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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:dateCreated |
1994-3-9
|
| pubmed:abstractText |
Introduction of GTP gamma S or other non-metabolic analogues of GTP into permeabilized myeloid granulocytes (mast cells, eosinophils, neutrophils) constitutes a sufficient stimulus to induce exocytosis. We concentrate on mast cells. Exocytosis from cells permeabilized in isotonic glutamate solution proceeds in the absence of ATP and at exceedingly low levels (< 10(-9) M) of Ca2+. Mg2+ strongly promotes GTP gamma S-induced exocytosis but this requirement can be spared and then obliterated by lifting Ca2+ through 10(-7) to 10(-6) M. GTP provides only a modest support to exocytosis but becomes almost equipotent with GTP gamma S when Mg2+ is excluded. Ca2+ alone is unable to induce exocytosis. We envisage that the terminal stage of exocytosis (membrane fusion) requires activation of GE, a putative GTPase so far undefined as a molecular entity. Ca2+, presumed to act through a Ca(2+)-binding protein (CE, also undefined) supports exocytosis by promoting the exchange of guanine nucleotides on GE. In the absence of Mg2+ the onset of exocytosis is characterized by delays that have concentration-dependent (binding) and independent components. The latter are sensitive to the identity of the stimulating nucleotide (GTP < GTP gamma S < Gpp [NH]p) and may reflect activation of GE. The activation by Ca2+ and Mg2+ and the delays preceding onset of GTP gamma S-triggered exocytosis are reminiscent of the action of glucagon and Mg2+ in the activation of adenylate cyclase in hepatocyte membranes. The cell-physiological description predicts GE to be an alpha beta gamma heterotrimeric GTP-binding protein with functional similarity to GS.
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:issn |
0300-5208
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
176
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
164-79; discussion 180-4
|
| pubmed:dateRevised |
2009-9-29
|
| pubmed:meshHeading | |
| pubmed:year |
1993
|
| pubmed:articleTitle |
A cell-physiological description of GE, a GTP-binding protein that mediates exocytosis.
|
| pubmed:affiliation |
Department of Physiology, University College London, UK.
|
| pubmed:publicationType |
Journal Article,
In Vitro,
Review,
Research Support, Non-U.S. Gov't
|