Carbon dioxide-dependent regulation of NF-{kappa}B family members RelB and p100 gives molecular insight into CO2-dependent immune regulation [Molecular Bases of Disease]

CO2 is a physiological gas normally produced in the body during aerobic respiration. Hypercapnia (elevated blood pCO2 > ≈ 50mmHg) is a feature of several lung pathologies e.g. chronic obstructive pulmonary disease (COPD). Hypercapnia is associated with increased susceptibility to bacterial infections and suppression of inflammatory signaling. The NF-κB pathway has been implicated in these effects, however, the molecular mechanisms underpinning cellular sensitivity of the NF-κB pathway to CO2 is not fully elucidated. Here we identify several novel CO2-dependent changes in the NF-κB pathway. NF-κB family members p100 and RelB translocate to the nucleus in response to CO2. A cohort of RelB protein-protein interactions (e.g. with Raf-1 and IκBα) are altered by CO2 exposure, while others are maintained (e.g. with p100). RelB is processed by CO2 in a manner dependent on a key C-terminal domain located in its transactivation domain. Loss of the RelB transactivation domain alters NF-κB -dependent transcriptional activity and loss of p100 alters sensitivity of RelB to CO2. Thus, we provide molecular insight into the CO2-sensitivity of the NF-κB pathway and implicate altered RelB/p100-dependent signaling in the CO2-dependent regulation of inflammatory signaling.

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