title: Important role of raft aggregation in the signaling events of cold-induced platelet activation.
abstract: When human platelets are chilled below 20 degrees C, they undergo cold-induced activation. We have previously shown that cold activation correlates with the main phospholipid phase transition (10-20 degrees C) and induces the formation of large raft aggregates. In addition, we found that the glycoprotein CD36 is selectively enriched within detergent-resistant membranes (DRMs) of cold-activated platelets and is extremely sensitive to treatment with methyl-beta-cyclodextrin (MbetaCD). Here, we further studied the partitioning of downstream signaling molecules within the DRMs. We found that the phospholipase Cgamma2 (PLCgamma2) and the protein tyrosine kinase Syk do not partition exclusively within the DRMs, but their distribution is perturbed by cholesterol extraction. In addition, PLCgamma2 activity increases in cold-activated cells compared to resting platelets and is entirely inhibited after treatment with MbetaCD. The Src-family protein tyrosine kinases Src and Lyn preferentially partition within the DRMs and are profoundly affected by removal of cholesterol. These kinases are non-redundant in cold-activation. CD36, active Lyn, along with inactive Src and PLCgamma2 co-localize in small raft complexes in resting platelets. Cold-activation induces raft aggregation, resulting in changes in the activity of these proteins. These data suggest a crucial role of raft aggregation in the early events of cold-induced platelet activation.
authors.affiliation: Center for Biostabilization, University of California, Davis, CA 95616, USA. kgousset@jhu.edu
authors.forename: Karine
authors.initials: K
authors.lastname: Gousset
authors.forename: Nelly M
authors.initials: NM
authors.lastname: Tsvetkova
authors.forename: John H
authors.initials: JH
authors.lastname: Crowe
authors.forename: Fern
authors.initials: F
authors.lastname: Tablin
mesh_terms: D018955:CD36 Antigens / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D003080:Cold Temperature; D003505:Cyclodextrins; D006801:Humans; D021962:Membrane Microdomains / Q000737:chemistry / Q000502:physiology*; D008958:Models, Molecular; D051966:Phospholipase C gamma; D015539:Platelet Activation / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000737:chemistry / Q000378:metabolism; D047392:beta-Cyclodextrins; D019061:src-Family Kinases / Q000737:chemistry / Q000378:metabolism
chemical_list: D018955:CD36 Antigens; D003505:Cyclodextrins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D011505:Protein-Tyrosine Kinases; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma