Neuronal peptide release is limited by secretory granule mobility.
Neuropeptides are slowly released from a limited pool of secretory granules. To visualize this process, GFP-tagged preproatrial natriuretic factor (ANF) was expressed in nerve growth factor-treated PC12 cells. Biochemical and microfluorimetric experiments demonstrate that proANF-EGFP is packaged in granules that accumulate at neurite endings and is released in a Ca2+-dependent manner by secretagogs. Confocal microscopy shows that secretion is associated with depletion of granules distributed throughout the terminal. Fluorescence recovery after photobleaching and time-lapse particle tracking reveal that only a subpopulation of cytoplasmic secretory granules, similar in size to the releasable pool, can move quickly enough (D = 6 x 10(-11) cm2/s) to support release. Therefore, sustained secretory responses are limited by the number of mobile granules and their slow rate of diffusion.
Burke
N V
NV
Department of Pharmacology, University of Pittsburgh, Pennsylvania 15261, USA.
Han
W
W
Li
D
D
Takimoto
K
K
Watkins
S C
SC
Levitan
E S
ES
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000502:physiology*; D004058:Diffusion; D005453:Fluorescence; D014644:Genetic Variation; D049452:Green Fluorescent Proteins; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D016716:PC12 Cells; D011498:Protein Precursors / Q000378:metabolism; D051381:Rats; D016324:Sequence Tagged Sites; D013268:Stimulation, Chemical; D014018:Tissue Distribution
D008164:Luminescent Proteins; D009479:Neuropeptides; D011498:Protein Precursors; D049452:Green Fluorescent Proteins; D009320:Atrial Natriuretic Factor