Experts discover how calcium helps cells communicate

July 31st, 2008 - 3:50 pm ICT by IANS  

Washington, July 31 (IANS) Calcium helps facilitate communication among cells, but how cells and molecules manage to sense and respond to its fluctuations long remained a mystery. Johns Hopkins biomedical engineers have discovered how calcium sensor protein calmodulin can gauge both the local flow of calcium, through the closest channel, as well as global calcium flow entering the cell’s many channels.

“It’s like being at a cocktail party where the easiest person to listen to is the one closest to you, but we all have the ability to keep an ear out for other interesting conversations going on throughout the room,” says David Yue, a professor at Hopkins.

“It turns out that calmodulin is doing a similar thing, sensing the calcium coming through the closest channel through one ear while the other ear ‘listens’ to the calcium coming through distant channels across the cell.”

Normally, calmodulin is positioned right near each calcium channel. Several years ago, scientists discovered that calmodulin somehow can switch its sensory focus between local calcium and global calcium entering the cell through channels at a distance.

The calmodulin protein, explains Yue, is made of two ball-like lobes, and it’s these two lobes that act as the different calcium-sensing “ears.”

The C lobe listens locally and the N lobe listens globally, across the whole cell. To figure out how calmodulin’s two lobes can sense different sources of calcium, the team took a two-pronged approach.

First, they used computers to perform mathematical simulations that tested different potential calcium detection mechanisms of the calmodulin lobes.

Others have shown that the C lobe of calmodulin hangs onto calcium for a long time, whereas the N lobe lets go rapidly. Their simulations suggested that these slight differences in calcium holding time might play a role in calmodulin’s ability to sense both local and global calcium levels.

The study has been published in the medical journal Cell.

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