Cell lysate was prepared by homogenization in ice-cold modified RIPA Lysis Buffer with cocktail of protease inhibitors (Sigma). Cell debris was removed by centrifugation. Protein concentration was determined with Bradford assay (Bio-Rad protein assay, Microplate Standard assay). The lysate was mixed in 5X Sample Buffer to become final 1X Sample Buffer as Storage Buffer. The lysate was heated at 95°C for 5 min, and cooled rapidly.