Studies of the cellular and molecular aspects of Alzheimer's disease have focused upon cytoskeletal proteins, particularly the microtubule associated protein, Tan, which makes up neurofibrillary tangles. Neurotransmitter dysfunction has also been implicated in the Alzheimer's disease brain and such dysfunction is likely to result in or originate from some aspect of G protein-mediated signal transduction. This project represents an attempt to correlate the changes in G-protein mediated signaling with polymerization of Tau in the hope that clear linkage might be made between the cytoskeletal changes and the neurochemical changes of Alzheimer's disease, especially in relation to neurotransmitter responsiveness. This laboratory has been engaged, for the past several years, in efforts to demonstrate that cytoskeletal proteins, especially tubulin, interact directly with specific G proteins to regulate neurotransmitter- responsive enzymes such as adenylyl cyclase and phospholipase C. Tubulin regulation of phospholipase is biphasic. At low concentrations, tubulin activates Gq (the G protein which activates phospholipase Cbeta1) by forming a complex and transferring GTP directly. At high concentrations, tubulin inhibits the enzymes activation both by disrupting the coupling between muscarinic acetylcholine receptors and Gq as well as by binding the substrate, PIP2, directly. Thus, increased tubulin dimer concentration, resulting from increased calcium, could """"""""feedback inhibit"""""""" phospholipase C. In the Alzheimer's brain, this regulatory process may be disrupted by Tau and Tau polymers, since it appears that PIP2 may be crucial for the assembly of Tau as well. This project will attempt to test the interaction between Gq and tubulin and how Tau or PIP2 might modify that process. This will be done by studying the binding of the species (fluorescence and microscopy) and the activation by GTP transfer (fluorescence, photoaffinity and binding studies). Experiments will be done with purified protein components as well as with SF9 cells infected with baculovirus containing cDNA for (in various combinations) ml receptors, Gq and phospholipase Cbeta1. Effects of Tau and tubulin on the enzyme activity will be determined in the hope that a logical pathway for this richly articulated regulation can be described.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG015482-04
Application #
6169189
Study Section
National Institute on Aging Initial Review Group (NIA)
Program Officer
Snyder, D Stephen
Project Start
1997-09-01
Project End
2002-06-30
Budget Start
2000-07-01
Budget End
2001-06-30
Support Year
4
Fiscal Year
2000
Total Cost
$189,006
Indirect Cost
Name
University of Illinois at Chicago
Department
Physiology
Type
Schools of Medicine
DUNS #
121911077
City
Chicago
State
IL
Country
United States
Zip Code
60612
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Popova, Juliana S; Rasenick, Mark M (2003) G beta gamma mediates the interplay between tubulin dimers and microtubules in the modulation of Gq signaling. J Biol Chem 278:34299-308
Yu, Jiang-Zhou; Rasenick, Mark M (2002) Real-time visualization of a fluorescent G(alpha)(s): dissociation of the activated G protein from plasma membrane. Mol Pharmacol 61:352-9
Popova, Juliana S; Greene, Arin K; Wang, Jia et al. (2002) Phosphatidylinositol 4,5-bisphosphate modifies tubulin participation in phospholipase Cbeta1 signaling. J Neurosci 22:1668-78
Yu, Jiang-Zhou; Kuret, Jeff; Rasenick, Mark M (2002) Transient expression of fluorescent tau proteins promotes process formation in PC12 cells: contributions of the tau C-terminus to this process. J Neurosci Res 67:625-33

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