Keratin 8 Phosphorylation by Protein Kinase C δ Regulates Shear Stress-mediated Disassembly of Keratin Intermediate Filaments in Alveolar Epithelial Cells

Although the amiloride-sensitive epithelial sodium channel (ENaC) plays an important role in the modulation of alveolar liquid clearance, the precise mechanism of its regulation in alveolar epithelial cells is still under investigation. Protein kinase C (PKC) has been shown to alter ENaC expression and activity in renal epithelial cells, but much less is known about its role in alveolar epithelial cells. The objective of this study was to determine whether PKC activation modulates ENaC expression and transepithelial Na+ transport in cultured rat alveolar epithelial cells. Alveolar type II cells were isolated and cultured for 3 to 4 d before they were stimulated with phorbol 12-myristate 13-acetate (PMA 100 nmol/L) for 4 to 24 h. PMA treatment significantly decreased α, β, and γENaC expression in a time-dependent manner, whereas an inactive form of phorbol ester had no apparent effect. This inhibitory action was seen with only 5-min exposure to PMA, which suggested that PKC activation was very important for the reduction of αENaC expression. The PKC inhibitors bisindolylmaleimide at 2 µmol/L and Gö6976 at 2 µmol/L diminished the PMA-induced suppression of αENaC expression, while rottlerin at 1 µmol/L had no effect. PMA elicited a decrease in total and amiloride-sensitive current across alveolar epithelial cell monolayers. This decline in amiloride-sensitive current was not blocked by PKC inhibitors except for a partial inhibition with bisindolylmaleimide. PMA induced a decrease in rubidium uptake, indicating potential Na+-K+-ATPase inhibition. However, since ouabain-sensitive current in apically permeabilized epithelial cells was similar in PMA-treated and control cells, the inhibition was most probably related to reduced Na+ entry at the apical surface of the cells. We conclude that PKC activation modulates ENaC expression and probably ENaC activity in alveolar epithelial cells. Ca2+-dependent PKC is potentially involved in this response.Key words: alveolar epithelial cells, Na+ transport, Na+ channel, ENaC, protein kinase C, Na+-K+-ATPase, amiloride, gene expression.

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Mediator generation and signaling events in alveolar epithelial cells attacked byS. aureusα-toxin

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00156.2001 ◽

2002 ◽

Vol 282 (2) ◽

pp. L207-L214 ◽

Cited By ~ 45

Author(s):

Frank Rose ◽

Gabriele Dahlem ◽

Bernd Guthmann ◽

Friedrich Grimminger ◽

Ulrich Maus ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Epithelial Cells ◽

Nuclear Factor Κb ◽

Alveolar Epithelial Cells ◽

Target Cells ◽

Pyrrolidine Dithiocarbamate ◽

Nuclear Factor ◽

Alveolar Epithelial ◽

Kinase C

Staphylococcus aureus α-toxin is a pore-forming bacterial exotoxin that has been implicated as a significant virulence factor in human staphylococcal diseases. In primary cultures of rat pneumocyte type II cells and the human A549 alveolar epithelial cell line, purified α-toxin provoked rapid-onset phosphatidylinositol (PtdIns) hydrolysis as well as liberation of nitric oxide and the prostanoids PGE2, PGI2, and thromboxane A2. In addition, sustained upregulation of proinflammatory interleukin (IL)-8 mRNA expression and protein secretion occurred. “Priming” with low-dose IL-1β markedly enhanced the IL-8 response to α-toxin, which was then accompanied by IL-6 appearance. The cytokine response was blocked by the intracellular Ca2+-chelating reagent 1,2-bis(2-aminophenoxy)-ethane- N,N,N′ ,N′-tetraacetic acid, the protein kinase C inhibitor bis-indolyl maleimide I, as well as two independent inhibitors of nuclear factor-κB activation, pyrrolidine dithiocarbamate and caffeic acid phenethyl ester. We conclude that alveolar epithelial cells are highly reactive target cells of staphylococcal α-toxin. α-Toxin pore-associated transmembrane Ca2+flux and PtdIns hydrolysis-related signaling with downstream activation of protein kinase C and nuclear translocation of nuclear factor-κB are suggested to represent important underlying mechanisms. Such reactivity of the alveolar epithelial cells may be relevant for pathogenic sequelae in staphylococcal lung disease.

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Stimulation of phosphatidylcholine hydrolysis in type II alveolar epithelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1992.263.1.l42 ◽

1992 ◽

Vol 263 (1) ◽

pp. L42-L50

Author(s):

L. C. Dubrovin ◽

L. A. Brown

Keyword(s):

Signal Transduction ◽

Protein Kinase C ◽

Protein Kinase ◽

Alveolar Epithelial Cells ◽

Type Ii ◽

Alveolar Epithelial ◽

Kinase C ◽

Type Ii Pneumocytes ◽

Stimulation Of ◽

In Cells

The effects of phorbol 12-myristate 13-acetate (TPA) or ATP on phosphatidylcholine (PC) hydrolysis were investigated in cultured type II pneumocytes prelabeled with [3H]choline or 1-O-[3H]octadecyl-sn-glycero-3-phosphocholine ([3H]lyso-PAF). In cells prelabeled with [3H]choline, TPA or ATP stimulated an increase in [3H]choline, [3H]phosphocholine, and [3H]glycerophosphocholine. The formation of these choline metabolites was associated with a concomitant loss of [3H]PC but not from disaturated PC or phosphatidylinositol. In cells prelabeled with [3H]lyso-PAF, the formation of [3H]phosphatidic acid (PA) and then [3H]1,2-DG was stimulated by TPA or ATP and was associated with a loss of 3H from PC but not from disaturated PC or phosphatidylinositol. There was a concentration-dependent formation of [3H]1,2-DG and [3H]PA in response to ATP. Downregulation of protein kinase C with TPA abolished the stimulation of PC hydrolysis. In addition to the generation of metabolites indicative of phospholipase C and/or D activity, [3H]lyso-PC, a product of phospholipase A2, was also generated in response to TPA. These findings suggest an important role for PC breakdown in signal transduction in type II pneumocytes.

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Dopamine-induced Exocytosis of Na,K-ATPase Is Dependent on Activation of Protein Kinase C-ε and -δ

Molecular Biology of the Cell ◽

10.1091/mbc.01-07-0323 ◽

2002 ◽

Vol 13 (4) ◽

pp. 1381-1389 ◽

Cited By ~ 74

Author(s):

Karen M. Ridge ◽

Laura Dada ◽

Emilia Lecuona ◽

Alejandro M. Bertorello ◽

Adrian I. Katz ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Atpase Activity ◽

Basolateral Membrane ◽

Specific Inhibitor ◽

Alveolar Epithelial Cells ◽

Protein Abundance ◽

Alveolar Epithelial ◽

Kinase C ◽

Late Endosomes

The purpose of this study was to define mechanisms by which dopamine (DA) regulates the Na,K-ATPase in alveolar epithelial type 2 (AT2) cells. The Na,K-ATPase activity increased by twofold in cells incubated with either 1 μM DA or a dopaminergic D1agonist, fenoldopam, but not with the dopaminergic D2agonist quinpirole. The increase in activity paralleled an increase in Na,K-ATPase α1 and β1 protein abundance in the basolateral membrane (BLM) of AT2 cells. This increase in protein abundance was mediated by the exocytosis of Na,K-pumps from late endosomal compartments into the BLM. Down-regulation of diacylglycerol-sensitive types of protein kinase C (PKC) by pretreatment with phorbol 12-myristate 13-acetate or inhibition with bisindolylmaleimide prevented the DA-mediated increase in Na,K-ATPase activity and exocytosis of Na,K-pumps to the BLM. Preincubation of AT2 cells with either 2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]-3-(1H-indol-3-yl)maleimide (Gö6983), a selective inhibitor of PKC-δ, or isozyme-specific inhibitor peptides for PKC-δ or PKC-ε inhibited the DA-mediated increase in Na,K-ATPase. PKC-δ and PKC-ε, but not PKC-α or -β, translocated from the cytosol to the membrane fraction after exposure to DA. PKC-δ– and PKC-ε–specific peptide agonists increased Na,K-ATPase protein abundance in the BLM. Accordingly, dopamine increased Na,K-ATPase activity in alveolar epithelial cells through the exocytosis of Na,K-pumps from late endosomes into the basolateral membrane in a mechanism-dependent activation of the novel protein kinase C isozymes PKC-δ and PKC-ε.

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