RESUMEN
Repeat associated non-AUG (RAN) translation is found in a growing number of microsatellite expansion diseases, but the mechanisms remain unclear. We show that RAN translation is highly regulated by the double-stranded RNA-dependent protein kinase (PKR). In cells, structured CAG, CCUG, CAGG, and G4C2 expansion RNAs activate PKR, which leads to increased levels of multiple RAN proteins. Blocking PKR using PKR-K296R, the TAR RNA binding protein or PKR-KO cells, reduces RAN protein levels. p-PKR is elevated in C9orf72 ALS/FTD human and mouse brains, and inhibiting PKR in C9orf72 BAC transgenic mice using AAV-PKR-K296R or the Food and Drug Administration (FDA)-approved drug metformin, decreases RAN proteins, and improves behavior and pathology. In summary, targeting PKR, including by use of metformin, is a promising therapeutic approach for C9orf72 ALS/FTD and other expansion diseases.
Asunto(s)
Esclerosis Amiotrófica Lateral/metabolismo , Proteína C9orf72 , Metformina/farmacología , Biosíntesis de Proteínas/efectos de los fármacos , eIF-2 Quinasa , Animales , Encéfalo/metabolismo , Encéfalo/patología , Proteína C9orf72/genética , Proteína C9orf72/metabolismo , Modelos Animales de Enfermedad , Demencia Frontotemporal/metabolismo , Humanos , Ratones , Ratones Transgénicos , Repeticiones de Microsatélite/genética , eIF-2 Quinasa/genética , eIF-2 Quinasa/metabolismoRESUMEN
Most of the modulating effects of cannabinoids on pain are through putative cannabinoid CB1 and CB2 receptors. However, the involvement of other receptors is also suggested. Cannabinoid compounds with analgesic activity such as palmitoylethanolamide (PEA) show low affinity to CB1 and CB2 receptors, yet selectively activate GPR55 receptors. The objective of the present study was to evaluate the possible role of spinal CB1 and GPR55 receptors on antinociceptive activity of PEA in formalin test as well as in the spinal expression of IL1-ß in rat. Intrathecal (i.t.) administration of PEA (1, 10 µg) significantly decreased both pain-related scores in formalin test and IL1-ß expression in rat spinal cord. Pretreatment of rats with low doses of CB1 receptor antagonist/GPR55 receptor agonist AM251 (10, 100 ng; i.t.), did not attenuated the effect of PEA, yet even significantly increased the effect of PEA on IL1-ß expression in rat spinal cord. Interestingly, i.t. administration of low doses of AM251 per se significantly decreased both pain related behavior and spinal IL1-ß expression in formalin test. These findings suggest the possible involvement of receptors other than CB1 receptors in spinal pain pathways, such as GPR55, in pain modulating activity of cannabinoids.