Opposing effects of protein kinase Calpha and protein kinase Cepsilon on collagen expression by human lung fibroblasts are mediated via MEK/ERK and caveolin-1 signaling.
The roles of MEK, ERK, the epsilon and alpha isoforms of protein kinase C (PKC), and caveolin-1 in regulating collagen expression were studied in normal lung fibroblasts. Knocking down caveolin-1 gave particularly striking results. A 70% decrease caused a 5-fold increase in MEK/ERK activation and collagen expression. The combined data reveal a branched signaling pathway. In its central portion MEK activates ERK, leading to increased collagen expression. Two branches converge on MEK/ERK. In one, increased PKCepsilon leads to MEK/ERK activation. In another, increased PKCalpha induces caveolin-1 expression, which in turn inhibits MEK/ERK activation and collagen expression. Lung fibroblasts from scleroderma patients with pulmonary fibrosis showed altered signaling. Consistent with their overexpression of collagen, scleroderma lung fibroblasts contain more activated MEK/ERK and less caveolin-1 than normal lung fibroblasts. Because cutaneous fibrosis is the hallmark of scleroderma, we also studied dermal fibroblasts. As in lung, there was more activated MEK/ERK in cells from scleroderma patients than in control cells, and MEK inhibition decreased collagen expression. However, the distinctive levels of PKCepsilon, PKCalpha, and caveolin-1 in lung and dermal fibroblasts from scleroderma patients and control subjects indicate that the links between these signaling proteins and MEK/ERK must function differently in the four cell types. Finally, we confirmed the relevance of these signaling cascades in vivo. The combined results demonstrate that a branched signaling pathway involving MEK, ERK, PKCepsilon, PKCalpha, and caveolin-1 regulates collagen expression in normal lung tissue and is perturbed during fibrosis.
Tourkina
Elena
E
Division of Rheumatology and Immunology, Medical University of South Carolina, Charleston, South Carolina 29425, USA. tourkine@musc.edu
Gooz
Pal
P
Pannu
Jaspreet
J
Bonner
Michael
M
Scholz
Dimitri
D
Hacker
Sharon
S
Silver
Richard M
RM
Trojanowska
Maria
M
Hoffman
Stanley
S
D000818:Animals; D002070:Butadienes / Q000378:metabolism; D051242:Caveolin 1; D022461:Caveolins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D005355:Fibrosis / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008168:Lung / Q000166:cytology* / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D009570:Nitriles / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D012595:Scleroderma, Systemic / Q000235:genetics / Q000378:metabolism / Q000473:pathology
D002070:Butadienes; C495540:CAV1 protein, human; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009570:Nitriles; D016376:Oligonucleotides, Antisense; C113580:U 0126; D003094:Collagen; C497256:Prkce protein, mouse; C496628:PRKCA protein, human; C497255:PRKCE protein, human; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases