Calcium-dependent translocation of synaptotagmin to the plasma membrane in the dendrites of developing neurones

• Published in: Brain research. Molecular brain research. Vol. 96; no. 1; pp. 1 - 13
• Main Authors: Schwab, Yannick, Mouton, Jérôme, Chasserot-Golaz, Sylvette, Marty, Isabelle, Maulet, Yves, Jover, Emmanuel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30.11.2001; Elsevier
• Subjects: Animals; Biochemistry, Molecular Biology; Biological and medical sciences; Calcium - metabolism; Calcium Channels, L-Type - analysis; Calcium-Binding Proteins; Cell Membrane - chemistry; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cells, Cultured; Dendrites - chemistry; Dendrites - metabolism; Dendrites - ultrastructure; Development. Senescence. Regeneration. Transplantation; Fundamental and applied biological sciences. Psychology; Hypothalamus - cytology; Hypothalamus - growth & development; L-type Ca 2+ channel; Life Sciences; Membrane Fusion - physiology; Membrane Glycoproteins - analysis; Membrane Glycoproteins - metabolism; Membrane Potentials - physiology; Membrane Proteins - analysis; Microscopy, Electron; Nerve Tissue Proteins - analysis; Nerve Tissue Proteins - metabolism; Neuronal depolarisation; Neurons - metabolism; Neurons - ultrastructure; Rat; Rats; Rats, Wistar; Ryanodine receptor; Ryanodine Receptor Calcium Release Channel - analysis; SNARE protein; SNARE Proteins; Synaptotagmin I; Synaptotagmins; Syntaxin 1; Vertebrates: nervous system and sense organs; Vesicular Transport Proteins; Cellular and molecular biology; SNARE protein; Neuronal depolarisation; Rat; Ryanodine receptor; L-type Ca 2+ channel; Vertebrata; Mammalia; Neuron; Calcium; Rodentia; Plasma membrane; Development; Ionic channel; Synaptotagmin; In vitro; Dendrite
• ISSN: 0169-328X; 1872-6941
• DOI: 10.1016/S0169-328X(01)00244-3

In neurones, the morphological complexity of the dendritic tree requires regulated growth and the appropriate targeting of membrane components. Accurate delivery of specific supplies depends on the translocation and fusion of transport vesicles. Vesicle SNAREs (soluble N-ethylmaleimide sensitive factor attachment protein receptors) and target membrane SNAREs play a central role in the correct execution of fusion events, and mediate interactions with molecules that endow the system with appropriate regulation. Synaptotagmins, a family of Ca 2+-sensor proteins that includes neurone-specific members involved in regulating neurotransmitter exocytosis, are among the molecules that can tune the fusion mechanism. Using immunocytochemistry, confocal and electron microscopy, the localisation of synaptotagmin I in the dendrites of cultured rat hypothalamic neurones was demonstrated. Synaptotagmin labelling is concentrated at dendritic branch points, and in microprocesses. Following depolarisation, the N-terminal domain of synaptotagmin was detected at the extracellular surface of the dendritic plasma membrane. The insertion of synaptotagmin in the plasma membrane was elicited by L-type Ca 2+ channel activation and by mobilisation of the internal ryanodine-sensitive Ca 2+stores. Furthermore, the localisation of L-type Ca 2+ channels and of ryanodine receptors, relative to the localisation of synaptotagmin in dendrites, suggests that both Ca 2+ entry and intracellular Ca 2+ stores may contribute to the fusion of dendritic transport vesicles with the membrane. Fusion is likely to involve SNAP-25 and syntaxin 1 as both proteins were also identified in dendrites. Taken together these results suggest a putative regulatory role of synaptotagmins in the membrane fusion events that contribute to shaping the dendritic tree during development.