Production of phosphatidylinositol 3,4,5-trisphosphate and phosphatidic acid in platelet rafts: evidence for a critical role of cholesterol-enriched domains in human platelet activation.
Glycosphingolipid- and cholesterol-enriched membrane microdomains, called rafts, can be isolated from several mammalian cells, including platelets. These microdomains appear to play a critical role in signal transduction in several hematopoietic cells, but their function in blood platelets remains unknown. Herein, we first characterized the lipid composition, including the fatty acid composition of phospholipids, of human platelet rafts. Then their role in platelet activation process was investigated. Interestingly, thrombin stimulation led to morphological changes of rafts correlating with the production of lipid second messengers in these microdomains. Indeed, we could demonstrate for the first time that a large part of the stimulation-dependent production of phosphatidic acid and phosphoinositide 3-kinase products was concentrated in rafts. Moreover, cholesterol depletion with methyl-beta-cyclodextrin disrupted platelet rafts, dramatically decreased the agonist-dependent production of these lipid signaling molecules, and impaired platelet secretion and aggregation. Cholesterol repletion restored the physiological platelet responses. Altogether our data indicate that rafts are highly dynamic platelet membrane structures involved in critical signaling mechanisms linked to the production of lipid second messengers. The demonstration of phosphatidylinositol 3,4,5-trisphosphate production in rafts may have general implications for the understanding of the role of this key second messenger found ubiquitously in higher eucaryotic cells.
Bodin
S
S
Institut Fédératif de Recherche en Immunologie Cellulaire et Moléculaire, Université Paul Sabatier, Institut National de la Santé et de la Recherche Médicale, Unité 326, Hôpital Purpan, 31059 Toulouse Cedex, France.
Giuriato
S
S
Ragab
J
J
Humbel
B M
BM
Viala
C
C
Vieu
C
C
Chap
H
H
Payrastre
B
B
D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000097:blood*; D003094:Collagen / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D021962:Membrane Microdomains / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000097:blood*; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis* / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D015290:Second Messenger Systems; D013917:Thrombin / Q000494:pharmacology
D010712:Phosphatidic Acids; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; C060980:phosphatidylinositol 3,4-diphosphate; D003094:Collagen; D002784:Cholesterol; D013917:Thrombin