Premium
The TRP Ca 2+ channel assembled in a signaling complex by the PDZ domain protein INAD is phosphorylated through the interaction with protein kinase C (ePKC)
Author(s) -
Huber Armin,
Sander Philipp,
Bähner Monika,
Paulsen Reinhard
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)00248-8
Subject(s) - pdz domain , phosphorylation , signal transduction , microbiology and biotechnology , phospholipase c , rhodopsin , biology , protein kinase c , protein phosphorylation , scaffold protein , protein kinase a , immunoprecipitation , kinase , biochemistry , chemistry , retinal , gene
Photoreceptors which use a phospholipase C‐mediated signal transduction cascade harbor a signaling complex in which the phospholipase Cβ (PLCβ), the light‐activated Ca 2+ channel TRP, and an eye‐specific protein kinase C (ePKC) are clustered by the PDZ domain protein INAD. Here we investigated the function of ePKC by cloning the Calliphora homolog of Drosophila ePKC, by precipitating the TRP signaling complex with anti‐ePKC antibodies, and by performing phosphorylation assays in isolated signaling complexes and in intact photoreceptor cells. The deduced amino acid sequence of Calliphora ePKC comprises 685 amino acids (MW=78 036) and displays 80.4% sequence identity with Drosophila ePKC. Immunoprecipitations with anti‐ePKC antibodies led to the co‐precipitation of PLCβ, TRP, INAD and ePKC but not of rhodopsin. Phorbolester‐ and Ca 2+ ‐dependent protein phosphorylation revealed that, apart from the PDZ domain protein INAD, the Ca 2+ channel TRP is a substrate of ePKC. TRP becomes phosphorylated in isolated signaling complexes. TRP phosphorylation in intact photoreceptor cells requires the presence of extracellular Ca 2+ in micromolar concentrations. It is proposed that ePKC‐mediated phosphorylation of TRP is part of a negative feedback loop which regulates Ca 2+ influx through the TRP channel.