Regulation of eosinophil adhesion by lysophosphatidylcholine via a non-store-operated Ca2+ channel.
We examined the mechanism by which lysophosphatidylcholine (LPC) regulates beta2-integrin-mediated adhesion of eosiniophils. Eosinophils were isolated from blood of mildly atopic volunteers by negative immunomagnetic selection. beta2-integrin-dependent adhesion of eosinophils to plated bovine serum albumin (BSA) was measured by residual eosinophil peroxidase activity. LPC caused maximal adhesion of eosinophils to plated BSA at 4 microM. Lysophosphatidylinositol, which has a similar molecular shape, mimicked the effect of LPC on eosinophil adhesion, while neither lysophosphatidylserine nor lysophosphatidylethanolamine had any effect. Phosphatidylethanolamine, a lipid that has a molecular orientation that is the inverse of LPC, blocked eosinophil adhesion caused by LPC. Unlike platelet-activating factor, a G-protein-coupled receptor agonist, LPC did not cause Ca2+-store depletion, but caused increased Ca2+ influx upon addition of Ca2+ to extracellular medium. This influx was not inhibited by U73122, a phospholipase C inhibitor, demonstrating independence from the G protein-activated phospholipase C pathway. Ca2+ influx was inhibited by either preincubation of phosphotidylethanolamine or La3+, a broad spectrum blocker of cation channels. LPC induced up-regulation of the active conformation of CD11b, which was blocked by preincubation with phosphatidylethanolamine. These data suggest that LPC causes a non-store-operated Ca2+ influx into eosinophils, which subsequently activates CD11b/CD18 to promote eosinophil adhesion.
Zhu
Xiangdong
X
Section of Pulmonary and Critical Care Medicine, Department of Medicine, MC6076, University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA. xzhu@medicine.bsd.uchicago.edu
Learoyd
Jonathan
J
Butt
Sanober
S
Zhu
Lilly
L
Usatyuk
Peter V
PV
Natarajan
Viswanathan
V
Munoz
Nilda M
NM
Leff
Alan R
AR
D039481:CD11b Antigen / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D004533:Egtazic Acid / Q000494:pharmacology; D004804:Eosinophils / Q000166:cytology* / Q000187:drug effects*; D019204:GTP-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D016177:Macrophage-1 Antigen / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility / Q000187:drug effects; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000378:metabolism
D039481:CD11b Antigen; D015220:Calcium Channels; D008244:Lysophosphatidylcholines; D016177:Macrophage-1 Antigen; D010714:Phosphatidylethanolamines; D012333:RNA, Messenger; D050051:Transient Receptor Potential Channels; D012710:Serum Albumin, Bovine; C483858:phosphatidylethanolamine; D004533:Egtazic Acid; D019204:GTP-Binding Proteins