Cathepsin B-like proteolysis and MARCKS degradation in sub-lethal NMDA-induced collapse of dendritic spines.
Sub-lethal excitotoxic injury to dendrites can elicit loss or shrinkage of dendritic spines. Here, we used a cell culture model of sub-lethal NMDA-induced injury to investigate a role for proteolysis in spine collapse. Transient incubation with NMDA-induced spine collapse and spine F-actin loss within 10 min, an effect not mimicked by the actin assembly inhibitor latrunculin A. NMDA-induced spine collapse was significantly attenuated by preincubation with broad-spectrum cysteine protease inhibitors. Results obtained using several class-specific protease inhibitors suggested that this protective effect was due to specific blockade of cathepsin B/L type protease activity, since selective inhibitors of only these proteases significantly attenuated spine loss. Cathepsin B-like immunoreactivity was observed at synaptic sites, but lysosomes were not. Immunoblot analysis showed that MARCKS (myristoylated-alanine-rich C-kinase substrate), a known substrate of cathepsin B, was specifically degraded in response to intense NMDA receptor stimulation. This effect was blocked by preincubation with a cathepsin B-selective inhibitor. Together these data suggest a model in which NMDA-induced spine collapse involves cathepsin B-like proteolysis of MARCKS, and possibly other proteins that regulate the actin-based cytoskeleton.
Department of Cell Biology and Institute for Childhood and Neurological Diseases, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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Graber
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Maiti
Shelley
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Halpain
D000818:Animals; D002401:Cathepsin B / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D003712:Dendrites / Q000187:drug effects / Q000473:pathology*; D005434:Flow Cytometry; D006624:Hippocampus / Q000166:cytology / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D016202:N-Methylaspartate / Q000633:toxicity*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats
D047908:Intracellular Signaling Peptides and Proteins; C000619712:Marcks protein, rat; D008565:Membrane Proteins; D011480:Protease Inhibitors; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D016202:N-Methylaspartate; D002401:Cathepsin B