Roles of Src-like adaptor protein 2 (SLAP-2) in GPVI-mediated platelet activation SLAP-2 and GPVI signaling.
BACKGROUND
Glycoprotein VI (GPVI) /Fc receptor gamma (FcRγ)-chain complex is one of the collagen receptors in platelets and responsible for the majority of the intracellular signaling events through a similar pathway to immune receptors. Src-like adaptor protein 2 (SLAP-2) is a recently characterized adaptor protein predominantly expressed in hematopoietic cells. In T cells, SLAP-2 was reported to associate with several tyrosine phosphorylated proteins, and function as a negative regulator of signaling downstream of T cell antigen receptor by virtue of its interaction with the ubiquitin ligase c-Cbl. But the data regarding the presence and role of SLAP-2 proteins in platelets is limited.


OBJECTIVE
We describe the characterization of SLAP-2 in human platelets.


METHODS
Human platelets were analyzed by Western blot analysis, immunoprecipitation, and pull down assay, etc.


RESULTS
Immunoprecipitation revealed the presence of two forms of SLAP-2 with approximately 28 kD and 25 kD, and following stimulation of GPVI, the additional form with approximately 32 kD apppeared. We have found that upon GPVI activation, SLAP-2 translocated from the Triton X-100-soluble fraction to the Triton X-100-insoluble cytoskeleton fraction, with concomitant association with Syk, c-Cbl, and LAT.


CONCLUSIONS
SLAP-2 appears to play a role in regulating signaling pathways by bringing important signaling molecules such as c-Cbl and Syk into proximity of cytoskeletal substrates. In platelets, SLAP-2 may have function as a negative regulator of GPVI-mediated signaling by interacting with c-Cbl, being similar to that reported in T cells.
Sugihara
Sayaka
S
Department of Hematology and Oncology, Division of Clinical and Experimental Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Japan.
Katsutani
Shinya
S
Deckmyn
Hans
H
Fujimura
Kingo
K
Kimura
Akiro
A
D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D015539:Platelet Activation; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; C110810:LAT protein, human; D008565:Membrane Proteins; D010980:Platelet Membrane Glycoproteins; C441328:SLA2 protein, human; C098341:platelet membrane glycoprotein VI; D050721:Proto-Oncogene Proteins c-cbl; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); C000606896:SYK protein, human; D000072377:Syk Kinase; C067419:CBL protein, human