We used fluorescence imaging of individual exocytic events together with electron microscopy to study the regulation of dense core granule-to-plasma membrane fusion and granule-to-granule fusion events that occur during secretion from rat pituitary lactotrophs. Stimulating secretion with elevated extracellular potassium, with the calcium ionophore ionomycin, or with thyrotropin releasing hormone or vasoactive intestinal polypeptide resulted in abundant exocytic structures. Approximately 67% of these structures consisted of multiple granules fused together sharing a single exocytic opening with the plasma membrane, i.e., compound exocytosis. For all of these stimulation conditions there appeared to be a finite number of plasma membrane fusion sites, ∼11 sites around each cellular equator. However, a granule could fuse directly with another granule that had already fused with the plasma membrane even before all plasma membrane sites were occupied. Granule-to-plasma membrane and granule-to-granule fusion events were subject to different regulations. Forskolin, which can elevate cAMP, increased the number of granule-to-granule fusion events without altering the number of granule-to-plasma membrane fusion events. In contrast, the phorbol ester PMA, which activates protein kinase C increased both granule-to-granule and granule-to-plasma membrane fusion events. These results provide a cellular mechanism that can account for the previously demonstrated potentiation of secretion from lactotrophs by cAMP- and PKC-dependent pathways.
Skip Nav Destination
Article navigation
21 August 2000
Article|
August 21 2000
Differential Regulation of Granule-to-Granule and Granule-to-Plasma Membrane Fusion during Secretion from Rat Pituitary Lactotrophs
Amanda J. Cochilla,
Amanda J. Cochilla
aDepartment of Physiology and Biophysics, University of Colorado Medical School, Denver, Colorado 80220
Search for other works by this author on:
Joseph K. Angleson,
Joseph K. Angleson
bDepartment of Biological Sciences, University of Denver, Denver, Colorado 80208
Search for other works by this author on:
William J. Betz
William J. Betz
aDepartment of Physiology and Biophysics, University of Colorado Medical School, Denver, Colorado 80220
Search for other works by this author on:
Amanda J. Cochilla
aDepartment of Physiology and Biophysics, University of Colorado Medical School, Denver, Colorado 80220
Joseph K. Angleson
bDepartment of Biological Sciences, University of Denver, Denver, Colorado 80208
William J. Betz
aDepartment of Physiology and Biophysics, University of Colorado Medical School, Denver, Colorado 80220
Abbreviations used in this paper: IBMX, 3-isobutyl-1-methylxanthine; PKC, protein kinase C; PRL, prolactin; TRH, thyrotropin releasing hormone; VIP, vasoactive intestinal polypeptide.
Received:
May 05 2000
Revision Requested:
June 19 2000
Accepted:
June 21 2000
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 2000 The Rockefeller University Press
2000
The Rockefeller University Press
J Cell Biol (2000) 150 (4): 839–848.
Article history
Received:
May 05 2000
Revision Requested:
June 19 2000
Accepted:
June 21 2000
Connected Content
Citation
Amanda J. Cochilla, Joseph K. Angleson, William J. Betz; Differential Regulation of Granule-to-Granule and Granule-to-Plasma Membrane Fusion during Secretion from Rat Pituitary Lactotrophs. J Cell Biol 21 August 2000; 150 (4): 839–848. doi: https://doi.org/10.1083/jcb.150.4.839
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSee also
Email alerts
Advertisement
Advertisement