FIBROBLAST CONTRACTILITY WITHOUT AN INCREASE IN BASAL MYOSIN LIGHT-CHAIN PHOSPHORYLATION IN WILD-TYPE CELLS AND CELLS EXPRESSING THE CATALYTIC DOMAIN OF MYOSIN LIGHT-CHAIN KINASE
K. Obara et al., FIBROBLAST CONTRACTILITY WITHOUT AN INCREASE IN BASAL MYOSIN LIGHT-CHAIN PHOSPHORYLATION IN WILD-TYPE CELLS AND CELLS EXPRESSING THE CATALYTIC DOMAIN OF MYOSIN LIGHT-CHAIN KINASE, The Journal of biological chemistry, 270(32), 1995, pp. 18734-18737
We investigated the role of myosin light chain (MLC(20)) phosphorylati
on (MLC-P) in non-muscle contractility by comparing MLC-P and the cont
ractile properties of wild type 3T3 fibroblasts and 3T3 fibroblasts ex
pressing the catalytic domain of myosin light chain kinase (tMK), MLC-
P is 0.96 mol of PO4/mol of MLC(20) in cells expressing tMK compared t
o 0.20 mol of PO4/mol of MLC(20) in control cells, Expressing tMK also
results in a 2-fold increase in cortical stiffness compared to contro
l cells. Contractile properties were quantified by growing wild type a
nd transfected fibroblasts in collagen and attaching the ensuing fiber
s to an apparatus for performing mechanical measurements, Serum stimul
ation resulted in a dose-dependent increase in force with maximal forc
e generated in the presence of 30% (v/v) serum. Surprisingly, MLC-P di
d not increase in wild type cells following stimulation with 30% serum
, and tMK expression did not affect the contractile properties of fibe
rs made from these cells. Moreover, the dose responses to serum, maxim
al force, force-Velocity relationships, and dynamic stiffness were sim
ilar in the wild type cells and fibroblasts expressing tMK. These data
demonstrate that non-muscle cells can generate force without an incre
ase in MLC-P, and that an increase in MLC-P does not affect the contra
ctile properties of fibroblast fibers.