title: Granzyme B-induced neurotoxicity is mediated via activation of PAR-1 receptor and Kv1.3 channel.
abstract: Increasing evidence supports a critical role of T cells in neurodegeneration associated with acute and subacute brain inflammatory disorders. Granzyme B (GrB), released by activated T cells, is a cytotoxic proteinase which may induce perforin-independent neurotoxicity. Here, we studied the mechanism of perforin-independent GrB toxicity by treating primary cultured human neuronal cells with recombinant GrB. GrBactivated the protease-activated receptor (PAR)-1 receptor on the neuronal cell surface leading to decreased intracellular cyclic AMP levels. This was followed by increased expression and translocation of the voltage gated potassium channel, Kv1.3 to the neuronal cell membrane. Similar expression of Kv1.3 was also seen in neurons of the cerebral cortex adjacent to active inflammatory lesions in patients with multiple sclerosis. Kv1.3 expression was followed by activation of Notch-1 resulting in neurotoxicity. Blocking PAR-1, Kv1.3 or Notch-1 activation using specific pharmacological inhibitors or siRNAs prevented GrB-induced neurotoxicity. Furthermore, clofazimine protected against GrB-induced neurotoxicity in rat hippocampus, in vivo. These observations indicate that GrB released from T cells induced neurotoxicity by interacting with the membrane bound Gi-coupled PAR-1 receptor and subsequently activated Kv1.3 and Notch-1. These pathways provide novel targets to treat T cell-mediated neuroinflammatory disorders. Kv1.3 is of particular interest since it is expressed on the cell surface, only under pathological circumstances, and early in the cascade of events making it an attractive therapeutic target.
authors.affiliation: Section of Infections of Nervous System, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Tongguang
authors.initials: T
authors.lastname: Wang
authors.forename: Myoung-Hwa
authors.initials: MH
authors.lastname: Lee
authors.forename: Elliot
authors.initials: E
authors.lastname: Choi
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Pardo-Villamizar
authors.forename: Sung Bin
authors.initials: SB
authors.lastname: Lee
authors.forename: In Hong
authors.initials: IH
authors.lastname: Yang
authors.forename: Peter A
authors.initials: PA
authors.lastname: Calabresi
authors.forename: Avindra
authors.initials: A
authors.lastname: Nath
mesh_terms: D000818:Animals; D002452:Cell Count; D002991:Clofazimine / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D053804:Granzymes / Q000633:toxicity*; D006801:Humans; D051664:Kv1.3 Potassium Channel / Q000378:metabolism*; D009103:Multiple Sclerosis / Q000378:metabolism / Q000473:pathology; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009498:Neurotoxins / Q000633:toxicity*; D059748:Proteolysis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D051881:Receptor, Notch1 / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000378:metabolism*
chemical_list: D051664:Kv1.3 Potassium Channel; C497761:NOTCH1 protein, human; D009498:Neurotoxins; D051881:Receptor, Notch1; D044463:Receptor, PAR-1; D002991:Clofazimine; D053804:Granzymes