RGD Reference Report - The level of the glycogen targetting regulatory subunit R5 of protein phosphatase 1 is decreased in the livers of insulin-dependent diabetic rats and starved rats. - Rat Genome Database

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The level of the glycogen targetting regulatory subunit R5 of protein phosphatase 1 is decreased in the livers of insulin-dependent diabetic rats and starved rats.

Authors: Browne, GJ  Delibegovic, M  Keppens, S  Stalmans, W  Cohen, PT 
Citation: Browne GJ, etal., Biochem J. 2001 Dec 1;360(Pt 2):449-59.
RGD ID: 2306167
Pubmed: PMID:11716774   (View Abstract at PubMed)
PMCID: PMC1222246   (View Article at PubMed Central)

Hepatic glycogen synthesis is impaired in insulin-dependent diabetic rats owing to defective activation of glycogen synthase by glycogen-bound protein phosphatase 1 (PP1). The identification of three glycogen-targetting subunits in liver, G(L), R5/PTG and R6, which form complexes with the catalytic subunit of PP1 (PP1c), raises the question of whether some or all of these PP1c complexes are subject to regulation by insulin. In liver lysates of control rats, R5 and R6 complexes with PP1c were found to contribute significantly (16 and 21% respectively) to the phosphorylase phosphatase activity associated with the glycogen-targetting subunits, G(L)-PP1c accounting for the remainder (63%). In liver lysates of insulin-dependent diabetic and of starved rats, the phosphorylase phosphatase activities of the R5 and G(L) complexes with PP1c were shown by specific immunoadsorption assays to be substantially decreased, and the levels of R5 and G(L) were shown by immunoblotting to be much lower than those in control extracts. The phosphorylase phosphatase activity of R6-PP1c and the concentration of R6 protein were unaffected by these treatments. Insulin administration to diabetic rats restored the levels of R5 and G(L) and their associated activities. The regulation of R5 protein levels by insulin was shown to correspond to changes in the level of the mRNA, as has been found for G(L). The in vitro glycogen synthase phosphatase/phosphorylase phosphatase activity ratio of R5-PP1c was lower than that of G(L)-PP1c, suggesting that R5-PP1c may function as a hepatic phosphorylase phosphatase, whereas G(L)-PP1c may be the major hepatic glycogen synthase phosphatase. In hepatic lysates, more than half the R6 was present in the glycogen-free supernatant, suggesting that R6 may have lower affinity for glycogen than R5 and G(L)



Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process

  

Cellular Component

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Ppp1r3bRatglycogen granule  IDA  RGD 
Ppp1r3cRatglycogen granule  IDA  RGD 
Ppp1r3dRatglycogen granule  IDA  RGD 

Molecular Function

  
Object SymbolSpeciesTermQualifierEvidenceWithNotesSourceOriginal Reference(s)
Ppp1r3bRatenzyme binding  IMP  RGD 
Ppp1r3cRatenzyme binding  IMP  RGD 
Ppp1r3dRatenzyme binding  IMP  RGD 
Ppp1r3bRatphosphoprotein phosphatase activity contributes_toIDA  RGD 
Ppp1r3cRatphosphoprotein phosphatase activity contributes_toIDA  RGD 
Ppp1r3dRatphosphoprotein phosphatase activity contributes_toIDA  RGD 

Molecular Pathway Annotations    Click to see Annotation Detail View

RGD Manual Annotations


  
Objects Annotated

Genes (Rattus norvegicus)
Ppp1r3b  (protein phosphatase 1, regulatory subunit 3B)
Ppp1r3c  (protein phosphatase 1, regulatory subunit 3C)
Ppp1r3d  (protein phosphatase 1, regulatory subunit 3D)

Genes (Mus musculus)
Ppp1r3b  (protein phosphatase 1, regulatory subunit 3B)
Ppp1r3c  (protein phosphatase 1, regulatory subunit 3C)
Ppp1r3d  (protein phosphatase 1, regulatory subunit 3D)

Genes (Homo sapiens)
PPP1R3B  (protein phosphatase 1 regulatory subunit 3B)
PPP1R3C  (protein phosphatase 1 regulatory subunit 3C)
PPP1R3D  (protein phosphatase 1 regulatory subunit 3D)


Additional Information