Structural Dynamics of Amyloid β Peptide Binding to Acetylcholine Receptor and Virtual Screening for Effective Inhibitors

The interaction between Amyloid β(Aβ) peptide and acetylcholine receptor is the key for our understanding of how Aβ fragments block the ion channels within the synapses and thus induce Alzheimer’s disease.Here,molecular docking and molecular dynamics(MD)simulations were performed for the structural dynamics of the docking complex consisting of Aβ and α7-n ACh R(α7 nicotinic acetylcholine receptor),and the inter-molecular interactions between ligand and receptor were revealed.The results show that Aβ_(25-35) is bound toα7-n ACh R through hydrogen bonds and complementary shape,and the Aβ_(25-35) fragments would easily assemble in the ion channel of α7-n ACh R,then block the ion transfer process and induce neuronal apoptosis.The simulated amide-I band of Aβ_(25-35) in the complex is located at 1650.5 cm^(-1),indicating the backbone of Aβ_(25-35) tends to present random coil conformation,which is consistent with the result obtained from cluster analysis.Currently existing drugs were used as templates for virtual screening,eight new drugs were designed and semi-flexible docking was performed for their performance.The results show that,the interactions between new drugs and α7-n ACh R are strong enough to inhibit the aggregation of Aβ_(25-35) fragments in the ion channel,and also be of great potential in the treatment of Alzheimer’s disease.

Sphingosine 1-phosphate acts as an activator for the porcine Gpr3 of constitutively active G protein-coupled receptors

We cloned the complete coding sequences of porcine Gpr3, Gpr6, and Gpr12 genes. Further, on the basis of their high levels of sequence similarity, these genes are identified as a subfamily of G protein-coupled receptors. These putative protein sequences also showed high sequence identity with other mammalian orthologs, including several highly conserved motifs. A wide expression of the Gpr3 gene in pigs was observed through tissue distribution analysis by reverse transcriptase-polymerase chain reaction （RT-PCR） and real-time PCR, specially in the brain, pituitary, fat, liver and oocyte, where its strong expression was observed. The Gpr3 gene was found to be located on chromosome 6 and a single exon coded for the entire open reading frame. Expression of porcine Gpr3 in HEK293 cells resulted in constitutive activation of adenylate cyclase （AC） similar in amplitude to that produced by fully stimulated Gs coupled receptors. Moreover, sphingosine 1-phosphate （S1P） could increase AC activation via the constitutively active Gpr3 receptor. When a Gpr3-green fluorescent protein （GFP） construct was expressed in HEK293 cells, GFP-labeled Gpr3 protein was shown to be localized in the plasmalemma and subcellular membranes. After S1P treatment, agonist-mediated internalization could be visualized by confocal microscopy. In short, our findings suggest the porcine Gpr3, Gpr6, and Gpr12 genes as a subfamily of G protein-coupled receptors, and porcine Gpr3 was a constitutively active G protein-coupled receptor. Constitutive activation of AG and agonist-mediated internalization of Gpr3 receptor could be modulated by the S1 P, suggesting that S1P might act as an activator for porcine Gpr3 receptor.