Cooperative signaling by alpha 5 beta 1 and alpha 4 beta 1 integrins regulates metalloproteinase gene expression in fibroblasts adhering to fibronectin.
Rabbit synovial fibroblasts (RSF) express basal levels of the metalloproteinases (MMP) collagenase, stromelysin-1 and 92-kD gelatinase when plated on intact fibronectin (FN), but elevated levels when plated on either the central RGD-containing cell-binding region of FN (120FN) or antibody against the alpha 5 beta 1 integrin, suggesting that domains outside 120FN may suppress the induction of MMP (Werb, Z., P. M. Tremble, O. Behrendtsen, E. Crowley, and C.H. Damsky. 1989. J. Cell Biol. 109:877-889). We therefore attempted to reconstitute the basal signaling of intact FN by plating RSF on 120FN together with domains of FN outside this region. Large COOH-terminal fragments containing both the heparin-binding and HICS domains suppressed MMP when combined with 120FN. To map the active sequences, peptides from this region and larger fragments that did, or did not, include the CS-1 portion of IIICS were tested. Only CS-1 peptide, or larger fragments containing CS-1, suppressed MMP expression induced by 120FN. In contrast, peptide V from the heparin-binding region, shown previously to stimulate focal contact formation, further enhanced MMP expression by RSF when present on the substrate with 120FN. RSF expressed alpha 4 beta 1 integrin, the receptor for CS-1, and the anti-alpha 4 mAb blocked the ability of CS-1 to suppress MMP induction by 120FN. These results show that signals modulating MMP expression and focal contact assembly are regulated independently, and that cooperative signaling by alpha 5 beta 1 and alpha 4 beta 1 integrins plays a dominant role in regulating expression of these extracellular matrix-remodeling genes in response to FN. This work demonstrates directly the modular way in which information in the extracellular matrix is detected and processed by cell surface receptors.
Huhtala
P
P
Department of Stomatology, University of California, San Francisco 94143, USA.
Humphries
M J
MJ
McCarthy
J B
JB
Tremble
P M
PM
Werb
Z
Z
Damsky
C H
CH
D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D002478:Cells, Cultured; D017364:Collagenases / Q000096:biosynthesis / Q000235:genetics; D005109:Extracellular Matrix / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology; D005353:Fibronectins / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000502:physiology; D011233:Precipitin Tests; D011817:Rabbits; D017469:Receptors, Fibronectin; D015398:Signal Transduction / Q000502:physiology*; D013329:Structure-Activity Relationship; D013489:Suppression, Genetic; D013583:Synovial Membrane / Q000166:cytology
D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D010446:Peptide Fragments; D017469:Receptors, Fibronectin; D017364:Collagenases; D008666:Metalloendopeptidases