A Review of the Phytochemistry and Biological Activities of Echinopsis Radix.

The main varieties of Echinopsis Radix recorded in the Chinese Pharmacopoeia are the roots of Echinops latifolius Tausch or Echinops grijsii Hance. However, the chemical constituents and biological activities of this herb have not been reviewed. In order to clarify the chemical constituents of the main varieties of this herb and improve the quality of Chinese medicinal material resources, this paper systematically reviewed their chemical constituents and related biological activities. Phytochemical investigations reveal eighty-five compounds including fort y-nine thiophenes (1-49), eight flavonoids (50-57), seven caffeic acids and its derivatives (58-64), eight sesquiterpenoids (65-72), and thirteen triterpenoids and other compounds (73-85) were reported from Echinopsis Radix. The review of biological activities suggests that thiophenes are the main secondary metabolites of the medicinal material which exert antitumor, insecticidal and antifungal activities. In addition, caffeic acid and its derivatives and sesquiterpenes are potential active ingredients worthy of further study. This review provides an important scientific basis for the development of active ingredients and resource quality evaluation of Echinopsis Radix.

Multifunctional Manganese-Nucleotide Laccase-Mimicking Nanozyme for Degradation of Organic Pollutants and Visual Assay of Epinephrine via Smartphone.

As a natural green catalyst, laccase has extensive application in the fields of environmental monitoring and pollutant degradation. However, susceptibility to environmental influences and poor reusability seriously hinder its application. To address these concerns, for the first time, manganese ion replaced copper ion as the active center to coordinate with guanosine monophosphate (GMP) for synthesizing mimic laccase with high catalytic activity. Compared with natural laccase, the laccase-like nanozyme (Mn-GMPNS) demonstrated superior thermal stability, acid-base resistance, salt tolerance, reusability, and substrate universality. Benefiting from the high catalytic activity of Mn-GMPNS, epinephrine, a significant neurotransmitter and hormone associated with numerous diseases, was visually detected within 10 min and a portable assay by smartphone. More encouragingly, Mn-GMPNS can efficiently degrade dye pollutants, achieving a decolorization rate over 70% within 30 min. Thus, the coordination between manganese ion and nucleotide demonstrated the potential in rational design of nanozymes with high catalytic activity, low cost, good stability, and good biocompatibility.

Unveiling the Anticancer Mechanism of Echinops davuricus: Isolation and Evaluation of AKR1B10 Inhibitors.

Five compounds (1-5), one long-chain fatty acid (1), two thiophenes (2 and 3), one alkaloid (4), and one phenyl ester (5), were isolated from the aerial part of Echinops davuricus. The structures of the products were established by performing detailed nuclear magnetic resonance (NMR) analysis, and the structure of compound 1 was determined via high-resolution electrospray ionization mass spectrometry (HRESIMS) and NMR. Compounds 1, 4, and 5 were isolated from Echinops davuricus for the first time. Based on network pharmacology methods, AKR1B10 was selected as a key anticancer target. Compounds 1 and 5 exhibited significant AKR1B10 inhibitory activities, with IC50 values of 156.0±1.00 and 146.2±1.50 nM, respectively, with epalrestat used as the positive control (81.09±0.61 nM). Additionally, the interactions between the active compounds and AKR1B10 were evaluated via molecular docking. Ultimately, the GO and KEGG enrichment analysis indicated that the key signaling pathways associated with the active compounds may be related to the PI3K-Akt, MAPK, apoptotic, cellular senescence, and TNF signaling pathways and the human diseases corresponding to the targets are cancer. Our study reveals for the first time the anticancer properties of Echinops davuricus and provides a comprehensive understanding of its application in traditional medicine.

Development of AKR1B10 inhibitors from Ajuga nipponensis based on diseases and targets.

Ten compounds (1-10) including one new neoclerodane diterpenoid (1) and nine known compounds were isolated from the whole plants of Ajuga nipponensis. Their structures were established by performing detailed analysis of NMR, the structure of 1 was determined using HRESIMS, 1D and 2D NMR, UV, and IR. Compounds 1 and 4-10 were isolated from Ajuga nipponensis for the first time. And it was the first time to report compounds 9 and 10 as natural products. Based on network pharmacology methods, 45 key targets were selected, which were compounds mapping to diseases. And compounds 2, 3, 7, and a (ajugacumbin B) exhibited excellent AKR1B10 inhibitory activities, with IC50 values of 53.05 ± 0.75, 87.22 ± 0.85, 61.85 ± 0.66, and 85.19±1.02 nM respectively, with Epalrestat used as the positive control (82.09 ± 1.62 nM). Additionally, the interaction between active compounds and AKR1B10 had been discussed according to the molecular docking results. Ultimately, the analysis of GO and KEGG enrichment indicated that the key signaling pathway of the active compounds may be related to prostate cancer. Our study results demonstrate the hypoglycemic and anti-tumor properties of A. nipponensis for the first time, and provide a comprehensive understanding of its application in traditional medicine. Furthermore, this article establishes a reference for further research on the optimized experimental design of novel AKR1B10 inhibitors.

A meta-analysis examined the effect of stoma on surgical site wound infection in colorectal cancer.

To assess the impact of a stoma on surgical site wound infection in colorectal cancer, we conducted a meta-analysis. A thorough review of the literature up to September 2022 revealed that 3223 participants had colorectal cancer at the start of the investigations; 258 of them had a stoma, while 2965 did not have a stoma. Using dichotomous or contentious methods and a random or fixed-effect model, odds ratios (OR) and mean difference (MD) with 95% confidence intervals (CIs) were estimated to evaluate the impact of a stoma on surgical site wound infection in colorectal cancer. The stoma present had significantly higher surgical site wound infections (OR, 4.37; 95% CI, 3.08-6.21; P < 0.001) with no heterogeneity (I2 = 12%) compared to stoma absent in colorectal cancer. The stoma present had significantly higher surgical site wound infections compared to the stoma absent in colorectal cancer. The low number of selected studies in the meta-analysis calls for care when analysing the results.

Comparative de novo Transcriptome Analysis of Two Cultivars With Contrasting Content of Oil and Fatty Acids During Kernel Development in Torreya grandis.

Vegetable oil is an indispensable nutritional resource for human health and mainly characterized by the composition and content of fatty acids (FAs). As a commercial species of gymnosperm, Torreya grandis produces oil-rich nuts with high unsaturated fatty acids content in the mature kernels. In this study, two cultivars, T. grandis 'Xifei' and T. grandis 'Dielsii,' with distinct oil content were employed to compare the profiles of FAs accumulation during kernel development. The accumulation rate of oil content was significantly different between 'Xifei' and 'Dielsii.' Besides, the final oil content of 'Xifei' (52.87%) was significantly higher than that of 'Dielsii' (41.62%) at maturity. The significant differences in main FAs were observed at almost each kernel development stages between the two cultivars. C16:0, C18:1, and C20:3 FA exhibited different accumulation patterns between cultivars. The content and the initiation of accumulation of C20:3 FA were different between the two cultivars. To explore the molecular mechanism associated with different content of oil and FAs between two cultivars, de novo transcriptome of kernels was compared between 'Xifei' (high oil) and 'Dielsii' (low oil) at three stages of oil accumulation, respectively. Totally 142,213 unigenes were assembled and 16,379 unigenes with a length of over 1,000 nt were successfully annotated, including 139 unigenes related to FA biosynthesis, elongation, and metabolism. Compared with 'Dielsii,' totally 1,476, 2,140, and 1,145 differentially expressed genes (DEGs) were upregulated in 'Xifei' at the stage of the initiative, the rapid rise, and the stationary oil accumulation, respectively; the number of downregulated DEGs reached 913, 1,245, and 904, respectively. Relative expressions of 11 DEGs involved in FAs biosynthesis and metabolism were confirmed by RT-qPCR. Abundant differentially expressed transcription factors and pathway DEGs were correlated to oil and FAs according to Pearson's correlation analysis between transcriptome and metabolites (oil and FAs), suggesting their contributions to the differential oil and FAs between the two cultivars during kernel development of T. grandis. To conclude, our findings can provide novel insights into the developmental differences in metabolites and de novo transcriptome correlated to lipid accumulation and FA synthesis of kernels between cultivars with contrasting oil deposits and demystify the regulatory mechanism of high oil accumulation in T. grandis.

High-Throughput Screening Campaign Identified a Potential Small Molecule RXFP3/4 Agonist.

Relaxin/insulin-like family peptide receptor 3 (RXFP3) belongs to class A G protein-coupled receptor family. RXFP3 and its endogenous ligand relaxin-3 are mainly expressed in the brain with important roles in the regulation of appetite, energy metabolism, endocrine homeostasis and emotional processing. It is therefore implicated as a potential target for treatment of various central nervous system diseases. Since selective agonists of RXFP3 are restricted to relaxin-3 and its analogs, we conducted a high-throughput screening campaign against 32,021 synthetic and natural product-derived compounds using a cyclic adenosine monophosphate (cAMP) measurement-based method. Only one compound, WNN0109-C011, was identified following primary screening, secondary screening and dose-response studies. Although displayed agonistic effect in cells overexpressing the human RXFP3, it also showed cross-reactivity with the human RXFP4. This hit compound may provide not only a chemical probe to investigate the function of RXFP3/4, but also a novel scaffold for the development of RXFP3/4 agonists.

Intracellular AGR2 transduces PGE2 stimuli to promote epithelial-mesenchymal transition and metastasis of colorectal cancer.

Human anterior gradient homolog 2 (AGR2) reportedly acts as an oncogene in multiple types of cancers. As a secreted protein, the oncogenic roles of extracellular AGR2 have been the focus of the increasing number of studies. In contrast, the oncological functions of intracellular AGR2 (iAGR2) remain elusive. Here, we report that intracellular AGR2 (iAGR2) is sufficient to promote CRC metastasis. iAGR2 binds to KDEL receptors (KDELRs) via its KTEL motif to activate downstream Gs-PKA signaling. Activated PKA upregulates the expression of NF-κB subunit c-Rel (REL) and acetylates histone H3 at lysine 9 (H3K9ac) to promote the transcription of SNAIL and SLUG. AGR2 can be upregulated by prostaglandin E2 (PGE2) via EP4-PI3K-AKT pathway and is indispensable for PGE2-induced CRC metastasis. AGR2 knockdown enhances therapeutic effects of a COX-2 inhibitor, celecoxib, in CRC metastasis. Collectively, our study reveals a promoting role and molecular mechanisms of iAGR2 in CRC metastasis and uncovers a new tumor microenvironment signal regulating AGR2 expression, which may provide new targets for treating metastatic CRC.

Common and specific altered amplitude of low-frequency fluctuations in Parkinson's disease patients with and without freezing of gait in different frequency bands.

Freezing of gait (FOG), a disabling symptom of Parkinson's disease (PD), severely affects PD patients' life quality. Previous studies found neuropathologies in functional connectivity related to FOG, but few studies detected abnormal regional activities related to FOG in PD patients. In the present study, we analyzed the amplitude of low-frequency fluctuations (ALFF) to detect brain regions showing abnormal activity in PD patients with FOG (PD-with-FOG) and without FOG (PD-without-FOG). As different frequencies of neural oscillations in brain may reflect distinct brain functional and physiological properties, we conducted this study in three frequency bands, slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), and classical frequency band (0.01-0.08 Hz). We acquired rs-fMRI data from 18 PD-with-FOG patients, 18 PD-without-FOG patients, and 17 healthy controls, then calculated voxel-wise ALFF across the whole brain and compared ALFF among the three groups in each frequency band. We found: (1) in slow-5, both PD-with-FOG and PD-without-FOG patients showed lower ALFF in the bilateral putamen compared to healthy controls, (2) in slow-4, PD-with-FOG patients showed higher ALFF in left inferior temporal gyrus (ITG) and lower ALFF in right middle frontal gyrus (MFG) compared to either PD-without-FOG patients or healthy controls, (3) in classical frequency band, PD-with-FOG patients also showed higher ALFF in ITG compared to either PD-without-FOG patients or healthy controls. Furthermore, we found that ALFF in MFG and ITG in slow-4 provided the highest classification accuracy (96.7%) in distinguishing PD-with-FOG from PD-without-FOG patients by using a stepwise multivariate pattern analysis. Our findings indicated frequency-specific regional spontaneous neural activity related to FOG, which may help to elucidate the pathogenesis of FOG.

AGR2 is controlled by DNMT3a-centered signaling module and mediates tumor resistance to 5-Aza in colorectal cancer.

Human anterior gradient-2 (AGR2), a member of protein disulfide isomerase (PDI) family, is upregulated in various human cancers and reportedly has oncogenic activities. However, the functional roles of AGR2 and its regulation in colorectal cancer (CRC) remain unclear. Here, we showed that AGR2 promoted CRC tumorigenesis and progression in vitro and in vivo and acted as an independent prognostic factor of poor outcome. AGR2 was negatively regulated by DNA methyltransferase 3a (DNMT3a) through directly methylating AGR2 promoter and by a DNMT3a-SPRY2-miR-194 axis. Moreover, AGR2 mediated the resistance to 5-Aza-2'-deoxycytidine (5-Aza) treatment. Knockdown of AGR2 improved the therapeutic effect of 5-Aza in human CRC xenograft tumor model. Thus, our work supports AGR2's oncogenic role in CRC, reveals DNMT3a-mediated epigenetic modulation on AGR2 promoter, and uncovers a new DNMT3a signaling module controlling expression of AGR2. Upregulated AGR2 offset 5-Aza mediated epigenetic therapy. This work might provide potential targets for clinical anti-cancer therapy.

MiR-494 acts as a tumor promoter by targeting CASP2 in non-small cell lung cancer.

MiR-494 plays an important role in several types of human cancers, including non-small cell lung cancer (NSCLC). Although the role of miR-494 has been investigated in several studies, the expression profile and underlying mechanism are still poorly understood. In this study, we found that overexpression of miR-494 promoted the proliferation and colony formation of NSCLC cells and reduced their sensitivity to cisplatin-induced apoptosis. By using microarray and Dual luciferase reporter assays, we further showed that caspase-2 (CASP2) is a functional target of miR-494, and the expression of CASP2 is inversely associated with miR-494 in vitro. In addition, miR-494 promoted the proliferation and colony formation of NSCLC cells and reduced their sensitivity to cisplatin-induced apoptosis by targeting CASP2. Therefore, our results suggest that miR-494 plays an oncomiR role in NSCLC cells and may be a candidate biomarker for malignant transformation and a therapeutic target of NSCLC.

Alterations of regional homogeneity in freezing of gait in Parkinson's disease.

INTRODUCTION: Freezing of gait (FOG) is a serious complication in patients with Parkinson's disease (PD), and is more common in the late state of the disease. The high risk of falling in patients with FOG impacts their quality of life. OBJECTIVE: To explore altered neuroactivity related to cognitive and executive function of PD patients with FOG. METHODS: Fourteen PD patients with FOG (FOG+), 20 PD patients without FOG (FOG-), and 18 normal controls (NC) were enrolled. Functional MRI data of all PD patients were collected during OFF medication state. Data were analyzed using software of DPARSF and REST. Resting brain activity was measured by regional homogeneity (ReHo). ANOVA test was performed for ReHo among FOG, PD, and NC groups. RESULTS: ReHo alterations of left supplementary motor area (SMA) (Brodmann 6), left superior frontal region (Brodmann 9), and the right putamen (Brodmann 48) were significantly different among the three groups. The ReHo values within left SMA (Brodmann 6) and left superior frontal region (Brodmann 9) were significantly decreased in FOG+ patients compared with FOG- patients. CONCLUSION: Changes in neural hypoactivity within the frontal region and SMA appear to be associated with FOG in PD patients, which suggests that the mechanism underlying FOG may relate to disruption of execution and cognition.

Outcomes of transconjunctival sutureless 27-gauge vitrectomy for vitreoretinal diseases.

AIM: To evaluate the safety and efficacy profile of 27-gauge (27G) pars plana vitrectomy (PPV) for the treatment of various vitreoretinal diseases. METHODS: The clinical outcomes of 61 eyes (58 patients) with various vitreoretinal diseases following 27G PPV were retrospectively reviewed. RESULTS: Surgical indications included rhegmatogenous retinal detachment (n=24), full-thickness macular hole (n=12), diabetic retinopathy (n=11), vitreous hemorrhage (n=6), Eales disease (n=4), pathological myopia-related vitreous floater (n=2), and macular epiretinal membrane (n=2). The mean follow-up was 166.4±61.3d (range 98-339d). The mean logMAR best-corrected visual acuity (BCVA) improved from 1.7±1.1 [0.02 decimal visual acuity (VA) equivalent] preoperatively to 1.2±1.0 (0.06 decimal VA equivalent) at the last postoperative visit (P<0.001). The mean operative time was 49.9min. With the exception of complicated cataract in one eye, no intraoperative complications were encountered. No case required conversion to conventional 20-, 23- or 25G instrumentation in all surgical maneuvers except for silicone oil infusion, which required a 25G oil injection syringe. Postoperative complications included transient ocular hypertension, vitreous hemorrhage, persistent intraocular pressure elevation, subconjunctival oil leakage, and recurrent retinal detachment. No cases of hypotony, endophthalmitis, and sclerotomy-related tears were observed. CONCLUSION: The current results suggest that 27G PPV system is a safe and effective treatment for various vitreoretinal diseases. When learning to perform 27G PPV, surgeons may encounter a learning curve and should gradually expand surgical indications from easy to pathologically complicated cases.

Impact of International Collaborative Training Programs on Medical Students' Research Ability.

International collaborative training programs for graduate students are widespread, but studies on their educational impact are limited. As an advanced cancer institute in China, Cancer Hospital Chinese Academy of Medical Science (CHCAMS) attaches great importance to international exchanges and cooperation within graduate education. The Department of Epidemiology of CHCAMS has been involved in several existing international training programs and has also launched a short-term training program in cooperation with foreign universities and institutes from 2008. Fogarty International Clinical Research Scholars and Fellows (FICRS-F) Program and the Fulbright-Fogarty Fellowship Program are the most typical examples of our practice in international cooperation on graduate education over these years. Our department has gained substantial experience in graduate-level international collaborative training, focused on cancer epidemiology. This paper is a brief introduction to the practice of different programs in our department and students' achievements during and after training. Moreover, we attempt to serve as a reference and help promote the training of graduate students pursuing careers in cancer research or global health by other universities or research institutes.

Long non-coding RNA growth arrest specific transcript 5 acts as a tumour suppressor in colorectal cancer by inhibiting interleukin-10 and vascular endothelial growth factor expression.

Long non-coding RNAs (lncRNAs) are highly involved in diverse biological processes of human malignancies. The expression profile and underlying mechanism of lncRNA growth arrest specific transcript 5 (GAS5) in colorectal cancer (CRC) is poorly understood. In this study, we found that GAS5 was commonly downregulated in CRC tissues, serum of CRC patients and CRC cell lines. Knockdown of GAS5 promoted CRC cell proliferation and colony formation, whereas overexpression of GAS5 produced the opposite result. We further demonstrated that knockdown of GAS5 increased the expression and secretion of interleukin-10 (IL-10) and vascular endothelial growth factor (VEGF-A) via NF-κB and Erk1/2 pathways. Neutralization of IL-10 and VEGF-A reduced tumour proliferation caused by GAS5 knockdown. Moreover, GAS5 expression showed a statistically significant correlation with the mRNA levels of IL-10 and VEGF-A in CRC tissues. We further illustrated that GAS5 was markedly downregulated and negatively correlated with the cytokine expression in a mouse model of colitis-associated cancer (CAC). These results delineate a novel mechanism of lncRNA GAS5 in suppressing colorectal carcinogenesis. The cytokines IL-10 and VEGF-A inhibited by GAS5 may provide targets for lncRNA-based therapies for CRC.

Accuracy of triage strategies for human papillomavirus DNA-positive women in low-resource settings: A cross-sectional study in China.

OBJECTIVE: CareHPV is a human papillomavirus (HPV) DNA test for low-resource settings (LRS). This study assesses optimum triage strategies for careHPV-positive women in LRS. METHODS: A total of 2,530 Chinese women were concurrently screened for cervical cancer with visual inspection with acetic acid (VIA), liquid-based cytology and HPV testing by physician- and self-collected careHPV, and physician-collected Hybrid Capture 2 (HC2). Screen-positive women were referred to colposcopy with biopsy and endocervical curettage as necessary. HPV-positivity was defined as ≥1.0 relative light units/cutoff (RLU/CO) for both careHPV and HC2. Primary physician-HC2, physician-careHPV and self-careHPV and in sequential screening with cytology, VIA, or increased HPV test-positivity performance, stratified by age, were assessed for cervical intraepithelial neoplasia (CIN) grade 2/3 or worse (CIN2/3+) detection. RESULTS: The sensitivities and specificities of primary HPV testing for CIN2+ were: 83.8%, 88.1% for physician-careHPV; 72.1%, 88.2% for self-careHPV; and 97.1%, 86.0% for HC2. Physician-careHPV test-positive women with VIA triage had a sensitivity of 30.9% for CIN2+ versus 80.9% with cytology triage. Self-careHPV test-positive women with VIA triage was 26.5% versus 66.2% with cytology triage. The sensitivity of HC2 test-positive women with VIA triage was 38.2% versus 92.6% with cytology triage. The sensitivity of physician-careHPV testing for CIN2+ decreased from 83.8% at ≥1.0 RLU/CO to 72.1% at ≥10.00 RLU/CO, while the sensitivity of self-careHPV testing decreased from 72.1% at ≥1.0 RLU/CO to 32.4% at ≥10.00 RLU/CO; similar trends were seen with age-stratification. CONCLUSIONS: VIA and cytology triage improved specificity for CIN2/3 than no triage. Sensitivity with VIA triage was unsuitable for a mass-screening program. VIA provider training might improve this strategy. Cytology triage could be feasible where a high-quality cytology program exists. Triage of HPV test-positive women by increased test positivity cutoff adds another LRS triage option.

Glucagon-Like Peptide-1 and Its Class B G Protein-Coupled Receptors: A Long March to Therapeutic Successes.

The glucagon-like peptide (GLP)-1 receptor (GLP-1R) is a class B G protein-coupled receptor (GPCR) that mediates the action of GLP-1, a peptide hormone secreted from three major tissues in humans, enteroendocrine L cells in the distal intestine, α cells in the pancreas, and the central nervous system, which exerts important actions useful in the management of type 2 diabetes mellitus and obesity, including glucose homeostasis and regulation of gastric motility and food intake. Peptidic analogs of GLP-1 have been successfully developed with enhanced bioavailability and pharmacological activity. Physiologic and biochemical studies with truncated, chimeric, and mutated peptides and GLP-1R variants, together with ligand-bound crystal structures of the extracellular domain and the first three-dimensional structures of the 7-helical transmembrane domain of class B GPCRs, have provided the basis for a two-domain-binding mechanism of GLP-1 with its cognate receptor. Although efforts in discovering therapeutically viable nonpeptidic GLP-1R agonists have been hampered, small-molecule modulators offer complementary chemical tools to peptide analogs to investigate ligand-directed biased cellular signaling of GLP-1R. The integrated pharmacological and structural information of different GLP-1 analogs and homologous receptors give new insights into the molecular determinants of GLP-1R ligand selectivity and functional activity, thereby providing novel opportunities in the design and development of more efficacious agents to treat metabolic disorders.

G protein-coupled receptor GPR160 is associated with apoptosis and cell cycle arrest of prostate cancer cells.

G protein-coupled receptors (GPCRs) represent the largest membrane protein family implicated in the therapeutic intervention of a variety of diseases including cancer. Exploration of biological actions of orphan GPCRs may lead to the identification of new targets for drug discovery. This study investigates potential roles of GPR160, an orphan GPCR, in the pathogenesis of prostate cancer. The transcription levels of GPR160 in the prostate cancer tissue samples and cell lines, such as PC-3, LNCaP, DU145 and 22Rv1 cells, were significantly higher than that seen in normal prostate tissue and cells. Knockdown of GPR160 by lentivirus-mediated short hairpin RNA constructs targeting human GPR160 gene (ShGPR160) resulted in prostate cancer cell apoptosis and growth arrest both in vitro and in athymic mice. Differential gene expression patterns in PC-3 cells infected with ShGPR160 or scramble lentivirus showed that 815 genes were activated and 1193 repressed. Functional annotation of differentially expressed genes (DEGs) revealed that microtubule cytoskeleton, cytokine activity, cell cycle phase and mitosis are the most evident functions enriched by the repressed genes, while regulation of programmed cell death, apoptosis and chemotaxis are enriched significantly by the activated genes. Treatment of cells with GPR160-targeting shRNA lentiviruses or duplex siRNA oligos increased the transcription of IL6 and CASP1 gene significantly. Our data suggest that the expression level of endogenous GPR160 is associated with the pathogenesis of prostate cancer.

Landmark studies on the glucagon subfamily of GPCRs: from small molecule modulators to a crystal structure.

The glucagon subfamily of class B G protein-coupled receptors (GPCRs) has been proposed to be a crucial drug target for the tretmaent of type 2 diabetes. The challenges associated with determining the crystal structures of class B GPCRs relate to their large amino termini and the lack of available small molecule ligands to stabilize the receptor proteins. Following our discovery of non-peptidic agonists for glucagon-like peptide-1 receptor (GLP-1R) that have therapeutic effects, we initiated collaborative efforts in structural biology and recently solved the three-dimensional (3D) structure of the human glucagon receptor (GCGR) 7-transmembrane domain, providing in-depth information about the underlying signaling mechanisms. In this review, some key milestones in this endeavor are highlighted, including discoveries of small molecule ligands, their roles in receptor crystallization, conformational changes in transmembrane domains (TMDs) upon activation and structure-activity relationship analyses.