PP2AB56

PP2AB56 refers to the B56 family of regulatory subunits for the protein phosphatase 2A (PP2A) holoenzyme. PP2A is a major serine/threonine phosphatase present in eukaryotic cells, and its activity is determined by the combination of subunits that form the holoenzyme. The B56 subunits do not possess catalytic activity themselves but shape substrate specificity, cellular localization, and regulatory interactions of PP2A.

In humans, the B56 regulatory subunits are encoded by the PPP2R5A, PPP2R5B, PPP2R5C, PPP2R5D, and PPP2R5E genes, producing isoforms commonly referred to as B56α, B56β, B56γ, B56δ, and B56ε. These isoforms exhibit distinct expression patterns across tissues and developmental stages, enabling tissue- and context-specific PP2A functions. The B56 subunits form a heterotrimer with the core PP2A dimer, which consists of the scaffolding A subunit and the catalytic C subunit; the B56 subunit then governs substrate recognition and subcellular targeting.

Functionally, PP2A–B56 holoenzymes participate in a wide range of cellular processes, including regulation of cell cycle progression, DNA damage response, apoptosis, and signal transduction pathways such as those mediated by AKT and MAP kinases. By directing dephosphorylation of specific substrates, B56-containing holoenzymes influence processes like mitosis, cell growth, and differentiation, as well as transcriptional control in certain contexts. Their activity is modulated by post-translational modifications and interactions with other regulatory factors.

Aberrant expression or function of PP2AB56 subunits has been linked to diseases, notably cancer and developmental disorders, reflecting their central role in maintaining cellular signaling balance. Research into PP2AB56 continues to illuminate how regulatory diversity among B56 isoforms shapes PP2A function and cellular outcomes.