Immunoblot: Cells were lysed in RIPA buffer, 50 mM Tris-HCl (pH 8), 150 mM NaCl, 1% (v/v) NP40, 0.5% (v/v) Na-deoxycholate, 0.1% (v/v) SDS, and 1 tablet/10 mL Complete, Mini, EDTA-free protease inhibitors (Roche). SDS-PAGE and immunoblots were carried out using standard protocols.