Linking single integrin–ligand bond properties to cell adhesiveness under external forces exemplified by the VLA-4–VCAM-1 bond

Abstract

Cell adhesion is a complex event dictated by the properties of individual adhesion molecules. It is desirable to link their individual properties to the adhesive behavior of a whole cell. Here, we examine with atomic force microscopic (AFM) and flow chamber experiments how the exogenous activation of the major T cell integrin VLA-4 affects the adhesiveness of T-lymphocytes to the endothelial VLA-4 ligand, VCAM-1. The atomic force measurements are performed on substrates with different VCAM-1 densities to compare the properties of single adhesive bonds on low-density ligands with the effect of multiple bonds on higher ligand densities. We determine the basal off-rate and the potential width of the single adhesive VLA-4-VCAM-1 bond by Monte-Carlo simulations. We show that activating VLA-4 with magnesium increases the potential width of the bond from 0.18 nm to 0.44 nm, but hardly affects the basal off-rate of single VLA-4-VCAM-1 bonds measured at low VCAM-1 density, lowering it only from 1.2 s À1 to 0.9 s À1 . At higher VCAM-1 densities, the apparent off-rate of high avidity VLA-4-VCAM-1 interactions is significantly reduced by magnesium to <0.1 s À1 . In the flow chamber, both the frequency of T cell attachments to VCAM-1 and their lifetime rise after VLA-4 activation by magnesium. By extrapolating the single-molecule properties to whole cells, we suggest that exogenous stimulation with magnesium strongly increases the rate of VLA-4 rebinding to VCAM-1 and only slightly decreases the off-rate of single VLA-4-VCAM-1 bonds.

Probing the Interaction Forces of Prostate Cancer Cells with Collagen I and Bone Marrow Derived Stem Cells on the Single Cell Level

“…To quantify the adhesion forces between prostate cancer cells and the bone matrix protein Col-I as well as the bone marrow-derived mesenchymal stem cell line SCP1 on the single cell level, AFM based force spectroscopy was used [27]–[29].Cell to cell and cell to matrix adhesion experiments were performed in cell culture dishes with cells derived from prostate cancer bone (PC3) or lymph node metastasis (LNCaP). One of these cells was immobilized on the AFM force sensor ( Fig.…”

Correction: Probing the Interaction Forces of Prostate Cancer Cells with Collagen I and Bone Marrow Derived Stem Cells on the Single Cell Level

“…To quantify the adhesion forces between prostate cancer cells and the bone matrix protein Col-I as well as the bone marrowderived mesenchymal stem cell line SCP1 on the single cell level, AFM based force spectroscopy was used [27][28][29].Cell to cell and cell to matrix adhesion experiments were performed in cell culture dishes with cells derived from prostate cancer bone (PC3) or lymph node metastasis (LNCaP). One of these cells was immobilized on the AFM force sensor (Fig.…”

Immobilizing a single DNA molecule at the apex of AFM tips through picking and ligation

“…1 In particular, atomic force microscopy (AFM) is an important tool because it can sense pN-scale forces, and generate high resolution images of solid surfaces and biological samples, including cells. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In realizing single molecule interactions with AFM, important factors include optimizing layout of a probe molecule at the apex of a tip as well as providing appropriate data analysis methods to interpret the measured force value correctly. 18 For this end, various chemical modifications of the tip have been studied, [18][19][20] and several approaches were effective to enhance probability of observing single molecular interaction.…”