Dec. 31, 2009 The heartbeat is controlled by rapid conduction of
an electrical current between heart muscle cells. Central to
passage of the electrical current are structures known as gap
junctions, low resistance conduits that link heart muscle cells
and consist of proteins known as connexins. Many forms of heart
disease are associated with decreased gap junction coupling, and
these changes predispose to abnormal heartbeats, which can be
lethal. Robin Shaw and colleagues, at the University of
California at San Francisco, have now identified a reason why
there is decreased gap junction coupling in these situations
using human, mouse, and zebrafish heart tissue. The research
appears in the Journal of Clinical Investigation. In the study,
the protein EB1, which delivers connexins to gap junctions, was
found to be displaced in ischemic human hearts, stressed mouse
hearts, and isolated cells subjected to oxidative stress,
leading to decreased gap junction coupling. Further, in
zebrafish hearts, oxidative stress r