Author/Editor		Huber, Armin; Belušič, Gregor; Da Silva, Noel; Baehner, Monika; Gerdon, Gabriele; Drašlar, Kazimir; Paulsen, Reinhard
Title		The Calliphora rpa mutant lacks the PDZ domain-assembled INAD signalling complex
Type		članek
Source		Eur J Neurosci
Vol. and No.		Letnik 12
Publication year		2000
Volume		str. 3909-18
Language		eng
Abstract		The visual transduction cascade of fly photoreceptors is a G protein-coupled phospholipase C-signalling pathway which Is assembled into a supramolecular signalling complex by the PDZ (postsynaptic density protein-95, discs large, ZO-1) domain protein INAD (inactivation no afterpotential D). The norpA-encoded phospholipase C(beta, the light-activated transient receptor potential (TRP) Ca2+ channel and an eye-specific protein kinase C are bound to INAD and together form the core of the signalling complex. In the present study we show that the Calliphora rpa mutant, which has previously been hypothesized to represent an equlvalent of Drosophila norpA mutants, has normal amounts of norpA mRNA but fails to express inaD mRNA. Electrophysiological recordings from the eyes of the rpa mutant reveal that the electroretinogram is reduced (about 12 % of wild type) but not completely absent, and that it exhibits markedly prolonged deactivation kinetics. Furthermore, rpa mutants display a slow, light-dependent degeneration of the photoreceptor cells. With respect to the INAD signalling complex, the rpa mutant Is similar to the Drosophila inaD null mutant: not only INAD itself, but also the other core components of the INAD signalling complex, are reduced or absent in photoreceptor membranes of rpa flies. Residual TRP is localized throughout the plasma membrane of the photoreceptor cell, rather than being restricted to the microvillar photoreceptor membrane. (35S)methionine-labelling of newly synthesized retinal proteins reveals that TRP is synthesized in the rpa mutant at wild-type level, but is transported to or incorporated into the microvillar photoreceptor membrane at a much lower rate. We thus suggest, that the formation of the INAD signalling complex is required for specifically targeting its components to the photoreceptor membrane.
Descriptors		DROSOPHILA MELANOGASTER MUSCIDAE PHOTORECEPTORS, INVERTEBRATE PHOSPHOLIPASE C RNA, MESSENGER ELECTRORETINOGRAPHY BLOTTING, NORTHERN MEMBRANE PROTEINS IMMUNOHISTOCHEMISTRY PHENOTYPE MUTATION