Chlamydia pneumoniae directly interferes with HIF-1α stabilization in human host cells

Chlamydiaceae are obligate intracellular bacteria that cause endemic trachoma, sexually transmitted diseases and respiratory infections. The course of the diseases is determined by local inflammatory immune responses and the propensity of the pathogen to replicate within infected host cells. Both features require energy which is inseparably coupled to oxygen availability in the microenvironment. Hypoxia-inducible factor-1 (HIF-1) regulates crucial genes involved in the adaptation to low oxygen concentrations, cell metabolism and the innate immune response. Here we report that Chlamydia pneumoniae directly interferes with host cell HIF-α regulation in a biphasic manner. In hypoxia, C.pneumoniae infection had an additive effect on HIF-α stabilization resulting in enhanced glucose uptake during the early phase of infection. During the late phase of intracellular chlamydial replication, host cell adaptation to hypoxia was actively silenced by pathogen-induced HIF-1α degradation. HIF-1α was targeted by the chlamydial protease-like activity factor, which was secreted into the cytoplasm of infected cells. Direct interference with HIF-1α stabilization was essential for efficient C.pneumoniae replication in hypoxia and highlights a novel strategy of adaptive pathogen-host interaction in chlamydial diseases.