sentence: 16 It is well known that the protein phosphatase PP2A counteracts Akt1 by dephosphorylation , and hence may serve as a regulatory target of CycG.26 ,27 PP2A consists of 3 subunits , a constant catalytic subunit C ( Microtubule star [ Mts ] in Drosophila ; corresponding to mammalian PP2Ac ) , a scaffolding subunit A ( PP2A-29B in Drosophila ; corresponding to mammalian PP2A-A or PR65 ) and a context-dependent regulatory subunit B ( Twins [ Tws ] in Drosophila , corresponding to mammalian PP2A-B , B55 or PR55 ) or B ′ ( Widerborst [ Wdb ] and Well rounded [ Wrd ] in Drosophila , corresponding to mammalian PP2A-B ′ , B56 or PR61 and PR72 ) ( Fig. 2A ) .28 The regulatory B ′ - subunit Widerborst ( Wdb ) inhibits InR / TOR signaling by directing the PP2A to dephosphorylate Akt1.27 CycG protein directly binds to Wdb in vitro and in vivo , suggesting a mechanistic link in the regulation of PP2A .