Identification of a Munc13-sensitive step in chromaffin cell large dense-core vesicle exocytosis
Kwun Nok M Man,
Cordelia Imig,
Alexander M Walter,
Paulo S Pinheiro,
David R Stevens,
Jens Rettig,
Jakob B Sørensen,
Benjamin H Cooper,
Nils Brose,
Sonja M Wojcik
Affiliations
Kwun Nok M Man
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
Cordelia Imig
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
Alexander M Walter
Leibniz Institute for Molecular Pharmacology, Berlin, Germany
Paulo S Pinheiro
Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
David R Stevens
Department of Physiology, Saarland University, Homburg, Germany
Jens Rettig
Department of Physiology, Saarland University, Homburg, Germany
Jakob B Sørensen
Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
Benjamin H Cooper
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
Nils Brose
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
Sonja M Wojcik
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
It is currently unknown whether the molecular steps of large dense-core vesicle (LDCV) docking and priming are identical to the corresponding reactions in synaptic vesicle (SV) exocytosis. Munc13s are essential for SV docking and priming, and we systematically analyzed their role in LDCV exocytosis using chromaffin cells lacking individual isoforms. We show that particularly Munc13-2 plays a fundamental role in LDCV exocytosis, but in contrast to synapses lacking Munc13s, the corresponding chromaffin cells do not exhibit a vesicle docking defect. We further demonstrate that ubMunc13-2 and Munc13-1 confer Ca2+-dependent LDCV priming with similar affinities, but distinct kinetics. Using a mathematical model, we identify an early LDCV priming step that is strongly dependent upon Munc13s. Our data demonstrate that the molecular steps of SV and LDCV priming are very similar while SV and LDCV docking mechanisms are distinct.
