Glutamic Acid at Position 168 Is a Constitutive Activator of Tank Binding Kinase 1 Catalytic Function

TANK binding kinase 1 (TBK1) is serine/threonine protein kinase member of the inhibitor of nuclear factor-kB kinase family, with links to the etiology of familial as well as idiopathic Amyotrophic Lateral Sclerosis. It contributes to several regulatory cellular processes such as autophagy, inflammation and apoptosis. Reduction or loss of TBK1 kinase activity is associated with increased risk of ALS, and so understanding the molecular basis of this activity is an important research priority. In this current study, the role of the E168 residue, located adjacent to the active site of TBK1, has been assessed using a combination of artificial and naturally occurring variants found at this codon - evaluated using multiple readouts for TBK1 kinase activity. The results suggest that the negative charge resulting from the presence of a glutamic acid at this codon is a constitutive activator of TBK1 activity.