Myc-tagged mouse Grp1 (wild-type and T280D) in pENTR and pCDNA3.1 that are siRNA resistant have been described (Li et al., 2012 (link)). A PI4P biosensor, known as GFP-P4M-SidM, has also been described (Hammond et al., 2014 ), and was obtained from Addgene (plasmid #51469). 6xHis-tagged GRASP and IPCEF1 were generated by subcloning the coding sequence of GRASP and IPCEF1 into pET-15b vector (EMD Millipore, Billerica, MA). To generate GST fusions of Grp1, GRASP, and IPCEF1, the coding sequences of proteins were amplified by PCR, and then subcloned into pGEX-6P-1 vector (GE Healthcare, Pittsburgh, PA). Different forms of Myc-tagged Grp1 were subcloned and inserted into pENTR (Invitrogen, Carlsbad, CA). Point mutants were then generated by a QuikChange II XL site-directed mutagenesis kit (Stratagene, La Jolla, CA). Myc-Grp1 constructs in pLenti6.2 were further generated by recombination according to the Gateway protocol provided (Invitrogen). Lentiviral particles expressing Myc-Grp1 constructs were generated using a ViraPower Lentiviral Expression System (Invitrogen). 3T3-L1 fibroblast cell lines that stably express different forms of Myc-Grp1 were generated by lentiviral transduction followed by selection in 10 μg/ml blasticidin (Invitrogen).