The dark sides of the GPCR tree - research progress on understudied GPCRs

A large portion of the human GPCRome is still in the dark and understudied, consisting even of entire subfamilies of GPCRs such as odorant receptors, class A and C orphans, adhesion GPCRs, Frizzleds and taste receptors. However, it is undeniable that these GPCRs bring an untapped therapeutic potential that should be explored further. Open questions on these GPCRs span diverse topics such as deorphanisation, the development of tool compounds and tools for studying these GPCRs, as well as understanding basic signalling mechanisms. This review gives an overview of the current state of knowledge for each of the diverse subfamilies of understudied receptors regarding their physiological relevance, molecular mechanisms, endogenous ligands and pharmacological tools. Furthermore, it identifies some of the largest knowledge gaps that should be addressed in the foreseeable future and lists some general strategies that might be helpful in this process.

Structure-Based Discovery of Mouse Trace Amine-Associated Receptor 5 Antagonists

Trace amine-associated receptors (TAARs) were discovered in 2001 as new members of class A G protein-coupled receptors (GPCRs). With the only exception of TAAR1, TAAR members (TAAR2-9, also known as noncanonical olfactory receptors) were originally described exclusively in the olfactory epithelium and believed to mediate the innate perception of volatile amines. However, most noncanonical olfactory receptors are still orphan receptors. Given its recently discovered nonolfactory expression and therapeutic potential, TAAR5 has been the focus of deorphanization campaigns that led to the discovery of a few druglike antagonists. Here, we report four novel TAAR5 antagonists identified through high-throughput screening, which, along with the four ligands published in the literature, constituted our starting point to design a computational strategy for the identification of TAAR5 ligands. We developed a structure-based virtual screening protocol that allowed us to identify three new TAAR5 antagonists with a hit rate of 10%. Despite lacking an experimental structure, we accurately modeled the TAAR5 binding site by integrating comparative sequence- and structure-based analyses of serotonin receptors with homology modeling and side-chain optimization. In summary, we have identified seven new TAAR5 antagonists that could serve as lead candidates for the development of new treatments for depression, anxiety, and neurodegenerative diseases.

Modeling the Orthosteric Binding Site of the G Protein-Coupled Odorant Receptor OR5K1

With approximately 400 encoding genes in humans, odorant receptors (ORs) are the largest subfamily of class A G protein-coupled receptors (GPCRs). Despite its high relevance and representation, the odorant-GPCRome is structurally poorly characterized: no experimental structures are available, and the low sequence identity of ORs to experimentally solved GPCRs is a significant challenge for their modeling. Moreover, the receptive range of most ORs is unknown. The odorant receptor OR5K1 was recently and comprehensively characterized in terms of cognate agonists. Here, we report two additional agonists and functional data of the most potent compound on two mutants, L104^3.32 and L255^6.51. Experimental data was used to guide the investigation of the binding modes of OR5K1 ligands into the orthosteric binding site using structural information from AI-driven modeling, as recently released in the AlphaFold Protein Structure Database, and from homology modeling. Induced-fit docking simulations were used to sample the binding site conformational space for ensemble docking. Mutagenesis data guided side chain residue sampling and model selection. We obtained models that could better rationalize the different activity of active (agonist) versus inactive molecules with respect to starting models and also capture differences in activity related to minor structural differences. Therefore, we provide a model refinement protocol that can be applied to model the orthosteric binding site of ORs as well as that of GPCRs with low sequence identity to available templates.

P-036 Analysis of semen cryopreservation in a cohort of cancer patients

Study question

To investigate the possible correlation between different types of cancer and sperm quality in patients preserving their fertility and evaluate the reproductive outcomes of patients

Summary answer

Testicular cancer was associated with lower sperm volumes (p = 0.041), lower total sperm concentration (p = 0.009) and oligozoospermia (p < 0.001) compared to other cancers.

What is known already

The advancement in cancer treatments over the years frequently allowed a remission in most young patients. In males, spermatogonia are sensitive to chemotherapy and radiotherapy, causing an impairment of sperm production and competence. Moreover, up to two-thirds of patients with cancer have impaired semen parameters before any treatment but findings on whether and how specific types of malignancies can alter them remains heterogeneous. Today the advancement of Assisted Reproductive Technologies (ART) made male fertility preservation widely available, therefore counselling and sperm banking should be offered to all men in reproductive age with a diagnosis of cancer before any treatment.

Study design, size, duration

This was an observational cohort study conducted on cancer patients that underwent fertility preservation at the Center of reproductive Medicine and Surgery “P. Bertocchi” at the Department of Obstetrics and Gynecology in AUSL-IRCCS of Reggio Emilia, Italy between 2007 and 2018. The participation to the study was retrospectively proposed to all patients submitted to fertility preservation counselling from January 1st 2007 to March 28th 2018, and prospectively from March 29th 2018 to December 31st 2018.

Participants/materials, setting, methods

Semen parameters regarding volume, concentration, motility, and morphology were assessed according to the WHO criteria of 2010 in semen samples collected before any cancer treatment. Based on the macroscopic and microscopic evaluation of each sample, all those with at least cryptozoospermia were frozen. We also evaluated the reproductive outcomes of patients seeking a pregnancy with sperm frozen before cancer treatments. Semen parameters and pregnancy outcomes were compared between testicular versus other cancers.

Main results and the role of chance

During the study period, 329 patients were included with a mean age at enrollment of 32.7 ± 8.6 years. A successful cryopreservation was achieved in 94.5% of cases; the cryopreservation failed in 5.5% of cases, due to azoospermia or missed delivery samples. More than half of the cryopreservations were performed in patients affected by testicular cancer (53.3%), followed by those affected by Hodgkin (19.3%) and non-Hodgkin Lymphoma (13.5%), reflecting the increased incidence of these cancer histotypes in the age group of 20-40 years. Testicular cancer was associated with lower sperm volumes (p = 0.041) and lower total sperm concentration (p = 0.009) compared to other cancers. No difference was observed about sperm motility and morphology, while oligozoospermia was significantly more frequent in men with testicular cancer (p < 0.001). In the cohort, the 8.4% of patients thawed their samples; the usage rate and the embryo transfer rate were significantly higher (p = 0.04) among those with a testicular cancer, while pregnancy and livebirth rates did not differ between the two groups.

Limitations, reasons for caution

Relevant limitations of the study included: the absence of a follow-up on fertility status after cancer remission, missing data about spontaneous pregnancies, and information on the seminal status of each patient before cancer diagnosis, precluding any etiopathological consideration between neoplastic pathology and seminal parameters.

Wider implications of the findings

Male fertility preservation is feasible, easy to be performed, non-invasive and does not delay cancer treatments. Men affected by testicular cancer had worse semen parameters at cryopreservation, but pregnancy and livebirth rates were similar to those achieved by men with other cancers and similar to those achieved with fresh sperm.

Trial registration number

not applicable

P-585 The (decision) tree of fertility: an innovative decision-making algorithm in assisted reproduction technique

Study question

To develop a decisional algorithm able to predict pregnancy and live birth rates after controlled ovarian stimulation (COS), helping to decide whether to perform oocytes pick-up.

Summary answer

A systematic approach allows to identify ovarian follicles, female age and sperm motility as predictors of ART outcome, reducing the socio-economic burden of ART failure

What is known already

The physician needs to estimate a priori the female response after the COS phase, leaving an extreme variability in the proposed therapeutic regimens. Indeed, the most cost-effective ART management in terms of pregnancy and live birth rates is still far to be achieve and the clinical application of predictive models is still scanty, considering their limited predictive ability. A predictive model able to estimate the chances of success in the time point after ovarian stimulation and before the pick-up could guide the decision to prosecute or not the ongoing ART path

Study design, size, duration

A single centre, retrospective analysis of data was carried out, considering all couples attending the Fertility Centre of the Department of Obstetrics and Gynaecology of Reggio Emilia (Italy). All consecutive ART cycles performed from 1998 to December 2020 were retrospectively extracted and couples fulfilling inclusion criteria were included in the final dataset with final included 12,275 ART cycles. The strong ART outcomes were considered, i.e. biochemical and clinical pregnancy and live birth rates.

Participants/materials, setting, methods

Couple with both partners older than 18 years and attending fresh ART cycles are available are included in the study. The ART procedure was evaluated collecting several variables, considering male parameters, COS approach and variables of COS response. The fertilization rate was calculated as the ratio between the number of fertilized oocytes and the number of either injected (ICSI method) or inseminated (IVF cycles) oocytes.

Main results and the role of chance

The final database included 12,275 ART cycles, consisting of 7,826 ICSI (63.8%) and 4,449 IVF (36.2%) procedures. The 87.5% of the entire cohort (10,375 couples) were treated for primary couple infertility. Linear regression analyses highlighted a relationship between number of ovarian follicles >17 mm detected at ultrasound before pick-up (OF17), embryos number and fertilization rate, and biochemical and clinical pregnancy rates (p < 0.001), but not live birth rate. Decisional Tree (DT) were created for biochemical pregnancy (statistical power–SP:80.8%), clinical pregnancy (SP:85.4%) and live birth (SP:87.2%). Thresholds for OF17 entered in all DT, while sperm motility entered the biochemical pregnancy’s model, and female age entered the clinical pregnancy and live birth DT. In case of OF17<3, the chance of conceiving was <6% for all DT. Logistic regression analyses confirmed the relationship between strong ART outcomes and those variables detected before pick-up. Interestingly, these connections appeared only when pregnancy rates were considered, suggesting that the classical statistical approach is not able to overcome the higher number of biases influencing live birth rates. In the biochemical pregnancy decision tree, alongside to OF17, sperm motility entered the model introducing the threshold of 34%.

Limitations, reasons for caution

In the study were included only those cycles in which all ART variables were available. During the long interval of data collection, ART technologies evolved, as well as the regulatory rules for ART access. This data heterogeneity over the years could mitigate the reliability of results.

Wider implications of the findings

The identification of three decision trees helping the clinician to decide whether or not to perform oocytes pick-up, continuing the ongoing ART path. In mathematical models, three predictors of ART success at a very early stage emerged, such as ovarian follicles higher than 17 mm, sperm motility and female age.

Trial registration number

not applicable

Classification Model for the Second Extracellular Loop of Class A GPCRs

The extracellular loop 2 (ECL2) is the longest and the most diverse loop among class A G protein-coupled receptors (GPCRs). It connects the transmembrane (TM) helices 4 and 5 and contains a highly conserved cysteine through which it is bridged with TM3. In this paper, experimental ECL2 structures were analyzed based on their sequences, shapes, and intramolecular contacts. To take into account the flexibility, we incorporated into our analyses information from the molecular dynamics trajectories available on the GPCRmd website. Despite the high sequence variability, shapes of the analyzed structures, defined by the backbone volume overlaps, can be clustered into seven main groups. Conformational differences within the clusters can be then identified by intramolecular interactions with other GPCR structural domains. Overall, our work provides a reorganization of the structural information of the ECL2 of class A GPCR subfamilies, highlighting differences and similarities on sequence and conformation levels.

O-226 The microscopic se men improvement after surgical varicocele repair

Study question

Evaluation of the effect of varicocele correction on conventional and microscopic seminal parameters and evaluation of which factors might predict sperm improvement after surgical treatment.

Summary answer

The detailed morphologic sperm evaluation has been identified as a novel parameter expressing the post-surgical semen amelioration after varicocelectomy.

What is known already

Generally, varicocele develops during puberty and occurs more often on the left side for anatomic reasons. However, its diagnosis is commonly delayed, especially in asymptomatic cases, until the man consults an andrologist for couple infertility. A causative relationship between varicocele and impairment of semen quality has been largely investigated in the context of male infertility. Despite the florid literature available on this topic, the clinical benefit in terms of semen quality improvement after varicocele surgical repair remains controversial.

Study design, size, duration

An observational, retrospective clinical trial was carried out including patients undergoing surgical treatment for varicocele at the Day Surgery of the Urology Operative Unit of the Santa Maria Nuova Hospital-IRCCS of Reggio Emilia from September 2011 to March 2020. Primary outcome was the detailed morphologic microscopic sperm evaluation. Secondary outcomes were conventional semen analyses. Each patient was considered two times (before and after the surgery) and evaluated by both physical examination and ultrasonography.

Participants/materials, setting, methods

The inclusion criteria considered the patients with diagnosis of varicocele at ultrasound examination, attending surgical resolution and with at semen analyses before and after the surgery, were excluded patients with diagnosis of varicocele without surgical indication, and/or semen analyses performed only before or only after the surgery. In the statistical analysis a logistic multivariate regression analysis was performed in order to evaluate the change before and after surgery.

Main results and the role of chance

The post-surgical semen analysis was performed after a mean of 183.7 + 112.5 days since the surgery for a total of 121 males (mean age 24.6 + 4.1 years) enrolled. The surgical treatment leads to a significant increase in sperm concentration (p = 0.015) and percentage of progressive and total motility (p = 0.022 and p = 0.039, respectively), with a significant decrease in the percentage of immobile sperms (p = 0.013). In particular, semen concentration improved in 71.7% of patients (p = 0.010). Considering the detailed morphologic microscopic evaluation, a significant improvement was detected: head abnormalities showed a significant reduction, considering microcephaly (3.3 + 3.6 versus 2.2 + 2.9%, p = 0.015), macrocephaly (1.4 + 0.6 versus 1.2 + 0.9%, p = 0.043) and cytoplasmic appendix (1.4 + 0.8 versus 0.9 + 1.2%, p = 0.041). Moreover, surgery led to a significant reduction of tails abnormalities, considering absence (0.6 +2.3 versus 0.1 + 0.7, p = 0.048) and coiled tail (5.2 + 1.5 versus 6.6 + 2.0, p = 0.037). Thus, surgical varicocele resolution leads to a significant improvement in specific morphological semen parameters. The multivariate logistic analysis identified the ultrasound varicocele degree before surgery as a main predictor of the sperm concentration improvement (p = 0.016). The semen parameters improvement was higher for varicocele of I and II degree (p = 0.008).

Limitations, reasons for caution

The retrospective study design precluded from carrying out a case-control study to compare the surgical techniques. Moreover, the study design limited the availability of patients’ clinical data in order to performed a more comprehensive predictive analysis.

Wider implications of the findings

Using a complex statistical approach, it emerged that the greatest improvement in semen quality was obtained in case of mild varicocele, increasing the knowledge on the therapeutic potential of surgery. This result has clinical implications, since it could help to select those patients ‘to treat or not to treat’.

Trial registration number

none

Protein-protein interactions at a glance: Protocols for the visualization of biomolecular interactions

Protein-protein interactions (PPIs) play a key role in many biological processes and are intriguing targets for drug discovery campaigns. Advancements in experimental and computational techniques are leading to a growth of data accessibility, and, with it, an increased need for the analysis of PPIs. In this respect, visualization tools are essential instruments to represent and analyze biomolecular interactions. In this chapter, we reviewed some of the available tools, highlighting their features, and describing their functions with practical information on their usage.

In Silico Molecular Study of Tryptophan Bitterness

Tryptophan is an essential amino acid, required for the production of serotonin. It is the most bitter amino acid and its bitterness was found to be mediated by the bitter taste receptor TAS2R4. Di-tryptophan has a different selectivity profile and was found to activate three bitter taste receptors, whereas tri-tryptophan activated five TAS2Rs. In this work, the selectivity/promiscuity profiles of the mono-to-tri-tryptophans were explored using molecular modeling simulations to provide new insights into the molecular recognition of the bitter tryptophan. Tryptophan epitopes were found in all five peptide-sensitive TAS2Rs and the best tryptophan epitope was identified and characterized at the core of the orthosteric binding site of TAS2R4.

First Report of Cercospora apii Leaf Spot on Capsicum chinense in Brazil

In Brazil, Capsicum chinense Jacq. is the predominant species of commercial hot peppers because of its popular citrus-like aroma and adaptability to different soils and climates (4). In June 2010, 30 samples of C. chinense with severe leaf spot were collected from a field in the city of Viçosa, state of Minas Gerais, Brazil. Symptoms were observed on leaves, calyxes, fruits, and stems on most of the plants found in the area. On leaves, symptoms included amphigenous lesions that were initially circular to ellipsoid, 1 to 5 mm in diameter, whitish to tan in the center, and surrounded by a dark brown or reddish purple border. Lesions coalesce and turned necrotic with age. A fungus isolated from the lesions matched well with the description of Cercospora apii Fresen. It formed erumpent stromata that were dark brown and spherical to irregular; fascicule conidiophores were clear brown or pale, straight or curved, unbranched, geniculate, 22.5 to 80 × 5 to 7.5 μm, 0 to 3 septate, subtruncate apex; and conidia were solitary, hyaline to subhyaline, filiform, base truncate, tip acute, straight to curved, 12.5 to 140 × 3.5 to 5 μm, and 0 to 11 septate (1,2). A sample was deposited in the herbarium of the Universidade Federal de Viçosa, Minas Gerais, Brazil (VIC 31415). Identity was confirmed by amplifying part of the calmodulin gene with species-specific primers CercoCal-apii and CercoCal-R (3) of fungal DNA from a single-spore culture. In amplification reaction, initial denaturation step was done at 94°C for 5 min, followed by 40 cycles of denaturation at 94°C (30 s), annealing at 56°C (30 s), and elongation at 72°C (30 s). Primers CercoCal-apii and CercoCal-R amplified a single DNA product of 176 bp, and coupled with the morphological characteristics, confirmed the identity of the fungus as Cercospora apii. To check pathogenicity, a 6-mm-diameter plug of the isolate was removed from the expanding edge of a 21-day-old culture grown on potato dextrose agar (PDA) and placed in contact with the adaxial face of the leaves of 8-week-old C. chinense grown in 2-liter plastic pots with soil substrate. Six plants, one per pot, were inoculated with the isolate and six plants were inoculated with the fungus-free PDA plug. Inoculated plants were maintained in a moist chamber for 24 h and then subsequently kept in a greenhouse at 26°C. Leaf spot was observed in all inoculated plants 15 days after inoculation and symptoms were similar to those expressed in the field. The fungus was reisolated from the inoculated plants and matched well with the description of Cercospora apii. All fungus-free PDA inoculated plants remained healthy. Cercospora apii comprises a complex of 281 morphologically indistinguishable species that can infect an extremely wide host range (2). To our knowledge, this pathogen has the potential to cause significant damage to the hot pepper industry of Brazil. References: (1) C. Chupp. A Monograph of the Fungus Cercospora. Cornell University Press, Ithaca, NY, 1954. (2) P. W. Crous and U. Braun. CBS Biodivers. Ser. 1:1, 2003. (3) M. Groenewald et al. Phytopathology 95:951, 2005. (4) S. D. Lannes et al. Sci. Hortic. 112:266, 2007.

MATER protein as substrate of PKCepsilon in human cumulus cells

High activity of the phosphoinositide 3-kinase/Akt pathway in cumulus cells plays an important role in FSH regulation of cell function and Protein Kinase C epsilon (PKCepsilon) collaborates with these signalling pathways to regulate cell proliferation. Relevant roles in follicular development are played by Maternal Antigen That Embryos Require (MATER) that is a cumulus cell- and oocyte-specific protein dependent on the maternal genome. We recently demonstrated that human MATER localizes at specific domains of oocytes and, for the first time, also in cumulus cells. MATER contains a carboxy-terminal leucine-rich repeat domain involved in protein-protein interactions regulating different cellular functions. Here we investigated the functional role of MATER. Thus, we performed coimmunoprecipitation experiments using HEK293T cells expressing human MATER; a similar approach was then followed in human cumulus/follicular cells. In MATER(+)HEK293T cells, we observed that this protein acts as a phosphorylation substrate of PKCepsilon. Western blot experiments indicate that, unlike oocytes, human cumulus cells express PKCepsilon. Immunoprecipitation and confocal analysis suggest for the first time that MATER protein interacts with this protein kinase in cumulus cells under physiological conditions. Since PKCepsilon is known to collaborate with antiapoptotic signalling pathways, this suggests a novel mechanism for the function of MATER in follicular maturation.

Barriers to effective tuberculosis control: a qualitative study

SETTING

Emilia Romagna region, Italy.

OBJECTIVE

To explore chest and infectious disease physicians' views of barriers to effective tuberculosis (TB) control and possible solutions.

DESIGN

A series of nine focus groups including a total of 49 physicians.

RESULTS

Three categories of barriers to effective TB control were identified: 1) uncertainty about appropriate clinical practice in the treatment of specific sub-groups of patients, such as the elderly or immigrants; 2) organisational factors, such as the availability of diagnostic services and of sufficient resources; and 3) multiple barriers to a viable and effective TB control programme in a country with a low prevalence of TB.

CONCLUSIONS

The lack of integration and coordination of health services, as well as the scarcity of dedicated TB nurses, were perceived by the participants as crucial barriers to effective TB control. As a result of this study, a regional programme was started with the goals of quantifying the need for TB nurses and developing a better network for required health services. Qualitative studies such as this can be useful in improving TB control in a low-prevalence TB country, to identify problems and increase the participation of key professionals.

Lower embryonic loss rates among twin gestations following assisted reproduction

PURPOSE

To determine whether maternal age and number of transferred embryos influence early pregnancy losses in twin pregnancies compared to singletons following IVF/ICSI.

METHODS

We compared the pregnancy loss rates in singleton (n = 549) and twin (n = 252) gestations, stratified by maternal age (< or = 35 and > 35 years) and the number of transferred embryos (1-3 and 4-9).

RESULTS

Loss rates of singleton pregnancies were significantly higher than that in twins (OR 3.0, 95% CI 1.9, 4.9), especially among singletons conceived after transfer of 4-9 embryos (OR 5.0, 95% CI 2.2, 11.9). Younger mothers of twins had lower loss rates (OR 0.3, 95% CI 0.1, 0.9).

CONCLUSION

Twins have a significantly reduced spontaneous miscarriage rate compared with singletons following IVF/ICSI. Higher implantation rates per cycle (i.e., development of twins rather than one live embryo) may represent a better capacity of the uterus for early embryonic development.

Epitope analysis of immunoglobulins against gp20, a GPI-anchored protein of the human sperm surface homologous to leukocyte antigen CD52

Gp20 is a sialylglycoprotein of the human sperm surface related to maturation and capacitation and is homologous to CD52, a glycosyl- phosphatidyl-inositol (GPI)-anchored protein highly expressed in lymphocytes, monocytes, eosinophils, and epididymal cells, described by the monoclonal antibody family CAMPATH. The CAMPATH antigen is characterized by a very short peptide (12 amino acids) and an N-linked oligosaccharide chain bound to the asparagine located in the third position and a GPI anchor bound to the C-terminal serine. The CAMPATH epitope includes three amino acids at the C-terminus and part of the GPI anchor. It has been suggested that anti-gp20 interacts with the same peptide recognized by CAMPATH antibodies but with a different epitope, since it describes the corresponding antigen in a different way. For example, it localizes the corresponding antigen in the equatorial region of the sperm head when sperm are capacitated, whereas CAMPATH antibodies bind all over the sperm surface. Our results indicate that the anti-gp20 epitope does not include the peptide backbone, the GPI anchor, or the N-glycans but consists of O-linked oligosaccharide chains bound to a unique CD52 glycoform present both in sperm and leukocytes. This is suggested by results obtained using many different approaches, such as immunoblot analysis of gp20 after removal of N- and O-glycans and after jacalin (Artocarpus integrifolia agglutinin)-affinity chromatography.

[Infection by BK virus, a human papovavirus, in immunosuppressed children and in children with normal immunological defenses (author's transl)]

Human infection by BK virus (BKV), a human papovavirus isolated from the urine of a transplanted patient, occurs early in life and is very widespread. The clinical features of the primary infection are unknown. After the primary infection, BKV remains latent in the host tissues. Immunosuppression of the host induces the activation of the latent virus; BKV has been isolated only from immunosuppressed patients so far. In our study the incidence of BKV infection in immunosuppressed children and in children with normal immunological defenses was investigated both by antibody and virus research, the cultural research of the virus being performed in the urine and other specimens, such as nasal-pharyngeal swabs and cerebrospinal fluids. Our results show that the incidence of the primary infection in immunosuppressed children is comparable to the incidence in children with normal immunological defenses. Two antigenically identical viruses, which showed only partial correlation with BKV, were isolated from the urine of two immunosuppressed children. These two viruses were considered as a same antigenic variant of the BKV prototype. Of all the subjects examined, only 9 immunosuppressed children had antibodies to the newly isolated viruses.