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.
INSERM U532, Institut de Recherche sur la Peau, Université Paris VII, Hôpital Saint-Louis, Pavillon Bazin, France.
Delphine
D
Javelaud
Julien
J
Laboureau
Eric
E
Gabison
Franck
F
Verrecchia
Alain
A
Mauviel
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