phosphatase-2A 55 kD regulatory subunit B beta; PP2A subunit B-B-beta isoform; PP2A; subunit B-B55-beta isoform; PP2A subunit B-PR55-beta isoform; PP2A subunit B-R2-beta isoform (PPP2R2B)

Function

• B regulatory subunit of phosphatase 2A
• might modulate substrate selectivity & catalytic activity, & also might direct the localization of the catalytic enzyme to a particular subcellular compartment
• within the PP2A holoenzyme complex, isoform 2 is required to promote proapoptotic activity (putative)
• isoform 2 regulates neuronal survival through the mitochondrial fission & fusion balance (putative)

Structure

• belongs to the phosphatase 2A regulatory subunit B family
• contains 7 WD repeats
• N-terminal 26 residues of isoform 2 constitute a cryptic mitochondrial matrix import signal with critical basic & hydrophobic residues, necessary & sufficient for targeting the PP2A holoenzyme to the outer mitochondrial membrane
  • does not affect holoenzyme formation or catalytic activity
• the last WD repeat of isoform 2 constitutes a mitochondrial stop-transfer domain that confers resistance to the unfolding step process required for import thus preventing PPP2R2B matrix translocation & signal sequence cleavage

Compartment

• isoform 1:
  • cytoplasm, cytoskeleton (putative)
  • membrane
• isoform 2:
  • cytoplasm (putative)
  • mitochondrion (putative), mitochondrion outer membrane
  • under basal conditions, localizes to both cytosolic & mitochondrial compartments
• relocalizes from the cytosolic to the mitochondrial compartment during apoptosis
• targeting to the outer mitochondrial membrane involves an association with import receptors of the TOM complex & is required to promote proapoptotic activity (putative)

Alternative splicing

named isoforms=7

Expression

brain

Pathology

• defects in PPP2R2B are the cause of spinocerebellar ataxia 12

More general terms

• phosphatase-2A B subunit
• human longevity protein

Component of

• phosphatase-2A (ceramide-activated protein phosphatase)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=5521
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:5521
• OMIM: https://mirror.omim.org/entry/604325
• OMIM: https://mirror.omim.org/entry/604326
• UniProt: http://www.uniprot.org/uniprot/Q00005.html