Characterization of six CaMKIIα variants found in schizophrenia patients
The Ca2+/Calmodulin-dependent protein kinase II (CaMKII) is a central regulator of synaptic plasticity forms that are thought to underlie cognition. Impaired CaMKII signaling has been associated with various neurological conditions, including schizophrenia. Here, we characterize six different CaMKIIα variants that were detected in schizophrenia patients. R396stop was the only variant with dramatic disruption in the 12-meric holoenzyme structure as well as in GluN2B binding and synaptic localization. Additionally, R396stop impaired the CaMKII autophosphorylation at T286 that generates Ca2+-independent “autonomous” kinase activity. This impairment was expected based on the holoenzyme disruption, as T286 autophosphorylation occurs as a trans-subunit reaction between two subunits within a holoenzyme. Impaired T286 autophosphorylation was shared by the R8H mutation, the only mutation that additionally reduced stimulated kinase activity. None of the mutations affected levels of CaMKII expression in HEK293 cells. Thus, impaired CaMKII function was detected in only two of the six mutations tested. However, two of the mutations without detected biochemical effects have been later identified also in the general population, and not all mutations found in schizophrenia patients would be expected to cause disease. Nonetheless, for the R396stop mutation, the severity of the biochemical effects found here would predict a neurological phenotype.