Neuronal Secretion Principles

Within the secretory pathway, proteins and other cargo are transported from one compartment to another by vesicular traffic. Transport vesicles bud from donor membranes and dock to specific acceptor compartments. Over the past years many of the research involved in the secretory pathway has been performed on non-neuronal cells. The research of De Wit and her team focuses on neuronal cells. Their main goal is to understand by which mechanism secretory vesicles are transported to and dock into the synapse as well as biogenesis and recycling of secretory vesicles. As a model system we use genetically/pharmacologically manipulated synapses and adrenal chromaffin cells from several mutant mice that show a defect in the transport pathways of secretory vesicles to the synapse. Some mutants are linked to diseases like Schizophrenia and Epilepsy. To elucidate molecular and cellular mechanisms of neurosecretion her lab use mainly electron microscopical (EM) studies.

Previously, De Wit set-up a unique docking assay to investigate the molecular mechanisms and spatial organization of secretory vesicle docking in primary cultured mouse (mutant) chromaffin cells. To dissect vesicle docking principles, she applied EM combined with secretion assays in collaboration with members of the group of Dr. Neher (Göttingen, Germany) and Dr. Südhof (Dallas, USA). De Wit succeeded to perform a systematic analysis of the genetic cascades that orchestrate docking of secretory vesicles at their target. Her results were published in Science and Cell (see News).

Together, EM techniques such as morphometry and subcellular immunogold labelling allow us to identify the distribution/structure of cell organelles as well as the localization of certain regulatory/cargo proteins involved in the secretory pathway. When these proteins/organelles are not transported well this will be revealed by electron microscopy. Visualising this gives additional insight in the function of disease proteins, and is complementary with other techniques used in the CNCR and NCA. For example, the subcellular distribution of synaptic vesicle proteins can be analyzed and will address if it is affected after genetic/pharmacological manipulation. As such, EM studies are important for a fundamental understanding of neuronal protein (dys)function.

This year De Wit initiated the ‘BrainTrain’ consortium that was granted by the EU to train 15 PhD students at their start of their scientific career amongst different universities/enterprises in the EU and Japan (see BrainTrain). In addition, De Wit coordinates the EM core facility of NCA (see Electron Microscopy - Support Facilities - Neuroscience Campus Amsterdam).