Glucose-induced insulin secretion from pancreatic islets involves hydrolysis of arachidonic acid from phospholipids as an intermediary event. Accumulation of nonesterified arachidonate in islet membranes may influence both ion fluxes that trigger insulin secretion and fusion of secretory granule and plasma membranes. Recent findings indicate that plasmenylethanolamine species may also participate in fusion of such membranes, but HPLC and GC/MS analyses of islet secretory granule phospholipids suggested that they contain little plasmenylethanolamine. Here, electrospray ionization (ESI) mass spectrometry (MS) of intact phospholipid molecules is used to demonstrate that the most prominent components of all major glycerophospholipid head-group classes in islets are arachidonate-containing species. Such species contribute the majority of the ESI/MS negative ion current from rat and human islet glycerophosphoethanolamine (GPE), and the fraction of GPE negative ion current con tributed by plasmenylethanolamine species in rat islets is higher than that for rat liver or heart and similar to that for brain. The most prominent sn-2 substituent of plasmenylethanolamine species in brain is docosahexaenoate and in islets is arachidonate. Arachidonate-containing plasmenylethanolamine species are also prominent components of GPE from islet secretory granules and plasma membranes. Fusion of islet secretory granule and plasma membranes is demonstrated to be catalyzed by cytosolic components from insulinoma cells and rat brain with chromatographic similarities to a rabbit brain factor that specifically catalyzes fusion of plasmenylethanolamine-containing membranes.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
5P41RR000954-26
Application #
6665884
Study Section
Project Start
2002-08-01
Project End
2003-07-31
Budget Start
1997-10-01
Budget End
1998-09-30
Support Year
26
Fiscal Year
2002
Total Cost
$157,506
Indirect Cost
Name
Washington University
Department
Type
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
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