Binds to and modulates brain Na,K-ATPase subunits ATP1B1 and ATP1B3 and may thereby participate in the regulation of electrical excitability and synaptic transmission. May not display kinase activity. Also associates with the plasma membrane. Isoform 3 is present throughout the cell. Widely expressed in all tissues examined except in heart. Isoform 1 is expressed in high levels in the brain, skeletal muscle, spleen and testis. Isoform 7 expression has yet to be demonstrated. The protein kinase domain is predicted to be catalytically inactive. Belongs to the protein kinase superfamily. Truncated C-terminus.