The oligosaccharyl transferase (OST) protein complex mediates the N-linked glycosylation of substrate proteins in the endoplasmic reticulum (ER), which regulates stability, activity, and localization of its substrates. Although many OST substrate proteins have been identified, the physiological role of the OST complex remains incompletely understood. Here we show that the OST complex in C. elegans is crucial for ER protein homeostasis and defense against infection with pathogenic bacteria Pseudomonas aeruginosa (PA14), via immune-regulatory PMK-1/p38 MAP kinase. We found that genetic inhibition of the OST complex impaired protein processing in the ER, which in turn up-regulated ER unfolded protein response (UPR^ER). We identified vitellogenin VIT-6 as an OST-dependent glycosylated protein, critical for maintaining survival on PA14. We also showed that the OST complex was required for up-regulation of PMK-1 signaling upon infection with PA14. Our study demonstrates that an evolutionarily conserved OST complex, crucial for ER homeostasis, regulates host defense mechanisms against pathogenic bacteria.

寡糖基转移酶（OST）蛋白复合物介导内质网（ER）中底物蛋白的N联糖基化，从而调节底物的稳定性，活性和位置。尽管已鉴定出许多OST底物蛋白，但对OST复合物的生理作用仍未完全了解。在这里，我们显示了C中的OST复合体。线虫通过免疫调节性PMK-1 / p38 MAP激酶，对于ER蛋白稳态和抵抗病原菌铜绿假单胞菌（PA14）的感染至关重要。我们发现，对OST复合物的遗传抑制削弱了ER中的蛋白加工，进而上调了ER展开的蛋白反应（UPR ^ER）。我们确定卵黄蛋白原VIT-6是一种OST依赖性糖基化蛋白，对维持PA14的存活至关重要。我们还显示，OST复合物是感染PA14后PMK-1信号上调所必需的。我们的研究表明，进化上保守的OST复合物对ER稳态至关重要，它调节了针对病原菌的宿主防御机制。