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. 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. Predominantly localized in the nucleus in absence of PIK3CG/p120 (PubMed:12507995, PubMed:15611065). Colocalizes with PIK3CG/p120 in the cytoplasm (PubMed:12507995, PubMed:15611065). Translocated to the plasma membrane in a beta-gamma G protein-dependent manner (PubMed:12507995, PubMed:15611065). The heterodimerization region allows the binding to the catalytic subunit.