Contractile effects of polycations in permeabilized smooth muscle
(1998) In Journal of Muscle Research and Cell Motility 19(5). p.463-472- Abstract
- The polycations spermine, neomycin and polylysine potentiated Ca(2+)-activated force in beta-escin permeabilized guinea-pig ileum strips. The effect was inhibited by the calmodulin antagonists trifluoperazine, mastoparan and W13. Potentiation was slow or absent in chi-toxin permeabilized strips, indicating dependence on penetration of the polycations into cells. The effects of spermine and neomycin were maintained after extensive permeabilization by beta-escin, which eliminated the contractile effect of GTPgammaS. Replacement of ATP by CTP, which is not a substrate for myosin light chain kinase, inhibited contractile potentiation. Potentiation of Ca(2+)-activated contractions was associated with increased phosphorylation of the myosin... (More)
- The polycations spermine, neomycin and polylysine potentiated Ca(2+)-activated force in beta-escin permeabilized guinea-pig ileum strips. The effect was inhibited by the calmodulin antagonists trifluoperazine, mastoparan and W13. Potentiation was slow or absent in chi-toxin permeabilized strips, indicating dependence on penetration of the polycations into cells. The effects of spermine and neomycin were maintained after extensive permeabilization by beta-escin, which eliminated the contractile effect of GTPgammaS. Replacement of ATP by CTP, which is not a substrate for myosin light chain kinase, inhibited contractile potentiation. Potentiation of Ca(2+)-activated contractions was associated with increased phosphorylation of the myosin regulatory light chains (LC20). A contractile effect of polylysine and neomycin was also seen in Ca(2+)-free medium and after partial LC20 thiophosphorylation, indicating that phosphorylation-independent processes may contribute to the response. Although spermine does not cause contraction in Ca(2+)-free medium at physiological [MgATP], it did so when [MgATP] was lowered to 40 micron. Similar to high-[Mg2+], the rate of contraction on addition of ATP to strips incubated with microcystin-LR in inhibit phosphatase activity was increased by the polycations, but only at [Ca2+] < 0.3 micron. The results suggest that polycations increase Ca(2+)-activated force by inhibiting myosin phosphatase activity, thereby increasing myosin LC20 phosphorylation. However, additional activation mechanisms, evident at low [Ca2+] and at low [ATP] and possibly involving direct activation of myosin, contribute to their effect. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1112970
- author
- Swärd, Karl LU ; Dreja, Karl LU and Hellstrand, Per LU
- organization
- publishing date
- 1998
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Muscle Research and Cell Motility
- volume
- 19
- issue
- 5
- pages
- 463 - 472
- publisher
- Springer
- external identifiers
-
- pmid:9682133
- scopus:0031849195
- ISSN
- 0142-4319
- DOI
- 10.1023/A:1005368728376
- language
- English
- LU publication?
- yes
- id
- 1898d708-cfe7-4f83-a728-6bbaa8d19b12 (old id 1112970)
- date added to LUP
- 2016-04-01 16:39:23
- date last changed
- 2022-01-28 21:12:15
@article{1898d708-cfe7-4f83-a728-6bbaa8d19b12, abstract = {{The polycations spermine, neomycin and polylysine potentiated Ca(2+)-activated force in beta-escin permeabilized guinea-pig ileum strips. The effect was inhibited by the calmodulin antagonists trifluoperazine, mastoparan and W13. Potentiation was slow or absent in chi-toxin permeabilized strips, indicating dependence on penetration of the polycations into cells. The effects of spermine and neomycin were maintained after extensive permeabilization by beta-escin, which eliminated the contractile effect of GTPgammaS. Replacement of ATP by CTP, which is not a substrate for myosin light chain kinase, inhibited contractile potentiation. Potentiation of Ca(2+)-activated contractions was associated with increased phosphorylation of the myosin regulatory light chains (LC20). A contractile effect of polylysine and neomycin was also seen in Ca(2+)-free medium and after partial LC20 thiophosphorylation, indicating that phosphorylation-independent processes may contribute to the response. Although spermine does not cause contraction in Ca(2+)-free medium at physiological [MgATP], it did so when [MgATP] was lowered to 40 micron. Similar to high-[Mg2+], the rate of contraction on addition of ATP to strips incubated with microcystin-LR in inhibit phosphatase activity was increased by the polycations, but only at [Ca2+] < 0.3 micron. The results suggest that polycations increase Ca(2+)-activated force by inhibiting myosin phosphatase activity, thereby increasing myosin LC20 phosphorylation. However, additional activation mechanisms, evident at low [Ca2+] and at low [ATP] and possibly involving direct activation of myosin, contribute to their effect.}}, author = {{Swärd, Karl and Dreja, Karl and Hellstrand, Per}}, issn = {{0142-4319}}, language = {{eng}}, number = {{5}}, pages = {{463--472}}, publisher = {{Springer}}, series = {{Journal of Muscle Research and Cell Motility}}, title = {{Contractile effects of polycations in permeabilized smooth muscle}}, url = {{http://dx.doi.org/10.1023/A:1005368728376}}, doi = {{10.1023/A:1005368728376}}, volume = {{19}}, year = {{1998}}, }