The long-term objective of this proposal is to understand mechanisms of visual system plasticity. Such knowledge may prove vital to the prevention of amblyopia and the loss of stereopsis as well as to the restoration of vision following trauma or stroke. Visual system synaptic plasticity involves the NMDA subtype of glutamate receptor (NR), which is scaffolded by proteins that also interact with other glutamate receptors. A recent hypothesis is that two distinct protein complexes, consisting of NRs with different subunit compositions, NRscaffolding proteins (MAGUKs), and signaling proteins, are trafficked differently in response to visual system activity and mediate distinct glutamate-induced changes at developing synapses: an early system carries NRs enriched in the NR2B subunit and associated trafficking and signaling molecules; in response to light and eye- opening (EO), this system is replaced by a scaffolding complex with a different trafficking system and carrying NR2A-enriched NRs. To test this hypothesis, the proposed experiments focus on the superficial visual layers of the superior colliculus, which allow electrophysiological studies of changes in glutamate receptor function and synaptic refinement as well as biochemical studies of changes in synaptic protein complexes that may underlie these physiological changes.
Specific Aim I is to use coimmunoprecipitation experiments to determine if the postulated receptor-MAGUK-trafficking complexes exist in vivo when they are proposed to act in synaptic competition and refinement.
Specific Aim II is to determine if specific responses to EO are tightly linked to high dendritic levels of PSD-95. PSD-95 is the MAGUK protein that scaffolds the mature NR complex and that translocates to synaptic regions in response to EO. Anatomical studies will determine if new currents induced by EO are a consequence of dendritic sprouting, which has been associated with PSD-95-bound proteins. Whole-cell patch-clamping will test for a tight correlation between dendritic PSD-95 and refinement by asking if refinement is lost once PSD-95 is reduced to pre-EO levels after eye re-closure.
Specific Aim III is to use NR2A knock-out and PSD-95 knockout mice to attempt to directly test the hypothesis that the PSD-95/NR complex is critical to synaptic refinement and to glutamate current changes that occur in response to EO.
Specific Aim I V is to construct a hybrid NR2B/NR2A NR subunit that will allow a determination of the extent to which the biological roles of PSD-95 depend on its ability to localize specific NRs at the synapse as opposed to its ability to stimulate PSD-95-mediated signal transduction.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY014074-10A2
Application #
6681801
Study Section
Visual Sciences B Study Section (VISB)
Program Officer
Oberdorfer, Michael
Project Start
1994-08-08
Project End
2007-06-30
Budget Start
2003-07-01
Budget End
2004-06-30
Support Year
10
Fiscal Year
2003
Total Cost
$360,000
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
001425594
City
Cambridge
State
MA
Country
United States
Zip Code
02139
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Klapoetke, Nathan C; Murata, Yasunobu; Kim, Sung Soo et al. (2014) Independent optical excitation of distinct neural populations. Nat Methods 11:338-46
Bustos, Fernando J; Varela-Nallar, Lorena; Campos, Matias et al. (2014) PSD95 suppresses dendritic arbor development in mature hippocampal neurons by occluding the clustering of NR2B-NMDA receptors. PLoS One 9:e94037
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Zhao, Jian-Ping; Murata, Yasunobu; Constantine-Paton, Martha (2013) Eye opening and PSD95 are required for long-term potentiation in developing superior colliculus. Proc Natl Acad Sci U S A 110:707-12
Murata, Yasunobu; Constantine-Paton, Martha (2013) Postsynaptic density scaffold SAP102 regulates cortical synapse development through EphB and PAK signaling pathway. J Neurosci 33:5040-52
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Yoshii, Akira; Murata, Yasunobu; Kim, Jihye et al. (2011) TrkB and protein kinase M? regulate synaptic localization of PSD-95 in developing cortex. J Neurosci 31:11894-904
Yoshii, Akira; Constantine-Paton, Martha (2010) Postsynaptic BDNF-TrkB signaling in synapse maturation, plasticity, and disease. Dev Neurobiol 70:304-22
van Zundert, Brigitte; Zhao, Jiang-Ping; Constantine-Paton, Martha (2010) Synaptic drive at developing synapses: transient upregulation of kainate receptors. Dev Neurobiol 70:737-50

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