GZMK and rheumatoid arthritis: Commensurate with this importance, perturbations of GRK systems have been linked to diverse pathologies such as bipolar disease (Barrett et al., 2007), AD (Obrenovich et al., 2009), rheumatoid arthritis (Lombardi et al., 1999), multiple sclerosis (Vroon et al., 2005), and PD (Bychkov et al., 2008).