title: Synaptic scaffolding protein Homer1a protects against chronic inflammatory pain.
abstract: Glutamatergic signaling and intracellular calcium mobilization in the spinal cord are crucial for the development of nociceptive plasticity, which is associated with chronic pathological pain. Long-form Homer proteins anchor glutamatergic receptors to sources of calcium influx and release at synapses, which is antagonized by the short, activity-dependent splice variant Homer1a. We show here that Homer1a operates in a negative feedback loop to regulate the excitability of the pain pathway in an activity-dependent manner. Homer1a is rapidly and selectively upregulated in spinal cord neurons after peripheral inflammation in an NMDA receptor-dependent manner. Homer1a strongly attenuates calcium mobilization as well as MAP kinase activation induced by glutamate receptors and reduces synaptic contacts on spinal cord neurons that process pain inputs. Preventing activity-induced upregulation of Homer1a using shRNAs in mice in vivo exacerbates inflammatory pain. Thus, activity-dependent uncoupling of glutamate receptors from intracellular signaling mediators is a novel, endogenous physiological mechanism for counteracting sensitization at the first, crucial synapse in the pain pathway. Furthermore, we observed that targeted gene transfer of Homer1a to specific spinal segments in vivo reduces inflammatory hyperalgesia. Thus, Homer1 function is crucially involved in pain plasticity and constitutes a promising therapeutic target for the treatment of chronic inflammatory pain.
authors.affiliation: Pharmacology Institute, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Tappe
authors.forename: Matthias
authors.initials: M
authors.lastname: Klugmann
authors.forename: Ceng
authors.initials: C
authors.lastname: Luo
authors.forename: David
authors.initials: D
authors.lastname: Hirlinger
authors.forename: Nitin
authors.initials: N
authors.lastname: Agarwal
authors.forename: Justus
authors.initials: J
authors.lastname: Benrath
authors.forename: Markus U
authors.initials: MU
authors.lastname: Ehrengruber
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: During
authors.forename: Rohini
authors.initials: R
authors.lastname: Kuner
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002908:Chronic Disease; D000229:Dependovirus / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D025461:Feedback, Physiological; D000072233:Homer Scaffolding Proteins; D007249:Inflammation / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D010146:Pain / Q000378:metabolism* / Q000503:physiopathology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D002352:Carrier Proteins; D000072233:Homer Scaffolding Proteins; C000606623:Homer1 protein, mouse; C000606624:Homer1 protein, rat; D020033:Protein Isoforms; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; D012313:RNA; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium