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. OBJECTIVES: 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.
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. OBJECTIVES: 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.
Authors: Deya Cherpokova; Markus Bender; Martina Morowski; Peter Kraft; Michael K Schuhmann; Sarah M Akbar; Cheryl S Sultan; Craig E Hughes; Christoph Kleinschnitz; Guido Stoll; Leonard L Dragone; Steve P Watson; Michael G Tomlinson; Bernhard Nieswandt Journal: Blood Date: 2014-10-09 Impact factor: 22.113