The role of PSD-95 and cypin in morphological changes in dendrites following sublethal NMDA exposure.
Focal swelling or varicosity formation in dendrites and loss of dendritic spines are the earliest indications of glutamate-induced excitotoxicity. Although it is known that microtubule dynamics play a role in varicosity formation, very little is known about the proteins that directly impact microtubules during focal swelling and dendritic spine loss. Our laboratory has recently reported that the postsynaptic protein PSD-95 and its cytosolic interactor (cypin) regulate the patterning of dendrites in hippocampal neurons. Cypin promotes microtubule assembly, and PSD-95 disrupts microtubule organization. Thus, we hypothesized that cypin and PSD-95 may play a role in altering dendrite morphology and spine number in response to sublethal NMDA-induced excitotoxicity. Using an in vitro model of glutamate-induced toxicity in rat hippocampal cultures, we found that cypin overexpression or PSD-95 knockdown increases the percentage of neurons with varicosities and the number of varicosities along dendrites, decreases the size of varicosities after sublethal NMDA exposure, and protects neurons from NMDA-induced death. In contrast, cypin knockdown or PSD-95 overexpression results in opposite effects. We further show that cypin regulates the density of spines/filopodia: cypin overexpression decreases the number of protrusions per micrometer of dendrite while cypin knockdown results in an opposite effect. Cypin overexpression and PSD-95 knockdown attenuate NMDA-promoted decreases in protrusion density. Thus, we have identified a novel pathway by which the microtubule cytoskeleton is regulated during sublethal changes to dendrites.
Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8082, USA.
Chia-Yi
CY
Tseng
Bonnie L
BL
Firestein
D000704:Analysis of Variance; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003712:Dendrites / Q000187:drug effects*; D000076122:Disks Large Homolog 4 Protein; D004622:Embryo, Mammalian; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006148:Guanine Deaminase / Q000235:genetics / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D015739:Nocodazole / Q000494:pharmacology; D017239:Paclitaxel / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012269:Ribosomal Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014404:Tubulin / Q000235:genetics / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology
D002352:Carrier Proteins; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D018690:Excitatory Amino Acid Agonists; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; C489787:MAP2 protein, rat; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D012269:Ribosomal Proteins; D014404:Tubulin; D050257:Tubulin Modulators; C049650:ribosomal protein L9; D049452:Green Fluorescent Proteins; C007293:DAPI; D016202:N-Methylaspartate; C485728:Gda protein, rat; D006148:Guanine Deaminase; D017239:Paclitaxel; D015739:Nocodazole