The B regulatory subunit might modulate substrate selectivity and catalytic activity, and also might direct the localization of the catalytic enzyme to a particular subcellular compartment. The PP2A-PPP2R5C holoenzyme may activate TP53 and play a role in DNA damage-induced inhibition of cell proliferation. PP2A-PPP2R5C may also regulate the ERK signaling pathway through ERK dephosphorylation (By similarity). PP2A consists of a common heterodimeric core enzyme, composed of PPP2CA a 36 kDa catalytic subunit (subunit C) and PPP2R1A a 65 kDa constant regulatory 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. Interacts with SGO1 (By similarity). Interacts with SGO1; the interaction is direct. May interact with TP53 (By similarity). Interacts with IER3 and/or ERK kinases; regulates ERK dephosphorylation (By similarity). Interacts with CIP2A; this interaction stabilizes CIP2A (By similarity). Highest levels in heart, liver and brain. Lower levels in skeletal muscle, spleen, kidney and lung. Isoform 4 is testis-specific. Belongs to the phosphatase 2A regulatory subunit B56 family.