Mechanism of neurotrophic action of nobiletin in PC12D cells.
Nobiletin is a nonpeptide compound with a low molecular weight from a citrus fruit and has the activity to rescue bulbectomy-induced memory impairment. Here we describe that nobiletin itself induces neurite outgrowth in PC12D cells, a rat pheochromocytoma cell line, like NGF, and the molecular mechanism of its neurotrophic action. As cultured in the presence of nobiletin or NGF for 48 h and then assayed using a scanning electron microscope, PC12D cells treated with nobiletin showed morphology with flatter and larger cell bodies than the cells cultured with NGF. Nobiletin-induced neurite outgrowth was inhibited by PD98059 and U0126 but not K252a. Consistently, nobiletin caused a concentration-dependent enhancement of Erk/MAP kinase phosphorylation and a sustained increment of phosphorylation of MEK and Erk/MAP kinase, resulting in a stimulation of CREB phosphorylation and CRE-mediated transcription. This compound also increased intracellular cAMP and CRE-mediated transcription in the presence of forskolin and enhanced PKA activity to stimulate phosphorylation of multiple PKA substrates in PC12D cells. Furthermore, nobiletin preferentially inhibited Ca2+/CaM-dependent phosphodiesterase in vitro. This compound failed to stimulate phosphorylation of Erk5, which is known to be induced by NGF/TrkA signaling. These results suggest that nobiletin induces neurite outgrowth by activating a cAMP/PKA/ MEK/ Erk/MAP kinase-dependent but not TrkA-dependent signaling pathway coupling with CRE-mediated gene transcription and may thus become a novel type of biochemical probe for elucidation of the molecular mechanism of neuronal differentiation.[1]References
- Mechanism of neurotrophic action of nobiletin in PC12D cells. Nagase, H., Yamakuni, T., Matsuzaki, K., Maruyama, Y., Kasahara, J., Hinohara, Y., Kondo, S., Mimaki, Y., Sashida, Y., Tank, A.W., Fukunaga, K., Ohizumi, Y. Biochemistry (2005) [Pubmed]
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