The Gos28 SNARE Protein Mediates Intra-Golgi Transport of Rhodopsin and Is Required for Photoreceptor Survival

Erica E Rosenbaum,Eva Vasiljevic,Spencer C Cleland,Carlos Flores,Nansi Jo Colley

doi:10.1074/jbc.m114.585166

Erica E Rosenbaum, Eva Vasiljevic + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m114.585166

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Abstract

SNARE proteins play indispensable roles in membrane fusion events in many cellular processes, including synaptic transmission and protein trafficking. Here, we characterize the Golgi SNARE protein, Gos28, and its role in rhodopsin (Rh1) transport through Drosophila photoreceptors. Mutations in gos28 lead to defective Rh1 trafficking and retinal degeneration. We have pinpointed a role for Gos28 in the intra-Golgi transport of Rh1, downstream from α-mannosidase-II in the medial- Golgi. We have confirmed the necessity of key residues in Gos28's SNARE motif and demonstrate that its transmembrane domain is not required for vesicle fusion, consistent with Gos28 functioning as a t-SNARE for Rh1 transport. Finally, we show that human Gos28 rescues both the Rh1 trafficking defects and retinal degeneration in Drosophila gos28 mutants, demonstrating the functional conservation of these proteins. Our results identify Gos28 as an essential SNARE protein in Drosophila photoreceptors and provide mechanistic insights into the role of SNAREs in neurodegenerative disease.

Highlights

The Golgi SNARE, Gos28, plays important roles in vesicular transport during protein trafficking
Identification of Mutations in Drosophila gos28 —Flies harboring a mutation in gos28 were identified by screening the Zuker collection of ethyl methylsulfonate (EMS)-mutagenized Drosophila [37] for genetic loci that are critical for the proper expression of Rh1 protein
We characterize the role of Drosophila Gos28, in vivo, and demonstrate that mutations in gos28 lead to defects in Rh1 trafficking and retinal degeneration

Summary

Background

The Golgi SNARE, Gos, plays important roles in vesicular transport during protein trafficking. SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins constitute a universal machinery required for virtually all membrane fusion events in eukaryotic cells and are required for diverse cellular processes, including cell migration, hormone signaling, enzyme release, synaptic transmission, and the trafficking of proteins and lipids through intracellular compartments of the secretory pathway [1,2,3]. Because of their central roles in fundamental cellular processes, SNARE proteins have been linked to a wide variety of human diseases. We have demonstrated that human Gos can functionally replace its Drosophila homolog and rescue both the Rh1 trafficking defects and the retinal degeneration, showing that Gos is conserved from flies to humans

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