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Concanavalin A‐ and fetal‐calf‐serum‐induced rounding and myosin light chain phosphorylation in cultured smooth muscle cells
Author(s) -
Sasaki Yasuo,
Iwata Kunie,
Sasaki Yasuharu
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041440202
Subject(s) - concanavalin a , myosin , phosphorylation , myosin light chain kinase , biology , microfilament , biochemistry , microbiology and biotechnology , biophysics , anatomy , chemistry , cell , cytoskeleton , in vitro
Rabbit aorta smooth muscle cells (SMC) in long‐term culture retracted in less than 10 min in response to a sequential order of stimulations by concanavalin A (Con A) and fetal calf serum (FCS). With additional continuous stimulation by FCS, the SMC took on a circular shape and were anchored to the substrate by retraction fibrils. This rounding was observed only when the cells were sequentially stimulated by Con A and FCS. Depletion of intracellular Ca 2+ stores by the addition of EGTA and Ca 2+ ionophores inhibited the rounding. Transient phosphorylation of MLC 20 was observed in the initial stage during the SMC rounding. The extent of monophosphorylated MLC 20 increased for up to 5 min to a maximal value of 49%. The diphosphorylated form reached a maximal value of 29% within 2 min; then both forms of MLC 20 decreased. The process of the SMC rounding was inhibited by antimycin A or cytochalasins, in a dose‐dependent manner, findings which suggested a dependency on both metabolic energy and actin‐containing microfilaments. The smooth‐muscle‐relaxing agent, HA1077, also inhibited the process of SMC rounding. These observations suggest that a cellular contractile process might be involved in rounding of SMC.