Distinct complexes of yeast Snx4 family SNX‐BARs mediate retrograde trafficking of Snc1 and Atg27

• Published in: Traffic (Copenhagen, Denmark) Denmark), 2017-02, Vol.18 (2), p.134-144
• Main Authors: Ma, Mengxiao, Burd, Christopher G., Chi, Richard J.
• Format: Article
• Language: English
• Subjects: Atg27; Autophagy; Carrier Proteins - metabolism; endosome; Endosomes - metabolism; Fungal Proteins - metabolism; Golgi Apparatus - metabolism; Protein Transport - physiology; R-SNARE Proteins - metabolism; retromer; SNX‐BAR; Sorting Nexins - metabolism; Vesicular Transport Proteins - metabolism; Vps1; Yeast; Yeasts - metabolism
• ISSN: 1398-9219; 1600-0854
• DOI: 10.1111/tra.12462

The yeast SNX4 sub‐family of sorting nexin containing a Bin‐Amphiphysin‐Rvs domain (SNX‐BAR) proteins, Snx4/Atg24, Snx41 and Atg20/Snx42, are required for endocytic recycling and selective autophagy. Here, we show that Snx4 forms 2 functionally distinct heterodimers: Snx4‐Atg20 and Snx4‐Snx41. Each heterodimer coats an endosome‐derived tubule that mediates retrograde sorting of distinct cargo; the v‐SNARE, Snc1, is a cargo of the Snx4‐Atg20 pathway, and Snx4‐Snx41 mediates retrograde sorting of Atg27, an integral membrane protein implicated in selective autophagy. Live cell imaging of individual endosomes shows that Snx4 and the Vps5‐Vps17 retromer SNX‐BAR heterodimer operate concurrently on a maturing endosome. Consistent with this, the yeast dynamin family protein, Vps1, which was previously shown to promote fission of retromer‐coated tubules, promotes fission of Snx4‐Atg20 coated tubules. The results indicate that the yeast SNX‐BAR proteins coat 3 distinct types of endosome‐derived carriers that mediate endosome‐to‐Golgi retrograde trafficking. Live cell imaging of individual yeast endosomes shows that the Snx4 and the Vps5‐Vps17 retromer sorting nexins operate concurrently on a maturing endosome. The 3 Snx4 family proteins form 2 functionally distinct heterodimers: Snx4‐Atg20 and Snx4‐Snx41. Each heterodimer coats an endosome‐derived tubule that mediates retrograde sorting of distinct cargo; the v‐SNARE, Snc1, is a cargo of the Snx4‐Atg20 pathway, and Snx4‐Snx41 mediates retrograde sorting of Atg27, an integral membrane protein implicated in selective autophagy.