SINGLEMOLECULE FORCE SPECTROSCOPY OF MICROBIAL CELL ENVELOPE PROTEINS - Life at the Nanoscale: Atomic Force Microscopy of Live Cells - page 318

15.2.4.2 HBHA - HSPG interacons

The next question we addressed is whether similar interactions occur
between HBHA and HSPG receptors on host cells? To this end, we measured
the forces between HBHA tips and living A549 pneumocyte cells ( Fig. 15.4 ) .

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AFM imaging revealed that A549 cells were typically 50 μm in diameter and
showed two prominent features, i.e., the central round nucleus surrounded
by the lattened cytoplasm and membrane, and the underlying cytoskeleton
structures (actin ilaments). The speciic binding force measured at moderate
pulling velocity between single HBHA-HSPG pairs was about 50 pN, which

(a) (b)

(c)

(d)

Figure 15.4. SMFS of the HBHA-HSPG interaction. (a, b) Delection images of live
A549 pneumocytes. (c) Representative force curves recorded between a HBHA tip and
a A549 cell showing constant force plateaus. The tether extraction force F t increases
with the pulling velocity. (d) Suggested mechanism: the stressed receptors detached
from the cytoskeleton, leading to the extraction of membrane tethers. Reprinted with
permission from Dupres et al. 33