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Thr123 of rat G-substrate contributes to its action as a protein phosphatase inhibitor.

Authors: Endo, S  Nairn, AC  Greengard, P  Ito, M 
Citation: Endo S, etal., Neurosci Res 2003 Jan;45(1):79-89.
Pubmed: (View Article at PubMed) PMID:12507727

Rat G-substrate cDNA was isolated from a cerebellar library and characterized. The deduced amino acid sequence of rat G-substrate contained two putative phosphorylation sites for PKG at Thr72 and Thr123; the amino acid sequences (KPRRKDT(p)PA) around these sites are conserved in human, mouse and rabbit. G-substrate phosphorylated by PKG inhibited the catalytic subunits of both protein phosphatase-1 (IC(50) 14.1 nM) and -2A (IC(50) 5.9 nM). Mutation of Thr123 (site 2) to Ala significantly reduced the inhibition of both PP-1 and PP-2A, while mutation of Thr72 (site 1) to Ala had little effect on inhibitory activity. In situ hybridization analysis revealed that G-substrate mRNA was localized exclusively in cerebellar Purkinje cells. Immunoperoxidase staining showed that in Purkinje cells, G-substrate was present in somata, dendrites and axons. In rat cerebellar slices, activation of PKG with a nitric oxide (NO) donor, NOR3, or 8-Br-cGMP, increased phosphorylation of G-substrate, as demonstrated with a phosphorylation-specific antibody. These results characterize further the inhibition of PP-1 and PP-2A by phospho-G-substrate, and demonstrate its physiological phosphorylation in rat Purkinje cells.


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RGD Object Information
RGD ID: 632826
Created: 2003-08-29
Species: All species
Last Modified: 2003-08-29
Status: ACTIVE


RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.