At the postsynaptic density (PSD) of neuronal excitatory synapses, AMPA (AMPAR) and NMDA (NMDAR) glutamate receptors are linked to signaling proteins and the actin cytoskeleton in dendritic spines through a network of scaffolding proteins that play important roles during synaptic plasticity underlying learning and memory. AMPARs are recruited to dendritic spines through NMDAR activation during induction of long term potentiation (LTP) in hippocampal neurons through pathways that also increase spine size and actin polymerization. Phosphorylation of AMPAR-GluR1 subunits by the cAMP-dependent protein kinase (PKA) may promote surface expression of AMPARs recruited during LTP. In contrast, induction of long-term depression (LTD) leads to calcineurin-protein phosphatase 2B (CaN) mediated dephosphorylation of PKA phosphorylated GluR1, removal of AMPARs from synapses and depolymerization of spine actin followed by spine shrinkage. However, mechanisms for coordinately regulating AMPAR localization, phosphorylation, and spine structural plasticity are not well understood. A-kinase-anchoring protein (AKAP) 79/150 (human79/rodent150) is a PKA and CaN anchoring protein linked to NMDARs and AMPARs through PSD-95 and SAP97 membrane-associated guanylate kinase (MAGUK) scaffolds. AKAP79/150 is targeted to spines by an N-terminal basic region that binds phosphatidylinositol-4,5-bisphosphate (PIP2), F-actin, and cadherin adhesion molecules. Importantly, findings from the last funding period and recent preliminary studies indicate that AKAP79 is recruited to spines in LTP through palmitoylation of its targeting domain and that AKAP79 overexpression enhances dendritic spine size and AMPAR activity through MAGUK binding. In contrast, NMDAR-CaN signaling pathways implicated in AMPAR depression and spine shrinkage in LTD disrupt AKAP79/150 interactions with actin, MAGUKs and cadherins and lead to loss of the AKAP and anchored PKA from synapses. This AKAP79/150 translocation from spines depends on actin reorganization and phospholipase C (PLC) cleavage of PIP2, and preliminary studies suggest additional modulation by palmitoylation. Thus, AKAP79/150 is likely to play important structural and signaling roles in plasticity. Due to the complexity of PKA and CaN signaling in neurons and the multi-functionality of scaffold proteins such as AKAP79/150, it is a considerable challenge to understand the specific postsynaptic functions served by these proteins using simple pharmacologic, knock-out or RNAi approaches because these methods eliminate all functions at once. Thus, in this project we will pair RNAi knockdown with a mutant replacement approach in cultured rat neurons in addition to using a novel AKAP150 knock-in mutant mouse to probe the functions of specific AKAP79/150 membrane targeting motifs and protein-protein interactions in control of postsynaptic structure and function during induction of LTD and LTP. The hypotheses that we will be testing are that regulation of AKAP79/150 postsynaptic targeting and signaling by palmitoylation (Aim 1), MAGUK scaffolding interactions (Aim 1), and CaN anchoring (Aims 2 &3) coordinately regulate dendritic spine structure and AMPAR function in plasticity.

Public Health Relevance

The AKAP79/150-organized neuronal excitatory postsynaptic signaling processes we are studying that control dendritic spine structure and glutamate receptor function are believed to be relevant for mechanisms of altered synaptic plasticity and cognition in neurological disorders such as Alzheimer's and epilepsy and mental health disorders such as Down syndrome and schizophrenia. These same pathways also have relevance for understanding how excessive glutamate receptor activation leads to excitotoxic neuronal death in neurodegenerative diseases, brain injury and stroke. In particular, regulation of glutamate receptor activity and dendritic spine structural changes have been implicated in both plasticity and excitoxicity, thus understanding the role of AKAP79/150 in controlling these events through both its structural interactions and signaling functions is important for understanding basic synaptic processes that are altered in human disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS040701-12
Application #
8248318
Study Section
Synapses, Cytoskeleton and Trafficking Study Section (SYN)
Program Officer
Stewart, Randall R
Project Start
2000-12-01
Project End
2013-05-14
Budget Start
2012-04-01
Budget End
2013-05-14
Support Year
12
Fiscal Year
2012
Total Cost
$390,964
Indirect Cost
$125,463
Name
University of Colorado Denver
Department
Pharmacology
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
Freund, Ronald K; Graw, Sharon; Choo, Kevin S et al. (2016) Genetic knockout of the α7 nicotinic acetylcholine receptor gene alters hippocampal long-term potentiation in a background strain-dependent manner. Neurosci Lett 627:1-6
Sanderson, Jennifer L; Gorski, Jessica A; Dell'Acqua, Mark L (2016) NMDA Receptor-Dependent LTD Requires Transient Synaptic Incorporation of Ca²⁺-Permeable AMPARs Mediated by AKAP150-Anchored PKA and Calcineurin. Neuron 89:1000-15
Nieves-Cintrón, Madeline; Hirenallur-Shanthappa, Dinesh; Nygren, Patrick J et al. (2016) AKAP150 participates in calcineurin/NFAT activation during the down-regulation of voltage-gated K(+) currents in ventricular myocytes following myocardial infarction. Cell Signal 28:733-40
Freund, Ronald K; Gibson, Emily S; Potter, Huntington et al. (2016) Inhibition of the Motor Protein Eg5/Kinesin-5 in Amyloid β-Mediated Impairment of Hippocampal Long-Term Potentiation and Dendritic Spine Loss. Mol Pharmacol 89:552-9
Samelson, Bret K; Gore, Bryan B; Whiting, Jennifer L et al. (2015) A-kinase Anchoring Protein 79/150 Recruits Protein Kinase C to Phosphorylate Roundabout Receptors. J Biol Chem 290:14107-19
Nieves-Cintrón, Madeline; Nystoriak, Matthew A; Prada, Maria Paz et al. (2015) Selective down-regulation of KV2.1 function contributes to enhanced arterial tone during diabetes. J Biol Chem 290:7918-29
Woolfrey, Kevin M; Dell'Acqua, Mark L (2015) Coordination of Protein Phosphorylation and Dephosphorylation in Synaptic Plasticity. J Biol Chem 290:28604-12
Woolfrey, Kevin M; Sanderson, Jennifer L; Dell'Acqua, Mark L (2015) The palmitoyl acyltransferase DHHC2 regulates recycling endosome exocytosis and synaptic potentiation through palmitoylation of AKAP79/150. J Neurosci 35:442-56
Yu, Tian; Taussig, Matthew D; DiPatrizio, Nicholas V et al. (2015) Deficiency of Lipoprotein Lipase in Neurons Decreases AMPA Receptor Phosphorylation and Leads to Neurobehavioral Abnormalities in Mice. PLoS One 10:e0135113
Murphy, Jonathan G; Sanderson, Jennifer L; Gorski, Jessica A et al. (2014) AKAP-anchored PKA maintains neuronal L-type calcium channel activity and NFAT transcriptional signaling. Cell Rep 7:1577-88

Showing the most recent 10 out of 28 publications