671A Poster - 10. Cell biology: Cytoskeleton, organelles and trafficking
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Catarina Gaspar ^1,2; Ligia Vieira ¹; Cristiana Santos ¹; John Christianson ³; David Jakubec ⁴; Kvido Strisovsky ⁴; Colin Adrain ^2,5; Pedro Domingos ¹

Affiliations:
1) Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa (ITQB-NOVA); 2) Membrane Traffic Lab, Instituto Gulbenkian de Ciência (IGC); 3) University of Oxford; 4) Czech Academy of Sciences; 5) Queen’s University

Keywords:
j. endoplasmic reticulum; r. proteostasis

The ER membrane complex (EMC) is required for the biogenesis of a subset of tail anchored (TA) and polytopic membrane proteins, including Rhodopsin-1 (Rh1) and the TRP channel. To understand the physiological implications of EMC-dependent membrane protein biogenesis, we performed a bioinformatic identification of Drosophila TA proteins. From 254 predicted TA proteins, screening in larval eye discs identified 2 proteins that require EMC for their biogenesis: fan and Xport-A. Fan is required for male fertility in Drosophila and we show that EMC is also required for this process. Xport-A is essential for the biogenesis of both Rh1 and TRP, raising the possibility that disruption of Rh1 and TRP biogenesis in EMC mutants is secondary to the Xport-A defect. We show that EMC is required for Xport-A TMD membrane insertion and that EMC-independent Xport-A mutants rescue Rh1 and TRP biogenesis in EMC mutants. Finally, ER resident, N196-glycosylated Rh1 TMD1-5 accumulates in Xport-A and EMC6 mutants, revealing a role for Xport-A in a glycosylation-dependent triage mechanism during Rh1 biogenesis in the endoplasmic reticulum.