As the regulatory component of the serine/threonine-protein phosphatase 2A (PP2A) holoenzyme, modulates substrate specificity, subcellular localization, and responsiveness to phosphorylation. The phosphorylated form mediates the interaction between PP2A and AKT1, leading to AKT1 dephosphorylation. Component of the serine/threonine-protein phosphatase 2A complex (PP2A). This complex consists of a common heterodimeric core enzyme, composed of a 36 kDa catalytic subunit (subunit C) and a 65 kDa constant scaffold subunit (PR65 or subunit A), that associates with a variety of regulatory subunits. Proteins that associate with the core dimer include three families of regulatory subunits B (the R2/B/PR55/B55, R3/B''/PR72/PR130/PR59 and R5/B'/B56 families), the 48 kDa variable regulatory subunit, viral proteins, and cell signaling molecules (PubMed:23135275). Interacts with SGO1 (PubMed:16541025). Interacts with AKT1 (PubMed:21329884). Interacts with CUL3 and KLHL15; this interaction leads to proteasomal degradation (PubMed:23135275). Highest expression in brain. By retinoic acid; in neuroblastoma cell lines. Ubiquitinated by E3 CUL3-KLHL15 complex; this modification leads to proteasomal degradation. Belongs to the phosphatase 2A regulatory subunit B56 family.