Chemicals and reagents

For chemical dimerization experiments, rapamycin (Thermo Fisher; BP2963-1) was dissolved to 1 mM in DMSO as a stock and used at a final concentration of 1 µM in cells. Carbachol (Thermo Fisher; AC10824-0050) was prepared by dissolving in water to 50 mM and stored at −20°C. Atropine (Thermo Fisher; AC226680100) was dissolved to 25 mM in 100% ethanol and stored at −20°C. 30% H₂O₂ (EMD Millipore; HX0635-3) was stored at 4°C and prepared fresh in complete imaging media when used as an additive. A1 PI4KA inhibitor (Bojjireddy et al., 2014), a kind gift from Tamas Balla (National Institutes of Health, Bethesda, MD), was dissolved in DMSO to a 100-µM stock and stored at −20°C.