Stt3a, a key catalytic subunit of oligosaccharyltransferase (OST), is crucial for N-glycosylation, a process that modifies proteins by adding oligosaccharides. N-glycosylation is essential for protein stability, function, and various biological processes. It is involved in pathways like protein folding in the endoplasmic reticulum. Genetic models, such as knockout mouse models, are valuable for studying Stt3a's functions [2,4,5].

Knockout or inhibition of Stt3a in lung adenocarcinoma cell lines and mouse xenograft models suppressed cell proliferation, migration, invasion, and arrested the cell cycle, suggesting it promotes lung adenocarcinoma progression via the MAPK and PI3K/AKT signaling pathways [2]. In herpes simplex virus 1 (HSV-1) studies, cells lacking STT3B-OST activity and thus dependent on STT3A-OST for N-glycosylation, when treated with NGI-1 (an inhibitor of STT3A-OST), resulted in HSV-1 having cell type-dependent dysfunction [3]. In hepatocellular carcinoma, GMPS-mediated STT3A-dependent PD-L1 glycosylation modification drives tumor immune evasion, and targeting GMPS can suppress PD-L1 expression and tumor growth [1].

In conclusion, Stt3a-mediated N-glycosylation is essential for various biological processes and has implications in multiple diseases. Model-based research, especially KO/CKO mouse models, has revealed its role in promoting tumor progression in lung adenocarcinoma, affecting viral function in HSV-1, and contributing to tumor immune evasion in hepatocellular carcinoma, providing potential therapeutic targets for these diseases.

References:

1. Guo, Xinyu, Cui, Tianming, Sun, Linmao, Liu, Yao, Liu, Lianxin. 2024. A STT3A-dependent PD-L1 glycosylation modification mediated by GMPS drives tumor immune evasion in hepatocellular carcinoma. In Cell death and differentiation, , . doi:10.1038/s41418-024-01432-0. https://pubmed.ncbi.nlm.nih.gov/39690246/

2. Cheng, Jiahan, Xia, Liang, Hao, Xiaohu, Deng, Senyi, Liu, Lunxu. . Targeting STT3A produces an anti-tumor effect in lung adenocarcinoma by blocking the MAPK and PI3K/AKT signaling pathway. In Translational lung cancer research, 11, 1089-1107. doi:10.21037/tlcr-22-396. https://pubmed.ncbi.nlm.nih.gov/35832442/

3. Lu, Hua, Cherepanova, Natalia A, Gilmore, Reid, Contessa, Joseph N, Lehrman, Mark A. 2019. Targeting STT3A-oligosaccharyltransferase with NGI-1 causes herpes simplex virus 1 dysfunction. In FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 33, 6801-6812. doi:10.1096/fj.201802044RR. https://pubmed.ncbi.nlm.nih.gov/30811219/

4. Lu, Hua, Fermaintt, Charles S, Cherepanova, Natalia A, Yan, Nan, Lehrman, Mark A. 2018. Mammalian STT3A/B oligosaccharyltransferases segregate N-glycosylation at the translocon from lipid-linked oligosaccharide hydrolysis. In Proceedings of the National Academy of Sciences of the United States of America, 115, 9557-9562. doi:10.1073/pnas.1806034115. https://pubmed.ncbi.nlm.nih.gov/30181269/

5. Chang, Irene J, Byers, Heather M, Ng, Bobby G, Zhang, Bin, Lam, Christina. 2019. Factor VIII and vWF deficiency in STT3A-CDG. In Journal of inherited metabolic disease, 42, 325-332. doi:10.1002/jimd.12021. https://pubmed.ncbi.nlm.nih.gov/30701557/