title: Crosstalk between cdk5 and MEK-ERK signalling upon opioid receptor stimulation leads to upregulation of activator p25 and MEK1 inhibition in rat brain.
abstract: Cyclin-dependent kinase 5 (cdk5) participates in opioid receptor signalling through complex molecular mechanisms. The acute effects of selective μ-(fentanyl) and δ-(SNC-80) opioid receptor agonists, as well as the chronic effects of morphine (the prototypic opiate agonist mainly acting at μ-receptors), modulating cdk5 and activators p35/p25 and their interactions with neurotoxic/apoptotic factors, dopamine- and cAMP-regulated phosphoprotein of 32kDa (DARPP-32) and extracellular signal-regulated kinase (ERK) were quantified (Western Blot analyses) in the rat corpus striatum and/or cerebral cortex. To assess the involved mechanisms, MDL28170 was used to inhibit calpain activity and SL327 to disrupt MEK (ERK kinase)-ERK activation. Acute fentanyl (0.1mg/kg) and SNC-80 (10mg/kg) induced rapid (7-60 min) 2- to 4-fold increases of p25 content, without induction of cdk5/p25 pro-apoptotic c-Jun NH(2)-terminal protein kinase or aberrant cleavage of poly(ADP-ribose)-polymerase-1, a hallmark of apoptosis. In contrast, fentanyl and SNC-80 stimulated cdk5-mediated p-Thr75 DARPP-32 (+116-166%; PKA inhibition) and p-Thr286 MEK1 (+21-82%; MEK inactivation), and this latter effect resulted in uncoupling of MEK to ERK signals. Calpain inhibition with MDL28170 (cleavage of p35 to p25) attenuated fentanyl-induced p25 accumulation (-57%), but not the stimulation of p-Thr286 MEK1 or p-Thr75 DARPP-32. MEK-ERK inhibition with SL327 fully prevented fentanyl-induced p25 upregulation. Notably, chronic morphine treatment (10-100mg/kg for 6 days) also increased p25 content and p25/p35 ratio (and activated/inactivated MEK1) in rat brain cortex, which indicated that p25 upregulation persisted under the sustained stimulation of μ-opioid receptors. The results demonstrate that the acute stimulation of opioid receptors leads to upregulation of p25 activator through a MEK-ERK and calpain-dependent pathway, and to disruption of MEK-ERK signalling by a cdk5/p35-induced MEK1 inhibition. Moreover, the effects induced by the sustained stimulation of μ-receptors with morphine suggest the participation of cdk5/p25 complex in opiate-induced long-term neuroplasticity.
authors.affiliation: Laboratori de Neurofarmacologia, Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Universitat de les Illes Balears (UIB) and Redes Temáticas de Investigación Cooperativa en Salud-Red de Trastornos Adictivos (RETICS-RTA), Cra. Valldemossa km 7.5, E-07122 Palma de Mallorca, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ramos-Miguel
authors.forename: J A
authors.initials: JA
authors.lastname: García-Sevilla
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005283:Fentanyl / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D010770:Phosphotransferases / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: D001549:Benzamides; C492235:Cdk5r1 protein, rat; D004791:Enzyme Inhibitors; D009292:Narcotic Antagonists; D009294:Narcotics; D010879:Piperazines; D011957:Receptors, Opioid; C088464:4-(alpha-(4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl)-N,N-diethylbenzamide; D009270:Naloxone; C499322:Parp1 protein, rat; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D010770:Phosphotransferases; D051360:Cyclin-Dependent Kinase 5; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; D005283:Fentanyl