Nanomechanical mapping of first binding steps of a virus to animal cells

Abstract

Viral infection is initiated when a virus binds to cell surface receptors. Because the cell membrane is dynamic and heterogeneous, imaging living cells and simultaneously quantifying the first viral binding events is difficult. Here, we show an atomic force and confocal microscopy set-up that allows the surface receptor landscape of cells to be imaged and the virus binding events within the first millisecond of contact with the cell to be mapped at high resolution (<50 nm). We present theoretical approaches to contour the free-energy landscape of early binding events between an engineered virus and cell surface receptors. We find that the first bond formed between the viral glycoprotein and its cognate cell surface receptor has relatively low lifetime and free energy, but this increases as additional bonds form rapidly (≤1 ms). The formation of additional bonds occurs with positive allosteric modulation and the three binding sites of the viral glycoprotein are quickly occupied. Our quantitative approach can be readily applied to study the binding of other viruses to animal cells.

Progress in the Correlative Atomic Force Microscopy and Optical Microscopy

“…By fluorescently labelling the virus and the corresponding receptors expressed in cells, and functionalizing the AFM tip with the labelled virus, the authors could precisely localize and quantify the individual virus binding events (Figure 6). They also contoured the free-energy landscape for the first virus-receptor binding events [53]. The combination of colloidal probe AFM and confocal microscopy can be used to investigate the relationships between mechanical properties and the release of microcapsules that were useful for drug delivery [54,55].…”

Interactions between the breast cancer-associated MUC1 mucins and C-type lectin characterized by optical tweezers

“…The occurrence of the force unbinding events were determined based on differentiating the smoothed raw data to make the identification of force jumps more easy to distinguish from signals from the noise. The procedure employed to determine the force loading rate uses a linear approximation of the increase in force just prior to the unbinding event, and is previously reported [45]. The data segments of the force-traces just prior to the unbinding events are selected based on balancing the suppression of effect of noise in the data while conforming to the linear approximation.…”

Atomic Force Microscopy in Characterizing Cell Mechanics for Biomedical Applications: A Review

“…It is delighted that the performance of AFM has been continually improved and new AFM imaging modes are being created [167], [168], which will make AFM more appealing to researchers. The combined use of AFM and molecular techniques (e.g., combined with confocal microscopy which can visualize the target biomolecules by fluorescence labeling [169], [170]) can simultaneously acquire multiple complementary information, which will help us to real-time investigate the links between cell mechanics and cell structures. We expect that as more AFM single-cell mechanical studies are performed in the future, it will lead to a more comprehensive understanding of cell mechanics in cell states and pathological changes.…”