The TRP Ca2+ channel assembled in a signaling complex by the PDZ domain protein INAD is phosphorylated through the interaction with protein kinase C (ePKC)

FEBS Letters

Bähner, Monika¹  Paulsen, Reinhard¹  Sander, Philipp¹  Huber, Armin¹ 

[1] Zoological Institute I, University of Karlsruhe, P.O. Box 6980, 76128 Karlsruhe, Germany

关键词: Ca2+ channel;    Capacitative Ca2+ entry;    Drosophila;    PDZ domain;    Phototransduction;    Phospholipase C;    Phosphorylation;    Protein kinase C;    Rhodopsin;    Vision;   

DOI  :  10.1016/S0014-5793(98)00248-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Photoreceptors which use a phospholipase C-mediated signal transduction cascade harbor a signaling complex in which the phospholipase Cβ (PLCβ), the light-activated Ca²⁺ 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 Ca²⁺-dependent protein phosphorylation revealed that, apart from the PDZ domain protein INAD, the Ca²⁺ 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 Ca²⁺ in micromolar concentrations. It is proposed that ePKC-mediated phosphorylation of TRP is part of a negative feedback loop which regulates Ca²⁺ influx through the TRP channel.

【 授权许可】

Unknown