Matrix Gla Protein Binds to Fibronectin and Enhances Cell Attachment and Spreading on Fibronectin
MGP enhances cell attachment to fibronectin. (a) The -axis is HeLa cell binding indicated as absorbance at 595 nm. The -axis is the log of fibronectin concentration from 0 to 3.3 μg/mL either with 3 μg/mL MGP (◯) or control buffer (●). MGP did not enhance cell attachment for 0 fibronectin (not shown, logarithmic plot). (b) Anti-MGP IgG blocks the activity of MGP for enhancing cell attachment to fibronectin. Cell attachment was measured for control, 0.4 μg/mL fibronectin; MGP, 0.4 μg/mL fibronectin plus 3 μg/mL MGP; MGP + anti MGP, μg/mL fibronectin plus 3 μg/mL MGP plus 31 μg/mL anti-MGP IgG; and MGP + IgG, 0.4 μg/mL fibronectin plus μg/mL MGP plus 31 μg/mL rabbit polyclonal IgG. MGP and MGP + IgG were significantly different from control and MGP + antiMGP (). (c) The concentration of MGP enhances cell attachment in a dose responsive manner but does not change maximum cell binding to fibronectin. Experiments were performed as in (a) except that MGP concentrations of 0.0, 0.8, 3, and 6 are compared, and the highest concentration of fibronectin is 1.6 μg/mL. No MGP (◯); 0.8 μg/mL MGP (●); 3 μg/mL MGP (▵); and 6 μg/mL MGP (▲). Error bars are SEM for 4–6 replicate binding assays for each data point. Lines are nonlinear regression lines derived by Prism software. (d) MGP inhibits cell binding to vitronectin. VN, 0.2 μg/mL vitronectin; VN + MGP, 0.2 μg/mL vitronectin plus 0.8 μg/mL MGP. Error Bars are SEM for 8 replicate binding assays. The indicates significant difference ().