G. Hecht et A. Koutsouris, Myosin regulation of NKCC1: effects on cAMP-mediated Cl- secretion in intestinal epithelia, AM J P-CELL, 46(3), 1999, pp. C441-C447
Myosin regulation of NKCC1: effects on cAMP-mediated Cl- secretion in intes
tinal epithelia. Am. J. Physiol. 277 (Cell Physiol. 46): C441-C447, 1999.-T
he basally located actin cytoskeleton has been demonstrated previously to r
egulate Cl- secretion from intestinal epithelia via its effects on the Na+-
K+-2Cl cotransporter (NKCC1). In nontransporting epithelia, inhibition of m
yosin light chain kinase (MLCK) prevents cell-shrinkage-induced activation
of NKCC1. The aim of this study was to investigate the role of myosin in th
e regulation of secretagogue-stimulated Cl- secretion in intestinal epithel
ia. The human intestinal epithelial cell line T84 was used for these studie
s. Prevention of myosin light chain phosphorylation with the MLCK inhibitor
ML-9 or ML-7 and inhibition of myosin ATPase with butanedione monoxime (BD
M) attenuated cAMP but not Ca2+-mediated Cl- secretion. Both ML-9 and BDM d
iminished cAMP activation of NKCC1. Neither apical Cl- channel activity, ba
solateral K+ channel activity, nor Na+-K+-ATPase were affected by these age
nts. Cytochalasin D prevented such attenuation, cAMP-induced rearrangement
of basal actin microfilaments was prevented by both ML-9 and BDM. The phosp
horylation of mosin light chain and subsequent contraction of basal actin-m
yosin bundles are crucial to the cAMP-driven activation of NKCC1 and subseq
uent apical Cl- efflux.