TY - JOUR
T1 - Electrospray ionization/mass spectrometric analyses of human promonocytic U937 cell glycerolipids and evidence that differentiation is associated with membrane lipid composition changes that facilitate phospholipase A2 activation
AU - Hsu, Fong Fu
AU - Ma, Zhongmin
AU - Wohltmann, Mary
AU - Bohrer, Alan
AU - Nowatzke, William
AU - Ramanadham, Sasanka
AU - Turk, John
PY - 2000/6/2
Y1 - 2000/6/2
N2 - Upon differentiation, U937 promonocytic cells gain the ability to release a large fraction of arachidonate esterified in phospholipids when stimulated, but the mechanism is unclear. U937 cells express group IV phospholipase A2 (cPLA2), but neither its level nor its phosphorylation state increases upon differentiation. A group VI PLA2 (iPLA2) that is sensitive to a bromoenol lactone inhibitor catalyzes arachidonate hydrolysis from phospholipids in some cells and facilitates arachidonate incorporation into glycerophosphocholine (GPC) lipids in others, but it is not known whether U937 cells express iPLA2. We confirm that ionophore A23187 induces substantial [3H]arachidonate release from differentiated but not control U937 cells, and electrospray ionization mass spectrometric (ESI/MS) analyses indicate that differentiated cells contain a higher proportion of arachidonate-containing GPC species than control cells. U937 cells express iPLA2 mRNA and activity, but iPLA2 inhibition impairs neither [3H]arachidonate incorporation into nor release from U937 cells. Experiments with phosphatidate phosphohydrolase (PAPH) and phospholipase D (PLD) inhibitors coupled with ESI/MS analyses of PLD-PAPH products indicate that differentiated cells gain the ability to produce diacylglycerol (DAG) via PLD-PAPH. DAG promotes arachidonate release by a mechanism that does not require DAG hydrolysis, is largely independent of protein kinase C, and requires cPLA2 activity. This may reflect DAG effects on cPLA2 substrate state.
AB - Upon differentiation, U937 promonocytic cells gain the ability to release a large fraction of arachidonate esterified in phospholipids when stimulated, but the mechanism is unclear. U937 cells express group IV phospholipase A2 (cPLA2), but neither its level nor its phosphorylation state increases upon differentiation. A group VI PLA2 (iPLA2) that is sensitive to a bromoenol lactone inhibitor catalyzes arachidonate hydrolysis from phospholipids in some cells and facilitates arachidonate incorporation into glycerophosphocholine (GPC) lipids in others, but it is not known whether U937 cells express iPLA2. We confirm that ionophore A23187 induces substantial [3H]arachidonate release from differentiated but not control U937 cells, and electrospray ionization mass spectrometric (ESI/MS) analyses indicate that differentiated cells contain a higher proportion of arachidonate-containing GPC species than control cells. U937 cells express iPLA2 mRNA and activity, but iPLA2 inhibition impairs neither [3H]arachidonate incorporation into nor release from U937 cells. Experiments with phosphatidate phosphohydrolase (PAPH) and phospholipase D (PLD) inhibitors coupled with ESI/MS analyses of PLD-PAPH products indicate that differentiated cells gain the ability to produce diacylglycerol (DAG) via PLD-PAPH. DAG promotes arachidonate release by a mechanism that does not require DAG hydrolysis, is largely independent of protein kinase C, and requires cPLA2 activity. This may reflect DAG effects on cPLA2 substrate state.
UR - http://www.scopus.com/inward/record.url?scp=0034596018&partnerID=8YFLogxK
U2 - 10.1074/jbc.M908342199
DO - 10.1074/jbc.M908342199
M3 - Article
C2 - 10748096
AN - SCOPUS:0034596018
SN - 0021-9258
VL - 275
SP - 16579
EP - 16589
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 22
ER -