Germacrone alleviates okadaic acid-induced neurotoxicity in PC12 cells via M1 muscarinic receptor-mediated Galphaq (Gq)/phospholipase C beta (PLCß)/ protein kinase C (PKC) signaling.

Alzheimer's disease (AD) is a neurodegenerative disorder with prominent individual morbidity and mortality among elderly people. Germacrone (Germ) has been reported to exert dominant protective roles in multiple human diseases, and neurological diseases are also included. The intention of this paper is to determine the impacts of Germ on okadaic acid (OA)-treated PC12 cells and confirm the hidden regulatory mechanism. First, PC12 cells were induced by OA in the absence or presence of Germ. Cell counting kit-8 assay was to monitor cell proliferation. Western blot was to test the protein levels of cholinergic muscarinic M1 receptor (CHRM1), Galphaq (Gq), phospholipase C beta (PLCß) and protein kinase C (PKC). The levels of reactive oxygen species (ROS) and other oxidative stress markers were evaluated using corresponding kits. ELISA was used to estimate the levels of AD markers. RT-qPCR was used to examine the mRNA levels of beta-site amyloid-precursor-protein-cleaving enzyme 1 (BACE-1) and apolipoprotein E (APOE). The results uncovered that Germ enhanced the proliferation of OA-insulted PC12 cells, elevated the protein level of CHRM1 and activated the Gq/PLCß/PKC signaling. Moreover, after OA-induced PC12 cells were administered with Germ, insufficiency of CHRM1 impeded cell proliferation, enhanced oxidative stress and neuron injury and inactivated the Gq/PLCß/PKC signaling. Furthermore, the addition of Gq inhibitor UBO-QIC, PLCß inhibitor U73122 or PKC inhibitor Go6983 reversed the enhanced proliferation, the reduced oxidative stress and neuron injury in OA-treated PC12 cells caused by Germ. Collectively, Germ modulated M1 muscarinic receptor-mediated Gq/PLCß/PKC signaling, thereby alleviating OA-induced PC12 cell injury.

Substrate specificity of protein tyrosine phosphatase: differential behavior of SHP-1 and SHP-2 towards signal regulation protein SIRPalpha1.

The substrate specificity of catalytic domains and the activation of full length protein tyrosine phosphatases, SHP-1 and SHP-2 have been investigated using synthetic phosphotyrosyl peptides derived from SIPRalpha1. We found that the catalytic domains of SHP-1 and SHP-2 exhibit different substrate specificity towards a longer trideca-peptide pY(469+3) ((-7)RPEDTLTpYADLDM(+5)) and not to the shorter decapeptide pY(469) ((-5)EDTLTpYADLD(+4)), the former being the substrate of SHP-2 only. Furthermore, the activation of full-length SHP-1 and not the SHP-2 by the deca/trideca-peptides suggested SIRPalpha 1 to be possibly acting as both an upstream activator and a substrate for SHP-1, and merely as the downstream substrate for SHP-2 in signaling events.