Functions of neuronal Synaptobrevin in the post-Golgi transport of Rhodopsin in Drosophila photoreceptors.

Polarized transport is essential for constructing multiple plasma membrane domains in the cell. Drosophila photoreceptors are an excellent model system to study the mechanisms of polarized transport. Rab11 is the key factor regulating the post-Golgi transport of rhodopsin 1 (Rh1; also known as NinaE), a photoreceptive protein, to the rhabdomere, a photoreceptive plasma membrane. Here, we found that neuronal Synaptobrevin (nSyb) colocalizes with Rab11 on the trans-side of Golgi stacks and post-Golgi vesicles at the rhabdomere base, and nSyb deficiency impairs rhabdomeric transport and induces accumulation of Rh1 and vesicles in the cytoplasm; this is similar to the effects of Rab11 loss. These results indicate that nSyb acts as a post-Golgi SNARE toward rhabdomeres. Surprisingly, in Rab11-, Rip11- and nSyb-deficient photoreceptors, illumination enhances cytoplasmic accumulation of Rh1, which colocalizes with Rab11, Rabenosyn5, nSyb and Arrestin 1 (Arr1). Arr1 loss, but not Rab5 dominant negative (Rab5DN) protein expression, inhibits the light-enhanced cytoplasmic Rh1 accumulation. Rab5DN inhibits the generation of Rh1-containing multivesicular bodies rather than Rh1 internalization. Overall, these results indicate that exocytic Rh1 mingles with endocytosed Rh1 and is then transported together to rhabdomeres.

Stratum is required for both apical and basolateral transport through stable expression of Rab10 and Rab35 in Drosophila photoreceptors.

Post-Golgi transport for specific membrane domains, also termed polarized transport, is essential for the construction and maintenance of polarized cells. Highly polarized Drosophila photoreceptors serve as a good model system for studying the mechanisms underlying polarized transport. The Mss4 Drosophila ortholog, Stratum (Strat), controls basal restriction of basement membrane proteins in follicle cells, and Rab8 acts downstream of Strat. We investigated the function of Strat in fly photoreceptors and found that polarized transport in both the basolateral and the rhabdomere membrane domains was inhibited in Strat-deficient photoreceptors. We also observed 79 and 55% reductions in Rab10 and Rab35 levels, respectively, but no reduction in Rab11 levels in whole-eye homozygous clones of Stratnull. Moreover, Rab35 was localized in the rhabdomere, and loss of Rab35 resulted in impaired Rh1 transport to the rhabdomere. These results indicate that Strat is essential for the stable expression of Rab10 and Rab35, which regulate basolateral and rhabdomere transport, respectively, in fly photoreceptors.

Rab10, Crag and Ehbp1 regulate the basolateral transport of Na+K+ATPase in Drosophila photoreceptors.

Cells in situ are often polarized and have multiple plasma membrane domains. To establish and maintain these domains, polarized transport is essential, and its impairment results in genetic disorders. Nevertheless, the underlying mechanisms of polarized transport have not been elucidated. Drosophila photoreceptor offers an excellent model for studying this. We found that Rab10 impairment significantly reduced basolateral levels of Na+K+ATPase, mislocalizing it to the stalk membrane, which is a domain of the apical plasma membrane. Furthermore, the shrunken basolateral and the expanded stalk membranes were accompanied with abnormalities in the Golgi cisternae of Rab10-impaired retinas. The deficiencies of Rab10-GEF Crag or the Rab10 effector Ehbp1 phenocopied Rab10 deficiency, indicating that Crag, Rab10 and Ehbp1 work together for polarized trafficking of membrane proteins to the basolateral membrane. These phenotypes were similar to those seen upon deficiency of AP1 or clathrin, which are known to be involved in the basolateral transport in other systems. Additionally, Crag, Rab10 and Ehbp1 colocalized with AP1 and clathrin on the trans-side of Golgi stacks. Taken together, these results indicate that AP1 and clathrin, and Crag, Rab10 and Ehbp1 collaborate in polarized basolateral transport, presumably in the budding process in the trans-Golgi network.

Evaluation of a 12-mm diameter covered self-expandable end bare metal stent for malignant biliary obstruction.

Background and study aims Biliary metallic stents are used to drain unresectable malignant distal biliary obstructions. This study aimed to evaluate the efficacy of a novel 12-mm-diameter covered, self-expandable end bare metal stent (12-mm CSEEMS). Patients and methods We evaluated 99 patients with unresectable malignant distal biliary obstructions treated with covered biliary metallic stents. Of the 99 patients, 33 underwent 12-mm CSEEMS placement between June 2015 and April 2017 (12-mm-CSEEMS group) and 66 underwent 10-mm fully-covered self-expandable metal stent (FCSEMS) placement between January 2010 and July 2015 (10-mm-FCSEMS group). The overall survival (OS), the recurrent biliary obstruction (RBO), cause of RBO, time to RBO (TRBO) and adverse events in 12-mm-CSEEMS group and 10-mm-FCSEMS group were evaluated retrospectively. Results The OS tended to be longer in the 12-mm-CSEEMS group (log rank, P  = 0.081) and TRBO was significantly longer in the 12-mm-CSEEMS group (log rank, P  = 0.001) than in the 10-mm-FCSEMS group. Both univariate (HR, 0.449; 95 % CI, 0.27967 - 0.72215; P  = 0.001) and multivariate (HR, 0.458; 95 % CI, 0.28395 - 0.73744; P  = 0.001) Cox hazard analysis found that risk of RBO was significantly lower in 12-mm CSEEMS than in 10-mm FCSEMS. There were no significant differences between the 12-mm-CSEEMS group and 10-mm-FCSEMS group regarding the cause of RBO and adverse events. Conclusions The 12-mm CSEEMS showed a low risk of RBO compared with 10-mm FCSEMS and was considered to be effective and safe for draining unresectable malignant distal biliary obstruction.

HLA-DQ gene polymorphisms are associated with hepatocellular carcinoma and hepatitis B surface antigen in chronic hepatitis B virus infection.

AIM: Genome-wide association studies have revealed that single nucleotide polymorphism (SNP) of human leukocyte antigen (HLA)-DQ is associated with the clearance of hepatitis B surface antigen (HBsAg) in acute hepatitis B virus (HBV) infection. We examined the effects of SNPs on the development of hepatocellular carcinoma (HCC) and markers of HBV in chronic HBV infection. METHODS: The SNPs of HLA-DQ (rs2856718 and rs7453920) were determined in 299 patients with chronic HBV infection. RESULTS: In 224 hepatitis B e antigen (HBeAg)-negative patients, those with rs2856718 genotype AG + GG had significantly lower hepatitis B core-related antigen levels (P = 0.0184), less frequent treatment with nucleotide/nucleoside analogs (NAs) (P = 0.0433), and less frequent HCC development (P = 0.0256) than those with genotype AA. Multivariate analysis selected age (P = 0.0460), platelet count (P = 0.0481), γ-glutamyl transpeptidase (P = 0.0030), and nucleotide/nucleoside analog treatment (P = 0.0003) as factors independently associated with HCC development. HBeAg-negative patients with rs7453920 genotype GG had significantly lower HBsAg levels (P < 0.0001), a higher prevalence of HBV genotype C (P = 0.0063), and a lower prevalence of the wild-type basal core promoter region (P = 0.0045) than those with genotype AA + AG. Multivariate analysis selected age (P < 0.0001), platelet count (P = 0.0021), HBV DNA levels (P = 0.0314), wild type of precore region (P = 0.0015), and rs7453920 (P < 0.0001) as factors independently associated with HBsAg levels. CONCLUSION: This study revealed an association between rs2856718 and HCC development and an association between rs7453920 and HBsAg levels.