Abstract

The calcium-binding protein calmodulin (CaM) is thought to modulate the P/Q-type calcium channel of neurons in two ways: to facilitate and then to inhibit channel opening. DeMaria et al . have fleshed out the molecular details of this dual regulation and report that the two competing processes are accommodated by calcium binding to two different lobes of CaM. Calcium binding to the COOH-terminal lobe stimulated channel opening, whereas calcium binding to the NH 2 -terminal lobe inhibited channel activity in transfected cells. They also found that calcium-bound CaM exerted these effects through a region called IQ in the receptor's alpha subunit, and not a previously identified region called the CaM binding site. The authors further discovered that calcium-free CaM appears preassociated with the resting channel and this may facilitate a rapid response to calcium. C. D. DeMaria, T. W. Soong, B. A. Alseikhan, R. S. Alvania, D. T. Yue, Calmodulin bifurcates the local Ca 2+ signal that modulates P/Q-type Ca 2+ channels. Nature 411 : 484-489 (2001). [Online Journal]

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