Normal platelets possess the soluble form of IL-6 receptor.
Interleukin 6 is a multifunctional cytokine that exerts its biological activity through binding to an 80 Kd specific receptor (IL-6Ralpha) and a 130 Kd signal-transducing unit (gp130). A 55 Kd soluble IL-6R (IL-6sR) has also been described which, after binding to IL-6 is also able to activate gp130. The presence of IL-6Ralpha was described in some megakaryoblastic cell lines but is still controversial in normal megakaryocytes. In this study we demonstrate the presence of intraplatelet IL-6sR by Western blot through the appearance of a 55 Kd protein and the finding of detectable amounts of IL-6sR in the platelet content by ELISA technique. Besides, we showed IL-6sR release during platelet activation induced by thrombin and a complex of ADP and epinephrine. IL-6Ralpha on platelet membrane could not be found neither by Western blot nor by flow cytometry. The IL-6sR released during platelet activation and complexed to IL-6 could act on cell types such as endothelial cells that do not possess IL-6Ralpha through binding to gp130.Besides, since we could not find IL-6R on platelet membrane, the potentiating effect of IL-6 on platelet function could be explained through binding of IL-6sR/IL-6 complex to platelet membrane gp130.
Marta
Rosana F
RF
Sección Hematología Investigación, Instituto de Investigaciones Médicas Alfredo Lanari, Facultad de Medicina, Universidad de Buenos Aires, Combatientes de Malvinas 3150, 1427 Buenos Aires, Argentina.
Goette
Nora P
NP
Lev
Paola R
PR
Chazarreta
Carlos D
CD
Pirola
Carlos J
CJ
Molinas
Felisa C
FC
D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D058966:Contactins; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D015539:Platelet Activation; D011485:Protein Binding; D019947:Receptors, Interleukin-6 / Q000096:biosynthesis*; D013917:Thrombin / Q000378:metabolism
D058966:Contactins; D019006:Neural Cell Adhesion Molecules; D019947:Receptors, Interleukin-6; D013917:Thrombin