Uncovering the mechanistic bases of autoantibody-induced selective GM-CSF signaling

• Applicant: Professor Dr. Jacob Piehler
• Subject Area: Biophysics ; Immunology ; Cell Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565928191

The granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine with important functions in hematopoiesis and immunity by regulating differentiation and activity within the entire myeloid cell lineage. While already being a successful drug for treatment of patients with compromised hematopoiesis, excessive GM-CSF activation has been implicated in inflammatory conditions such as rheumatoid arthritis, osteoarthritis, and cytokine-release syndrome. Current anti-GM-CSF antibodies in clinical trials are effective but raise safety concerns, including risks of pulmonary alveolar proteinosis and increased susceptibility to infections. This highlights the need for selective and balanced therapeutic approaches that preserve essential GM-CSF functions while mitigating overactivation. Interestingly, the Taiwanese partner of this project has identified unique monoclonal auto-antibodies (mAbs) derived from cryptococcosis patients, which modulate GM-CSF signaling by selectively inhibiting only a subset of downstream signaling pathways, leading to less aggressive cellular responses. The German partner has found by live-cell single-molecule imaging techniques that these mAbs reduce but not abrogate GM-CSF-induced receptor heterodimerization in the plasma membrane, probably by reducing the agonist binding affinity to the beta common receptor subunit (βCR). This collaborative research project aims to uncover the biophysical mechanisms underlying GM-CSF-targeting by these auto-mAbs, pinpoint the implications for selective downstream signal activation and engineer GM-CSF agonists with receptor binding characteristics mimicking the modulation exerted by the auto-mAbs. To this end, the Taiwanese partner will dissect the biological effects of auto-mAbs on GM-CSF signaling in primary myeloid cells, identify alterations in inflammatory chemokine production and assess the effects on monocyte differentiation and activation (Aim 1). The German partner will resolve receptor assembly, dynamics and endocytic trafficking by advanced fluorescence imaging techniques using labeled GM-CSF and auto-mAbs (Aim 2). Based on these insights, the partners will rationally introduce mutations into βCR binding site of GM-CSF to modulate on- and off-rates at the cells surface and validate altered biological functionalities in cellular systems (Aim 3). The findings from these studies will provide a broader picture of signaling plasticity encoded in the GM-CSF signaling axes and guide the rational design of GM-CSF agonists with partial, more selective functions for improved therapeutic application.

• DFG Programme: Research Grants
• International Connection: Taiwan
• Partner Organisation: National Science and Technology Council (NSTC)
• Cooperation Partner: Professor Dr. Cheng-Lung Ku