scholarly journals Dephosphorylation of the catenins p120 and p100 in endothelial cells in response to inflammatory stimuli

1999 ◽  
Vol 338 (2) ◽  
pp. 471-478 ◽  
Author(s):  
Marianne J. RATCLIFFE ◽  
Caroline SMALES ◽  
James M. STADDON
Keyword(s):  
Endothelial Cells ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Tight Junction ◽  
Adherens Junction ◽  
Receptor Activation ◽  
Protein Kinase C Inhibitors ◽  
Kinase C ◽  
Inflammatory Stimuli ◽  
Tight Junction Permeability

Inflammatory mediators such as histamine and thrombin increase the tight-junction permeability of endothelial cells. Tight-junction permeability may be independently controlled, but is dependent on the adherens junction, where adhesion is achieved through homotypic interaction of cadherins, which in turn are associated with cytoplasmic proteins, the catenins. p120, also termed p120cas/p120ctn, and its splice variant, p100, are catenins. p120, originally discovered as a substrate of the tyrosine kinase Src, is also a target for a protein kinase C-stimulated pathway in epithelial cells, causing its serine/threonine dephosphorylation. The present study shows that pharmacological activation of protein kinase C stimulated a similar pathway in endothelial cells. Activation of receptors for agents such as histamine (H1), thrombin and lysophosphatidic acid in the endothelial cells also caused serine/threonine dephosphorylation of p120 and p100, suggesting physiological relevance. However, protein kinase C inhibitors, although blocking the effect of pharmacological activation of protein kinase C, did not block the effects due to receptor activation. Calcium mobilization and the myosin-light-chain-kinase pathway do not participate in p120/p100 signalling. In conclusion, endothelial cells possess protein kinase C-dependent and -independent pathways regulating p120/p100 serine/threonine phosphorylation. These data describe a new connection between inflammatory agents, receptor-stimulated signalling and pathways potentially influencing intercellular adhesion in endothelial cells.

scholarly journals Stiff Substrates Enhance Endothelial Oxidative Stress in Response to Protein Kinase C Activation

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Rebecca Lownes Urbano ◽  
Swathi Swaminathan ◽  
Alisa Morss Clyne
Keyword(s):  
Oxidative Stress ◽  
Endothelial Cells ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Arterial Stiffness ◽  
Adherens Junction ◽  
Cell Junctions ◽  
Substrate Stiffness ◽  
Endothelial Monolayer ◽  
Kinase C

Arterial stiffness, which increases with aging and hypertension, is an independent cardiovascular risk factor. While stiffer substrates are known to affect single endothelial cell morphology and migration, the effect of substrate stiffness on endothelial monolayer function is less understood. The objective of this study was to determine if substrate stiffness increased endothelial monolayer reactive oxygen species (ROS) in response to protein kinase C (PKC) activation and if this oxidative stress then impacted adherens junction integrity. Porcine aortic endothelial cells were cultured on varied stiffness polyacrylamide gels and treated with phorbol 12-myristate 13-acetate (PMA), which stimulates PKC and ROS without increasing actinomyosin contractility. PMA-treated endothelial cells on stiffer substrates increased ROS and adherens junction loss without increased contractility. ROS scavengers abrogated PMA effects on cell-cell junctions, with a more profound effect in cells on stiffer substrates. Finally, endothelial cells in aortae from elastin haploinsufficient mice (Eln+/-), which were stiffer than aortae from wild-type mice, showed decreased VE-cadherin colocalization with peripheral actin following PMA treatment. These data suggest that oxidative stress may be enhanced in endothelial cells in stiffer vessels, which could contribute to the association between arterial stiffness and cardiovascular disease.

scholarly journals Protein kinase C activation leads to dephosphorylation of occludin and tight junction permeability increase in LLC-PK1 epithelial cell sheets

2000 ◽  
Vol 113 (18) ◽  
pp. 3187-3196 ◽  
Author(s):  
H. Clarke ◽  
A.P. Soler ◽  
J.M. Mullin
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tight Junction ◽  
Phorbol Ester ◽  
Electrical Resistance ◽  
Rapid Change ◽  
Transepithelial Electrical Resistance ◽  
Kinase C ◽  
Tight Junction Permeability ◽  
Triton X

Activation of protein kinase C by exposure of LLC-PK1 renal epithelial cells to 10(−7) M TPA, a tumor promoting phorbol ester, results in a rapid and sustained increase in paracellular permeability as evidenced by a decrease in transepithelial electrical resistance. Occludin, the first identified transmembrane protein to be localized to the tight junction of both epithelial and endothelial cells is thought play an important role in tight junction barriers. Although transepithelial electrical resistance fell to less than 20% of initial values within 1 hour of TPA exposure, transmission electron microscopy showed no change in the gross morphology of the tight junction of cells treated with 10(−7) M TPA for up to 2 hours. Immunofluorescence microscopy revealed a more rapid change in the membrane distribution of ZO-1 compared to occludin in the TPA-treated cells. Immunoblot analysis indicated that occludin levels in total cell lysates as well as cytosolic, membrane (Triton-X soluble) and cytoskeletal (Triton-X insoluble) fractions remained unchanged for at least 2 hours in cells treated with 10(−7) M TPA compared to their corresponding control cells. As the phosphorylation state of occludin is thought to be important in both tight junction assembly and regulation, the effect of phorbol ester treatment on the phosphorylation of occludin was investigated. Surprisingly, activation of protein kinase C with 10(−7) M TPA resulted in a time-dependent decrease in threonine phosphorylation of occludin which correlated closely with the rapid decrease in transepithelial electrical resistance. This dephosphorylation of occludin, occurring after activation of a serine/threonine kinase by TPA, suggested that protein kinase C was not acting directly on this tight junction target protein. If occludin dephosphorylation is involved in increasing tight junction permeability, then protein kinase C is apparently further upstream in the signaling pathway regulating epithelial barrier function, with a downstream serine/threonine phosphatase acting upon occludin.

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