The majority of excitatory neuronal input occurs at dendritic spines;remodeling of these structures leads to concurrent changes in neuronal function essential for normal neural development and processing. Furthermore, dysregulation of this phenomenon underlies numerous neurological and neurodegenerative disorders. In addition to signaling at synapses, signaling pathways to the nucleus are thought to be important for changes in dendritic spine morphology and neuronal plasticity. However, the signal transduction networks that regulate spine modulation are not well understood. AF-6 is a PDZ-domain-containing protein abundantly expressed at adhesion junctions and is involved in dendritic spine remodeling. Pathways upstream of AF-6, including NMDA receptor (NMDAR), estrogen (E2) and N-cadherin-dependent signaling, have been associated with modulating dendritic spine morphology via an AF-6 dependent pathway. In our preliminary data, we demonsrate that these pathways can also induce AF-6 translocation to the nucleus. Thus AF-6 is an ideal candidate to mediate dendritic spine morphogenesis by signaling in distinct subcellular compartments.
The aim of this proposal is to determine the role of differential AF-6 translocation in regulating dendritic spine morphogenesis in cultured cortical neurons. First, we will characterize the time-dependent localization of AF-6 in NMDAR, E2 and N-cadherin-mediated signaling by using immunocytochemistry and Western-blotting techniques. We will also assess the role of the various AF-6 domains in its translocation by overexpressing truncated or mutated AF-6 constructs. Next, we will use immunocytochemistry to determine changes in spine expression induced by NMDAR, E2 and N-cadherin-mediated signaling or the overexpression of altered AF-6 constructs. Lastly, we will intervene with AF-6 translocation and then assess alterations in spine morphology. To this end, we will prevent AF-6 from localizing to synapses or the nucleus using specifically modified AF-6 constructs and we will force AF-6 into the nucleus using a nuclear localization signal. Results from these studies will foster a better understanding of the signaling pathways regulating dendritic spine morphogenesis and provide insight into the mechanisms governing synaptic plasticity in health and disease.

Public Health Relevance

The goal of this project is to understand how brain cells change in response to signals from other brain cells. These changes are essential for normal brain function but also become disrupted in various brain disorders. Findings from these studies will help us to better understand the cause of certain brain disorders and potentially identify new forms of treatment.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Predoctoral Individual National Research Service Award (F31)
Project #
5F31MH087043-03
Application #
8242074
Study Section
Special Emphasis Panel (ZRG1-F03A-F (20))
Program Officer
Rosemond, Erica K
Project Start
2010-04-01
Project End
2013-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
3
Fiscal Year
2012
Total Cost
$33,850
Indirect Cost
Name
Northwestern University at Chicago
Department
Physiology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
VanLeeuwen, Jon-Eric; Rafalovich, Igor; Sellers, Katherine et al. (2014) Coordinated nuclear and synaptic shuttling of afadin promotes spine plasticity and histone modifications. J Biol Chem 289:10831-42
Deo, Anthony J; Cahill, Michael E; Li, Siyu et al. (2012) Increased expression of Kalirin-9 in the auditory cortex of schizophrenia subjects: its role in dendritic pathology. Neurobiol Dis 45:796-803
Penzes, Peter; Cahill, Michael E; Jones, Kelly A et al. (2011) Dendritic spine pathology in neuropsychiatric disorders. Nat Neurosci 14:285-93
Penzes, Peter; Vanleeuwen, Jon-Eric (2011) Impaired regulation of synaptic actin cytoskeleton in Alzheimer's disease. Brain Res Rev 67:184-92