Original Article

The effects of Salmonella enterica cell extract on the gene expression of bleomycin hydrolase, puromycin-sensitive aminopeptidase, and thimet oligopeptidase in human colorectal adenocarcinoma cells

Abstract

Background and Objectives: Salmonella enterica survival depends on evading CD8+ T-cell recognition, a process governed by the MHC Class I antigen presentation pathway. The cytosolic aminopeptidases—bleomycin hydrolase (BH), puromycin-sensitive aminopeptidase (PSA), and thimet oligopeptidase (TOP)—are critical "final trimmers" that generate the precise peptide epitopes required for MHC Class I loading. This study investigated whether S. enterica cell extract modulates the transcriptional expression of these key enzymes in HT-29 cells, potentially revealing a mechanism of immune evasion mediated by bacterial structural components.
Materials and Methods: Human colorectal adenocarcinoma HT-29 cells were treated with varying concentrations of S. enterica extract. The gene expression levels of BH, PSA, and TOP were quantified using qRT-PCR at multiple time points (6, 12, 24, 48, and 72 hours) post-treatment. Data were statistically analyzed to evaluate significant modulations relative to untreated controls.
Results: The transcriptional response to S. enterica extract was highly selective, with TOP demonstrating the most robust and rapid induction. Significant upregulation of TOP occurred as early as 6 hours post-treatment and reached its maximum induction at 48 hours. Conversely, BH levels remained largely indistinguishable from untreated controls. PSA expression showed no statistically significant alterations relative to the control group throughout the study. These findings suggest that S. enterica components preferentially target the "terminator" peptidase TOP to potentially disrupt the MHC Class I antigen presentation pathway.
Conclusion: S. enterica cell extract significantly and selectively alters the expression of TOP, a critical cytosolic peptidase involved in the final stages of antigen processing. This targeted modulation likely serves as a mechanism for immune evasion by facilitating the destruction of immunogenic epitopes, thereby rendering infected cells less visible to the adaptive immune system.

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IssueVol 18 No 2 (2026) QRcode
SectionOriginal Article(s)
Keywords
Aminopeptidases HT-29 cells Salmonella enterica Cysteine endopeptidases Metalloendopeptidases
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How to Cite
1.
Mardani R, Borhaniasl M, Ghatee MA, Khosravani SA, Sharifi K, Jahanbin K, Sharifi A. The effects of Salmonella enterica cell extract on the gene expression of bleomycin hydrolase, puromycin-sensitive aminopeptidase, and thimet oligopeptidase in human colorectal adenocarcinoma cells. Iran J Microbiol. 2026;18(2):217-225.