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Ca2+-independent smooth muscle contraction. a novel function for integrin-linked kinase
J T Deng1, J E Van Lierop, C Sutherland
1Smooth Muscle Research Group and Canadian Institutes of Health Research Group in Regulation of Vascular Contractility, Department of Biochemistry, University of Calgary Faculty of Medicine, Calgary, Alberta T2N 4N1, Canada.
The Journal of Biological Chemistry
|March 30, 2001
Summary
Integrin-linked kinase phosphorylates myosin light chain, regulating smooth muscle contraction independently of calcium. This identifies a new mechanism for muscle motility.
Area of Science:
- Cell Biology
- Muscle Physiology
- Biochemistry
Background:
- Smooth muscle contraction is typically regulated by calcium ions and myosin light chain kinase.
- Agonists can induce contraction without altering calcium levels by inhibiting myosin light chain phosphatase.
- A calcium-independent pathway for smooth muscle contraction involving myosin phosphorylation has been observed.
Purpose of the Study:
- To identify the kinase responsible for calcium-independent myosin light chain phosphorylation in smooth muscle.
- To investigate the role of integrin-linked kinase (ILK) in smooth muscle contraction.
Main Methods:
- Cloning and sequencing of chicken gizzard integrin-linked kinase (ILK) cDNA.
- Expression of ILK in E. coli and in vitro phosphorylation assays of myosin light chain.
- Subcellular fractionation to isolate different ILK populations.
Main Results:
- Identified integrin-linked kinase (ILK) as a kinase that phosphorylates myosin light chain at Ser(19) and Thr(18) independently of calcium.
- Demonstrated that a Triton X-100-insoluble fraction of ILK phosphorylates myosin in a calcium-independent manner.
- Confirmed ILK as a functional protein-serine/threonine kinase.
Conclusions:
- Integrin-linked kinase plays a novel role in regulating smooth muscle contraction through calcium-independent myosin phosphorylation.
- ILK may also be involved in the regulation of nonmuscle cell motility.
- This study confirms ILK's function as a protein kinase in a novel context.