Ceramide chain length-dependent protein sorting into selective endoplasmic reticulum exit sites

Protein sorting in the secretory pathway is crucial to maintain cellular compartmentalization and homeostasis. In addition to coat-mediated sorting, the role of lipids in driving protein sorting during secretory transport is a longstanding fundamental question that still remains unanswered. Here, we conduct 3D simultaneous multicolor high-resolution live imaging to demonstrate in vivo that newly synthesized glycosylphosphatidylinositol-anchored proteins having a very long chain ceramide lipid moiety are clustered and sorted into specialized endoplasmic reticulum exit sites that are distinct from those used by transmembrane proteins. Furthermore, we show that the chain length of ceramide in the endoplasmic reticulum membrane is critical for this sorting selectivity. Our study provides the first direct in vivo evidence for lipid chain length-based protein cargo sorting into selective export sites of the secretory thway.
This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO; grant number BFU2017-89700-P to M.M.), “VI Own Research Plan” of the University of Seville (VIPPIT-2020-I.5 to M.M.), and Grants-in-Aid for Scientific Research from Japan Society for the Promotion of Science (JP25221103, JP17H06420, and JP18H05275 to A.N. and K. K.; and JP19H02922 to M.N. and K.F.). S.V. and V.Z. acknowledge support from the Swiss National Science Foundation (grant no. 163966) and from the Swiss National Supercomputing Centre (CSCS) under project IDs s726 and s842. H.R. is supported by the Swiss National Science Foundation and the NCCR Chemical Biology (grants 184949 and 185898). This research was funded by the “VI Own Research Plan “of the University of Seville (VIPPIT-2020-I.5); “V Own Research Plan” of the University of Seville (VPPI-US) contract (cofounded by the European Social Fund) to S.L.; University of Seville fellowship to S.R.-G.; Ministry of Education, Culture, and Sport (MECD) fellowship to S.S.-B.; and contract from the University of Seville by the Youth Employment Initiative to A.C.-G.