title: Tissue kallikrein protects neurons from hypoxia/reoxygenation-induced cell injury through Homer1b/c.
abstract: Previous studies have demonstrated that human tissue kallikrein (TK) gene delivery protects against mouse cerebral ischemia/reperfusion (I/R) injury through bradykinin B2 receptor (B2R) activation. We have also reported that exogenous TK administration can suppress glutamate- or acidosis-induced neurotoxicity through the extracellular signal-regulated kinase1/2 (ERK1/2) pathway. To further explore the neuroprotection mechanisms of TK, in the present study we performed immunoprecipitation analysis and identified a scaffolding protein Homer1b/c using MALDI-TOF MS analysis. Here, we tested the hypothesis that TK reduces cell injury induced by oxygen and glucose deprivation/reoxygenation (OGD/R) through activating Homer1b/c. We found that TK increased the expression of Homer1b/c in a concentration- and time-dependent manner. Moreover, TK facilitated the translocation of Homer1b/c to the plasma membrane under OGD/R condition by confocal microscope assays. We also observed that overexpression of Homer1b/c showed the neuroprotection against OGD/R-induced cell injury by enhancing cell survival, reducing LDH release, caspase-3 activity and cell apoptosis. However, the knockdown of Homer1b/c by small interfering RNA showed the opposite effects, indicating that Homer1b/c had protective effects against OGD/R-induced neuronal injury. More interestingly, TK exerted its much more significantly neuroprotective effects after Homer1b/c overexpression, whereas it exerted its reduced effects after Homer1b/c knockdown. In addition, TK pretreatment increased the phosphorylation of the ERK1/2 and Akt-GSK3β through Homer1b/c activation. The beneficial effects of Homer1b/c were abolished by the ERK1/2 or PI3K antagonist. Therefore, we propose novel signaling mechanisms involved in the anti-hypoxic function of TK through activation of Homer1b/c-ERK1/2 and Homer1b/c-PI3K-Akt signaling pathways.
authors.affiliation: Department of Neurology, Huashan Hospital, Fudan University, Shanghai 200040, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Su
authors.forename: Yuping
authors.initials: Y
authors.lastname: Tang
authors.forename: Houguang
authors.initials: H
authors.lastname: Zhou
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Dong
mesh_terms: D017209:Apoptosis; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D000072233:Homer Scaffolding Proteins; D006801:Humans; D047468:Immunoprecipitation; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020840:Tissue Kallikreins / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D002352:Carrier Proteins; D005419:Flavonoids; D000072233:Homer Scaffolding Proteins; D034741:RNA, Small Interfering; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D038362:Glycogen Synthase Kinase 3; D020840:Tissue Kallikreins; D053148:Caspase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one