Cannabidiol skews biased agonism at cannabinoid CB1 and CB2 receptors with smaller effect in CB1-CB2 heteroreceptor complexes

Currently, biased agonism is at the center stage of drug development approaches. We analyzed effects of a battery of cannabinoids plus/minus cannabidiol (CBD) in four functional parameters (cAMP levels, phosphorylation of extracellular signal–regulated kinases (ERK1/2), β-arrestin recruitment and label-free/DMR) in HEK-293T cells expressing cannabinoid receptors, CB or CB, or CB-CB heteroreceptor complexes. In all cases two natural agonists plus two selective synthetic agonists were used. Furthermore, the effect of cannabidiol, at a dose (100 nM) that does not allow significant binding to the orthosteric center of either receptor, was measured. From the huge amount of generated data, we would like to highlight that the two psychotropic molecules (Δ-tetrahydrocannabinol/THC and CP-55940) showed similar bias in CBR and that the bias of THC was particularly relevant toward MAPK pathway. Furthermore, THC did not activate the G protein coupled to CBR. Interestingly, the biased agonism was reduced when assays were performed in cells expressing the two receptors, thus suggesting that the heteromer allows less functional selectivity. In terms of cannabidiol action, the phytocannabinoid altered the functional responses, likely by allosteric means, and modified potency, agonist IC/EC values and biased agonism in qualitative and/or quantitative different ways depending on the agonist. The effect of cannabidiol on anandamide actions on both cannabinoid receptors was particularly noteworthy as was significantly different from that of other compounds. Results are a compendium of data on biased agonism on cannabinoid receptors in the absence and presence of cannabidiol. In addition, for the first time, GPCR biased agonism is characterized in an heteromeric context.This work was partially supported by grants from the Spanish Ministry of Economy and Competitiveness (Ref. no. BFU2015-64405-R and SAF2017-84117-R; they may include FEDER funds) and by grant 201413-30 from: Fundació la Marató de TV3Peer Reviewe

Expression of P. falciparum var Genes Involves Exchange of the Histone Variant H2A.Z at the Promoter

Plasmodium falciparum employs antigenic variation to evade the human immune response by switching the expression of different variant surface antigens encoded by the var gene family. Epigenetic mechanisms including histone modifications and sub-nuclear compartmentalization contribute to transcriptional regulation in the malaria parasite, in particular to control antigenic variation. Another mechanism of epigenetic control is the exchange of canonical histones with alternative variants to generate functionally specialized chromatin domains. Here we demonstrate that the alternative histone PfH2A.Z is associated with the epigenetic regulation of var genes. In many eukaryotic organisms the histone variant H2A.Z mediates an open chromatin structure at promoters and facilitates diverse levels of regulation, including transcriptional activation. Throughout the asexual, intraerythrocytic lifecycle of P. falciparum we found that the P. falciparum ortholog of H2A.Z (PfH2A.Z) colocalizes with histone modifications that are characteristic of transcriptionally-permissive euchromatin, but not with markers of heterochromatin. Consistent with this finding, antibodies to PfH2A.Z co-precipitate the permissive modification H3K4me3. By chromatin-immunoprecipitation we show that PfH2A.Z is enriched in nucleosomes around the transcription start site (TSS) in both transcriptionally active and silent stage-specific genes. In var genes, however, PfH2A.Z is enriched at the TSS only during active transcription in ring stage parasites. Thus, in contrast to other genes, temporal var gene regulation involves histone variant exchange at promoter nucleosomes. Sir2 histone deacetylases are important for var gene silencing and their yeast ortholog antagonises H2A.Z function in subtelomeric yeast genes. In immature P. falciparum parasites lacking Sir2A or Sir2B high var transcription levels correlate with enrichment of PfH2A.Z at the TSS. As Sir2A knock out parasites mature the var genes are silenced, but PfH2A.Z remains enriched at the TSS of var genes; in contrast, PfH2A.Z is lost from the TSS of de-repressed var genes in mature Sir2B knock out parasites. This result indicates that PfH2A.Z occupancy at the active var promoter is antagonized by PfSir2A during the intraerythrocytic life cycle. We conclude that PfH2A.Z contributes to the nucleosome architecture at promoters and is regulated dynamically in active var genes

The Variant rs1867277 in FOXE1 Gene Confers Thyroid Cancer Susceptibility through the Recruitment of USF1/USF2 Transcription Factors

In order to identify genetic factors related to thyroid cancer susceptibility, we adopted a candidate gene approach. We studied tag- and putative functional SNPs in genes involved in thyroid cell differentiation and proliferation, and in genes found to be differentially expressed in thyroid carcinoma. A total of 768 SNPs in 97 genes were genotyped in a Spanish series of 615 cases and 525 controls, the former comprising the largest collection of patients with this pathology from a single population studied to date. SNPs in an LD block spanning the entire FOXE1 gene showed the strongest evidence of association with papillary thyroid carcinoma susceptibility. This association was validated in a second stage of the study that included an independent Italian series of 482 patients and 532 controls. The strongest association results were observed for rs1867277 (OR[per-allele] = 1.49; 95%CI = 1.30–1.70; P = 5.9×10−9). Functional assays of rs1867277 (NM_004473.3:c.−283G>A) within the FOXE1 5′ UTR suggested that this variant affects FOXE1 transcription. DNA-binding assays demonstrated that, exclusively, the sequence containing the A allele recruited the USF1/USF2 transcription factors, while both alleles formed a complex in which DREAM/CREB/αCREM participated. Transfection studies showed an allele-dependent transcriptional regulation of FOXE1. We propose a FOXE1 regulation model dependent on the rs1867277 genotype, indicating that this SNP is a causal variant in thyroid cancer susceptibility. Our results constitute the first functional explanation for an association identified by a GWAS and thereby elucidate a mechanism of thyroid cancer susceptibility. They also attest to the efficacy of candidate gene approaches in the GWAS era