The unexpected effect of the protease CPAF from Chlamydia trachomatisis to increase the global synthesis of the host proteins

Abstract

Abstract MHC-I molecules are involved in the predisposition to several immune diseases. Reactive arthritis (ReA) is strongly linked with Chlamydia trachomatisinfection and HLA-B*27. However, how the MHC-I can contribute to the pathology is not well understood. Chlamydiais an intracellular pathogen and one of its main pathogenic factors is CPAF. This enzyme is secreted to the cytosol of the host during infection and there are no data regarding its global effect on the protein degradation and how could affect the ligands presented by MHC-I molecules. T-REx-293 cells stably transfected with CPAF were induced with doxycycline and its effects on several known substrates were assayed by Western blot. Moreover, its unknown effects on the global proteome were evaluated by label-free quantitation (LFQ) using a Q-Exactive plus mass spectrometer. Additionally, MHC-I complexes were purified by immunoprecipitation and the eluted peptides were analyzed by MS. CPAF is highly active degrading known substrates such as Vimentin and RFX5, but also showed an unexpected and profound effect on the cellular proteome increasing the expression of many proteins with a wide range of functions, mostly related to transcription and translation pathways. More than 3000 MHC-I-restricted peptides were identified showing that the peptidome is altered when CPAF is induced, increasing the diversity and altering the physicochemical properties of the peptides. As conclusion, CPAF deeply alters the host proteome contributing to alter the peptide supply of the antigen processing pathway which affect the composition of the MHC-I-associated immunopeptidome. These data suggest that the generation of “new ligands” could be a new pathogenic mechanism of C. trachomatisin ReA. Supported by grants Fondecyt 11170969 and Fondequip EQM190142 from ANID, Chile.