biophysics, University of Miami Medical School, Miami, USA
In this review, we briefly summarize what is known about the properties of the three families of gap junction proteins, connexins, innexins and pannexins, emphasizing their importance as intercellular channels that provide ionic and metabolic coupling and as non-junctional channels that can function as a paracrine signaling pathway. We discuss that two distinct groups of proteins form gap junctions in deuterostomes (connexins) and protostomes (innexins), and that channels formed of the deuterostome homologues of innexins (pannexins) differ from connexin channels in terms of important structural features and activation properties. These differences indicate that the two families of gap junction proteins serve distinct, complementary functions in deuterostomes. In several tissues, including the CNS, both connexins and pannexins are involved in intercellular communication, but have different roles. Connexins mainly contribute by forming the intercellular gap junction channels, which provide for junctional coupling and define the communication compartments in the CNS. We also provide new data supporting the concept that pannexins form the non-junctional channels that play paracrine roles by releasing ATP and, thus, modulating the range of the intercellular Ca2+-wave transmission between astrocytes in culture.
(Received December 19 2007)
(Revised February 05 2008)
(Accepted February 08 2008)
c1 Correspondence should be addressed to Dr Eliana Scemes, Albert Einstein College of Medicine, Kennedy Center, room#203, 1410, Pelham Parkway, Bronx, NY, 10461, USA phone: +1 718 430 3303 email: [email protected]