The Arl3 and Arl1 GTPases co‐operate with Cog8 to regulate selective autophagy via Atg9 trafficking

The Arl3‐Arl1 GTPase cascade plays important roles in vesicle trafficking at the late Golgi and endosomes. Subunits of the conserved oligomeric Golgi (COG) complex, a tethering factor, are important for endosome‐to‐Golgi transport and contribute to the efficient functioning of the cytoplasm‐to‐vacuole targeting (Cvt) pathway, a well‐known selective autophagy pathway. According to our findings, the Arl3‐Arl1 GTPase cascade co‐operates with Cog8 to regulate the Cvt pathway via Atg9 trafficking. arl3cog8Δ and arl1cog8Δ exhibit profound defects in aminopeptidase I maturation in rich medium. In addition, the Arl3‐Arl1 cascade acts on the Cvt pathway via dynamic nucleotide binding. Furthermore, Atg9 accumulates at the late Golgi in arl3cog8Δ and arl1cog8Δ cells under normal growth conditions but not under starvation conditions. Thus, our results offer insight into the requirement for multiple components in the Golgi‐endosome system to determine Atg9 trafficking at the Golgi, thereby regulating selective autophagy. Adenosine diphosphate (ADP)‐ribosylation factor (Arf)‐like small GTPase had been reported to participate in different vesicle transport events. In this study, we show that Arl3‐Arl1 small GTPase cascade co‐operates with the subunit of conserved oligomeric Golgi (COG) complex to control Cvt pathway but not non‐selective autophagy. The yeast strains with dysfunction of Arl3‐Arl1 cascade and COG complex accumulate Atg9 at the late Golgi in nutrient‐rich condition, thereby causing the defect of Cvt pathway. Thus, 2 Golgi‐endosomal traffic components co‐ordinately regulate the Cvt pathway by regulating Atg9 trafficking at the Golgi.