Revealing the nanoscale organization of B lymphocyte surface receptors and their lipid environment using super resolution imaging approaches

• Applicants: Dr. Niklas Engels; Dr. Felipe Opazo
• Subject Area: Immunology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455603379

B cells are key elements of the adaptive immune system as they have the capability to recognize specific pathogens and to produce protective antibodies. The detection of foreign molecules (antigens) is carried out by B cell antigen receptors (BCRs), which are embedded within the cellular plasma membrane. The BCR is critically regulated by coreceptors that either enhance or reduce its activity and thus can either promote or repress the production of antibodies. The interplay of these different cell surface receptors is a molecular decision-making process that furthermore involves circumambient plasma membrane lipids. However, the spatial organization of all of these components as well as the way by which they act together to allow for an appropriate cellular response remain unclear. Recently, we have developed a methodology to determine the organization of cell surface receptors with high accuracy and precision that relies on high-resolution imaging. The method is based on the efficient staining of plasma membrane-localized molecules with precisely labeled high-affinity small molecular probes in combination with super-resolution microscopy. This approach will be used to decipher the topology of different BCR isotypes in relation to the regulatory coreceptors CD19, CD22 and CD45. The imaging approaches will be accompanied by functional signaling studies and mutational analyses to obtain a detailed picture of the molecular interactions between the different cell surface receptors that ultimately control antibody production. Furthermore, we will elucidate the distribution and organization of signaling-active plasma membrane lipids by using different super-resolution imaging techniques. To this end, we will employ isotope-labeled affinity probes and the metabolic labeling of lipids to ascertain their localization in relation to B cell surface receptors using nanometer secondary ion mass spectrometry (nanoSIMS) imaging. Our work will substantially extend our knowledge about the interplay and interactions of immune receptors and plasma membrane constituents and thus will advance our understanding of the molecular decision-making processes that control humoral immunity and auto-immunity.

• DFG Programme: Research Grants