Subunit composition and developmental regulation of hepatic protein phosphatase 2A (PP2A).
The prototypical form of the Ser/Thr phosphatase PP2A is a heterotrimeric complex consisting of catalytic subunit (C), and A and B regulatory subunits. C-terminal methylation of PP2A-C influences holoenzyme assembly. Using late gestation development in the rat as an in vivo model of liver growth, we found that PP2A-C protein and activity levels were higher in fetal compared to adult liver extracts. However, unmethylated PP2A-C was much higher in the adult extracts. In MonoQ fractionation, unmethylated C eluted separately from methylated C, which was present predominantly in ABC heterotrimers. Gel filtration chromatography revealed that some unmethylated C was present as free catalytic subunit in adult liver. In addition, a significant proportion of PP2A was in inactive forms that may involve novel regulatory subunits. Our results indicate that methylation of PP2A-C appears to be a primary determinant for the biogenesis of PP2A heterotrimers.
Yoo
Sunny J-S
SJ
Department of Pediatrics, Rhode Island Hospital and Brown University, Providence, RI 02903, USA.
Boylan
Joan M
JM
Brautigan
David L
DL
Gruppuso
Philip A
PA
D000818:Animals; D020134:Catalytic Domain; D005333:Fetus; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D008099:Liver / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000378:metabolism*; D054648:Protein Phosphatase 2; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D021122:Protein Subunits; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2