title: Matrix metalloproteinase activity stimulates N-cadherin shedding and the soluble N-cadherin ectodomain promotes classical microglial activation.
abstract: Matrix metalloproteinases (MMPs) are a family of enzymes that are typically released from intracellular stores to act on specific extracellular substrates. MMP expression and activity can be increased in a neuronal activity-dependent manner, and further increased in response to tissue injury. MMP substrates include cell adhesion molecules (CAMs) that are abundantly expressed in the brain and well positioned for membrane proximal cleavage. Importantly, CAM integrity is important to synaptic structure and axon-myelin interactions, and shed ectodomains may themselves influence cellular function.
  
  
  
  In the present study, we have examined proteolysis of N-cadherin (N-cdh) by MMP-7, a family member that has been implicated in disorders including HIV dementia, multiple sclerosis, and major depression. With in vitro digest assays, we tested N-cdh cleavage by increasing concentrations of recombinant enzyme. We also tested MMP-7 for its potential to stimulate N-cdh shedding from cultured neural cells. Since select CAM ectodomains may interact with cell surface receptors that are expressed on microglial cells, we subsequently tested the N-cdh ectodomain for its ability to stimulate activation of this cell type as determined by nuclear translocation of NF-κB, Iba-1 expression, and TNF-α release.
  
  
  
  We observed that soluble N-cdh increased Iba-1 levels in microglial lysates, and also increased microglial release of the cytokine TNF-α. Effects were associated with increased NF-κB immunoreactivity in microglial nuclei and diminished by an inhibitor of the toll-like receptor adaptor protein, MyD88.
  
  
  
  Together, these in vitro results suggest that soluble N-cdh may represent a novel effector of microglial activation, and that disorders with increased MMP levels may stimulate a cycle in which the products of excess proteolysis further exacerbate microglial-mediated tissue injury. Additional in vivo studies are warranted to address this issue.
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA. kec84@georgetown.edu.
authors.forename: Katherine
authors.initials: K
authors.lastname: Conant
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Daniele
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: P Lorenzo
authors.initials: PL
authors.lastname: Bozzelli
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: Tsion
authors.initials: T
authors.lastname: Abdi
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Edwards
authors.affiliation: Jagiellonian Center of Innovation, Krakow, Poland.
authors.forename: Arek
authors.initials: A
authors.lastname: Szklarczyk
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: India
authors.initials: I
authors.lastname: Olchefske
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA.
authors.forename: David
authors.initials: D
authors.lastname: Ottenheimer
authors.affiliation: Department of Neuroscience, Georgetown University School of Medicine, Washington, D.C., USA. Kathleen.maguirezeiss@georgetown.edu.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Maguire-Zeiss
mesh_terms: D000072197:ADAM10 Protein / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D015820:Cadherins / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C491049:Aif1 protein, mouse; D015820:Cadherins; D002135:Calcium-Binding Proteins; C489083:Cdh2 protein, mouse; D008840:Microfilament Proteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D009842:Oligopeptides; D010975:Platelet Aggregation Inhibitors; C046617:arginyl-glycyl-aspartyl-serine; D020782:Matrix Metalloproteinases; D000072197:ADAM10 Protein
keywords: MMP; Matrix metalloproteinase; Microglia; MyD88; TLR; TNF; Toll-like receptor; Tumor necrosis factor