Regulatory mechanism of Chlamydia trachomatis GlgA protein expression and secretion

Abstract:

[Background] The secreted proteins of Chlamydia trachomatis play important roles in chlamydia interaction with host cell, development cycle and pathogenesis. Our previously study have found that C. trachomatis glycogen synthase (GlgA) to be a newly chlamydia secreted protein, however, the secretion mechanism and the roles of GlgA in chlamydial pathogenesis is still unknown. [Objective] We studied regulatory mechanism of C. trachomatis GlgA protein expression and secretion, to provide experimental basis for studying chlamydia pathogenic mechanism. [Methods] SignalP 4.1 software was amplified to predict GlgA protein N terminal signal peptide. C. trachomatis infected HeLa cells were treated individually with C16 compounds, C1 compounds, or their combination to observe the effect of blocking type II or type III secretion system on GlgA secretion. Novobiocin treatment, plaque-forming assay, as well as shuttle plasmid transformation technique were used to construct either plasmid-free or plasmid-compensate C. trachomatis strains, then the strains were further identified by detecting both the plasmid encoding gene and protein. Indirect immunofluorescence assay was done to evaluate the effects of the plasmid deletion on GlgA protein expression and secretion. [Results] The full length GlgA is predicted to contain no putative signal peptide at its N terminus. Neither C16 nor C1 compounds inhibited GlgA secretion into the cytosol of chlamydia-infected cells. The plasmid-encoded gene pgp7, the plasmid-encoded protein Pgp3, the genome-encoded protein GlgA were all detected in the cultures infected with either wild type serovar D or CTD1-pGFP::SW2 transformant but not the plasmid-free CTD1 organisms. [Conclusion] The expression and secretion of GlgA protein is not dependent on bacteria type II or III secretion system, but closely related to the plasmid of C. trachomatis.

Key words:Chlamydia trachomatis, Glycogen synthase GlgA, Secreted protein, Plasmid-free organisms