Slow cycling of unphosphorylated myosin is inhibited by calponin, thus keeping smooth muscle relaxed
(1997) In Proceedings of the National Academy of Sciences 94(14). p.7655-7660- Abstract
- A key unanswered question in smooth muscle biology is whether phosphorylation of the myosin regulatory light chain (RLC) is sufficient for regulation of contraction, or if thin-filament-based regulatory systems also contribute to this process. To address this issue, the endogenous RLC was extracted from single smooth muscle cells and replaced with either a thiophosphorylated RLC or a mutant RLC (T18A/S19A) that cannot be phosphorylated by myosin light chain kinase. The actin-binding protein calponin was also extracted. Following photolysis of caged ATP, cells without calponin that contained a nonphosphorylatable RLC shortened at 30% of the velocity and produced 65% of the isometric force of cells reconstituted with the thiophosphorylated... (More)
- A key unanswered question in smooth muscle biology is whether phosphorylation of the myosin regulatory light chain (RLC) is sufficient for regulation of contraction, or if thin-filament-based regulatory systems also contribute to this process. To address this issue, the endogenous RLC was extracted from single smooth muscle cells and replaced with either a thiophosphorylated RLC or a mutant RLC (T18A/S19A) that cannot be phosphorylated by myosin light chain kinase. The actin-binding protein calponin was also extracted. Following photolysis of caged ATP, cells without calponin that contained a nonphosphorylatable RLC shortened at 30% of the velocity and produced 65% of the isometric force of cells reconstituted with the thiophosphorylated RLC. The contraction of cells reconstituted with nonphosphorylatable RLC was, however, specifically suppressed in cells that contained calponin. These results indicate that calponin is required to maintain cells in a relaxed state, and that in the absence of this inhibition, dephosphorylated cross-bridges can slowly cycle and generate force. These findings thus provide a possible framework for understanding the development of latch contraction, a widely studied but poorly understood feature of smooth muscle. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1112281
- author
- Malmqvist, Ulf LU ; Trybus, K M ; Yagi, S ; Carmichael, J and Fay, F S
- publishing date
- 1997
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Proceedings of the National Academy of Sciences
- volume
- 94
- issue
- 14
- pages
- 7655 - 7660
- publisher
- National Academy of Sciences
- external identifiers
-
- pmid:9207148
- scopus:0030832240
- ISSN
- 1091-6490
- language
- English
- LU publication?
- no
- id
- 403a0a58-ce93-48ab-9736-fb42720f9aae (old id 1112281)
- alternative location
- http://www.pnas.org/content/94/14/7655.full
- date added to LUP
- 2016-04-01 11:46:36
- date last changed
- 2022-01-26 18:02:23
@article{403a0a58-ce93-48ab-9736-fb42720f9aae,
abstract = {{A key unanswered question in smooth muscle biology is whether phosphorylation of the myosin regulatory light chain (RLC) is sufficient for regulation of contraction, or if thin-filament-based regulatory systems also contribute to this process. To address this issue, the endogenous RLC was extracted from single smooth muscle cells and replaced with either a thiophosphorylated RLC or a mutant RLC (T18A/S19A) that cannot be phosphorylated by myosin light chain kinase. The actin-binding protein calponin was also extracted. Following photolysis of caged ATP, cells without calponin that contained a nonphosphorylatable RLC shortened at 30% of the velocity and produced 65% of the isometric force of cells reconstituted with the thiophosphorylated RLC. The contraction of cells reconstituted with nonphosphorylatable RLC was, however, specifically suppressed in cells that contained calponin. These results indicate that calponin is required to maintain cells in a relaxed state, and that in the absence of this inhibition, dephosphorylated cross-bridges can slowly cycle and generate force. These findings thus provide a possible framework for understanding the development of latch contraction, a widely studied but poorly understood feature of smooth muscle.}},
author = {{Malmqvist, Ulf and Trybus, K M and Yagi, S and Carmichael, J and Fay, F S}},
issn = {{1091-6490}},
language = {{eng}},
number = {{14}},
pages = {{7655--7660}},
publisher = {{National Academy of Sciences}},
series = {{Proceedings of the National Academy of Sciences}},
title = {{Slow cycling of unphosphorylated myosin is inhibited by calponin, thus keeping smooth muscle relaxed}},
url = {{http://www.pnas.org/content/94/14/7655.full}},
volume = {{94}},
year = {{1997}},
}