Activity

Bioactivation of the antidepressant and smoking cessation drug bupropion is catalyzed predominantly by cytochrome P4502B6 (CYP2B6). The metabolite hydroxybupropion derived from t-butylhydroxylation is considered to contribute to the antidepressant and smoking-cessation effects of the parent drug. Bupropion hydroxylation is the canonical in vitro and in vivo probe for CYP2B6 activity. P450 also requires obligate partnership with P450 oxidoreductase (POR). Human CYP2B6 and POR genes are highly polymorphic. Some CYP2B6 variants affect bupropion disposition. This investigation evaluated the influence of several human CYP2B6 and POR genetic variants on stereoselective bupropion metabolism, using an insect cell coexpression system containing CYP2B6, POR and cytochrome b5. Based on intrinsic clearances, relative activities for S,S-hydroxybupropion formation were in the order CYP2B6.4>CYP2B6.1>CYP2B6.17>CYP2B6.5>CYP2B6.6≈CYP2B6.26≈CYP2B6.19>CYP2B6.7> CYP2B6.9>>CYP2B6.16 and CYP2B6.18; relative activities for R,R-hydr metabolism, suggesting no clinical consequence of this polymorphism. These CYP2B6 polymorphisms may portend diminished in vivo bupropion hydroxylation and predict additional clinically important variant alleles. The American Society for Pharmacology and Experimental Therapeutics.The regulation of transposable element (TE) activity by small RNAs is a ubiquitous feature of germlines. However, despite the obvious benefits to the host in terms of ensuring the production of viable gametes and maintaining the integrity of the genomes they carry, it remains controversial whether TE regulation evolves adaptively. We examined the emergence and evolutionary dynamics of repressor alleles after P-elements invaded the Drosophila melanogaster genome in the mid 20th century. In many animals including Drosophila, repressor alleles are produced by transpositional insertions into piRNA clusters, genomic regions encoding the Piwi-interacting RNAs (piRNAs) that regulate TEs. We discovered that ~94% of recently collected isofemale lines in the Drosophila melanogaster Genetic Reference Panel (DGRP) contain at least one P-element insertion in a piRNA cluster, indicating that repressor alleles are produced by de novo insertion at an exceptional rate. Furthermore, in our sample of ~200 genomes, we uncovered no fewer than 80 unique P-element insertion alleles in at least 15 different piRNA clusters. Finally, we observe no footprint of positive selection on P-element insertions in piRNA clusters, suggesting that the rapid evolution of piRNA-mediated repression in D. melanogaster was driven primarily by mutation. Our results reveal for the first time how the unique genetic architecture of piRNA production, in which numerous piRNA clusters can encode regulatory small RNAs upon transpositional insertion, facilitates the non-adaptive rapid evolution of repression. Published by Cold Spring Harbor Laboratory Press.In the central nervous system, melastatin transient receptor potential (TRPM) channels function as receptors for the neurosteroid pregnenolone sulfate (PregS). The expression and function of TRPM3 has been explored in adult retina, though its role during development is unknown. We found, during the second postnatal week in mice, TRPM3 immunofluorescence labeled distinct subsets of inner retinal neurons, including a subset of retinal ganglion cells (RGCs), similar to what has been reported in the adult. Labeling for a TRPM3 promoter-driven reporter confirmed expression of the TRPM3 gene in RGCs and revealed additional expression in nearly all Müller glial cells. Using two-photon calcium imaging, we show that PregS and the synthetic TRPM3 agonist CIM0216 induced prolonged calcium transients in RGCs, which were mostly absent in TRPM3 knockout (KO) mice. These prolonged calcium transients were not associated with strong membrane depolarizations but induced cFOS expression. To elucidate the impact of PregS-activat3 responds to PregS, producing prolonged calcium transients in a subset of retinal ganglion cells (RGCs) and increasing the frequency of spontaneous synaptic current onto RGCs. The PregS-mediated increase in spontaneous synaptic activity was absent in the TRPM3 KO retina. In addition, the absence of TRPM3 signaling reduced wave frequency. Thus, we show that TRPM3 and the endogenous neurosteroid, PregS, function in modulating spontaneous activity in the retina during development. Copyright © 2020 Webster et al.BACKGROUND The underlying etiology of colorectal cancer (CRC) includes both genetic variation and environmental exposures. The main aim of this study was to search for interaction effects between well-established environmental risk factors and published common genetic variants exerting main effects on CRC risk. METHODS We used a two-phase approach (i) Discovery phase (2,652 incident CRC cases and 10,608 controls from UK Biobank) and (ii) Validation phase (1,656 cases and 2,497 controls from the Study of Colorectal Cancer in Scotland). Interactions with nominal P less then 0.05 in phase I were taken forward for validation in phase II. Furthermore, we constructed a weighted genetic risk score (GRS) of CRC risk for each individual and studied interactions between the GRS and the environmental risk factors. selleck chemical RESULTS Seventy of the 1,500 tested interactions were nominally significant in phase I. After testing these 70 interactions in phase II, an interaction between rs11903757 (2q32.3/NABP1) and body mass index (BMI) was nominally significant (P=0.02) with the same direction of effects. The rs11903757*BMI interaction was also significant (ratio of odds ratios =1.26; 95% CI, 1.10-1.44; Pinteraction=6.03×10-4; Pheterogeneity=0.63) in a meta-analysis combining results from both phases. No interactions were significant in phase II after accounting for multiple testing. No interactions involving the GRS were found with statistical significance. CONCLUSIONS Limited evidence of gene-environment interactions in CRC risk was observed. There are potential modifications of the rs11903757 effect by BMI on CRC risk. IMPACT Our findings might contribute to identifying subpopulations with different susceptibility to the effect of BMI on CRC risk. Copyright ©2020, American Association for Cancer Research.