Carbon dioxide-dependent regulation of NF-κB family members RelB and p100 gives molecular insight into CO 2 -dependent immune regulation.

CO ₂ is a physiological gas normally produced in the body during aerobic respiration. Hypercapnia (elevated blood pCO ₂ >≈50 mm Hg) is a feature of several lung pathologies, e.g. chronic obstructive pulmonary disease. 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 CO ₂ are not fully elucidated. Here, we identify several novel CO ₂ -dependent changes in the NF-κB pathway. NF-κB family members p100 and RelB translocate to the nucleus in response to CO ₂ A cohort of RelB protein-protein interactions ( e.g. with Raf-1 and IκBα) are altered by CO ₂ exposure, although others are maintained ( e.g. with p100). RelB is processed by CO ₂ 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 CO ₂ Thus, we provide molecular insight into the CO ₂ sensitivity of the NF-κB pathway and implicate altered RelB/p100-dependent signaling in the CO ₂ -dependent regulation of inflammatory signaling.
(© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)