Group IIA secretory phospholipase A2 stimulates exocytosis and neurotransmitter release in pheochromocytoma-12 cells and cultured rat hippocampal neurons.
Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.
Institute of Molecular and Cell Biology, National University of Singapore 117609, Singapore.
S
S
Wei
W Y
WY
Ong
M M
MM
Thwin
C W
CW
Fong
A A
AA
Farooqui
P
P
Gopalakrishnakone
W
W
Hong
D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D054501:Group II Phospholipases A2; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology; D007608:Kainic Acid / Q000494:pharmacology; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009410:Nerve Degeneration / Q000139:chemically induced / Q000201:enzymology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D016716:PC12 Cells; D018408:Patch-Clamp Techniques; D010741:Phospholipases A / Q000378:metabolism* / Q000494:pharmacology; D054467:Phospholipases A2; D017729:Presynaptic Terminals / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D013572:Synaptic Vesicles / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D018377:Neurotransmitter Agents; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2; D007608:Kainic Acid