Chlamydia pneumoniae facilitates its development by recruiting PI4P to inclusion bodies via the Cpn0308-ACBD3-PI4KB pathway

ABSTRACT Chlamydia pneumoniae (Cpn) is an obligate intracellular parasitic pathogen that replicates inside a membrane-bound vacuole termed the inclusion. This compartment is modified by chlamydial inclusion membrane proteins (Incs), which interact with host proteins to facilitate chlamydial development and pathogenicity. Among these, Cpn0308 localizes specifically to the inclusion membrane. Our previous study demonstrated that exogenously expressed Cpn0308 can interact with host protein ACBD3; here, we demonstrate this interaction during actual Cpn infection using endogenous proteins. This interplay proved critical for Cpn development, as ACBD3 knockout in HeLa cells led to significantly smaller inclusions, delayed transition from elementary bodies (EBs) to reticulate bodies (RBs), and reduced bacterial copy numbers. Mechanistically, the Cpn0308-ACBD3 interaction facilitates the recruitment of Phosphatidylinositol 4-kinase 3β (PI4KB) to the inclusion vicinity. This recruitment enhances the production and localization of Phosphatidylinositol 4-phosphate (PI4P) within Cpn - infected HeLa cells. Conversely, PI4KB and PI4P levels were markedly diminished in Cpn-infected ACBD3-knockout cells, whereas their expression remained unchanged in uninfected knockout cells. Furthermore, pharmacological inhibition of PI4KB with PIK93 impaired PI4P synthesis and suppressed Cpn replication. In conclusion, we propose a mechanism wherein the Cpn inclusion membrane protein Cpn0308 engages host ACBD3 to recruit PI4KB around the inclusion, which subsequently catalyzes PI4P production, thereby promoting the development and progression of C. pneumoniae infection.