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An interaction network between the SNARE VAMP7 and Rab GTPases within a ciliary membrane-targeting complex
Vasundhara Kandachar1, Beatrice M Tam2, Orson L Moritz2
1Department of Surgery, Division of Ophthalmology, University of New Mexico, Albuquerque, NM 87131, USA.
Journal of Cell Science
|November 9, 2018
Summary
This study reveals how VAMP7 (vesicle-associated membrane protein 7) is sorted into rhodopsin transport carriers, crucial for building light-sensing organelles in vertebrate rod photoreceptors. It highlights VAMP7
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Vertebrate rod photoreceptor cilia are essential light-sensing organelles.
- The Arf4-rhodopsin complex initiates the assembly of these organelles.
- Understanding the trafficking of VAMP7 (vesicle-associated membrane protein 7) is key to photoreceptor development.
Purpose of the Study:
- To investigate the role of VAMP7 in the sorting of rhodopsin into transport carriers.
- To elucidate the molecular interactions governing VAMP7 trafficking within photoreceptors.
- To define the contribution of VAMP7's domains to its intracellular transport.
Main Methods:
- Co-localization studies of VAMP7 with rhodopsin and trafficking factors.
- Analysis of interactions between VAMP7 and Rab GTPases (Rab11, Rab8) and their effectors (Rabin8, FIP3).
- Expression of VAMP7 mutants in transgenic animals to assess domain function in vivo.
Main Results:
- VAMP7 colocalizes with rhodopsin in rhodopsin transport carriers (RTCs) and interacts with the Rab11-Rabin8-Rab8 module.
- Rab11 and Rab8 bind VAMP7's longin domain (LD), while Rabin8 interacts with its SNARE domain.
- Mutations in VAMP7's R-SNARE motif disrupt its intracellular trafficking, indicating its importance for transport rather than SNARE complex formation.
Conclusions:
- VAMP7 is a critical component in the conserved ciliary targeting network for rhodopsin transport.
- The study clarifies the assembly of SNAREs (soluble NSF attachment protein receptors) by Arf and Rab networks in membrane trafficking.
- This work provides insights into the molecular mechanisms underlying the biogenesis of photoreceptor light-sensing organelles.
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