Downregulation of the cAMP/PKA Pathway in PC12 Cells Overexpressing NCS-1
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It is well known that dopamine imbalances are associated with many psychiatric disorders and that the dopaminergic receptor D2 is the main target of antipsychotics. Recently it was shown that levels of two proteins implicated in dopaminergic signaling, Neuronal calcium sensor-1 (NCS-1) and DARPP-32, are altered in the prefrontal cortex (PFC) of both schizophrenic and bipolar disorder patients. NCS-1, which inhibits D2 internalization, is upregulated in the PFC of both patients. DARPP-32, which is a downstream effector of dopamine signaling, integrates the pathways of several neurotransmitters and is downregulated in the PFC of both patients. Here, we used PC12 cells stably overexpressing NCS-1 (PC12-NCS-1 cells) to address the function of this protein in DARPP-32 signaling pathway in vitro. PC12-NCS-1 cells displayed downregulation of the cAMP/PKA pathway, with decreased levels of cAMP and phosphorylation of CREB at Ser133. We also observed decreased levels of total and phosphorylated DARPP-32 at Thr34. However, these cells did not show alterations in the levels of D2 and phosphorylation of DARPP-32 at Thr75. These results indicate that NCS-1 modulates PKA/cAMP signaling pathway. Identification of the cellular mechanisms linking NCS-1 and DARPP-32 may help in the understanding the signaling machinery with potential to be turned into targets for the treatment of schizophrenia and other debilitating psychiatric disorders.
KeywordsNCS-1 DARPP-32 pDARPP-32(Thr34) pCREB(Ser133) PC12 Schizophrenia
Financial support from CNPq Universal grant, Programa Institutos do Milênio/CNPq/FINEP, and John Simon Guggenheim Foundation. MAR-S and MVG are CNPq research fellows. BRS and DVFR are recipients of CAPES scholarships, RPS and MMM are recipients of CNPq scholarships, and KCLT and DMM are CNPq fellows. I would like to thank B. Lindsey and M. Mattocks for their suggestions and revisions to the English writing of this manuscript.
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