Département de chimie moléculaire

Integrin $\alpha$v$\beta$3 is overexpressed on neoendothelial cells and frequently on tumor cells. The authors have developed a peptide-like scaffold (regioselectively addressable functionalized template, RAFT), which holds four cyclo(-RGDfK-) (cRGD) motifs and proved that this mol. (called regioselectively addressable functionalized template-arginine-glycine-aspartic acid, RAFT-RGD) targets integrin $\alpha$v$\beta$3 in vitro and in vivo. Using fluorescence correlation spectroscopy (FCS), the authors measured the const. of affinity (KD) of the RAFT-RGD for purified integrins. KD values rose from 3.87 nmol/l for RAFT-RGD to 41.70 nmol/l for cyclo(-RGDfK-). In addn., RAFT-RGD inhibited $\alpha$v$\beta$3 lateral mobility in the cell membrane, probably due to the formation of integrin clusters as demonstrated by fluorescence recovery after photobleaching (FRAP). This was confirmed by electron microscopy data, which established the formation of mol. complexes contg. two integrins in the presence of RAFT-RGD but not cRGD or regioselectively addressable functionalized template-arginine-alanine- aspartic acid (RAFT-RAD). Using an ELISA, the authors proved that 1 $μ$mol/l RAFT-RGD increased by 79{%} $\alpha$v$\beta$3 internalization via clathrin-coated vesicles. Conversely, cRGD was internalized without modifying $\alpha$v$\beta$3 internalization. Although RGD has been known for {\textgreater}20 years, this is the first study to formerly establish the relationships among multimeric presentation, increased affinity, and subsequent integrin-mediated cointernalization. These results strongly support the rationale for using multimeric RGD-peptides as targeting vectors for imaging, diagnosis, or therapy of cancers. [on SciFinder(R)]