Key result
Cyclic strain cuts diphosphorylated MLC20 by ~62% in aortic smooth muscle cells.
Why the study?
The role of cyclic strain in regulating 20 kDa myosin light chain phosphorylation in cultured smooth muscle cells was unknown.
Does cyclic strain stimulate dephosphorylation of MLC20 in vascular smooth muscle cells?
Does cyclic strain stimulate dephosphorylation of MLC20 in vascular smooth muscle cells?
Cyclic strain induces dephosphorylation of MLC20 in vascular smooth muscle cells, potentially via activation of MLC20 phosphatase or inhibition of phosphorylation.
Hypothesis-generating for mechanical control of vascular tone; does not support practice change and requires in vivo confirmation.
The role of cyclic strain in the regulation of 20 kDa myosin light chain phosphorylation (MLC20) in cultured smooth muscle cells (SMC) is unknown. The objective of this study was to determine whether cyclic strain stimulates the dephosphorylation of MLC20 in serum-fed SMC displaying a high basal level of phosphorylation. Confluent bovine aortic SMC were subjected to 10% average strain at 60 cycles per minute for 30 and 60 minutes. Basal MLC20 phosphorylation (N = non,M = mono,D = di) of serum-fed SMC was as follows: N = 34%:M = 27%:D = 39%. After 60 min of cyclic strain, both mono and diphosphorylated MLC20 were decreased to 21 and 15% respectively. The strain-induced dephosphorylation of MLC20 was partially inhibited by the protein phosphatase 1/2A inhibitor, calyculin A (5 nM). However, phosphorylase a phosphatase activities in Triton-soluble and insoluble fractions of SMC were unaffected by cyclic strain. The data suggest that cyclic strain causes dephosphorylation of MLC20 in SMC which may be partially due to activation of MLC20 phosphatase and/or inhibition of MLC20 phosphorylation.
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Mills et al. (1994) studied this question. Cyclic strain vs. Basal state was evaluated on MLC20 phosphorylation. Cyclic strain for 60 minutes decreased mono- and diphosphorylated MLC20 in cultured bovine aortic smooth muscle cells from 27% and 39% to 21% and 15%, respectively.
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