Glutamate Deregulation in Ketamine-Induced Psychosis—A Potential Role of PSD95, NMDA Receptor and PMCA Interaction

Abstract

Ketamine causes psychotic episodes and is often used as pharmacological model of psychotic-like behavior in animals. There is increasing evidence that molecular mechanism of its action is more complicated than just N-methyl-D-aspartic acid (NMDA) receptor antagonism and involves interaction with the components of calcium homeostatic machinery, in particular plasma membrane calcium pump (PMCA). Therefore, in this study we aimed to characterize brain region-specific effects of ketamine on PMCA activity, interaction with NMDA receptor through postsynaptic density protein 95 (PSD95) scaffolding proteins and glutamate release from nerve endings. In our study, ketamine induced behavioral changes in healthy male rats consistent with psychotic effects. In the same animals, we were able to demonstrate significant inhibition of plasma membrane calcium ATPase (PMCA) activity in cerebellum, hippocampus and striatum. The expression level and isoform composition of PMCAs were also affected in some of these brain compartments, with possible compensatory effects of PMCA1 substituting for decreased expression of PMCA3. Expression of the PDZ domain-containing scaffold protein PSD95 was induced and its association with PMCA4 was higher in most brain compartments upon ketamine treatment. Moreover, increased PSD95/NMDA receptor direct interaction was also reported, strongly suggesting the formation of multiprotein complexes potentially mediating the effect of ketamine on calcium signaling. We further support this molecular mechanism by showing brain region-specific changes in PSD95/PMCA4 spatial colocalization. We also show that ketamine significantly increases synaptic glutamate release in cortex and striatum (without affecting total tissue glutamate content), inducing the expression of vesicular glutamate transporters and decreasing the expression of membrane glutamate reuptake pump excitatory amino acid transporters 2 (EAAT2). Thus, ketamine-mediated PMCA inhibition, by decreasing total Ca2+ clearing potency, may locally raise cytosolic Ca2+ promoting excessive glutamate release. Regional alterations in glutamate secretion can be further driven by PSD95-mediated spatial recruitment of signaling complexes including glutamate receptors and calcium pumps, representing a novel mechanism of psychogenic action of ketamine.

Transcriptional changes in response to ketamine ester-analogs SN 35210 and SN 35563 in the rat brain

“…These proteins are components of the postsynaptic density network that connects many membrane proteins, including the excitatory neurotransmitter receptors NMDA, AMPA and mGlut, to the actin cytoskeleton. The association of ketamine with dysregulation of genes involved in postsynaptic density has been reported previously [19–21]; and Yang and colleagues [22] observed increased dendritic filopodia after 4 h of anaesthesia with ketamine-xylazine. Furthermore, the anaesthetic effect of halothane is enhanced in mice following disruption to PSD95-PDZ2 with intraperitoneal injection of a Tat-PSD95-PDZ2 fusion protein [23].…”

“…Lisek et al [21] studied the effects of ketamine on psychosis and showed that ketamine increases synaptic glutamate release in the cortex and striatum. This was associated with an increased expression of glutamate transporters, VGLUT1 (SLC17A7) and VGLUT2 (SLC17A6), and a decreased expression of membrane glutamate reuptake pump excitatory amino acid transporter 2 (EAAT2) (a.k.a.…”

Combined Treatment with Low-Dose Ionizing Radiation and Ketamine Induces Adverse Changes in CA1 Neuronal Structure in Male Murine Hippocampi

“…Similarly, it was shown that high-dose (1 Gy, 10 Gy) cranial gamma-radiation caused increased expression of PSD-95 in the hippocampus of adult mice 30 days after irradiation [25]. Administration of high-dose ketamine (30 mg kg −1 over five consecutive days) was shown to immediately increase the level of PSD-95 in the synaptosomes of adult male Wistar rats [42]. Lower doses of ketamine (10 mg kg −1 ) did not produce effects on the total level of PSD-95 in the hippocampal membranes of mice immediately (30 min) after administration [43].…”

Polysialic acid in the rat brainstem and thoracolumbar spinal cord: Distribution, cellular location, and comparison with mouse

“…Specificity of the antibody was verified by western blotting in mouse and rat brain tissue lysate, where a single band of approximately 62 kDa corresponding to EAAT2 protein was identified (manufacturer's technical information). The antibody has also been used in western blotting of rat brain tissue lysates detecting a 62 kDa (Lisek et al, 2017) and a 67 kDa band (Omeragic, Hoque, Choi, & Bendayan, 2017). The current staining pattern was similar to that previously seen in mouse (Matott, Kline, & Hasser, 2017) and rat nucleus of solitary tract (NTS) (Matott, Ruyle, Hasser, & Kline, 2016).…”