title: LTP induction translocates cortactin at distant synapses in wild-type but not Fmr1 knock-out mice.
abstract: Stabilization of long-term potentiation (LTP) depends on reorganization of the dendritic spine actin cytoskeleton. The present study tested whether this involves activity-driven effects on the actin-regulatory protein cortactin, and whether such effects are disturbed in the Fmr1 knock-out (KO) model of fragile X syndrome, in which stabilization of both actin filaments and LTP is impaired. LTP induced by theta burst stimulation (TBS) in hippocampal slices from wild-type mice was associated with rapid, broadly distributed, and NMDA receptor-dependent decreases in synapse-associated cortactin. The reduction in cortactin content was blocked by blebbistatin, while basal levels were reduced by nocodazole, indicating that cortactin's movements into and away from synapses are regulated by microtubule and actomyosin motors, respectively. These results further suggest that synapse-specific LTP influences cytoskeletal elements at distant connections. The rapid effects of TBS on synaptic cortactin content were absent in Fmr1 KOs as was evidence for activity-driven phosphorylation of the protein or its upstream kinase, ERK1/2. Phosphorylation regulates cortactin's interactions with actin, and coprecipitation of the two proteins was reduced in the KOs. We propose that, in the KOs, excessive basal phosphorylation of ERK1/2 disrupts its interactions with cortactin, thereby blocking the latter protein's use of actomyosin transport systems. These impairments are predicted to compromise the response of the subsynaptic cytoskeleton to learning-related afferent activity, both locally and at distant sites.
authors.affiliation: Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1275, USA.
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Seese
authors.forename: Alex H
authors.initials: AH
authors.lastname: Babayan
authors.forename: Adam M
authors.initials: AM
authors.lastname: Katz
authors.forename: Conor D
authors.initials: CD
authors.lastname: Cox
authors.forename: Julie C
authors.initials: JC
authors.lastname: Lauterborn
authors.forename: Gary
authors.initials: G
authors.lastname: Lynch
authors.forename: Christine M
authors.initials: CM
authors.lastname: Gall
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D051356:Cortactin / Q000378:metabolism*; D004558:Electric Stimulation / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics / Q000502:physiology*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000235:genetics / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D015739:Nocodazole / Q000494:pharmacology; D010766:Phosphorylation; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D013569:Synapses / Q000378:metabolism* / Q000502:physiology; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D000199:Actins; D051356:Cortactin; D004791:Enzyme Inhibitors; D051860:Fragile X Messenger Ribonucleoprotein 1; D006576:Heterocyclic Compounds, 4 or More Rings; D015739:Nocodazole; D050257:Tubulin Modulators; C497684:Fmr1 protein, mouse; C472645:blebbistatin