TY - JOUR
T1 - Spontaneous formation of L-isoaspartate and gain of function in fibronectin
AU - Curnis, Flavio
AU - Longhi, Renato
AU - Crippa, Luca
AU - Cattaneo, Angela
AU - Dondossola, Eleonora
AU - Bachi, Angela
AU - Corti, Angelo
PY - 2006/11/24
Y1 - 2006/11/24
N2 - Isoaspartate formation in extracellular matrix proteins, by aspartate isomerization or asparagine deamidation, is generally viewed as a degradation reaction occurring in vivo during tissue aging. For instance, non-enzymatic isoaspartate formation at RGD-integrin binding sites causes loss of cell adhesion sites, which in turn can be enzymatically "repaired" to RGD by protein-L-isoAsp-O-methyltransferase. We show here that isoaspartate formation is also a mechanism for extracellular matrix activation. In particular, we show that deamidation of Asn263 at the Asn-Gly-Arg (NGR) site in fibronectin N-terminal region generates an α vβ3-integrin binding site containing the L-isoDGR sequence, which is enzymatically "deactivated" to DGR by protein-L-isoAsp-O-methyltransferase. Furthermore, rapid NGR-to-isoDGR sequence transition in fibronectin fragments generates αvβ 3 antagonists (named "isonectins") that competitively bind RGD binding sites and inhibit endothelial cell adhesion, proliferation, and tumor growth. Time-dependent generation of isoDGR may represent a sort of molecular clock for activating latent integrin binding sites in proteins.
AB - Isoaspartate formation in extracellular matrix proteins, by aspartate isomerization or asparagine deamidation, is generally viewed as a degradation reaction occurring in vivo during tissue aging. For instance, non-enzymatic isoaspartate formation at RGD-integrin binding sites causes loss of cell adhesion sites, which in turn can be enzymatically "repaired" to RGD by protein-L-isoAsp-O-methyltransferase. We show here that isoaspartate formation is also a mechanism for extracellular matrix activation. In particular, we show that deamidation of Asn263 at the Asn-Gly-Arg (NGR) site in fibronectin N-terminal region generates an α vβ3-integrin binding site containing the L-isoDGR sequence, which is enzymatically "deactivated" to DGR by protein-L-isoAsp-O-methyltransferase. Furthermore, rapid NGR-to-isoDGR sequence transition in fibronectin fragments generates αvβ 3 antagonists (named "isonectins") that competitively bind RGD binding sites and inhibit endothelial cell adhesion, proliferation, and tumor growth. Time-dependent generation of isoDGR may represent a sort of molecular clock for activating latent integrin binding sites in proteins.
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U2 - 10.1074/jbc.M604812200
DO - 10.1074/jbc.M604812200
M3 - Article
C2 - 17015452
AN - SCOPUS:33846020967
SN - 0021-9258
VL - 281
SP - 36466
EP - 36476
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 47
ER -