title: Presynaptically localized cyclic GMP-dependent protein kinase 1 is a key determinant of spinal synaptic potentiation and pain hypersensitivity.
abstract: Synaptic long-term potentiation (LTP) at spinal neurons directly communicating pain-specific inputs from the periphery to the brain has been proposed to serve as a trigger for pain hypersensitivity in pathological states. Previous studies have functionally implicated the NMDA receptor-NO pathway and the downstream second messenger, cGMP, in these processes. Because cGMP can broadly influence diverse ion-channels, kinases, and phosphodiesterases, pre- as well as post-synaptically, the precise identity of cGMP targets mediating spinal LTP, their mechanisms of action, and their locus in the spinal circuitry are still unclear. Here, we found that Protein Kinase G1 (PKG-I) localized presynaptically in nociceptor terminals plays an essential role in the expression of spinal LTP. Using the Cre-lox P system, we generated nociceptor-specific knockout mice lacking PKG-I specifically in presynaptic terminals of nociceptors in the spinal cord, but not in post-synaptic neurons or elsewhere (SNS-PKG-I(-/-) mice). Patch clamp recordings showed that activity-induced LTP at identified synapses between nociceptors and spinal neurons projecting to the periaqueductal grey (PAG) was completely abolished in SNS-PKG-I(-/-) mice, although basal synaptic transmission was not affected. Analyses of synaptic failure rates and paired-pulse ratios indicated a role for presynaptic PKG-I in regulating the probability of neurotransmitter release. Inositol 1,4,5-triphosphate receptor 1 and myosin light chain kinase were recruited as key phosphorylation targets of presynaptic PKG-I in nociceptive neurons. Finally, behavioural analyses in vivo showed marked defects in SNS-PKG-I(-/-) mice in several models of activity-induced nociceptive hypersensitivity, and pharmacological studies identified a clear contribution of PKG-I expressed in spinal terminals of nociceptors. Our results thus indicate that presynaptic mechanisms involving an increase in release probability from nociceptors are operational in the expression of synaptic LTP on spinal-PAG projection neurons and that PKG-I localized in presynaptic nociceptor terminals plays an essential role in this process to regulate pain sensitivity.
authors.affiliation: Pharmacology Institute, University of Heidelberg, Heidelberg, Germany. luoceng@fmmu.edu.cn
authors.forename: Ceng
authors.initials: C
authors.lastname: Luo
authors.forename: Vijayan
authors.initials: V
authors.lastname: Gangadharan
authors.forename: Kiran Kumar
authors.initials: KK
authors.lastname: Bali
authors.forename: Rou-Gang
authors.initials: RG
authors.lastname: Xie
authors.forename: Nitin
authors.initials: N
authors.lastname: Agarwal
authors.forename: Martina
authors.initials: M
authors.lastname: Kurejova
authors.forename: Anke
authors.initials: A
authors.lastname: Tappe-Theodor
authors.forename: Irmgard
authors.initials: I
authors.lastname: Tegeder
authors.forename: Susanne
authors.initials: S
authors.lastname: Feil
authors.forename: Gary
authors.initials: G
authors.lastname: Lewin
authors.forename: Erika
authors.initials: E
authors.lastname: Polgar
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Todd
authors.forename: Jens
authors.initials: J
authors.lastname: Schlossmann
authors.forename: Franz
authors.initials: F
authors.lastname: Hofmann
authors.forename: Da-Lu
authors.initials: DL
authors.lastname: Liu
authors.forename: San-Jue
authors.initials: SJ
authors.lastname: Hu
authors.forename: Robert
authors.initials: R
authors.lastname: Feil
authors.forename: Thomas
authors.initials: T
authors.lastname: Kuner
authors.forename: Rohini
authors.initials: R
authors.lastname: Kuner
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology; D017353:Gene Deletion; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism; D017774:Long-Term Potentiation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism / Q000473:pathology; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D010146:Pain / Q000378:metabolism / Q000473:pathology*; D018408:Patch-Clamp Techniques; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D013379:Substrate Specificity; D009435:Synaptic Transmission; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D000634:Aminoquinolines; D015815:Cell Adhesion Molecules; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; C041715:6-anilino-5,8-quinolinedione; D062965:Cyclic GMP-Dependent Protein Kinase Type I; D017869:Cyclic GMP-Dependent Protein Kinases; C569720:Prkg1 protein, mouse; D006162:Guanylate Cyclase