| Summary: | 碩士 === 國立政治大學 === 神經科學研究所 === 104 === Protein kinase CK2 is a multifunctional serine/threonine protein kinase and involves in many neurophysiological functions including neuronal plasticity and neuroprotection, but its molecular mechanisms are not well investigated. Previous studies have shown that CK2 protein levels and activity are more elevated in the striatum than other brain areas. DARPP-32 (Dopamine- and cAMP-regulated phosphoprotein, Mr 32 kDa) is also highly enriched in striatal medium spiny GABAergic neurons and has been found the Ser102 residue is a phosphorylation site for CK2. Many studies have revealed that Ser34/Thr75 phosphorylation of DARPP-32 mediates dopamine signaling pathway which affects the physiological function and behavior in drug abuse. However, whether Ser102 phosphorylation by CK2 in the MSN controls motor behaviors is still unclear. Glutamic acid decarboxylase 67 (GAD67) which is one of the enzymes responsible for the synthesis of neurotransmitter GABA in the MSN and its dysfunction is presented relationship with Parkinson’s disease-induced behavior deficits. But the cellular regulatory mechanism of GAD67 is not fully studies. The aims of this proposal are to investigate the signaling relationship between CK2, DARPP-32 and GAD67 reflecting on neurotransmitter content in striatum and motor behavior in rats.
The present results demonstrates that DARPP-32 Ser102 phosphorylation status and GAD67 mRNA levels are increased by wild-type CK2 plasmid DNA transfection. CK2 siRNA treatment also decreased DARPP-32 protein levels and Ser102 phosphorylation status, GAD67 protein and mRNA levels as well as GABA levels in the striatum. On the other hand, DARPP-32 siRNA transfection decreased GAD67 protein and mRNA levels, as also GABA levels in the striatum. TH Ser40 phosphorylation level in the substantia nigra. Striatal GABA levelds were decreased by transfection of mutant DARPP-32 S102A, which mimics the un-phosphorylated by CK2. Co-express CK2 and DARPP-32 S102A plasmid DNA reduced GABA level which was induced by CK2alone. The striatal CK2 or DARPP-32 siRNA transfection decreased Tyrosine Hydroxylase (TH) protein level or TH Ser40 phosphorylation level in the substantia nigra. Furthermore, DA agonist SKF38393 induced motor behavior promotion was inhibited by CK2 siRNA transfection. All the current results suggest that cellular signaling of DARPP-32 Ser102 phosphorylation by CK2 not only mediates GAD67 protein expression and biosynthesis of GABA neurotransmitter in striatum and motor behavior of rats, but also might affect TH protein level and phosphorylation status in the substantia nigra.
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