title: The serine protease inhibitor TLCK attenuates intrinsic death pathways in neurons upstream of mitochondrial demise.
abstract: It is well-established that activation of proteases, such as caspases, calpains and cathepsins are essential components in signaling pathways of programmed cell death (PCD). Although these proteases have also been linked to mechanisms of neuronal cell death, they are dispensable in paradigms of intrinsic death pathways, e.g. induced by oxidative stress. However, emerging evidence implicated a particular role for serine proteases in mechanisms of PCD in neurons. Here, we investigated the role of trypsin-like serine proteases in a model of glutamate toxicity in HT-22 cells. In these cells glutamate induces oxytosis, a form of caspase-independent cell death that involves activation of the pro-apoptotic protein BH3 interacting-domain death agonist (Bid), leading to mitochondrial demise and ensuing cell death. In this model system, the trypsin-like serine protease inhibitor Nα-tosyl-l-lysine chloromethyl ketone hydrochloride (TLCK) inhibited mitochondrial damage and cell death. Mitochondrial morphology alterations, the impairment of the mitochondrial membrane potential and ATP depletion were prevented and, moreover, lipid peroxidation induced by glutamate was completely abolished. Strikingly, truncated Bid-induced cell death was not affected by TLCK, suggesting a detrimental activity of serine proteases upstream of Bid activation and mitochondrial demise. In summary, this study demonstrates the protective effect of serine protease inhibition by TLCK against oxytosis-induced mitochondrial damage and cell death. These findings indicate that TLCK-sensitive serine proteases play a crucial role in cell death mechanisms upstream of mitochondrial demise and thus, may serve as therapeutic targets in diseases, where oxidative stress and intrinsic pathways of PCD mediate neuronal cell death.
authors.affiliation: Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, Karl-von-Frisch-Straße 1, 35032, Marburg, Germany, christina.reuther@med.uni-muenchen.de.
authors.forename: C
authors.initials: C
authors.lastname: Reuther
authors.forename: G K
authors.initials: GK
authors.lastname: Ganjam
authors.forename: A M
authors.initials: AM
authors.lastname: Dolga
authors.forename: C
authors.initials: C
authors.lastname: Culmsee
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D015398:Signal Transduction; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology*; D014108:Tosylphenylalanyl Chloromethyl Ketone / Q000494:pharmacology
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D015842:Serine Proteinase Inhibitors; D014107:Tosyllysine Chloromethyl Ketone; D018698:Glutamic Acid; D014108:Tosylphenylalanyl Chloromethyl Ketone