Signaling lipid coding of presynapse formation and function in health and disease

• Applicant: Professor Volker Haucke, Ph.D.
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells ; Cell Biology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550824611

Chemical neurotransmission at synapses is mediated by the action potential induced fusion of neurotransmitter-filled synaptic vesicles (SVs) at specialized active zone (AZ) release sites comprised of scaffold proteins and voltage-gated calcium channels. Following exocytic fusion SVs are recycled by compensatory endocytosis and reformation of release-competent SVs. Recent data suggest that the exo-endocytic cycling of SV membranes is integrated with phosphoinositide lipid signaling. Moreover, we have revealed an important function for phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2], a rare endolysosomal signaling lipid synthesized by PIKFYVE, in presynapse biogenesis in developing neurons. How precisely signaling phospholipids such as PI(3,5)P2 act remains incompletely understood. Recent work has uncovered Annexin A11 (ANXA11) as a putative PI(3,5)P2 effector protein on late endosomes or lysosomes in axons of human neurons. ANXA11 was found to play a role in tethering membraneless RNA granules to actively-transported lysosomes involving its intrinsic membrane-binding and phase-separating properties. This facilitates the efficient transport of RNA to distal regions of the neuron. We hypothesize that PIKFYVE via association of its lipid product PI(3,5)P2 with Annexins (e.g. ANXA11) controls the axonal transport of RNA granule-associated lysosomes and other types of lysosome-related organelles (e.g. synaptic vesicle (SV) precursors) to support axonal and synaptic function and, thereby, counteract axonal degeneration (for example in ALS or FTD). In the proposed collaborative project, we will test this hypothesis at multiple levels: We combine CRIPSR/Cas9-based genome-engineering in human stem cell derived excitatory neurons with live correlative light and electron microscopy and quantitative proteomics to unravel the PIKFYVE interactome, localization and physiological regulation in human neurons. Moreover, we integrate data from axonal ribosome profiling, lyso-IP-based proteomics to determine the impact of PIKFYVE KO on axonal RNA transport and the axonal translatome and proteome and, use patient-derived motoneurons to analyse how PIKFYVE contributes to ALS pathology. In parallel sets of studies, we probe the role of ANXA11 in PI(3,5)P2-dependent axonal transport of lysosome-related organelles and associated synaptic proteins and in synaptic function. We predict our studies to provide groundbreaking new insights into the roles of PI(3,5)P2 and associated annexin proteins in the control of axonal transport and presynaptic function in health and disease.

• DFG Programme: Research Grants
• International Connection: South Korea
• Cooperation Partner: Professor Dr. Sunghoe Chang