Matrix metalloproteinase activity stimulates N-cadherin shedding and the soluble N-cadherin ectodomain promotes classical microglial activation

Katherine Conant, Stefano Daniele, P. Lorenzo Bozzelli, Tsion Abdi, Amanda Edwards, Arek Szklarczyk, India Olchefske, David Ottenheimer, Kathleen Maguire-Zeiss

Research output: Contribution to journalArticle

Abstract

Background: 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. Methods: 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. Results: 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. Conclusions: 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.

LanguageEnglish (US)
Article number56
JournalJournal of Neuroinflammation
Volume14
Issue number1
DOIs
StatePublished - Mar 17 2017
Externally publishedYes

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Cadherins
Matrix Metalloproteinases
Cell Adhesion Molecules
Matrix Metalloproteinase 7
Proteolysis
Tumor Necrosis Factor-alpha
Myeloid Differentiation Factor 88
AIDS Dementia Complex
Aptitude
Toll-Like Receptors
Wounds and Injuries
Cell Surface Receptors
Enzymes
Myelin Sheath
Multiple Sclerosis
Axons
Cultured Cells
Depression
Cytokines
Membranes

Keywords

  • Matrix metalloproteinase
  • Microglia
  • MMP
  • MyD88
  • TLR
  • TNF
  • Toll-like receptor
  • Tumor necrosis factor

ASJC Scopus subject areas

  • Neuroscience(all)
  • Immunology
  • Neurology
  • Cellular and Molecular Neuroscience

Cite this

Matrix metalloproteinase activity stimulates N-cadherin shedding and the soluble N-cadherin ectodomain promotes classical microglial activation. / Conant, Katherine; Daniele, Stefano; Bozzelli, P. Lorenzo; Abdi, Tsion; Edwards, Amanda; Szklarczyk, Arek; Olchefske, India; Ottenheimer, David; Maguire-Zeiss, Kathleen.

In: Journal of Neuroinflammation, Vol. 14, No. 1, 56, 17.03.2017.

Research output: Contribution to journalArticle

Conant, Katherine ; Daniele, Stefano ; Bozzelli, P. Lorenzo ; Abdi, Tsion ; Edwards, Amanda ; Szklarczyk, Arek ; Olchefske, India ; Ottenheimer, David ; Maguire-Zeiss, Kathleen. / Matrix metalloproteinase activity stimulates N-cadherin shedding and the soluble N-cadherin ectodomain promotes classical microglial activation. In: Journal of Neuroinflammation. 2017 ; Vol. 14, No. 1.
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AU - Conant, Katherine

AU - Daniele, Stefano

AU - Bozzelli, P. Lorenzo

AU - Abdi, Tsion

AU - Edwards, Amanda

AU - Szklarczyk, Arek

AU - Olchefske, India

AU - Ottenheimer, David

AU - Maguire-Zeiss, Kathleen

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AB - Background: 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. Methods: 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. Results: 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. Conclusions: 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.

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