Role of cyclin-dependent kinase 5 in psychosis and the modulatory effects of cannabinoids.
Cyclin-dependent kinase 5 (CDK5) is a serinethreonine kinase that has emerged as a key regulator of neurotransmission in complex cognitive processes. Its expression is altered in treated schizophrenia patients, and cannabinoids modulate CDK5 levels in the brain of rodents. However, the role of this kinase, and its interaction with cannabis use in first-episode psychosis (FEP) patients is still not known. Hence, we studied the expression changes of CDK5 and its signaling partner, postsynaptic density protein 95 (PSD95) in olfactory neuroepithelial (ON) cells of FEP patients with (FEPc) and without (FEPnc) prior cannabis use, and in a dual-hit mouse model of psychosis. In this model, adolescent mice were exposed to the cannabinoid receptor 1 agonist (CB1R) WIN-55,212-2 (WIN 1 mgkg) during 21 days, and to the N-methyl-d-aspartate receptor (NMDAR) blocker phencyclidine (PCP 10 mgkg) during 10 days. FEPc showed less social functioning deficits, lower CDK5 and higher PSD95 levels than FEPnc. These changes correlated with social skills, but not cognitive deficits. Consistently, exposure of ON cells from FEPnc patients to WIN in vitro reduced CDK5 levels. Convergent results were obtained in mice, where PCP by itself induced more sociability deficits, and PSD95CDK5 alterations in the prefrontal cortex and hippocampus than exposure to PCP-WIN. In addition, central blockade of CDK5 activity with roscovitine in PCP-treated mice restored both sociability impairments and PSD95 levels. We provide translational evidence that increased CDK5 could be an early indicator of psychosis associated with social deficits, and that this biomarker is modulated by prior cannabis use.