UPR signaling plays an important role in the defense response against <i>C</i>. <i>jejuni</i> infection.

(A-C) HeLa cells were transfected with the pENTR-PERK vector, the pENTR-IRE1 vector, the pENTR-ATF6 vector, or a non-target shRNA control vector, and transcriptional levels of each target were analyzed using qPCR. Each mRNA was normalized to the housekeeping gene β-actin. (D and E) HeLa and INT407 cells, transfected with pENTR-PERK vector, pENTR-IRE1 vector pENTR-ATF6 vector, or non-target shRNA control vector, were infected by C. jejuni for 3 h, and intracellular bacteria numbers were estimated with a gentamicin protection assay (*p < 0.05, **p < 0.01, by t-test, n = 3–6). Each experiment was repeated three times (D was repeated four times).