Protein extraction

For whole cell extraction, cells were collected and washed. For viral protein extraction, HIV-1 particles were collected, washed, and concentrated by centrifuging at 100,000 × g for 2 h at 4 °C. RIPA Lysis Buffer was then added to cell or viral pellet and vortexed for 60 s. The mixture was incubated on ice for 45 min and homogenized with a small gauge needle by drawing 3 times. After homogenizing, the mixture was centrifuged at 14,000 × g for 10 min at 4 °C to collect the supernatant (whole cell proteins or viral proteins).

For membrane protein extraction, cells were washed with cold PBS and membrane proteins were extracted with membrane protein extraction kit (BioVision) following the protocol manufacture provided.