MOLECULAR ARCHITECTURE OF THE DOCKING MACHINERY FOR NEUROTRANSMITTER RELEASE

Exocytosis of neurotransmitters and hormones is essential for brain function and neuroendocrine-signaling. Prior to exocytosis, neurotransmitter-containing vesicles dock to the target membrane. Recently it was shown that only a fraction of docked-vesicles fuse upon Ca2+-influx and their release-readiness seems determined by their proximity to Ca2+-channels. For many years the molecular docking machinery was unknown. The applicant (VENI-916-36-043) resolved the minimal docking machinery in neuroendocrine cells using electron-microscopic (EM)-analyses and also found that docking is controlled by sub-membrane cytoskeleton. The importance of these docking-proteins is illustrated by the fact that they are strongly linked to brain-disorders, in particular neurodegenerative-diseases and mental-illnesses, and also associate with intelligence. Currently, it is unclear how these docking-proteins operate in synapses and regulate synaptic vesicle docking near Ca2+-channels. In addition it is unknown how the unique composition of sub-membrane cytoskeleton may help to orchestrate this docking process. Finally, from observations by total-internal-reflection-fluorescence-microscopy (TIRF) it seems that secretory vesicles show different motility-behaviour before they fuse, but it is unclear how these vesicle-dynamics relate to docking and positioning relative to Ca2+-channels. This requires novel high-resolution imaging-techniques. Here, the applicant aims to elucidate the molecular architecture and spatial organization of the docking machinery. To reach her aim she will address how docking-proteins linked to neurological-disorders orchestrate correct vesicle-positioning to Ca2+-channels and relate this to vesicle-dynamics, release-readiness as well as the sub-membrane cytoskeleton. She will undertake novel ultrastructural-studies in neuronal cells expressing mutated docking-proteins. Her study will help to understand neurological-disorders linked to these docking-genes in the human brain. The proposed research will promote continuation of EM-expertise on the VUA-campus after retirement of UHD Dr. Van Minnen. The Netherlands is famous for its EM history, but modern EM-expertise among young scientists/UDs is rare and insufficient. This grant helps to prevent loss of such expertise and boost innovation in Dutch EM-research.