Subunit composition and developmental regulation of hepatic protein phosphatase 2A (PP2A) |
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Authors: | Yoo Sunny J-S Boylan Joan M Brautigan David L Gruppuso Philip A |
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Affiliation: | Department of Pediatrics, Rhode Island Hospital and Brown University, Providence, RI 02903, USA. |
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Abstract: | 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. |
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Keywords: | Signal transduction Fetal development Liver Hepatocyte Regeneration |
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