Glutamate is the predominant rapid excitatory neurotransmitter in the mammalian CNS and is involved in several forms of plasticity in the developing and adult nervous system. Excessive activation of glutamate receptors contributes to brain damage observed in acute insults to the CNS, including ischemia and head trauma. The extracellular concentrations of glutamate are controlled by a family of sodium-dependent transporters. We and others have found that the activity of one of these transporters, called EAAC1, can be rapidly increased by either activation of protein kinase C (PKC) or the platelet-derived growth factor receptor. These affects are associated with a redistribution of EAAC1 from a subcellular compartment to the cell surface and are independent of synthesis of new transporters. Based on our preliminary studies, we would like to pursue the following four specific aims: 1) We propose to examine the signaling molecules that are required for the PDGF-dependent redistribution of EAAC1. 2) We have recently found that EAAC1 constitutively recycles between the plasma membrane and intracellular compartments with a half-life of approximately 5-7 min. We propose to determine if EAAC1 is internalized by a caveolin-dependent endocytosis pathway and begin to identify the subcellular compartments used for recycling of EAAC1. 3) We have found that EAAC1 forms complexes with protein interacting with C kinase (PICK1) and the alpha subtype of PKC. We propose to identify domains required for these interactions and to determine how these interactions affect EAAC1 trafficking. 4) The mechanisms that regulate EAAC1 trafficking and one of the glutamate receptors appear to be quite similar, and a signal that increases EAAC1 decreases GluR2. We propose to use a variety of approaches to determine if EAAC1 and ionotropic glutamate receptors are regulated in this apparently complementary fashion using other approaches to chemically induce either long term depression (LTD) or long term potentiation (LTP). We are intrigued by this regulation because EAAC1 is enriched in areas where synaptic transmission is highly plastic and in neurons that are exquisitely sensitive to excitotoxic insults. EAAC1 is localized on the post-synaptic membrane and is perisynaptic surrounding GluRs where it is ideally situated to fine-tune synaptic transmission. We suspect that understanding the regulation of EAAC1 could have implications for understanding glutamate toxicity and/or synaptic plasticity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS039011-08
Application #
7367901
Study Section
Special Emphasis Panel (ZRG1-MDCN-A (05))
Program Officer
Silberberg, Shai D
Project Start
1999-05-15
Project End
2010-02-28
Budget Start
2008-03-01
Budget End
2010-02-28
Support Year
8
Fiscal Year
2008
Total Cost
$327,585
Indirect Cost
Name
Children's Hospital of Philadelphia
Department
Type
DUNS #
073757627
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Gonzalez, Marco I; Krizman-Genda, Elizabeth; Robinson, Michael B (2007) Caveolin-1 regulates the delivery and endocytosis of the glutamate transporter, excitatory amino acid carrier 1. J Biol Chem 282:29855-65
Sheldon, Amanda L; Robinson, Michael B (2007) The role of glutamate transporters in neurodegenerative diseases and potential opportunities for intervention. Neurochem Int 51:333-55
Waxman, Elisa A; Baconguis, Isabelle; Lynch, David R et al. (2007) N-methyl-D-aspartate receptor-dependent regulation of the glutamate transporter excitatory amino acid carrier 1. J Biol Chem 282:17594-607
Fournier, Keith M; Robinson, Michael B (2006) A dominant-negative variant of SNAP-23 decreases the cell surface expression of the neuronal glutamate transporter EAAC1 by slowing constitutive delivery. Neurochem Int 48:596-603
Sheldon, Amanda L; Gonzalez, Marco I; Robinson, Michael B (2006) A carboxyl-terminal determinant of the neuronal glutamate transporter, EAAC1, is required for platelet-derived growth factor-dependent trafficking. J Biol Chem 281:4876-86
Krizman-Genda, Elizabeth; Gonzalez, Marco I; Zelenaia, Olga et al. (2005) Evidence that Akt mediates platelet-derived growth factor-dependent increases in activity and surface expression of the neuronal glutamate transporter, EAAC1. Neuropharmacology 49:872-82
Gonzalez, Marco I; Robinson, Michael B (2004) Protein kinase C-dependent remodeling of glutamate transporter function. Mol Interv 4:48-58
Kalandadze, Avtandil; Wu, Ying; Fournier, Keith et al. (2004) Identification of motifs involved in endoplasmic reticulum retention-forward trafficking of the GLT-1 subtype of glutamate transporter. J Neurosci 24:5183-92
Gonzalez, Marco I; Robinson, Michael B (2004) Neurotransmitter transporters: why dance with so many partners? Curr Opin Pharmacol 4:30-5
Fournier, Keith M; Gonzalez, Marco I; Robinson, Michael B (2004) Rapid trafficking of the neuronal glutamate transporter, EAAC1: evidence for distinct trafficking pathways differentially regulated by protein kinase C and platelet-derived growth factor. J Biol Chem 279:34505-13

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