Cell line differences in bacterially translocated ExoS ADP-ribosyltransferase substrate specificity.

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Pseudomonas aeruginosa utilizes a type III secretory (TTS) system to translocate effector proteins like Exoenzyme S (ExoS) into host cells.
• ExoS is an ADP-ribosyltransferase (ADPRT) that modifies host cell proteins, impacting cellular functions.
• Differences in ExoS activity across various cell types suggest host cell-specific interactions.

Purpose of the Study:

• To investigate the differential effects of bacterial translocated ExoS on human epithelial versus murine fibroblastic cells.
• To identify the cellular mechanisms underlying variations in ExoS substrate modification.
• To determine if host cell origin influences ExoS ADP-ribosyltransferase activity and its impact on host cell function.

Main Methods:

• Comparative analysis of ExoS functional effects on human epithelial and murine fibroblastic cells.
• Assessment of ExoS-mediated ADP-ribosylation of low-molecular-mass G (LMMG) proteins.
• Investigation of bacterial adherence and ExoS internalization efficiencies.
• Examination of substrate modification patterns across diverse mammalian cell lines (human, simian, rodent).

Main Results:

• Human epithelial cells showed increased sensitivity to ExoS, affecting proliferation, morphology, and re-adherence compared to murine fibroblasts.
• ExoS ADP-ribosylated a broader range of LMMG proteins in human epithelial cells than in murine fibroblasts.
• The differences in substrate modification were not due to variations in bacterial adherence or ExoS internalization.
• Rodent cell lines consistently displayed limited LMMG protein ADP-ribosylation, while human and simian cells showed more extensive modification.
• Substrate modification patterns were independent of cellular transformation and cell type.

Conclusions:

• Eukaryotic cell properties, particularly those related to animal origin, significantly influence ExoS substrate targeting by its ADPRT activity.
• Host cell-specific interactions dictate the extent of ExoS-mediated protein modification.
• These variations in substrate modification impact the severity of ExoS effects on host cell functions, highlighting the importance of host-pathogen interactions in disease pathogenesis.