Smooth muscle contraction is essential to the normal function of many organ systems within the body. Therefore, an understanding of its normal contractile process is required before studying disease states such as hypertension in which smooth muscle function may be abnormal. The ability of smooth muscle to sustain prolonged isometric contractions with very little energy consumption (i.e. ATP) may relate to the most basic contractile unit, the myosin crossbridge, and its cyclic interaction with actin. Although the smooth muscle crossbridge cycle may be qualitatively similar to that in skeletal muscle, its mode of regulation is quite different. Specifically, phosphorylation of smooth muscle's 20kD myosin light chain initiates contraction and crossbridge cycling. However, the degree of light chain phosphorylation may also modulate the crossbridge cycling rate. To characterize the effect of light chain phosphorylation on the crossbridge cycling rate, single actin filament velocity will be measured as the actin interacts with synthetic smooth muscle myosin filaments containing known proportions of dephosphorylated and phosphorylated crossbridges. In addition, techniques will be developed for recording force sustained by a single actin filament as it interacts with a myosin coated glass coverslip. The motility assay provides a unique opportunity to probe the most basic contractile mechanism in muscle at the molecular level.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL045161-01
Application #
3364101
Study Section
Physiology Study Section (PHY)
Project Start
1990-07-01
Project End
1995-06-30
Budget Start
1990-07-01
Budget End
1991-06-30
Support Year
1
Fiscal Year
1990
Total Cost
Indirect Cost
Name
University of Vermont & St Agric College
Department
Type
Schools of Medicine
DUNS #
066811191
City
Burlington
State
VT
Country
United States
Zip Code
05405
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Nguyen, T T; Hayes, E; Mulieri, L A et al. (1996) Maximal actomyosin ATPase activity and in vitro myosin motility are unaltered in human mitral regurgitation heart failure. Circ Res 79:222-6
VanBuren, P; Harris, D E; Alpert, N R et al. (1995) Cardiac V1 and V3 myosins differ in their hydrolytic and mechanical activities in vitro. Circ Res 77:439-44
Harris, D E; Stromski, C J; Hayes, E et al. (1995) Thiophosphorylation independently activates each head of smooth muscle myosin in vitro. Am J Physiol 269:C1160-6
VanBuren, P; Waller, G S; Harris, D E et al. (1994) The essential light chain is required for full force production by skeletal muscle myosin. Proc Natl Acad Sci U S A 91:12403-7
VanBuren, P; Work, S S; Warshaw, D M (1994) Enhanced force generation by smooth muscle myosin in vitro. Proc Natl Acad Sci U S A 91:202-5
Harris, D E; Work, S S; Wright, R K et al. (1994) Smooth, cardiac and skeletal muscle myosin force and motion generation assessed by cross-bridge mechanical interactions in vitro. J Muscle Res Cell Motil 15:11-9
Solaro, R J; Gambassi, G; Warshaw, D M et al. (1993) Stereoselective actions of thiadiazinones on canine cardiac myocytes and myofilaments. Circ Res 73:981-90
Harris, D E; Warshaw, D M (1993) Smooth and skeletal muscle actin are mechanically indistinguishable in the in vitro motility assay. Circ Res 72:219-24
Harris, D E; Warshaw, D M (1993) Smooth and skeletal muscle myosin both exhibit low duty cycles at zero load in vitro. J Biol Chem 268:14764-8

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