Activation of β_2-Adrenergic Receptor Induced by Three Catecholamine Agonists:a Docking and Molecular Dynamics Study

We studied the activation of β2-adrenergic receptor（β2AR） by norepinephrine, epinephrine and isoprote- renol using docking and molecular dynamics（MD） simulation. The simulation was done on the assumption that β2AR was surrounded with explicit water and infinite lipid bilayer membrane at body temperature. So the result should be close to that under the physiological conditions. We calculated the structure of binding sites in β2AR for the three ac- tivators. We also simulated the change of the conformation ofβ2AR in the transmembrane regions（TMs）, in the mo- lecular switches, and in the conserved DRY（Aspartic acid, Arginine and Tyrosine） motif. This study provides detailed information concerning the structure ofβ2AR during activation process.

SNP Identification in α_(2A)-Adrenergic Receptor Gene in Chinese and the Effect on Gene Expression

Objective: To scan single nucleotide polymorphism ( SNP ) in Chinese alpha-2Aadrenergic receptor (α_(2A)-AR) gene and study the effects of the SNP on the gene expression.Methods: The complete sequence of α_(2A)-AR gene was analyzed with automated DNA sequencer to scanSNPs. Genomic DNA was extracted from whole blood and a 239 bp fragment containing the G/Cpolymorphism was amplified with PCR using a pair of. specific primers. PCR-RFLP was used to performthe genotyping of the SNP at the site-1 296 bp of the people in the North of China. Electrophoresismobility shift assay ( EMSA ) was used to study the binding of the 390 bp fragments (- 1 414-1 025bp) with G or C at the site-1 296 bp and nuclear extracts . Results: In our study, two SNPs werefound in α_(2A)-AR gene. Allele frequencies of the SNP at the site-1 296 bp were 0.61 and 0.39 forG and C , and the genotype frequencies were 0.34 , 0.54 and 0.13 for GG, GC and CC respectively fromthe people in the North of China. In the EMSA, a specific binding appeared in the complex ofnuclear extracts and DNA with C at-1 296 bp . Conclusion: Two SNPs exist in α_(2A)-AR gene from thepeople in the North of China , and DNA fragment with allele C of the SNP at the site-1 296 bp couldbind with a specific protein, which could influence the gene expression.

A novel β_(2)-AR agonist,Higenamine,induces β-arrestin-biased signaling

The biased ligands in G protein-coupled receptors(GPCRs)have opened new avenues for developing safer and more effective drugs.However,the identification of such biased ligands as drug candidates is highly desirable.Here,we report that Higenamine,a compound isolated from a Chinese herb,functions as a novel β-arrestin-biased ligand of the β_(2)-adrenergic receptor(β_(2)-AR).The radioligand binding assays demonstrated that Higenamine was the ligand of β_(2)-AR.Higenamine induced phosphorylation of extracellular signal-regulated kinase 1/2(ERK1/2),which can be blocked by propranolol,an inhibitor of β_(2)-AR.The Gi protein inhibitor,pertussis toxin,had no effect on the phosphorylation of ERK1/2 induced by Higenamine.Furthermore,Higenamine induced ERK1/2 phosphorylation through transactivation of Epithelial growth factor receptor(EGFR).We also found that Higenamine-induced-ERK1/2 phosphorylation is dependent on β-arrestin1/2,and HG inhibits Doxorubicin-induced cardiomyocyte apoptosis.Our results identify Higenamine as a novel biased ligand via the β-arrestin-dependent pathway.These findings give us a better understanding of Higenamine’s potential role in designing diagnostic and therapeutic strategies.

Activating Connexin43 gap junctions primes adipose tissue for therapeutic intervention

Adipose tissue is a promising target for treating obesity and metabolic diseases.However,pharmacological agents usually fail to effectively engage adipocytes due to their extraordinarily large size and insufficient vascularization,especially in obese subjects.We have previously shown that during cold exposure,connexin43(Cx43)gap junctions are induced and activated to connect neighboring adipocytes to share limited sympathetic neuronal input amongst multiple cells.We reason the same mechanism may be leveraged to improve the efficacy of various pharmacological agents that target adipose tissue.Using an adipose tissue-specific Cx43 overexpression mouse model,we demonstrate effectiveness in connecting adipocytes to augment metabolic efficacy of theβ_(3)-adrenergic receptor agonist Mirabegron and FGF21.Additionally,combing those molecules with the Cx43 gap junction channel activator danegaptide shows a similar enhanced efficacy.In light of these findings,we propose a model in which connecting adipocytes via Cx43 gap junction channels primes adipose tissue to pharmacological agents designed to engage it.Thus,Cx43 gap junction activators hold great potential for combination with additional agents targeting adipose tissue.