Confluence switch signaling regulates ECM composition and the plasmin proteolytic cascade in keratinocytes.
In culture, cell confluence generates signals that commit actively growing keratinocytes to exit the cell cycle and differentiate to form a stratified epithelium. Using a comparative proteomic approach, we studied this 'confluence switch' and identified a new pathway triggered by cell confluence that regulates basement membrane (BM) protein composition by suppressing the uPA-uPAR-plasmin pathway. Indeed, confluence triggers adherens junction maturation and enhances TGF-β and activin A activity, resulting in increased deposition of PAI-1 and perlecan in the BM. Extracellular matrix (ECM)-accumulated PAI-1 suppresses the uPA-uPAR-plasmin pathway and further enhances perlecan deposition by inhibiting its plasmin-dependent proteolysis. We show that perlecan deposition in the ECM strengthens cell adhesion, inhibits keratinocyte motility and promotes additional accumulation of PAI-1 in the ECM at confluence. In agreement, during wound-healing, perlecan concentrates at the wound-margin, where BM matures to stabilize keratinocyte adhesion. Our results demonstrate that confluence-dependent signaling orchestrates not only growth inhibition and differentiation, but also controls ECM proteolysis and BM formation. These data suggest that uncontrolled integration of confluence-dependent signaling, might favor skin disorders, including tumorigenesis, not only by promoting cell hyperproliferation, but also by altering protease activity and deposition of ECM components.
INSERM, U634, 06107 Nice,  France.
Adrien
A
Botta
Frédéric
F
Delteil
Amel
A
Mettouchi
Andhira
A
Vieira
Soline
S
Estrach
Luc
L
Négroni
Caroline
C
Stefani
E
E
Lemichez
Guerrino
G
Meneguzzi
Laurent
L
Gagnoux-Palacios
D028341:Activins / Q000378:metabolism; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D002448:Cell Adhesion; D002454:Cell Differentiation; D002465:Cell Movement; D049109:Cell Proliferation; D015536:Down-Regulation; D005109:Extracellular Matrix / Q000378:metabolism*; D025461:Feedback, Physiological; D005341:Fibrinolysin / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D010958:Plasminogen / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D040901:Proteomics; D055293:Receptors, Urokinase Plasminogen Activator / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing
D019812:Heparan Sulfate Proteoglycans; D017395:Plasminogen Activator Inhibitor 1; D055293:Receptors, Urokinase Plasminogen Activator; D016212:Transforming Growth Factor beta; C422405:activin A; D028341:Activins; C071927:perlecan; D010958:Plasminogen; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator