2019 Cell Reports.pdf

Leukocyte adhesion requires b2-integrin activation.
Resting integrins exist in a bent-closed conformation—
i.e., not extended (E
) and not high affinity
(H
)—unable to bind ligand. Fully activated E+H+ integrin
binds intercellular adhesion molecules (ICAMs)
expressed on the opposing cell in trans. E
H
transitions
to E+H+ through E+H
or through E
H+, which
binds to ICAMs on the same cell in cis. Spatial
patterning of activated integrins is thought to be
required for effective arrest, but no high-resolution
cell surface localization maps of activated integrins
exist. Here, we developed Super-STORM by
combining super-resolution microscopy with molecular
modeling to precisely localize activated integrin
molecules and identify the molecular patterns of activated
integrins on primary human neutrophils. At the
time of neutrophil arrest, E
H+ integrins face each
other to form oriented (non-random) nanoclusters.
To address the mechanism causing this pattern, we
blocked integrin binding to ICAMs in cis, which significantly
relieved the face-to-face orientation.