scholarly journals Comparison of Cysteine String Protein (Csp) and Mutant α-SNAP Overexpression Reveals a Role for Csp in Late Steps of Membrane Fusion in Dense-Core Granule Exocytosis in Adrenal Chromaffin Cells

2000 ◽  
Vol 20 (4) ◽  
pp. 1281-1289 ◽  
Author(s):  
Margaret E. Graham ◽  
Robert D. Burgoyne
2001 ◽  
Vol 29 (4) ◽  
pp. 467-472 ◽  
Author(s):  
R. D. Burgoyne ◽  
R. J. Fisher ◽  
M. E. Graham ◽  
L. P. Haynes ◽  
A. Morgan

The study of regulated exocytosis uniquely allows the direct measurement of intracellular membrane fusion events in real time. We have exploited this to examine factors that regulate not only the extent but also the dynamics of single fusion/release events. The general strategy used has been to assess exocytosis in transiently transfected PC12 or adrenal chromaffin cells. We aimed to design mutant constructs based on in vitro biochemistry, in some cases informed by knowledge of protein structure. Using this approach we have demonstrated an inhibitory role for the putative Rab3 effector Noc2 that requires interaction with Rab3. Using carbon-fibre amperometry on adrenal chromaffin cells, we have demonstrated regulation of the kinetics of single granule release events consistent with changes in fusion pore dynamics and switches between full fusion and ‘kiss-and-run’ fusion. These studies have demonstrated a late role for cysteine string protein in exocytosis. In addition, they have focused attention on a key role for Munc18 in the regulation of post-fusion events that affect fusion pore dynamics.


1995 ◽  
Vol 130 (5) ◽  
pp. 1063-1070 ◽  
Author(s):  
L H Chamberlain ◽  
D Roth ◽  
A Morgan ◽  
R D Burgoyne

We have used stage-specific assays for MgATP-dependent priming and for Ca(2+)-activated triggering in the absence of free MgATP to examine the effects of alpha-SNAP, 14-3-3 proteins and calmodulin on regulated exocytosis in permeabilized adrenal chromaffin cells. All three proteins lead to a Ca(2+)-dependent increase in catecholamine secretion. Both alpha-SNAP and 14-3-3 proteins stimulated in a priming but not in a triggering assay. In contrast, calmodulin was stimulatory in triggering but not priming. The effects of alpha-SNAP and 14-3-3 proteins were likely to be due to distinct mechanisms of action since they differed in Ca(2+)-dependency, time course and extent of stimulation and their effects were additive. alpha-SNAP and 14-3-3 proteins did not appear to exert their priming action through changes in synthesis of phosphatidylinositol (4,5) bisphosphate. The data show that these three proteins have distinct stage-specific actions on exocytosis and indicate that alpha-SNAP acts in an early MgATP-requiring stage and not in the late Ca(2+)-triggered steps immediately prior to membrane fusion as previously suggested.


2015 ◽  
Vol 128 (7) ◽  
pp. 1365-1374 ◽  
Author(s):  
Z. Hao ◽  
L. Wei ◽  
Y. Feng ◽  
X. Chen ◽  
W. Du ◽  
...  

1999 ◽  
Vol 19 (17) ◽  
pp. 7375-7383 ◽  
Author(s):  
Abdeladim Elhamdani ◽  
Thomas F. J. Martin ◽  
Judith A. Kowalchyk ◽  
Cristina R. Artalejo

2012 ◽  
Vol 90 (6) ◽  
pp. 791-801 ◽  
Author(s):  
Nan Wang ◽  
Andy K. Lee ◽  
Lei Yan ◽  
Michael R. Simpson ◽  
Amy Tse ◽  
...  

Catecholamine-containing small dense core granules (SDCGs, vesicular diameter of ∼100 nm) are prominent in carotid glomus (chemosensory) cells and some neurons, but the release kinetics from individual SDCGs has not been studied in detail. In this study, we compared the amperometric signals from glomus cells with those from adrenal chromaffin cells, which also secrete catecholamine but via large dense core granules (LDCGs, vesicular diameter of ∼200–250 nm). When exocytosis was triggered by whole-cell dialysis (which raised the concentration of intracellular Ca2+ ([Ca2+]i) to ∼0.5 µmol/L), the proportion of the type of signal that represents a flickering fusion pore was 9-fold higher for glomus cells. Yet, at the same range of quantal size (Q, the total amount of catecholamine that can be released from a granule), the kinetics of every phase of the amperometric spike signals from glomus cells was faster. Our data indicate that the last phenomenon involved at least 2 mechanisms: (i) the granule matrix of glomus cells can supply a higher concentration of free catecholamine during exocytosis; (ii) a modest elevation of [Ca2+]i triggers a form of rapid “kiss-and-run” exocytosis, which is very prevalent among glomus SDCGs and leads to incomplete release of their catecholamine content (and underestimation of their Q value).


Author(s):  
Joe A. Mascorro ◽  
Robert D. Yates

Extra-adrenal chromaffin organs (abdominal paraganglia) constitute rich sources of catecholamines. It is believed that these bodies contain norepinephrine exclusively. However, the present workers recently observed epinephrine type granules in para- ganglion cells. This report investigates catecholamine containing granules in rabbit paraganglia at the ultrastructural level.New Zealand white rabbits (150-170 grams) were anesthetized with 50 mg/kg Nembutal (IP) and perfused with 3% glutaraldehyde buffered with 0.2M sodium phosphate, pH 7.3. The retroperitoneal tissue blocks were removed and placed in perfusion fluid for 4 hours. The abdominal paraganglia were dissected from the blocks, diced, washed in phosphate buffer and fixed in 1% osmic acid buffered with phosphate. In other animals, the glutaraldehyde perfused tissue blocks were immersed for 1 hour in 3% glutaraldehyde/2.5% potassium iodate buffered as before. The paraganglia were then diced, separated into two vials and washed in the buffer. A portion of this tissue received osmic acid fixation.


1997 ◽  
Vol 73 ◽  
pp. 226
Author(s):  
Kazuo Minakuchi ◽  
Hitoshi Houchi ◽  
Masanori Yoshizumi ◽  
Yasuko Ishimura ◽  
Kyoji Morita ◽  
...  

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