title: A novel Syk-dependent mechanism of platelet activation by the C-type lectin receptor CLEC-2.
abstract: The snake venom rhodocytin has been reported to bind to integrin alpha2beta1 and glycoprotein (GP) Ibalpha on platelets, but it is also able to induce activation independent of the 2 receptors and of GPVI. Using rhodocytin affinity chromatography, we have identified a novel C-type lectin receptor, CLEC-2, in platelets that confers signaling responses to rhodocytin when expressed in a cell line. CLEC-2 has a single tyrosine residue in a YXXL motif in its cytosolic tail, which undergoes tyrosine phosphorylation upon platelet activation by rhodocytin or an antibody to CLEC-2, but not to collagen, thrombin receptor agonist peptide (TRAP), or convulxin. Tyrosine phosphorylation of CLEC-2 and other signaling proteins by rhodocytin is inhibited by the Src family kinase inhibitor PP2. Further, activation of murine platelets by rhodocytin is abolished in the absence of Syk and PLCgamma2, and partially reduced in the absence of LAT, SLP-76, and Vav1/Vav3. These findings define a novel signaling pathway in platelets whereby activation of CLEC-2 by rhodocytin leads to tyrosine phosphorylation of its cytosolic tail, binding of Syk and initiation of downstream tyrosine phosphorylation events, and activation of PLCgamma2. CLEC-2 is the first C-type lectin receptor to be found on platelets which signals through this novel pathway.
authors.affiliation: Department of Clinical and Laboratory Medicine, University of Yamanashi, Shimokato Tamaho Nakakoma, Yamanashi 409-3898, Japan.
authors.forename: Katsue
authors.initials: K
authors.lastname: Suzuki-Inoue
authors.forename: Gemma L J
authors.initials: GL
authors.lastname: Fuller
authors.forename: Angel
authors.initials: A
authors.lastname: García
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Eble
authors.forename: Stefan
authors.initials: S
authors.lastname: Pöhlmann
authors.forename: Osamu
authors.initials: O
authors.lastname: Inoue
authors.forename: T Kent
authors.initials: TK
authors.lastname: Gartner
authors.forename: Sascha C
authors.initials: SC
authors.lastname: Hughan
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Pearce
authors.forename: Gavin D
authors.initials: GD
authors.lastname: Laing
authors.forename: R David G
authors.initials: RD
authors.lastname: Theakston
authors.forename: Edina
authors.initials: E
authors.lastname: Schweighoffer
authors.forename: Nicole
authors.initials: N
authors.lastname: Zitzmann
authors.forename: Takashi
authors.initials: T
authors.lastname: Morita
authors.forename: Victor L J
authors.initials: VL
authors.lastname: Tybulewicz
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozaki
authors.forename: Steve P
authors.initials: SP
authors.lastname: Watson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D015153:Blotting, Western; D003094:Collagen / Q000378:metabolism; D003435:Crotalid Venoms / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000502:physiology; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D037181:Lectins, C-Type / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D010446:Peptide Fragments; D051966:Phospholipase C gamma / Q000235:genetics / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation; D015539:Platelet Activation; D010974:Platelet Aggregation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology; D011964:Receptors, Gastrointestinal Hormone; D011971:Receptors, Immunologic / Q000276:immunology / Q000378:metabolism*; D017476:Receptors, Neuropeptide Y; D018179:Receptors, Thrombin; D015398:Signal Transduction; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism; D014757:Viper Venoms / Q000378:metabolism*
chemical_list: C412373:AG 1879; D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D003435:Crotalid Venoms; D004792:Enzyme Precursors; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; C491734:Lat protein, mouse; D037181:Lectins, C-Type; D008565:Membrane Proteins; C102315:Npy6r protein, mouse; D010446:Peptide Fragments; D010750:Phosphoproteins; D051567:Proto-Oncogene Proteins c-vav; D011743:Pyrimidines; D011964:Receptors, Gastrointestinal Hormone; D011971:Receptors, Immunologic; D017476:Receptors, Neuropeptide Y; D018179:Receptors, Thrombin; C092947:SLP-76 signal Transducing adaptor proteins; C496619:Vav1 protein, mouse; C496622:Vav3 protein, mouse; D014757:Viper Venoms; C112292:rhodocytin protein, Calloselasma rhodostoma; C072032:thrombin receptor peptide (42-55); C086309:thrombin receptor peptide SFLLRNP; C028890:convulxin; D014443:Tyrosine; D003094:Collagen; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D051966:Phospholipase C gamma