Disruption of basal JNK activity differentially affects key fibroblast functions important for wound healing.
We used both a gene knockout approach and pharmacologic modulation to study the implication of the JNK pathway in regulating fibroblast motility, capacity to contract mechanically unloaded collagen gels, and type I collagen gene expression in vitro. These parameters, which are important for tissue repair, are positively regulated by transforming growth factor (TGF)-beta, a cytokine viewed as playing a master role during wound healing. We demonstrate that basal JNK activity is critical for fibroblast motility because (a) mouse embryo jnk-/- fibroblasts exhibit significantly lower ability to close mechanically induced cell layer wounds than their wild-type (wt) counterparts, and (b) wound closure by human dermal fibroblasts is dramatically impaired by the specific JNK inhibitor SP600125. junAA fibroblasts, in which amino acids Ser63 and Ser73 of c-Jun are replaced by two Ala residues so that c-Jun cannot be phosphorylated by JNK, also exhibited impaired motility, suggesting that c-Jun phosphorylation by JNK is critical for fibroblast migration. In sharp contrast to their lesser motility on plastic, jnk-/- and junAA fibroblasts contracted free-floating, mechanically unloaded, collagen lattices markedly faster than wt fibroblasts. Furthermore, basal mRNA steady-state levels for types I and III collagen genes were similar in jnk-/- and wt fibroblasts. Likewise, overexpression of a dominant-negative mutant form of MKK4 in dermal fibroblasts did not affect collagen expression. We also demonstrate that basal JNK activity does not affect either TGF-beta-induced collagen gene expression or lattice contraction, whereas on the other hand, the blockage of motility initiated by JNK inhibition cannot be overcome by TGF-beta. Together these results demonstrate discrete, yet significant and highly specific, regulation of fibroblast functions important for wound healing by basal JNK activity.
Javelaud
Delphine
D
INSERM U532, Institut de Recherche sur la Peau, Université Paris VII, Hôpital Saint-Louis, Pavillon Bazin, France.
Laboureau
Julien
J
Gabison
Eric
E
Verrecchia
Franck
F
Mauviel
Alain
A
D002465:Cell Movement / Q000235:genetics; D003094:Collagen / Q000502:physiology; D005347:Fibroblasts / Q000201:enzymology / Q000502:physiology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014945:Wound Healing / Q000235:genetics*
D016212:Transforming Growth Factor beta; D003094:Collagen; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases