Extracellular α-synuclein is important in the pathogenesis of Parkinson disease (PD) and also as a potential biomarker when tested in the cerebrospinal fluid (CSF). The performance of blood plasma or serum α-synuclein as a biomarker has been found to be inconsistent and generally ineffective, largely due to the contribution of peripherally derived α-synuclein. In this study, we discovered, via an intracerebroventricular injection of radiolabeled α-synuclein into mouse brain, that CSF α-synuclein was readily transported to blood, with a small portion being contained in exosomes that are relatively specific to the central nervous system (CNS). Consequently, we developed a technique to evaluate the levels of α-synuclein in these exosomes in individual plasma samples. When applied to a large cohort of clinical samples (267 PD, 215 controls), we found that in contrast to CSF α-synuclein concentrations, which are consistently reported to be lower in PD patients compared to controls, the levels of plasma exosomal α-synuclein were substantially higher in PD patients, suggesting an increased efflux of the protein to the peripheral blood of these patients. Furthermore, although no association was observed between plasma exosomal and CSF α-synuclein, a significant correlation between plasma exosomal α-synuclein and disease severity (r=0.176, p=0.004) was observed, and the diagnostic sensitivity and specificity achieved by plasma exosomal α-synuclein were comparable to those determined by CSF α-synuclein. Further studies are clearly needed to elucidate the mechanism involved in the transport of CNS α-synuclein to the periphery, which may lead to a more convenient and robust assessment of PD clinically.

Summary Assembly of 30S ribosomal subunits from their protein and RNA components requires extensive refolding of the 16S rRNA and is assisted by 10–20 assembly factors in bacteria. We probed the structures of 30S assembly intermediates in E. coli cells, using a synchrotron X-ray beam to generate hydroxyl radical in the cytoplasm. Widespread differences between mature and pre-30S complexes in the absence of assembly factors RbfA and RimM revealed global reorganization of RNA-protein interactions prior to maturation of the 16S rRNA and showed how RimM reduces misfolding of the 16S 3′ domain during transcription in vivo. Quantitative 14N/15N mass spectrometry of affinity-purified pre-30S complexes confirmed the absence of tertiary assembly proteins and showed that N-terminal acetylation of proteins S18 and S5 correlates with correct folding of the platform and central pseudoknot. Our results indicate that cellular factors delay specific RNA folding steps to ensure the quality of assembly.

Objective To determine the role of the aryl hydrocarbon receptor (AHR) in colitis-associated colorectal tumorigenesis. Summary Background Data Colorectal cancer (CRC) is the third most commonly diagnosed cancer in both men and women in United States. Chronic intestinal inflammation increases the risk for the development of CRC. We questioned the involvement of AHR, a transcriptional regulator for intestinal innate immunity and inflammation, in the colitis-associated tumorigenesis. Methods We used a mouse model for chemically-induced colorectal tumorigenesis by treatment of azoxymethane (AOM) and sodium dextran sulfate (DSS). We examined the role of AHR using Ahr-deletion mouse model and I3C treatment. Tumor incidence, number and location were visually counted. Tumor multiplicities were evaluated and compared using GraphPad Prism software (version 6, LaJolla, CA). Results In Ahr null mice, the tumor incidence was 32% increased and the mean tumor number was approximately 3 time increased compared to WT mice (7 v 2.4, P<0.05). The tumor number was 92% decreased by treatment of I3C in WT mice, while the chemopreventive effect of I3C was not observed in Ahr null mice (P<0.05). Conclusions We found that the AHR may play a protective role in colitis-associated colorectal tumorigenesis. This work supports the application of AHR agonists such as I3C as a chemopreventive therapy for CRC in human patient.