ACELL September 46/3
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Turner, J. R., J. M. Angle, E. D. Black, J. L. Joyal, D. B. Sacks, and J. L. Madara. PKC-dependent regulation of transepithelial resistance: roles of MLC and MLC kinase. Am. J. Physiol. 277 (Cell Physiol. 46): C554–C562, 1999.— The mechanisms by which protein kinase C (PKC) activation results in increased transepithelial resistance (TER) are unknown [G. Hecht, B. Robinson, and A. Koutsouris. Am. J. Physiol. 266 (Gastrointest. Liver Physiol. 29): G214–G221, 1994]. We have previously shown that phosphorylation of the regulatory light chain of myosin II (MLC) is associated with decreases in TER and have suggested that contraction of the perijunctional actomyosin ring (PAMR) increases tight junction (TJ) permeability [J. R. Turner, B. K. Rill, S. L. Carlson, D. Carnes, R. Kerner, R. J. Mrsny, and J. L. Madara. Am. J. Physiol. 273 (Cell Physiol. 42): C1378–C1385, 1997]. We therefore hypothesized that PKC activation alters TER via relaxation of the PAMR. Activation of PKC by the phorbol ester phorbol 12-myristate 13-acetate (PMA) resulted in a progressive dose-dependent increase in TER that was apparent within 15 min (111% of controls) and maximal within 2 h (142% of controls). Similar increases were induced by a diacylglycerol analog, and the effects of both PMA and the diacylglycerol analog were prevented by the PKC inhibitor bisindolylmaleimide I. PMA treatment caused progressive decreases in MLC phosphorylation, by 12% at 15 min and 41% at 2 h. Phosphorylation of MLC kinase (MLCK) increased by 64% within 15 min of PMA treatment and was stable over 2 h (51% greater than that of controls). Thus increases in MLCK phosphorylation preceded decreases in MLC phosphorylation. These data suggest that PKC regulates TER via decreased phosphorylation of MLC, possibly due to inhibitory phosphorylation of MLCK. The decreased phosphorylation of MLC likely reduces PAMR tension, leading to decreased TJ permeability.
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ACELL September 46/3
Dodd, J. S., J. A. Raleigh, and T. S. Gross. Osteocyte hypoxia: a novel mechanotransduction pathway. Am. J. Physiol. 277 (Cell Physiol. 46): C598–C602, 1999.—Bone is a unique tissue in which to examine mechanotransduction due to its essential role in weight bearing. Within bone, the osteocyte is an ideal cellular mechanotransducer candidate. Because osteocytes reside distant from the blood supp...
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Zeiske, Wolfgang, Ilse Smets, Marcel Ameloot, Paul Steels, and Willy Van Driessche. Intracellular pH shifts in cultured kidney (A6) cells: effects on apical Na1 transport. Am. J. Physiol. 277 (Cell Physiol. 46): C469–C479, 1999.—We report, for the epithelial Na1 channel (ENaC) in A6 cells, the modulation by cell pH (pHc) of the transepithelial Na1 current (INa), the current through the individu...
متن کاملACELL September 46/3
Shepard, Allan R., and James L. Rae. Electrically silent potassium channel subunits from human lens epithelium. Am. J. Physiol. 277 (Cell Physiol. 46): C412–C424, 1999.—We describe the cloning and characterization of the first human members, hKv9.1 and hKv9.3, of the electrically silent delayed-rectifying-like K1 channel subfamily. Their modulatory effects on the electrically active subfamily m...
متن کاملACELL September 46/3
Stevens, Randel J., Jeffery S. Weinert, and Nelson G. Publicover. Visualization of origins and propagation of excitation in canine gastric smooth muscle. Am. J. Physiol. 277 (Cell Physiol. 46): C448–C460, 1999.—The origin and spread of excitation were visualized with fluo 3 fluorescence in tissues isolated from canine gastric antrum. Sheets of circular muscle (5 3 6 mm) had at least 1 (30%) and...
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JOHN M. PARK,1 ROSALYN M. ADAM,1 CRAIG A. PETERS,1 PAUL D. GUTHRIE,1 ZIJIE SUN,2 MICHAEL KLAGSBRUN,3 AND MICHAEL R. FREEMAN3 1Urologic Laboratory, Department of Urology, 3Laboratory for Surgical Research, Children’s Hospital, and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115; and 2Departments of Surgery and Genetics, Stanford University School of Medicine, Stanford,...
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