Expressed cerebellar-type inositol 1,4,5-trisphosphate receptor, P₄₀₀, has calcium release activity in a fibroblast L cell line

Abstract

P₄₀₀, inositol 1,4,5-trisphosphate receptor (InsP₃-R), is a key protein to understanding the mechanisms of inositol 1,4,5-trisphosphate (InsP₃)-mediated Ca²⁺ mobilization. We obtained the cerebellar-type P₄₀₀/InsP₃-R cDNA and generated an L cell transfectant (L15) that produces cDNA-derived P₄₀₀/InsP₃-R. In membranes, this protein displays high affinity, specificity, and capacity for InsP₃, as does the cerebellar P₄₀₀/InsP₃-R. InsP₃ can also induce greater ⁴⁵Ca²⁺ release from the membrane vesicles of L15 cells than from those of control L cells. These results provide direct evidence that the cDNA-derived P₄₀₀/InsP₃-R protein is actually involved in physiological Ca²⁺ mobilization, through binding to InsP₃ molecules in the same manner as the cerebellar P₄₀₀/InsP₃-R.