Multiple forms of "kiss-and-run" exocytosis revealed by evanescent wave microscopy.
Exocytotic release of neuropeptides and hormones is generally believed to involve the complete merger of the secretory vesicle with the plasma membrane. However, recent data have suggested that "kiss-and-run" mechanisms may also play a role. Here, we have examined the dynamics of exocytosis in pancreatic MIN6 beta cells by imaging lumen- (neuropeptide Y/pH-insensitive yellow fluorescent protein; NPY.Venus) or vesicle membrane-targeted fluorescent probes (synaptobrevin-2/enhanced green fluorescent protein; synapto.pHluorin, or phosphatase on the granule of insulinoma-enhanced green fluorescent protein, phogrin.EGFP) by evanescent wave microscopy. Unexpectedly, NPY.Venus release events occurred much less frequently (13%-40% maximal rate) than those of synapto.pHluorin, even though the latter molecule, but not phogrin.EGFP, usually diffused away from the site of fusion. Thus, the majority of exocytosis occurs in these cells by kiss-and-run events that involve either the release of small molecules only, small molecules and selected membrane proteins, or all soluble cargoes ("pure," "mixed," and "full" kiss-and-run, respectively). Changes in the activity of synaptotagmin IV, achieved here by overexpression of the wild-type protein, may allow different stimuli to alter the ratio of these events, and thus the release of selected vesicle cargoes.
Tsuboi
Takashi
T
Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, BS8 1TD, Bristol, United Kingdom.
Rutter
Guy A
GA
D002135:Calcium-Binding Proteins; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009478:Neuropeptide Y; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D050683:R-SNARE Proteins; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D050857:Synaptotagmins
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D050683:R-SNARE Proteins; C494292:SYT4 protein, human; D050857:Synaptotagmins; C102889:PTPRN2 protein, human; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8