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(Circulation Research. 2002;91:85.)
© 2002 American Heart Association, Inc.

Editorials

Connexin Diversity

Discriminating the Message

Mario Delmar

From the Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY.

Correspondence to Mario Delmar, MD, PhD, Department of Pharmacology, SUNY Upstate Medical University, 766 Irving Ave, Syracuse, NY 13210. E-mail delmarm@upstate.edu

Key Words: connexin • gap junctions • ion channels

An extract of the first 250 words of the full text is provided, because this article has no abstract.

In cardiac electrophysiology, gap junctions are often conceptualized as passive resistors that allow for electrical charge to move between cells. From that standpoint, gap junctions seem like rigid structures that sit idle between cells as small ions traverse across. Yet, although the importance of gap junctions in electrical synchronization is not questioned, it is generally accepted that these structures are more than electrical elements. Indeed, gap junctions are highly regulable molecular complexes present in the vast majority of cells in the body, including many cell types that are electrically nonexcitable. In addition to allowing the passage of ions, gap junctions allow the passage of small molecules as well. Hence, gap junctions provide not only electrical coupling to excitable cells but also metabolic coupling to all cell types where they are present.¹ Yet, although the nature of the message that carries electrical information is rather well understood (ions carrying charge), the nature of the molecule(s) providing metabolic coupling is mostly unknown. The answer to the obvious question remains elusive: what goes through gap junctions in living cells?

The answer to this question is complicated by the fact that not all gap junctions are exactly the same. Gap junctions are formed by the oligomerization of a protein called connexin (Figure). Six connexin subunits noncovalently bind to form a hemichannel (or connexon); two connexons, one provided by each cell, dock their extracellular domains and open a hydrophilic pore into the neighboring cytoplasmic spaces, forming a gap junction channel. Twenty connexins have . . . [Full Text of this Article]

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