CLEC-2 activates Syk through dimerization.

Journal article

The C-type lectin receptor CLEC-2 activates platelets through Src and Syk tyrosine kinases, leading to tyrosine phosphorylation of downstream adapter proteins and effector enzymes, including phospholipase-C gamma2. Signaling is initiated through phosphorylation of a single conserved tyrosine located in a YxxL sequence in the CLEC-2 cytosolic tail. The signaling pathway used by CLEC-2 shares many similarities with that used by receptors that have 1 or more copies of an immunoreceptor tyrosine-based activation motif, defined by the sequence Yxx(L/I)x(6-12)Yxx(L/I), in their cytosolic tails or associated receptor chains. Phosphorylation of the conserved immunoreceptor tyrosine-based activation motif tyrosines promotes Syk binding and activation through binding of the Syk tandem SH2 domains. In this report, we present evidence using peptide pull-down studies, surface plasmon resonance, quantitative Western blotting, tryptophan fluorescence measurements, and competition experiments that Syk activation by CLEC-2 is mediated by the cross-linking through the tandem SH2 domains with a stoichiometry of 2:1. In support of this model, cross-linking and electron microscopy demonstrate that CLEC-2 is present as a dimer in resting platelets and converted to larger complexes on activation. This is a unique mode of activation of Syk by a single YxxL-containing receptor.

Authors: Hughes, C; Pollitt, A; Mori, J; Eble, J; Tomlinson, MG

• Publication status: Published
• Journal: Blood
• Volume: 115
• Issue: 14
• Pages: 2947-2955
• Publication date: 2010-04-01
• DOI: 10.1182/blood-2009-08-237834
• EISSN: 1528-0020
• ISSN: 0006-4971
• Language: English
• Keywords: Membrane Glycoproteins; Humans; Phospholipase C gamma; Platelet Activation; Signal Transduction; Intracellular Signaling Peptides and Proteins; Amino Acid Motifs; Lectins, C-Type; Protein Multimerization; src Homology Domains; Enzyme Activation; Protein-Tyrosine Kinases; Blood Platelets