SNAREs (SNAP receptors) are the key components of protein complexes that drive membrane fusion. Here, we report the function of a SNARE, Syntaxin 5 (Syx5), in the development of photoreceptors in Drosophila. In wild type photoreceptors, Syx5 localizes to cis-Golgi, along with cis-Golgi markers, Rab1, and GM130. We observed that Syx5-deficient photoreceptors shows notable accumulation of these cis-Golgi markers accompanying drastic accumulation of vesicles between ER and Golgi cisternae. Extensive analysis of Rh1 (rhodopsin 1) trafficking revealed that in Syx5-deficient photoreceptors, Rh1 is exported from the ER with normal kinetics, retained in cis-Golgi region along with GM130 for a prolonged period, then subsequently degraded presumable by endoplasmic-reticulum-associated protein degradation (ERAD) after retrieved to the ER. Unlike our previous report of Rab6-deficient photoreceptors—where two apical transport pathways are specifically inhibited—vesicle transport pathways to all of plasma membrane domains are inhibited in Syx5-deficient photoreceptors, implying that Rab6 and Syx5 are acting in different steps of intra-Golgi transport These results indicate that Syx5 is crucial for membrane protein transport, presumably during ER-derived vesicle fusion to form cis-Golgi cisternae.
- Received July 27, 2016.
- Accepted August 25, 2016.
- © 2016. Published by The Company of Biologists Ltd
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