Soluble CLEC-2 is generated independently of ADAM10 and is increased in plasma in acute coronary syndrome: comparison with soluble GPVI
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Soluble forms of platelet membrane proteins are released upon platelet activation. We previously reported that soluble C-type lectin-like receptor 2 (sCLEC-2) is released as a shed fragment (Shed CLEC-2) or as a whole molecule associated with platelet microparticles (MP-CLEC-2). In contrast, soluble glycoprotein VI (sGPVI) is released as a shed fragment (Shed GPVI), but not as a microparticle-associated form (MP-GPVI). However, mechanism of sCLEC-2 generation or plasma sCLEC-2 has not been fully elucidated. Experiments using metalloproteinase inhibitors/stimulators revealed that ADAM10/17 induce GPVI shedding, but not CLEC-2 shedding, and that shed CLEC-2 was partially generated by MMP-2. Although MP-GPVI was not generated, it was generated in the presence of the ADAM10 inhibitor. Moreover, antibodies against the cytoplasmic or extracellular domain of GPVI revealed the presence of the GPVI cytoplasmic domain, but not the extracellular domain, in the microparticles. These findings suggest that most of the GPVI on microparticles are induced to shed by ADAM10; MP-GPVI is thus undetected. Plasma sCLEC-2 level was 1/32 of plasma sGPVI level in normal subjects, but both soluble proteins significantly increased in plasma of patients with acute coronary syndrome. Thus, sCLEC-2 and sGPVI are released by different mechanisms and released in vivo upon platelet activation.
KeywordsPlatelets Soluble CLEC-2 Soluble GPVI ADAM10 Biomarker
We thank Hideyuki Tanaka, Chiaki Komatsu, and Hisaichiro Nakazawa for their help of the study. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology (M.O.) and the Japan Society for the Promotion of Science (JSPS) through the Funding Program for Next Generation World-leading Researchers (NEXT Program, LS-052) (K.S-I.).
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Conflict of interest
Junya Nakamura and Mitsuru Oosawa are an ex-employee and an employee of LSI Medicine Corporation, respectively. Yukio Ozaki, Katsue Suzuki-Inoue, Junya Nakamura, and Mitsuru Oosawa have a patent related to this report (patent no. 6078845) in Japan.
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