Imaging direct, dynamin-dependent recapture of fusing secretory granules on plasma membrane lawns from PC12 cells.
During exocytosis, secretory granules fuse with the plasma membrane and discharge their content into the extracellular space. The exocytosed membrane is then reinternalized in a coordinated fashion. A role of clathrin-coated vesicles in this process is well established, whereas the involvement of a direct retrieval mechanism (often called kiss and run) is still debated. Here we report that a significant population of docked secretory granules in the neuroendocrine cell line PC12 fuses with the plasma membrane, takes up fluid-phase markers, and is retrieved at the same position. Fusion allows for complete discharge of small molecules, whereas GFP-labeled neuropeptide Y (molecular mass approximately equal 35 kDa) is only partially released. Retrieved granules were preferentially associated with dynamin. Furthermore, recapture is inhibited by guanosine 5'-[gamma-thio]triphosphate and peptides known to block dynamin function. We conclude that secretory granules can be recaptured immediately after formation of an exocytotic opening by an endocytic reaction that is spatially and temporally coupled to soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-dependent fusion, but is not a reversal of the fusion reaction.
Holroyd
Phillip
P
Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Lang
Thorsten
T
Wenzel
Dirk
D
De Camilli
Pietro
P
Jahn
Reinhard
R
D000818:Animals; D002474:Cell-Free System; D034281:Dynamins / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology; D016716:PC12 Cells; D051381:Rats; D050600:SNARE Proteins; D022142:Secretory Vesicles / Q000502:physiology*; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; D034281:Dynamins