Microtubules, which constitute one of the three known elements of the cytoskeleton, are dynamic structures which change their location and function during the cell cycle. We wish to determine the kinetic parameters for assembly and disassembly of microtubules and learn how these are influenced by solution variable, microtubule-associated proteins and drugs which bind to tubulin. Our long-term goal is to learn how the cytoskeleton is regulated during the cell cycle. Also, microtubules are the target for a number of antitumor drugs and development of better agents for cancer chemotherapy will be advanced by understanding how microtubules are regulated.
The specific aims of the proposed research include determination of the role of GTP hydrolysis in microtubule assembly. We wish to know how GTP is used in the nucleation and elongation processes, as well as when the GTP is hydrolyzed, in relation to the time that tubulin subunits are incorporated into microtubules. Studies of the effects of GDP on microtubule assembly and stability are projected, in order to elucidate the mechanism underlying a puzzling phenomenon: although tubulin-GDP subunits do not readily elongate microtubules, they are able to react so as to maintain microtubules in a metastable steady state. The GDP effects are also of interest since it has recently been found that the kinetics for microtubule assembly and disassembly cannot be accounted for in terms of the relatively simple protein condensation model of Oosawa. The Oosawa model does not consider the effects of GTP hydrolysis and the observed deviations from this theory suggest that the GTP hydrolysis is an important element in regulation of microtubules. We wish to further develop a kinetic model which we have recently derived for microtubule assembly and disassembly, which takes into account the GTP hydrolysis reaction.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE003246-20
Application #
3218840
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1976-06-01
Project End
1991-05-31
Budget Start
1989-06-01
Budget End
1990-05-31
Support Year
20
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Type
Schools of Dentistry/Oral Hygn
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
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Caplow, M; Shanks, J (1990) Mechanism for oscillatory assembly of microtubules. J Biol Chem 265:1414-8
Caplow, M; Ruhlen, R; Shanks, J et al. (1989) Stabilization of microtubules by tubulin-GDP-Pi subunits. Biochemistry 28:8136-41
Caplow, M; Shanks, J; Breidenbach, S et al. (1988) Kinetics and mechanism of microtubule length changes by dynamic instability. J Biol Chem 263:10943-51
Caplow, M; Shanks, J; Ruhlen, R L (1988) Temperature-jump studies of microtubule dynamic instability. J Biol Chem 263:10344-52
Caplow, M (1986) Location of the guanosine triphosphate (GTP) hydrolysis site in microtubules. Ann N Y Acad Sci 466:510-8
Caplow, M; Shanks, J; Brylawski, B P (1986) Differentiation between dynamic instability and end-to-end annealing models for length changes of steady-state microtubules. J Biol Chem 261:16233-40
Caplow, M; Reid, R (1985) Directed elongation model for microtubule GTP hydrolysis. Proc Natl Acad Sci U S A 82:3267-71
Caplow, M; Shanks, J; Brylawski, B P (1985) Concerning the location of the GTP hydrolysis site on microtubules. Can J Biochem Cell Biol 63:422-9
Caplow, M; Shanks, J; Brylawski, B P (1985) Concerning the anomalous kinetic behavior of microtubules. J Biol Chem 260:12675-9