The effects of proteasome on baseline and methamphetamine-dependent dopamine transmission.

The Ubiquitin Proteasome System (UPS) is a major multi-catalytic machinery, which guarantees cellular proteolysis and turnover. Beyond cytosolic and nuclear cell compartments, the UPS operates at the synapse to modulate neurotransmission and plasticity. In fact, dysregulations of the UPS are linked with early synaptic alterations occurring in a variety of dopamine (DA)-related brain disorders. This is the case of psychiatric conditions such as methamphetamine (METH) addiction. While being an extremely powerful DA releaser, METH impairs UPS activity, which is largely due to DA itself. In turn, pre- and post- synaptic neurons of the DA circuitry show a high vulnerability to UPS inhibition. Thus, alterations of DA transmission and UPS activity are intermingled within a chain of events underlying behavioral alterations produced by METH. These findings, which allow escaping the view of a mere implication of the UPS in protein toxicity-related mechanisms, indicate a more physiological role for the UPS in modulating DA-related behavior. This is seminal for those plasticity mechanisms which underlie overlapping psychiatric disorders such as METH addiction and schizophrenia.