Isolation and determination of PI(4,5)P2 proximal proteins

We screened proteins in close proximity to PI(4,5)P2 in epithelial cells. We established HaCaT cells stably expressing APEX2 N-terminally fused to the PH domain of PLCd1, which specifically binds to PI(4,5)P2. In the presence of hydrogen peroxide and biotin-phenol, proteins proximal to APEX2 are biotinylated by APEX2, allowing for their enrichment using streptavidin beads. APEX2-fused non-PI(4,5) P2-binding mutant of the PH domain of PLCd1 (R40L) was used as the negative control.