Measuring Integrin Conformational Change on the Cell Surface with Super-Resolution Microscopy

Publication date: 13 February 2018
Source:Cell Reports, Volume 22, Issue 7
Author(s): Travis I. Moore, Jesse Aaron, Teng-Leong Chew, Timothy A. Springer
We use super-resolution interferometric photoactivation and localization microscopy (iPALM) and a constrained photoactivatable fluorescent protein integrin fusion to measure the displacement of the head of integrin lymphocyte function-associated 1 (LFA-1) resulting from integrin conformational change on the cell surface. We demonstrate that the distance of the LFA-1 head increases substantially between basal and ligand-engaged conformations, which can only be explained at the molecular level by integrin extension. We further demonstrate that one class of integrin antagonist maintains the bent conformation, while another antagonist class induces extension. Our molecular scale measurements on cell-surface LFA-1 are in excellent agreement with distances derived from crystallographic and electron microscopy structures of bent and extended integrins. Our distance measurements are also in excellent agreement with a previous model of LFA-1 bound to ICAM-1 derived from the orientation of LFA-1 on the cell surface measured using fluorescence polarization microscopy.

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Teaser

Using super-resolution interferometric photoactivation and localization microscopy (iPALM), Moore et al. measure the nanometer scale conformational change that occurs upon activation of the leukocyte integrin LFA-1 on the surface of migrating T cells. The authors also measure the effect of antagonists on integrin conformation.


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