Commercially available antibodies were used as follows; citations and validation information may be found on the manufacturer's website where available. For immunoblotting, the following reagents were used: rabbit anti-HA tag [Cell Signaling Technology (CST) 3724, 1:1000, lot 8], mouse anti-GAPDH (EMD Millipore MAB374, 1:10,000 or 1:20,000, lot 3109750), rabbit anti-GORASP2 (Proteintech, 10598-1-AP, 1:2000, lot 00022940), rabbit anti-LC3B (CST 3868, 1:1000, lot 14), rabbit anti-TRIP11 (Proteintech, 26456-1-AP, 1:1000, lot 00043643), rabbit anti-Sec24B (CST 12042, 1:1000, lot 1), rabbit anti-Sec23IP (Atlas Antibodies, HPA043305, 1:1000, lot R39611), rabbit anti-Beclin-1 (CST 3738S, 1:1000, lot 3), mouse anti-HA tag (CST 2367, 1:1000, lot 5), Streptavidin-HRP (Thermo Fisher Scientific, 21130, 1:20,000, lot SB241752A), rabbit anti-α-tubulin (CST 2125, 1:5000, lot 11), mouse anti-ATF6 (Abcam, ab122897, 1:500, lot GR111809-71), rabbit anti-IRE1α (CST 3294, 1:1000, lot 11), rabbit anti-eIF2α (CST 9722, 1:1000, lot 15), rabbit anti-phospho-IRE1 (Abcam, ab124945, 1:2500, lot GR271918-24), rabbit anti-phospho-eIF2α (CST 9721, 1:1000, Lot 21), Peroxidase AffiniPure Donkey Anti-Rabbit IgG (Jackson ImmunoResearch, 711-035-152, 1:5000), Peroxidase AffiniPure Donkey Anti-Mouse IgG (Jackson ImmunoResearch, 715-035-150, 1:5000). For immunofluorescence and fluorescence microscopy, the following reagents were used: rabbit anti-LC3B (CST 3868, 1:200, lot 14), rabbit anti-GORASP2 (Proteintech, 10598-1-AP, 1:250, lot 00022940), mouse anti-GM130 (BD Biosciences, 610823, 1:50, lot 8033959), rabbit anti-HA tag (CST 3724, 1:100, lot 8), mouse anti-GRASP55 (Abcam, ab211532, 1:250, lot GR273456-2), sheep anti-GM130 (Novus Biologicals, AF8199, 10 µg ml−1, lot CIEQ0117051), rabbit anti-Sec16A (Atlas, Antibodies, HPA005684, 1:100, lot A84463), rabbit anti-Sec24B (CST 12042, 1:100, lot 1), DyLight Streptavidin-549 (Vector Laboratories, SA-5549, 1:250, lot ZC0830), Alexa Fluor 488 donkey anti-mouse (Invitrogen, A-21202, 1:1000, lot 2018296), Alexa Fluor 488 donkey anti-rabbit (Invitrogen, A-21206, 1:1000, lot 1981155), Alexa Fluor 568 donkey anti-mouse (Invitrogen, A10037, 1:1000, lot 2026157), Alexa Fluor 647 donkey anti-mouse (Invitrogen, A-31571, 1:1000, lot 2045337), Alexa Fluor 647 donkey anti-rabbit (Invitrogen, A-31573, 1:1000), Alexa Fluor 647 donkey anti-sheep (Invitrogen, A-21448, 1:1000, lot 2045339).