Regulatory subunit of the PI3K gamma complex. Required for recruitment of the catalytic subunit to the plasma membrane via interaction with beta-gamma G protein dimers. Required for G protein-mediated activation of PIK3CG (By similarity). Greatly activated by G gamma proteins. Heterodimer of a catalytic subunit (PIK3CG/p120) and a regulatory (PIK3R5a/p101) subunit. Interacts with beta-gamma G protein dimers (By similarity). Predominantly localized in the nucleus in absence of PIK3CG/p120. Colocalizes with PIK3CG/p120 in the cytoplasm. Translocated to the plasma membrane in a beta-gamma G protein-dependent manner. The heterodimerization region allows the binding to the catalytic subunit.