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The role of the calponin homology domain of smoothelin-like 1 (SMTNL1) in myosin phosphatase inhibition and smooth muscle contraction.
In this study, we provide further insight into the contribution of the smoothelin-like 1 (SMTNL1) calponin homology (CH)-domain on myosin light chain phosphatase (SMPP-1M) activity and smooth muscle contraction. SMTNL1 protein was shown to have inhibitory effects on SMPP-1M activity but not on myosin light chain kinase (MLCK) activity. Treatment of beta-escin permeabilized rabbit, ileal smooth muscle with SMTNL1 had no effect on the time required to reach half-maximal force (t(1/2)) during stimulation with pCa6.3 solution. The addition of recombinant SMTNL1 protein to permeabilized, smooth muscle strips caused a significant decrease in contractile force. While the calponin homology (CH)-domain was essential for maximal SMTNL1-associated relaxation, it alone did not cause significant changes in force. SMTNL1 was poorly dephosphorylated by PP-1C in the presence of the myosin targeting subunit (MYPT1), suggesting that phosphorylated SMTNL1 does not possess "substrate trapping" properties. Moreover, while full-length SMTNL1 could suppress SMPP-1M activity toward LC(20) in vitro, truncated SMTNL1 lacking the CH-domain was ineffective. In summary, our findings suggest an important role for the CH-domain in mediating the effects of SMTNL1 on smooth muscle contraction.
Duke Scholars
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Related Subject Headings
- Rabbits
- Protein Structure, Tertiary
- Myosin-Light-Chain Phosphatase
- Myosin-Light-Chain Kinase
- Muscle, Smooth
- Muscle Proteins
- Muscle Contraction
- Microfilament Proteins
- Kinetics
- Humans
Citation
![Journal cover image](https://secure.syndetics.com/index.aspx?isbn=/lc.gif&issn=1573-4919&client=dukeuniv)
Published In
DOI
EISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Rabbits
- Protein Structure, Tertiary
- Myosin-Light-Chain Phosphatase
- Myosin-Light-Chain Kinase
- Muscle, Smooth
- Muscle Proteins
- Muscle Contraction
- Microfilament Proteins
- Kinetics
- Humans