The overall objective of these studies is to further our understanding of how caldesmon contributes to the regulation of smooth muscle and non muscle actomyosins. The conceptual framework is a qualitative model that describes the coordinated interaction of the four putative regulatory proteins: 1) myosin regulatory light chain (LC20) 2) tropomyosin, 3) calponin, and 4) caldesmon. The model is based on a simple two-state kinetic scheme, and incorporates the allostericIcooperative-activation model for thin filament regulation proposed by Eisenberg and Hill (27). The proposed studies will address the mechanism by which caldesmon interacts with tropomyosin, calponin, and the regulatory light chain of myosin to modulate contraction. Specifically, these studies will test the hypothesis that caldesmon inhibits the """"""""switching-on"""""""" of actin filaments, and thereby inhibits activation of dephosphorylated cross bridges. Our general approach to investigate the specific effects of tropomyosin and caldesmon on the actomyosin interaction will be to utilize purified proteins and recombinant peptides to reconstitute regulated actin filaments. We will employ an in vitro motility assay to measure unloaded thin-filament velocity. A recent modification of the motility assay allows us to also rapidly measure the force exerted on individual actin filaments under steady-state isometric conditions. These studies should yield new insights into the molecular mechanisms that govern actomyosin-based contraction in both smooth muscles and nonmuscle cells. As such these findings may be relevant not only to vascular disease states involving abnormal smooth muscle contraction, such as hypertension, but also those involving inappropriate cellular growth and proliferation such as atherosclerosis.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL054722-04
Application #
2910590
Study Section
Experimental Cardiovascular Sciences Study Section (ECS)
Program Officer
Lymn, Richard W
Project Start
1996-05-01
Project End
2000-06-30
Budget Start
1999-05-01
Budget End
2000-06-30
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of Vermont & St Agric College
Department
Physiology
Type
Schools of Medicine
DUNS #
066811191
City
Burlington
State
VT
Country
United States
Zip Code
05405
Nibbelink, Brian; Hemric, Mark E; Haeberle, Joe R (2004) Caldesmon tethers myosin V to actin and facilitates in vitro motility. J Muscle Res Cell Motil 25:141-8
Haeberle, J R (1999) Thin-filament linked regulation of smooth muscle myosin. J Muscle Res Cell Motil 20:363-70