We switched to a purely human model system to avoid any potential complications resulting from interspecies incompatibilities at the molecular level and repeated the vitronectin binding assay using Jurkat cells, human serum, and antibody to human vitronectin.
To test whether binding to late apoptotic cells is a specific feature of vitronectin, we performed staining of late apoptotic cells with antibodies to human vitronectin and human albumin.
The best hit overall was to human vitronectin.
The four osteoblast-adhesive peptides discussed in this paper are mapped on the 339 364 sequence (339MAPRPSLAKKQRFRHRNRKGYRSQRG364) located in the primary heparin-binding site of human vitronectin (HVP).
From this perspective, the explanation for inhibition of TRAP secretion by fibronectin might be that fibronectin prevents vitronectin in the serum from binding to the vitronectin receptor [34].
αvβ3 integrin binding to its vitronectin ligand is known to activate both PKC and Src [ 11, 45].
Studies on syndecan-1 role in cell adhesion by specific integrins show that this proteoglycan influences α2 β1, αV β3, and αV β5 integrins binding to collagen, vitronectin, and vitronectin/fibronectin, respectively [ 36– 36].
Integrin α8 regulates cell adhesion and migration by binding to Fn1, vitronectin, and tenascin-C in an RGD-dependent manner (Muller et al, 1995; Schnapp et al, 1995; Denda et al, 1998; Benoit et al, 2009).
Specificity of the vitronectin antibody was confirmed by ELISA demonstration of binding to purified recombinant vitronectin, but not fibronectin or collagen (not shown).
More recently, Lopez-Alemany et al. reported that plasminogen activator inhibitor-1 (PAI1) competes with αvβ3 integrins for binding to vitronectin and by this mechanism blocks insulin-induced migration in NIH3T3 cells and human umbilical vein endothelial cells[ 8].
