Secretagogue-triggered transfer of membrane proteins from neuroendocrine secretory granules to synaptic-like microvesicles

• Published in: Molecular biology of the cell 1999-08, Vol.10 (8), p.2619-2630
• Main Authors: Strasser, J E, Arribas, M, Blagoveshchenskaya, A D, Cutler, D F
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport; Calcium-Binding Proteins; Carbachol - pharmacology; Cell Membrane - metabolism; Cytoplasmic Granules - metabolism; Endosomes - metabolism; Horseradish Peroxidase - genetics; Horseradish Peroxidase - metabolism; Membrane Glycoproteins - metabolism; Membrane Proteins - genetics; Membrane Proteins - metabolism; Nerve Tissue Proteins - metabolism; Neurosecretory Systems - cytology; Neurosecretory Systems - metabolism; P-Selectin - genetics; P-Selectin - metabolism; PC12 Cells - drug effects; PC12 Cells - metabolism; PC12 Cells - secretion; R-SNARE Proteins; Rabbits; Rats; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Synaptic Vesicles - metabolism; Synaptophysin - drug effects; Synaptophysin - metabolism; Synaptotagmins; Transfection; Transferrin - metabolism
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.10.8.2619

The membrane proteins of all regulated secretory organelles (RSOs) recycle after exocytosis. However, the recycling of those membrane proteins that are targeted to both dense core granules (DCGs) and synaptic-like microvesicles (SLMVs) has not been addressed. Since neuroendocrine cells contain both RSOs, and the recycling routes that lead to either organelle overlap, transfer between the two pools of membrane proteins could occur during recycling. We have previously demonstrated that a chimeric protein containing the cytosolic and transmembrane domains of P-selectin coupled to horseradish peroxidase is targeted to both the DCG and the SLMV in PC12 cells. Using this chimera, we have characterized secretagogue-induced traffic in PC12 cells. After stimulation, this chimeric protein traffics from DCGs to the cell surface, internalizes into transferrin receptor (TFnR)-positive endosomes and thence to a population of secretagogue-responsive SLMVs. We therefore find a secretagogue-dependent rise in levels of HRP within SLMVs. In addition, the levels within SLMVs of the endogenous membrane protein, synaptotagmin, as well as a green fluorescent protein-tagged version of vesicle-associated membrane protein (VAMP)/synaptobrevin, also show a secretagogue-dependent increase.