Rat and rabbit antibodies to VAPB and PTPIP51 were generated by immunisation with GST-VAPB(1-220) and GST-PTPIP51(36-470) respectively20 (link). Rabbit anti-PTPIP51 was from Atlas, rabbit anti-hemagglutin (HA), mouse anti-α-tubulin (DM1A) and rabbit anti-Mitofusin2 were from Sigma. Rabbit anti-TOM20 was from Santa Cruz Biotechnology. Rabbit anti-GFP and mouse anti-βactin were from Abcam. Mouse PDI (RL77) was from Affinity Bioreagents. Rabbit anti-TDP-43 (12892-1-AP) was from Proteintech. Antibodies to total and ser9 phosphorylated (inactive) GSK3β were from BD Transduction Labs (mouse 610201) and Cell Signalling (rabbit 9336) respectively. The concentrations used for the different antibodies are shown in Supplementary Table 1. Secondary antibodies were horseradish peroxidase-coupled goat anti-mouse, anti-rabbit and anti-rat Igs (GE Healthcare), and Alexa fluorophore (350, 488 and 568) coupled goat anti-mouse and anti-rabbit IgGs (Invitrogen). AR-A014418 and CT99021 were from Abcam and Cayman respectively.