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Neuron. 1999 Aug;23(4):799-808.

Calmodulin mediates calcium-dependent inactivation of the cerebellar type 1 inositol 1,4,5-trisphosphate receptor.

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Department of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Japan.


The dependency of purified mouse cerebellar type 1 inositol 1,4,5-trisphosphate receptor (IP3R1)/Ca2+ channel function on cytoplasmic Ca2+ was examined. In contrast to the channels in crude systems, the purified IP3R1 reconstituted into planar lipid bilayers did not show the bell-shaped dependence on Ca2+. It was activated with increasing Ca2+ sublinearly without inhibition even up to 200 microM. The addition of calmodulin to the cytoplasmic side inhibited the channel at high Ca2+ concentrations. Calmodulin antagonists reversed the Ca2+-dependent inactivation of the native channels in cerebellar microsomes. These results indicate that the bell-shaped dependence on cytoplasmic Ca2+ is not an intrinsic property of the IP3R1, and the Ca2+-dependent inactivation is directly mediated by calmodulin.

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