Elucidating the structural and functional roles of filamentous proteins in immune signaling through cryo-EM helical reconstruction

Abstract

Filamentous structures are fundamental to immune signaling, with cryo-EM helical reconstruction playing an important role in uncovering their architecture. While cytosolic CARD-containing proteins have been extensively studied, the oligomerisation and structural dynamics of nuclear CARDs remain poorly understood. In this work, we characterise the helical assemblies and multimerisation properties of nuclear SP CARDs (NSP CARDs), identifying novel interaction surfaces that give rise to a unique helical architecture, distinct from the assemblies from by cytosolic CARDs. Similarly, helical reconstruction has been essential in resolving plant NLR filament structures, including L7TIR and SlNRC2, revealing novel cofactor and substrate interactions. Together, these findings reinforce the importance of helical reconstruction in decoding immune-related filamentous assemblies across diverse systems.