title: MMP-7 cleaves the NR1 NMDA receptor subunit and modifies NMDA receptor function.
abstract: Matrix metalloproteinases (MMPs) are zinc-dependent enzymes that play a role in the inflammatory response. These enzymes have been well studied in the context of cancer biology and inflammation. Recent studies, however, suggest that these enzymes also play roles in brain development and neurodegenerative disease. Select MMPs can target proteins critical to synaptic structure and neuronal survival, including integrins and cadherins. Here, we show that one member of the MMP family, MMP-7, which may be released from cells, including microglia, can target a protein critical to synaptic function. Through analysis of extracts from murine cortical slice preparations, we show that MMP-7 cleaves the NR1 subunit of the N-methyl-d-aspartate (NMDA) receptor to generate an N-terminal fragment of approximately 65 kDa. Moreover, studies with recombinant protein show that MMP-7-mediated cleavage of NR1 occurs at amino acid 517, which is extracellular and just distal to the first transmembrane domain. Data suggest that NR2A, which shares sequence homology with NR1, is also cleaved following treatment of slices with MMP-7, while select AMPA receptor subunits are not. Consistent with a potential effect of MMP-7 on ligand binding, additional experiments demonstrate that NMDA-mediated calcium flux is significantly diminished by MMP-7 pretreatment of cultures. In addition, the AMPA/NMDA ratio is increased by MMP-7 pretreatment. These data suggest that synaptic function may be altered in neurological conditions associated with increased levels of MMP-7.
authors.affiliation: Johns Hopkins University, Department of Neurology, Pathology Bldg. Rm. 625, 600 N. Wolfe St., Baltimore, MD 21287, USA.
authors.forename: Arek
authors.initials: A
authors.lastname: Szklarczyk
authors.forename: Osefame
authors.initials: O
authors.lastname: Ewaleifoh
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Beique
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: David
authors.initials: D
authors.lastname: Knorr
authors.forename: Norman
authors.initials: N
authors.lastname: Haughey
authors.forename: Tanya
authors.initials: T
authors.lastname: Malpica
authors.forename: Mark P
authors.initials: MP
authors.lastname: Mattson
authors.forename: Richard
authors.initials: R
authors.lastname: Huganir
authors.forename: Katherine
authors.initials: K
authors.lastname: Conant
mesh_terms: D000818:Animals; D001923:Brain Chemistry / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D006801:Humans; D007249:Inflammation / Q000201:enzymology; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000201:enzymology*; D009369:Neoplasms / Q000201:enzymology; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: C409466:NR1 NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D011994:Recombinant Proteins; C060932:MMP7 protein, human; D020783:Matrix Metalloproteinase 7