Detailed Western Blot Protocol

Western blot was performed as described previously^{25 (link)}. In brief, cells were lysed and cell debris was removed by centrifugation at top speed for 5 min at 4 °C. Proteins were resolved by 12% or 15% SDS-PAGE and transferred to nitrocellulose membranes. The membranes were blocked and sequentially incubated with corresponding primary and secondary antibodies with washing steps in between. Immunoblots were visualized by chemiluminescence using WesternBright ECL (Advansta). Unprocessed versions of original immunoblots can be found in Supplementary Figs. S6, S7, and S8. Several blots were cut prior to antibody hybridization for the simultaneous detection of different target proteins in the same sample.