Decreased expression of phospholipase C-beta 2 isozyme in human platelets with impaired function.
Platelets from a patient with a mild inherited bleeding disorder and abnormal platelet aggregation and secretion show reduced generation of inositol 1,4,5-trisphosphate, mobilization of intracellular Ca2+, and phosphorylation of pleckstrin in response to several G protein mediated agonists, suggesting a possible defect at the level of phospholipase C (PLC) activation (see accompanying report). A procedure was developed that allows quantitation of platelet PLC isozymes. After fractionation of platelet extracts by high-performance liquid chromatography, 7 out of 10 known PLC isoforms were detected by immunoblot analysis. The amount of these isoforms in normal platelets decreased in the order PLC-gamma 2 > PLC-beta 2 > PLC-beta 3 > PLC-beta 1 > PLC-gamma 1 > PLC-delta 1 > PLC-beta 4. Compared with normal platelets, platelets from the patient contained approximately one-third the amount of PLC-beta 2, whereas PLC-beta 4 was increased threefold. These results suggest that the impaired platelet function in the patient in response to multiple G protein mediated agonists is attributable to a deficiency of PLC-beta 2. They document for the first time a specific PLC isozyme deficiency in human platelets and provide an unique opportunity to understand the role of different PLC isozymes in normal platelet function.
Lee
S B
SB
Laboratory of Cell Signaling, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-0340, USA.
Rao
A K
AK
Lee
K H
KH
Yang
X
X
Bae
Y S
YS
Rhee
S G
SG
D001792:Blood Platelets / Q000201:enzymology* / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D005260:Female; D019204:GTP-Binding Proteins / Q000819:agonists; D006801:Humans; D007527:Isoenzymes / Q000097:blood / Q000172:deficiency*; D008875:Middle Aged; D054799:Phospholipase C beta; D010974:Platelet Aggregation / Q000187:drug effects; D010738:Type C Phospholipases / Q000097:blood / Q000172:deficiency*
D007527:Isoenzymes; D010738:Type C Phospholipases; D054799:Phospholipase C beta; D019204:GTP-Binding Proteins