Phosphorylation of the GARP Subunit Vps53 by Snf1 Leads to the Formation of a Golgi-Mitochondria Contact Site (GoMiCS) in Yeast

Abstract

The canonical function of the Golgi-associated retrograde protein (GARP) complex is the tethering of transport carriers. GARP belongs to the complexes associated with tethering containing helical rods (CATCHR) family and is a hetero-tetrameric complex consisting of the subunits Vps51, Vps52, Vps53 and Vps54. How the activity of GARP is regulated and if it possesses other functions besides tethering remains largely unknown. Here we identify the GARP subunit Vps53 as a novel regulatory target of the S. cerevisiae AMP kinase (AMPK) homolog Snf1. We find that Vps53 is both an in vivo and in vitro target of Snf1 and show that phosphorylation depends on the nature and quantity of the available carbon source. Phosphorylation of Vps53 does not affect the canonical trafficking pathway, but results in altered mitochondrial dynamics and the formation of a previously unknown contact site between the Golgi apparatus and mitochondria, termed GoMiCS. Our results provide an example of a subunit of a CATCHR complex with a constitutive function in membrane trafficking and an inducible role in organelle contact site formation. We anticipate our results to be the starting point for the characterization of this novel contact site.