Transient enhanced expression of p25 in striatal synaptosomes during the development and expression of d-amphetamine sensitization

MLESWKI, CECILIA, KRAPACHER, FAVIO, FERRERAS, SOLEDAD AND PAGLINI, GABRIELA

Merida, Mexico

Congreso; First Annual International Drug Abuse Research Society (IDARS) Meeting – ISN Satellite Meeting: New Research Frontiers and Advances in Drug Addiction; 2007

IDARS - ISN

Transient enhanced expression of p25 in striatal synaptosomes during the development and expression of D-amphetamine sensitization Mleswki, Cecilia, Krapacher, Favio, Ferreras, Soledad and Paglini, Gabriela Inst.Inv.Médica M. y M. Ferreyra- INIMEC-CONICET- Córdoba-Argentina -   The cellular and molecular mechanisms of sensitization in addictive process are still unclear. Recently, the chronic treatment with cocaine has been shown to up-regulate the expression of cyclin-dependent kinese 5 (cdk5) and its specific activator, p35, in the striatum, as a downstream target gene of DFosB and has been implicated in compensatory adaptive changes associated with psychostimulants treatments. Cdk5 is a serine/threonine kinases and its activation is achieved through the association with a regulatory subunit, either p35 or p39. P35 is cleaved by a protease calpain, which results in the generation of a truncate product termed p25, which contains all elements necessary for cdk5 activation. Cdk5/p35 complex plays an essential role in neuron development and survival. It has also been involved in neuronal trafficking, transport and in dopaminergic transmission, indicating its role either in presynaptic and postsynaptic signaling. Moreover, intraaccumbal infusion of cdk5 inhibitor, roscovitine, attenuates cocaine-induced increase spine density. Our goal is to obtain new and detailed evidences about the participation of cdk5 and its activators proteins in cellular and molecular mechanisms of amphetamine sensitization, as well as a plausible mechanism underlying psychostimulants-induced spine formation and/or stability. In this study we report that cdk5/p35 complex participates in acute and chronic D-amphetamine (AMPH)-evoked behavioral events. Surprisingly we show a transient enhanced expression of p25 accompanied with a strong synaptophysin and PSD-95 labels and a lasting raised expression of p35 in dorsal striatum synaptosomes after acute and chronic AMPH administration. PAK, a substrate for cdk5 that is involved in regulation of spine morphogenesis, is also enriched in the synaptosomal fraction of AMPH-treated rats. The fact that p35 and p25 efficiently activate cdk5, it would be reasonable to think that the complex cdk5/p35 displays different properties from cdk5/p25, taking into account that p35 is a very unstable protein with a half-life of 20-30 min, while p25 exhibits a considerably longer half-life. This propriety of p25 lead to special regulation of cdk5 kinase activity, and cdk5 could be subject to a different regulatory strategy in the recognition of particular substrates. Further characterization of PAK and other cdk5 substrates will hopefully shed light on the mechanisms involved in regulation of spine formation in the sensitization behavioural process by psychostimulants.