title: Upregulation of the GEF-H1 pathway after transient cerebral ischemia.
abstract: The microtubule-dependent GEF-H1 pathway controls synaptic re-networking and overall gene expression via regulating cytoskeleton dynamics. Understanding this pathway after ischemia is essential to developing new therapies for neuronal function recovery. However, how the GEF-H1 pathway is regulated following transient cerebral ischemia remains unknown. This study employed a rat model of transient forebrain ischemia to investigate alterations of the GEF-H1 pathway using Western blotting, confocal and electron microscopy, dephosphorylation analysis, and pull-down assay. The GEF-H1 activity was significantly upregulated by: (i) dephosphorylation and (ii) translocation to synaptic membrane and nuclear structures during the early phase of reperfusion. GEF-H1 protein was then downregulated in the brain regions where neurons were destined to undergo delayed neuronal death, but markedly upregulated in neurons that were resistant to the same episode of cerebral ischemia. Consistently, GTP-RhoA, a GEF-H1 substrate, was significantly upregulated after brain ischemia. Electron microscopy further showed that neuronal microtubules were persistently depolymerized in the brain region where GEF-H1 protein was downregulated after brain ischemia. The results demonstrate that the GEF-H1 activity is significantly upregulated in both vulnerable and resistant brain regions in the early phase of reperfusion. However, GEF-H1 protein is downregulated in the vulnerable neurons but upregulated in the ischemic resistant neurons during the recovery phase after ischemia. The initial upregulation of GEF-H1 activity may contribute to excitotoxicity, whereas the late upregulation of GEF-H1 protein may promote neuroplasticity after brain ischemia.
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Neurology, The First Teaching Hospital, Jilin University, Changchun, China.
authors.forename: Tianfei
authors.initials: T
authors.lastname: Luo
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Philip
authors.initials: P
authors.lastname: Roman
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Chunli
authors.initials: C
authors.lastname: Liu
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States; Department of Neurology, The First Teaching Hospital, Jilin University, Changchun, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Sun
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States.
authors.forename: Yujung
authors.initials: Y
authors.lastname: Park
authors.affiliation: Neurochemistry Laboratory of Brain Injury, Shock Trauma & Anesthesiology Research Center, University of Maryland School of Medicine, Baltimore, MD 21201, United States. Electronic address: bhu@anes.umm.edu.
authors.forename: Bingren
authors.initials: B
authors.lastname: Hu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis*; D002546:Ischemic Attack, Transient / Q000378:metabolism*; D008297:Male; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D009473:Neuronal Plasticity / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation
chemical_list: D020662:Guanine Nucleotide Exchange Factors
keywords: Brain ischemia; Cytoskeletal dynamics; GEF-H1; Gene expression; RhoA; Synaptic plasticity