Project B02 - Structural Mechanisms of MALT1 Signaling in T Cell Differentiation and Activation

In the last funding period, we solved the architecture of the helical BCL10-MALT1 core filament by cryo-electron microscopy (cryo-EM), defining the interface between the N-terminal MALT1 death domain (DD) and the BCL10 caspase recruitment domain (CARD) and by showing that the C-terminal MALT1 immunoglobulin and paracaspase domains protrude flexibly from this inner core to orchestrate binding of mediators and substrates at the filament periphery. Based on these discoveries, we will now analyze the recruitment of TRAF6 to the C-terminus of MALT1 as well as substrate binding to MALT1 by biochemical techniques, X-ray crystallography and cryo electron microscopy. To account for its regulation by phosphorylation, mono- and poly-ubiquitination we will purify the CBM proteins from human cells with the goal to analyze posttranslational-modified samples by cryo-electron microscopy (cryo-EM) or individual filaments by cryo-electron tomography (cryo-ET). Finally, we will develop a method to investigate the CBM complex filament assembly in T cells using in cellulo cryo-ET.