In vivo roles for matrix metalloproteinase-9 in mature hippocampal synaptic physiology and plasticity.
Extracellular proteolysis is an important regulatory nexus for coordinating synaptic functional and structural plasticity, but the identity of such proteases is incompletely understood. Matrix metalloproteinases (MMPs) have well-known, mostly deleterious roles in remodeling after injury or stroke, but their role in nonpathological synaptic plasticity and function in intact adult brains has not been extensively investigated. Here we address the role of MMP-9 in hippocampal synaptic plasticity using both gain- and loss-of-function approaches in urethane-anesthetized adult rats. Acute blockade of MMP-9 proteolytic activity with inhibitors or neutralizing antibodies impairs maintenance, but not induction, of long-term potentiation (LTP) at synapses formed between Schaffer-collaterals and area CA1 dendrites. LTP is associated with significant increases in levels of MMP-9 and proteolytic activity within the potentiated neuropil. By introducing a novel application of gelatin-substrate zymography in vivo, we find that LTP is associated with significantly elevated numbers of gelatinolytic puncta in the potentiated neuropil that codistribute with immunolabeling for MMP-9 and for markers of synapses and dendrites. Such increases in proteolytic activity require NMDA receptor activation. Exposing intact area CA1 neurons to recombinant-active MMP-9 induces a slow synaptic potentiation that mutually occludes, and is occluded by, tetanically evoked potentiation. Taken together, our data reveal novel roles for MMP-mediated proteolysis in regulating nonpathological synaptic function and plasticity in mature hippocampus.
Bozdagi
Ozlem
O
Fishberg Dept of Neuroscience, The Mount Sinai School of Medicine, New York, NY 10029-6574, USA.
Nagy
Vanja
V
Kwei
Kimberly T
KT
Huntley
George W
GW
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology*; D007074:Immunoglobulin G / Q000494:pharmacology; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000276:immunology / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
D004791:Enzyme Inhibitors; D005904:Glial Fibrillary Acidic Protein; D007074:Immunoglobulin G; C489787:MAP2 protein, rat; D061965:Matrix Metalloproteinase Inhibitors; D008869:Microtubule-Associated Proteins; C493475:Slc17a6 protein, rat; D050599:Vesicular Glutamate Transport Protein 2; D020780:Matrix Metalloproteinase 9