Editors' ChoiceCalcium signaling

A New Ligand for IP3 Receptors

Science's STKE  04 Jun 2002:
Vol. 2002, Issue 135, pp. tw197-TW197
DOI: 10.1126/stke.2002.135.tw197

Inositol trisphosphate (IP3) is a well-known second messenger that binds to the endoplasmic reticulum calcium channel, the IP3 Receptor (IP3R). Yang et al. identified members of the neuronal Ca2+ sensor proteins (CaBPs) as proteins that interacted with the cytosolic portion of the IP3R. These interactions were confirmed by colocalization and coimmunoprecipitation experiments from rat brain and transfected cells. In coimmunoprecipitation experiments with transfected cells, the binding of CaBP was enhanced by increasing calcium to the cells. Using an assay to measure single-channel currents from IP3R located on Xenopus oocyte nuclear membranes, the authors showed that CaBP1 stimulated the channel in the absence of IP3. CaBPs may be another mechanism, in addition to direct calcium binding by the receptor, by which IP3 sensitivity to calcium signals can be achieved.

J. Yang, S. McBride, D.-O. D. Mak, N. Vardi, K. Palczewski, F. Haeseleer, J. K. Foskett, Identification of a family of calcium sensors as protein ligands of inositol trisphosphate receptor Ca2+ release channels. Proc. Natl. Acad. Sci. U.S.A. 99, 7711-7716 (2002). [Abstract] [Full Text]