Rose Melanie, Dütting Eva, Schröder Nadja, Sticht Heinrich, Brandstätter Johann Helmut, Enz Ralf
Institut für Biochemie (Emil-Fischer-Zentrum), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.
Mol Cell Neurosci. 2008 Apr;37(4):808-19. doi: 10.1016/j.mcn.2008.01.004. Epub 2008 Jan 17.
Phosphorylation and dephosphorylation of neurotransmitter receptors represent an important mechanism to regulate synaptic signal transduction. Here, we identified PNUTS, a targeting subunit of protein phosphatase 1 (PP1) as a new binding partner of GABA(C) receptors. In the mammalian retina, PNUTS is co-expressed with GABA(C) receptors and PP1 in bipolar cells. PNUTS and PP1 were detected in membrane protein preparations of the retina and precipitate with GABA(C) receptor specific antibodies. Furthermore, PNUTS shuttles from the nucleus to the membrane in cells co-expressing GABA(C) receptors. We show simultaneous binding of PP1 and GABA(C) receptors to different domains of PNUTS, demonstrating that PNUTS cross-links PP1 and GABA(C) receptors. Finally, modeling studies showed that the PP1 docking motif of PNUTS fits into the binding pocket on the enzyme surface, despite a C-terminal adjacent proline. We suggest that PNUTS targets PP1 to synaptic sites, acting as a temporary bridge between the phosphatase and GABA(C) receptors.
神经递质受体的磷酸化和去磷酸化是调节突触信号转导的重要机制。在此，我们鉴定出蛋白磷酸酶1（PP1）的靶向亚基PNUTS是γ-氨基丁酸C型（GABA(C)）受体的新结合伴侣。在哺乳动物视网膜中，PNUTS与GABA(C)受体和PP1在双极细胞中共表达。在视网膜的膜蛋白制剂中检测到PNUTS和PP1，并且它们与GABA(C)受体特异性抗体一起沉淀。此外，在共表达GABA(C)受体的细胞中，PNUTS从细胞核穿梭至细胞膜。我们发现PP1和GABA(C)受体同时结合到PNUTS的不同结构域，表明PNUTS交联了PP1和GABA(C)受体。最后，建模研究表明，尽管PNUTS的C末端相邻有脯氨酸，但PNUTS的PP1对接基序仍适合酶表面的结合口袋。我们认为，PNUTS将PP1靶向突触位点，充当磷酸酶和GABA(C)受体之间的临时桥梁。
