Neuronal CO pathway identified

Carbon monoxide (CO) is synthesized in neurons by heme oxygenase-2 (HO2). Inhibition or genomic deletion of HO2 reduces neurotransmission in experimental models, suggesting that like nitric oxide (NO), CO may function as a gaseous neurotransmitter that must be rapidly synthesized following neuronal depolarization. This process is well understood for the release of NO, but the apparent absence of a pathway for rapid HO2 activation has led to doubts over the role of CO in neurotransmission. In the September 25 Neuron, Darren Boehning and colleagues at Johns Hopkins University School of Medicine describe a pathway in which HO2 is activated by CK2 (formerly known as casein kinase 2) both in vitro and in vivo, supporting a role for CO as a bona fide neurotransmitter (Neuron, 40:129-137, September 25 2003).

Boehning et al. observed that CK2 specifically phosphorylated and activated HO2 in vitro. They then demonstrated that CK2 also mediated phorbol ester–stimulated ...