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Imaging cell activation pathways

Cells translate environmental cues into intracellular responses by engaging cell membrane receptors. Delineating cell transduction pathways at the single molecule level requires cutting edge technology.
Imaging cell activation pathways
During cell activation, the transduction of information inside the cells depends on transient and heterogeneous signalling complexes that involve surface receptors, intracellular and adapter proteins. Such microclusters play a crucial role in T cell activation and affect the ability of the immune system to adequately respond to foreign pathogens.

Limitations in existing experimental techniques prohibit the elucidation of the structure, content, and organisation of signalling complexes. To image complexes downstream of the T cell receptor, the EU-funded PALM TCR COMPLEXES (Studying the structure and dynamics of TCR nucleated complexes at the single molecule level) project combined photoactivated localisation microscopy (PALM) with single molecule localisation microscopy (SMLM).

Researchers were particularly interested in modelling how single molecules that participate in signalling complexes are engaged in cell activation. They worked under the hypothesis that complexes have various levels of dynamic organisation, which serve the multiple functions of activated T cells.

Imaging results showed that signalling complexes are characterised by nano-scale organisation at the plasma membrane of activated T cells. Optical reconstruction of these images in multiple colours provided a resolution down to 20 nm, sufficient to facilitate the study of signalling complexes at the single molecule level.

Single molecule super-resolution imaging allowed scientists to study the complexity of molecular interactions, including potential cooperativity or competition in molecular binding. Their results demonstrated that signalling complexes cooperate during T cell activation. Furthermore, biophysical models and statistical methods were employed to resolve critical mechanisms of cell activation by signalling complexes.

The developed techniques are also relevant to other signalling systems and will greatly extend the understanding of the composition and formation of signalling complexes in cell activation in health and disease. Such knowledge will present novel opportunities for pharmacological intervention in diseases involving aberrant signalling and cellular malfunction such as in cancer.

Related information

Subjects

Life Sciences

Keywords

T cell activation, signalling, PALM TCR COMPLEXES, PALM, SMLM
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