RPN1 promotes the proliferation and invasion of breast cancer cells by activating the PI3K/AKT/mTOR signaling pathway

Ribophorin I (RPN1), a part of an N-oligosaccharyl-transferase complex, plays a vital role in the development of multiple cancers. However, its biological role in breast cancer has not been completely clarified. The RPN1 expression level was measured in breast cancer tissues and breast cancer cell lines (MCF7) using RT-qPCR. After down-regulating RPN1 expression by shRNA, the effects of RPN1 on the proliferation, migration and invasion of MCF7 cells were examined. Mechanistically, we assessed the effect of RPN1 on the PI3K/ AKT/mTOR signaling pathway. We found that RPN1 level was up-regulated in breast cancer tissues and cells compared with adjacent non-tumor tissues or MCF10A cells. RPN1 knockdown induced apoptosis and attenuated the proliferation, migration, and invasion of MCF7 cells. Moreover, RPN1 knockdown lowered the levels of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR, which were rescued by 740Y-P, a PI3K activator. 740Y-P also reversed the effects of RPN1 knockdown on apoptosis, proliferation, migration, and invasion in MCF7 cells. Taken together, RPN1 promotes the proliferation, migration, and invasion of breast cancer cells via the PI3K/AKT/mTOR signaling pathway.

A Non-structural 1 Protein G53D Substitution Attenuates a Clinically Tested Live Dengue Vaccine

The molecular basis of dengue virus (DENV) attenuation remains ambiguous and hampers a targeted approach to derive safe but nonetheless immunogenic live vaccine candidates. Here, we take advantage of DENV serotype 2 PDK53 vaccine strain, which recently and successfully completed a phase-3 clinical trial, to identify how this virus is attenuated compared to its wild-type parent, DENV2 16681. Site-directed mutagenesis on a 16681 infectious clone identifies a single G53D substitution in the non-structural 1 (NS1) protein that reduces 16681 infection and dissemination in both Aedes aegypti, as well as in mammalian cells to produce the characteristic phenotypes of PDK53. Mechanistically, NS1 G53D impairs the function of a known host factor, the endoplasmic reticulum (ER)-resident ribophorin 1 protein, to properly glycosylate NS1 and thus induce a host antiviral gene through ER stress responses. Our findings provide molecular insights on DENV attenuation on a clinically tested strain.