Cell
Volume 83, Issue 3, 3 November 1995, Pages 463-472
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Article
Calcineurin associated with the inositol 1,4,5-trisphosphate receptor-FKBP12 complex modulates Ca2+ flux

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Abstract

The immunosuppressant drug FK506 binds to the immunophilin protein FKBP12 and inhibits its prolyl isomerase activity. Immunosuppresive actions, however, are mediated via an FK506-FKBP12 inhibition of the Ca2+-activated phosphatase calcineurin. Physiologic cellular roles for FKBP12 have remained unclear. FKBP12 is physically associated with the RyR and IP3R Ca2+ channels in the absence of FK506, with added FK506 disrupting these complexes. Dissociation of FKBP12 results in alteration of channel Ca2+ conductance in both cases. We now report that calcineurin is physiologically associated with the IP3R-FKBP12 and RyR-FKBP12 receptor complexes and that this interaction can be disrupted by FK506 or rapamycin. Calcineurin anchored to the IP3R via FKBP12 regulates the phosphorylation status of the receptor, resulting in a dynamic Ca2+-sensitive regulation of IP3-mediated Ca2+ flux.

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