Last updated: Oct.30,2014 at 1am PST
A
common protein plays a different role than previously thought in the opening
and closing of channels that let ions flow in and out of our cells, researchers
at Johns Hopkins report. Those channels are critical to life, as having the
right concentrations of sodium and calcium
ions in cells enables healthy brain communication, heart contraction and many
other processes. The new study reveals that a form of calmodulin long thought
to be dormant actually opens these channels wide. The finding is likely to
bring new insight into disorders caused by faulty control of these channels, such
as cardiac arrhythmias,
epilepsy
and Parkinson's
disease, the researchers say.
The dynamic interplay of calcium-free calmodulin
(white yang domain) and calcium-bound calmodulin (dark yin domain) controls the
opening of ion channels, shown in the background. Credit: Manu Ben-Johny and
David Yue/Johns Hopkins Medicine
In
the current model, explains David Yue, M.D., Ph.D. , a professor of biomedical
engineering and neuroscience
at the Johns Hopkins University School of Medicine, calmodulin can do little
until it binds to calcium, which changes its shape and snaps it into action.
The activated calmodulin can then bind to a specialized control lever inside
calcium and sodium channels, which closes the channels.
The
new study revises this viewpoint by devising ways to deliver surges of
calcium-free calmodulin to channels. In so doing, "it can be seen that
calcium-free calmodulin is in no way dormant, but instead markedly boosts the
opening of calcium and sodium channels to begin with," Yue says. When
calcium binds to the "resident" calcium-free calmodulin on channels,
this initial enhancement dissipates. "The two forms of calmodulin are both
powerful, each imposing opposing actions that together maintain exquisite
control, akin to the 'yin-yang' balance in Chinese philosophy," Yue says.
"This insight into how the calmodulin-controlled lever works could
ultimately help in finding treatments for a plethora of conditions that stem
from faulty ion channels."
http://www.medicalnewstoday.com/releases/284586.php
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