Structural analysis and conformational dynamics of a holo-adhesion GPCR reveal interplay between extracellular and transmembrane domains.

Adhesion G Protein-Coupled Receptors (aGPCRs) are key cell-adhesion molecules involved in numerous physiological functions. aGPCRs have large multi-domain extracellular regions (ECR) containing a conserved GAIN domain that precedes their seven-pass transmembrane domain (7TM). Ligand binding and mechanical force applied on the ECR regulate receptor function. However, how the ECR communicates with the 7TM remains elusive, because the relative orientation and dynamics of the ECR and 7TM within a holoreceptor is unclear. Here, we describe the cryo-EM reconstruction of an aGPCR, Latrophilin3/ADGRL3, and reveal that the GAIN domain adopts a parallel orientation to the membrane and has constrained movement. Single-molecule FRET experiments unveil three slow-exchanging FRET states of the ECR relative to the 7TM within the holoreceptor. GAIN-targeted antibodies, and cancer-associated mutations at the GAIN-7TM interface, alter FRET states, cryo-EM conformations, and receptor signaling. Altogether, this data demonstrates conformational and functional coupling between the ECR and 7TM, suggesting an ECR-mediated mechanism of aGPCR activation.

Posttraumatic Stress Disorder After Spontaneous Coronary Artery Dissection: A Report of the International Spontaneous Coronary Artery Dissection Registry.

BACKGROUND: Myocardial infarction secondary to spontaneous coronary artery dissection (SCAD) can be traumatic and potentially trigger posttraumatic stress disorder (PTSD). In a large, multicenter, registry-based cohort, we documented prevalence of lifetime and past-month SCAD-induced PTSD, as well as related treatment seeking, and examined a range of health-relevant correlates of SCAD-induced PTSD. METHODS AND RESULTS: Patients with SCAD were enrolled in the iSCAD (International SCAD) Registry. At baseline, site investigators completed medical report forms, and patients reported demographics, medical/SCAD history, psychosocial factors (including SCAD-induced PTSD symptoms), health behaviors, and health status via online questionnaires. Of 1156 registry patients, 859 patients (93.9% women; mean age, 52.3 years) completed questionnaires querying SCAD-induced PTSD. Nearly 35% (n=298) of patients met diagnostic criteria for probable SCAD-induced PTSD in their lifetime, and 6.4% (n=55) met criteria for probable past-month PTSD. Of 811 patients ever reporting any SCAD-induced PTSD symptoms, 34.8% indicated seeking treatment for this distress. However, 46.0% of the 298 patients with lifetime probable SCAD-induced PTSD diagnoses reported never receiving trauma-related treatment. Younger age at first SCAD, fewer years since SCAD, being single, unemployed status, more lifetime trauma, and history of anxiety were associated with greater past-month PTSD symptom severity in multivariable regression models. Greater past-month SCAD-induced PTSD symptoms were associated with greater past-week sleep disturbance and worse past-month disease-specific health status when adjusting for various risk factors. CONCLUSIONS: Given the high prevalence of SCAD-induced PTSD symptoms, efforts to support screening for these symptoms and connecting patients experiencing distress with empirically supported treatments are critical next steps. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04496687.

A comparative study of diaryl urea molecules with and without sulfonamide group on Carbonic anhydrase IX and XII inhibition and its consequence on breast cancer cells.

To investigate the intrinsic relation between carbonic anhydrase inhibition and anticancer activity, we have prepared four sets of diaryl urea molecules and tested for the inhibition of hCA-IX and XII on two breast cancer cell lines. Among 21 compounds, compound J2 (with -SO2NH2 group) and J16 (without -SO2NH2 group) showed the best activity under normoxic and hypoxic conditions. The IC50 values of J16 for MDA-MB-231 and MCF-7 cells, under normoxic condition were 6.3 and 3.7 µM respectively, which are 1.9/3.3 and 15.8 times better than U-4-Nitro and SLC-0111 respectively. Whereas, under the hypoxic condition the corresponding values were 12.4 and 1.1 µM (MDA-MB-231 and MCF-7 cells respectively), which are equal/8 times better than U-4-Nitro. Whereas, J2 showed better IC50 value than U-4-Nitro (6.3 µM) under normoxic condition for both MDA-MB-231 and MCF-7 cells (1.9/2.7 times). Compound J2 inhibits the activity of hCA-IX and XII in nanomolar concentration [Ki values 4.09 and 9.10 nM respectively with selectivity ratio of 1.8 and 0.8 with hCA-II]. The crystal structure and modelling studies demonstrates that the inhibition of CAs arises due to the blocking of the CO2 coordination site of zinc in its catalytic domain. However, J16 was found to be unable to inhibit the activity of hCAs (Ki > 89000 nM). qPCR and western blot analysis showed a significant reduction (1.5 to 20 fold) of the transcription and expression of HIF1A, CA9 and CA12 genes in presence of J2 and J16. Both J2 and J16 found to reduce accumulation of HIF-1α protein by inhibiting the chaperone activity of hHSP70 with IC50 values of 19.4 and 15.3 µM respectively. Perturbation of the hCA-IX and XII activity by binding at active site or by reduced expression or by both leads to the decrease of intracellular pH, which resulted in concomitant increase of reactive oxygen species by 2.6/2.0 (MCF-7) and 2.9/1.8 (MDA-MB-231) fold for J2/J16. Increased cyclin D1 expression in presence of J2 and J16 was presumed to be indirectly responsible for the apoptosis of the cancer cells. Expression of the other apoptosis markers Bcl-2, Bim, caspase 9 and caspase 3 substantiated the apoptosis mechanism. However, decreased transcription/expression of HIF1A/HIF-1α and hCA-IX/XII also implies the inhibition of the extracellular signal-regulated kinase pathway by J2 and J16.

Drugs Prescribed for Asthma and Their Adverse Effects on Dental Health.

Asthma is a chronic, heterogeneous respiratory pathology characterized by reversible airway inflammation. Therapeutics focus on symptom reduction and control, aimed at preserving normal pulmonary function and inducing bronchodilatation. The objective of this review is to describe the adverse effects produced by anti-asthmatic drugs on dental health, according to the reported scientific evidence. A bibliographic review was carried out on databases, such as Web of science, Scopus, and ScienceDirect. Most anti-asthmatic medications are administered using inhalers or nebulizers, making it impossible to avoid contact of the drug with hard dental tissues and oral mucosa, and thus promoting a greater risk of oral alterations, mainly due to decreases in the salivary flow and pH. Such changes can cause diseases, such as dental caries, dental erosion, tooth loss, periodontal disease, bone resorption, as well as fungal infections, such as oral candidiasis.

Distribution of Dental Fluorosis in the Southern Zone of Ecuador: An Epidemiological Study.

In recent decades, the increase in fluoride exposure has raised the numbers of dental fluorosis in fluoridated and non-fluoridated communities In Ecuador, but the last national epidemiological study on DF was conducted more than a decade ago. The objective of this cross-sectional descriptive study was to determine the prevalence, distribution and severity of dental fluorosis (DF) using the Dean index in 1606 schoolchildren aged 6 to 12 years from urban and rural environments in provinces that make up the Southern Region of Ecuador. Participants met the inclusion criteria which were age, locality, informed consent document and no legal impediment. The results are presented using percentage frequency measures and chi-square associations. The prevalence of dental fluorosis was 50.1% in the areas of Azuay, Cañar and Morona Santiago, with no significant differences (x2 = 5.83, p = 0.054). The types of DF found most frequently were very mild and mild in all provinces; a moderate degree was more prevalent in Cañar (17%). There was no significant association (p > 0.05) between sex and the presence of dental fluorosis and, with respect to severity, the most frequent degree was moderate at the age of 12 years. The prevalence of dental fluorosis in the area evaluated is high, especially in the light and very light degrees, with a tendency toward moderate levels. It is necessary to carry out studies on the factors that are predisposing to the development of this pathology in the population studied. This research is an update regarding this pathology in Ecuador, so it is concluded that it is necessary to continue developing studies based on the findings obtained, thus contributing to the public health of the country.

Isoform- and ligand-specific modulation of the adhesion GPCR ADGRL3/Latrophilin3 by a synthetic binder.

Adhesion G protein-coupled receptors (aGPCRs) are cell-surface proteins with large extracellular regions that bind to multiple ligands to regulate key biological functions including neurodevelopment and organogenesis. Modulating a single function of a specific aGPCR isoform while affecting no other function and no other receptor is not trivial. Here, we engineered an antibody, termed LK30, that binds to the extracellular region of the aGPCR ADGRL3, and specifically acts as an agonist for ADGRL3 but not for its isoform, ADGRL1. The LK30/ADGRL3 complex structure revealed that the LK30 binding site on ADGRL3 overlaps with the binding site for an ADGRL3 ligand - teneurin. In cellular-adhesion assays, LK30 specifically broke the trans-cellular interaction of ADGRL3 with teneurin, but not with another ADGRL3 ligand - FLRT3. Our work provides proof of concept for the modulation of isoform- and ligand-specific aGPCR functions using unique tools, and thus establishes a foundation for the development of fine-tuned aGPCR-targeted therapeutics.

Ambulatory Sedation for Dental Procedures-Case of Cuenca, Ecuador.

In recent years, the dental treatment of children under sedation and/or general anesthesia on an outpatient basis has been developed as a behavioral management model in pediatric dentistry. The objective of this study was to establish the percentage of pediatric patients who required deep sedation on an outpatient basis in dental offices in the city of Cuenca, Ecuador. An observational study was conducted with a sample of 450 records of school- and preschool-age patients, where the variables were type and time of treatment, age, and sex. Statistical data were analyzed using the statistical program SPSS V.27 (IBM, Armonk, NY, USA). The highest percentage of children who received sedation were of preschool age. In general, there were three types of procedures per session, the most frequent being restorations (67%), followed by pulp treatment (49.8%) and, less frequently, minor surgery. The need for sedation for dental procedures is high in preschool patients, and ambulatory sedation has contributed to meeting this need. However, a regulation for its use is required at a national level.

Caries Experience and Treatment Needs in Urban and Rural Environments in School-Age Children from Three Provinces of Ecuador: A Cross-Sectional Study.

In Ecuador, national epidemiological surveys have not been updated; however, some regional studies in the northern areas of the country still report a high prevalence of dental caries. The aim of this study was to determine the experience, severity, and need for treatment of dental caries in school children aged 6 to 12 years in urban and rural settings in three provinces of southern Ecuador. This cross-sectional, relational study examined 1938 schoolchildren in the provinces of Azuay, Cañar, and Morona Santiago. The survey instruments were based mainly on the WHO manual Methods of Oral Health Surveys (dmft) for primary and permanent dentition (DMFT), as well as the prevalence, severity, and Significant Caries Index (SCI). The parametric Student's t-test was used to compare two groups, and the Spearman's Rho and Tau-c Kendall correlation coefficients were used to associate the categorical variables. Results: The prevalence of caries in the primary dentition was 78% and 89.2% in the permanent dentition. The dmft (M = 4.12, SD = 2.86) and DMFT (M = 3.62: SD = 3.07) placed the general group in a moderate caries index. The need for treatment was 90.68% in the primary dentition, while it was 87.99% in the permanent dentition. Caries severity in both dentitions was high (M = 7.74; SD = 3.42). Conclusions. Alarming indicators of caries experience and the need for treatment were observed in the population studied.

Métodos de diagnóstico molecular en la práctica odontológica / Molecular diagnostic methods in dental practice

El diagnóstico molecular, mediante la aplicación de técnicas molecu- lares, ha permitido estudiar microorganismos presentes en el inicio y progresión de la caries dental, enfermedad periodontal, y en los fracasos endodónticos. Las técnicas moleculares permiten la detección y cuan- tificación del material genético del ácido desoxirribonucleico (DNA), ácido ribonucleico (RNA) o proteínas, lo que posibilita el estudio del genoma completo o secuencias de DNA específicas. Estas técnicas surgen como una necesidad de detectar microorganismos de difícil o lento crecimiento en cultivos; la técnica más utilizada es la reacción en cadena de la polimerasa (PCR) que permite la amplificación de peque- ños segmentos de material genético al utilizar cebadores, por lo que es un método económico, preciso, sensible y rápido para la detección de microorganismos. El presente artículo de revisión bibliográfica servirá para informar sobre los avances de las técnicas moleculares utilizadas para el diagnóstico en la práctica odontológica (AU)

Molecular diagnosis, through the application of molecular techniques, has made it possible to study microorganisms present in the onset and progression of dental caries, periodontal disease, and endodontic failures. Molecular techniques allow the detection and quantification of the genetic material of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) or proteins, allowing the study of the complete genome or specific DNA sequences, they arise as a need to detect difficult or slow growing microorganisms in cultures. The most widely used technique is the polymerase chain reaction (PCR) that allows the amplification of small segments of genetic material using primers, it is an economical, precise, sensitive and fast method for the detection of microorganisms. This bibliographic review article will serve to report on the advances in molecular techniques used for diagnosis in dental practice (AU)

Phytotherapy: A Solution to Decrease Antifungal Resistance in the Dental Field.

The pathologies produced by fungi in the oral cavity in recent decades have become a health problem, with factors such as an imbalance of the local microbiota being the cause for their propagation. Conventional antifungal treatments, instead of being beneficial, have generated alterations that have led to antifungal resistance. The aim of this study was to investigate and describe phytotherapy resources as a possible solution to oral antifungal resistance. A bibliographic search was carried out on platforms such as PubMed, Scopus, ScienceDirect, Web of Science, and Google scholar. A total of 248 scientific articles were obtained, of which 108 met the inclusion criteria. Microorganisms of fungal origin currently show resistance to the different antifungals of conventional use, which is undoubtedly altering the oral health of human beings, but there are new therapeutic possibilities such as the active principles of various natural species.

Prevalence of Caries According to the ICDAS II in Children from 6 and 12 Years of Age from Southern Ecuadorian Regions.

In Ecuador, national data on dental caries are scarce and the detection of incipient enamel lesions has been omitted. The objective of this study was to determine the prevalence of caries in school children aged 6 and 12 years of both sexes, belonging to urban and rural areas of three provinces of the country, using the International Caries Detection and Assessment System (ICDAS II). The sample consisted of 665 children from public schools, examined according to ICDASII. Caries prevalence and caries index were established using ICDAS II 2-6/C-G and ICDAS II 4-6/E-G criteria for comparison with WHO indicators. The Mann−Whitney U statistical test was used for comparison of two groups, the effect size was measured with the correlation coefficient. and the Kruskal−Wallis H test (p < 0.05) for multiple comparisons. Caries prevalence exceeded 87% for primary and permanent dentition. There were no significant differences according to province (p ≤ 0.05). The caries index at 6 years was 6.57 and at 12 years 9.21. The SIC was high at 12 years in rural areas. The prevalence of caries in the population studied was high despite the preventive measures established by health agencies.

Younger Age Impacts Perceptions of Care Received in the Emergency Department Among Women with Spontaneous Coronary Artery Dissection.

Background: Spontaneous coronary artery dissection (SCAD) is a nonatherosclerotic etiology of acute coronary syndrome (ACS) that primarily affects younger women with few traditional cardiovascular disease risk factors. The primary objective of this study was to evaluate how younger age impacts the perception of care women receive in the emergency department (ED) at the time of their first or only SCAD. Methods: SCAD survivors were recruited using SCAD Alliance social media platforms to complete a one-time online survey regarding their experiences of seeking treatment for SCAD in the ED and their post-SCAD recovery. A total of 409 participants consented to participate in the parent study and data collected from the 367 participants who reported female gender were further analyzed. Results: Fewer participants <50 years old than would be expected under the null hypothesis (i.e., 65.5% observed vs. 71.2% expected, p = 0.009) reported perceived serious treatment by ED staff, more participants <50 years than would be expected under the null hypothesis (i.e., 12.0% observed vs. 9.3% expected, p = 0.049) reported perceived dismissive treatment by ED staff, and more participants <50 years than would be expected under the null hypothesis (i.e., 13.3% observed vs. 10.8% expected, p = 0.02) reported discharge from the ED without a diagnosis. Conclusions: Results of this study highlight the different experiences of younger SCAD survivors' engaging with providers in the ED. Further research regarding strategies for increasing ED providers' clinical interrogation of SCAD when treating and evaluating younger female patients presenting with ACS symptoms is indicated.

Is the use of a potassium nitrate dentifrice effective in reducing tooth sensitivity related to in-office bleaching? A randomized triple-blind clinical trial.

OBJECTIVE: The aims of this study were to evaluate whether the use of a dentifrice containing 5% potassium nitrate (KNO3 ) prior to and during in-office dental bleaching reduces bleaching-induced tooth sensitivity and affects bleaching efficiency. MATERIALS AND METHODS: Thirty-eight individuals were randomly distributed into two groups (n = 19). The experimental group performed toothbrushing using a dentifrice containing 5% KNO3 , one week before treatment and before the first and second bleaching sessions. In the control group, a placebo dentifrice without KNO3 was applied as described for the first group. Tooth sensitivity was recorded on visual analog scales (VAS) and numeric rating scales (NRS) immediately and up to 48 h after bleaching sessions. Color change at different time intervals, was evaluated with shade guide units (∆SGU) and a digital spectrophotometer (∆E CIELab 1976 and CIEDE2000) at baseline and 7, 15, and 30 days post-bleaching. Mann-Whitney test and t-test were used to evaluate TS intensity for NRS and VAS scales, respectively, and T-test was used for color difference evaluation. RESULTS: No significant difference in tooth sensitivity's absolute risk and intensity were observed between tested groups in any evaluated treatment time for NRS (p = 0.91) or VAS scales (p = 0.48). T-test showed no significant difference in both ∆E and ∆SGU tooth color among the experimental and control groups during the different evaluation times (p = 0.27). CONCLUSION: The use of a dentifrice containing 5% KNO3 does not prevent post-operatory tooth sensitivity but allows the same whitening efficiency as a regular dentifrice. CLINICAL SIGNIFICANCE: The use of a dentifrice-containing KNO3 did not prevent bleaching-induced tooth sensitivity when high-concentrated hydrogen peroxide was used for in-office bleaching.

Estado nutricional y caries de infancia temprana en niños de 0 a 3 años: Revisión de la literatura

Objetivo: Recopilar información relacionando el estado nutricional y la caries de infancia temprana en edades desde los 0 a 3 años. Materiales y métodos: Se realizó la búsqueda de artículos científicos desde el mes de noviembre 2020 hasta el mes de enero del 2021 tanto en español como en inglés en base de datos como: Google Scholar, Scielo, Pubmed, Dialnet, Science Direct, con el uso de las palabras clave: caries dental, conducta alimentaria, lactancia materna, desmineralización, sacarosa. Incluyendo artículos originales, y de revisión bibliográfica. Excluyendo artículos que no pertenecían al tema de nutrición y caries. Resultados: La caries de infancia temprana comienza poco después de la erupción dental, se transmite con mayor frecuencia verticalmente (de la madre al niño), siendo el microorganismo más cariogénico el Streptococcus mutans. Se ha demostrado por varios estudios que la desnutrición no se relaciona con caries de primera infancia, pero si el consumo excesivo de azúcares, la lactancia materna y el biberón nocturno frecuente. Por esta razón, en los infantes entre 0 y 3 años de edad se debe utilizar pastas fluoradas (1000-1100 ppm de flúor) con el fin de eliminar placa bacteriana y la formación de caries dental. Conclusiones: Existe una relación estrecha entre la nutrición y caries dental en niños de 0-3 años, pero el factor más importante es la intervención de los padres en aplicar los cuidados orales en infantes; es importante el conocimiento de los contenidos de azúcares en alimentos, con el fin de evitar la aparición de la caries de infancia temprana.

Sensibilidad y especificidad de pruebas moleculares en odontología / Sensitivity and specificity of molecular tests in dentistry

La biología molecular tiene mayor afinidad en las áreas de la salud, en odontología su principal aplicación ha sido en la identificación de microorganismos orales patógenos mediante el uso de secuencias genéticas específicas (ácido desoxirribonucleico [DNA], ácido ribonucleico [RNA] y proteínas). Las pruebas a nivel molecular se caracterizan por su rapidez, reproductibilidad, sensibilidad y especificidad de los microorganismos diana. El presente artículo de revisión bibliográfica servirá como herramienta para comprender los principios de las técnicas más destacadas como son: PCR estándar y RT-PCR en tiempo real, PCR con transcriptasa inversa, microarreglos y ensayo por inmunoabsorción ligado a enzimas (ELISA), además de sus ventajas y desventajas respecto a las pruebas convencionales (AU)

Molecular biology has a greater affinity in the areas of health. In dentistry, its main application has been the identification of pathogenic oral microorganisms, through the use of specific genetic sequences (deoxyribonucleic acid [DNA], ribonucleic acid [RNA] and proteins). Molecular tests are characterized by their rapidity, reproducibility, sensitivity and specificity of target microorganisms. This literature review article will serve as a tool to understand the principles of the most prominent techniques such as: Standard PCR, Real-time RT-PCR, Reverse transcriptase PCR, microarrays and Enzyme-linked immunosorbent assay (ELISA), in addition to their advantages and disadvantages with respect to conventional tests (AU)

Índice CPOD y limitación para hablar con claridad en escolares de 12 años, Cuenca-Ecuador / DMFT index and limitation in speaking clearly in 12-year-old schoolchildren, Cuenca, Ecuador

Objetivo: Determinar la relación entre CPO-D y la limitación autopercibida para hablar claro en escolares de 12 años de la parroquia El Batán (Cuenca, Ecuador). Materiales y métodos: Fue un estudio observacional, con un nivel relacional retrospectivo, que estuvo conformado por 154 fichas, que corresponde a 104 niñas y 50 niños. Se analizó las variables CPO-D y la limitación para hablar claro mediante estadística descriptiva, y la correlación se halló mediante la prueba estadística de Tau-b de Kendall. Resultados: El índice CPO-D, en general, fue muy bajo, con el 32,5%, seguido por el medio, con el 29,5%. El impacto de la limitación para hablar claro afectó al 35,6% para el sexo femenino y el 46,0% para el masculino. La relación fue significativa (p = 0,000) entre el CPO-D y la limitación para hablar claro, y su asociación fue baja y positiva (0,301). De acuerdo con el sexo, también mostró significancia y su asociación fue media para los niños (0,413) y baja para las niñas (0,261). Conclusión: Cerca de la tercera parte de los escolares mostró un índice bajo y medio de CPO-D. En cuanto a la limitación para hablar claro, menos de la tercera parte exhibió mucha limitación. Se encontró una correlación: entre mayor índice de caries dental mayor será la limitación autopercibida para hablar claro, aunque esta asociación fue baja, y afectó más a los niños que a las niñas de esta área urbana. (AU)

Objective: To determine the relationship between the decayed/missing/filled teeth (DMFT) index and self-perceived limitation in speaking clearly in 12-year-old schoolchildren from the ̈El Batán ̈ parish in Cuenca-Ecuador. Materials and methods: This was an observational study, with a retrospective relational level, consisting of 154 reports, corresponding to 104 girls and 50 boys. The DMFT variables and limitation to speak clearly were analyzed by descriptive statistics and correlation was determined by means of the Kendall's Tau-b statistical test. Results: The DMFT index was very low with 32.5%, followed by a medium of 29.5%; while the impact of the limitation to speak clearly affected 35.6% of the females and 46.0% of the males. The relationship between the DMFT index and the limitation to speak clearly was significant (p = 0.000), with a low positive association (0.301). It was also significant according to gender and with a medium association for boys (0.413) and low association for girls (0.261). Conclusion: About one third of schoolchildren showed a low and medium DMFT index. Less than one third of the children studied reported some limitation to speak clearly. There was a correlation between a higher index of dental cavities and a greater self-perceived limitation to speak clearly, although this association was low, affecting boys more frequently than girls in this urban area. (AU)

Alternative splicing controls teneurin-latrophilin interaction and synapse specificity by a shape-shifting mechanism.

The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs/ADGRLs) promotes excitatory synapse formation when LPHNs simultaneously interact with FLRTs. Insertion of a short alternatively-spliced region within TENs abolishes the TEN-LPHN interaction and switches TEN function to specify inhibitory synapses. How alternative-splicing regulates TEN-LPHN interaction remains unclear. Here, we report the 2.9 Å resolution cryo-EM structure of the TEN2-LPHN3 complex, and describe the trimeric TEN2-LPHN3-FLRT3 complex. The structure reveals that the N-terminal lectin domain of LPHN3 binds to the TEN2 barrel at a site far away from the alternatively spliced region. Alternative-splicing regulates the TEN2-LPHN3 interaction by hindering access to the LPHN-binding surface rather than altering it. Strikingly, mutagenesis of the LPHN-binding surface of TEN2 abolishes the LPHN3 interaction and impairs excitatory but not inhibitory synapse formation. These results suggest that a multi-level coincident binding mechanism mediated by a cryptic adhesion complex between TENs and LPHNs regulates synapse specificity.

Structural basis for adhesion G protein-coupled receptor Gpr126 function.

Many drugs target the extracellular regions (ECRs) of cell-surface receptors. The large and alternatively-spliced ECRs of adhesion G protein-coupled receptors (aGPCRs) have key functions in diverse biological processes including neurodevelopment, embryogenesis, and tumorigenesis. However, their structures and mechanisms of action remain unclear, hampering drug development. The aGPCR Gpr126/Adgrg6 regulates Schwann cell myelination, ear canal formation, and heart development; and GPR126 mutations cause myelination defects in human. Here, we determine the structure of the complete zebrafish Gpr126 ECR and reveal five domains including a previously unknown domain. Strikingly, the Gpr126 ECR adopts a closed conformation that is stabilized by an alternatively spliced linker and a conserved calcium-binding site. Alternative splicing regulates ECR conformation and receptor signaling, while mutagenesis of the calcium-binding site abolishes Gpr126 function in vivo. These results demonstrate that Gpr126 ECR utilizes a multi-faceted dynamic approach to regulate receptor function and provide relevant insights for ECR-targeted drug design.

The expanding functional roles and signaling mechanisms of adhesion G protein-coupled receptors.

The adhesion class of G protein-coupled receptors (GPCRs) is the second largest family of GPCRs (33 members in humans). Adhesion GPCRs (aGPCRs) are defined by a large extracellular N-terminal region that is linked to a C-terminal seven transmembrane (7TM) domain via a GPCR-autoproteolysis inducing (GAIN) domain containing a GPCR proteolytic site (GPS). Most aGPCRs undergo autoproteolysis at the GPS motif, but the cleaved fragments stay closely associated, with the N-terminal fragment (NTF) bound to the 7TM of the C-terminal fragment (CTF). The NTFs of most aGPCRs contain domains known to be involved in cell-cell adhesion, while the CTFs are involved in classical G protein signaling, as well as other intracellular signaling. In this workshop report, we review the most recent findings on the biology, signaling mechanisms, and physiological functions of aGPCRs.