title: HbS Binding to GP1bα Activates Platelets in Sickle Cell Disease.
abstract: Intravascular hemolysis increases the risk of thrombosis in hemolytic disorders. Our previous study showed that the binding of adult hemoglobin (HbA) to glycoprotein (GP) 1bα induced the activation of platelets. The elevated plasma Hb or platelet surface bound Hb positively correlated with platelet activation in patients with paroxysmal nocturnal hemoglobinuria (PNH). Furthermore, this study shows that the sickle Hb [HbS, occurs due to single nucleotide polymorphism at A>T of β-globin gene of Hb and causes sickle cell disease (SCD)] also bound to GP1bα and activated platelets in a concentration-dependent manner. The HbS bound to glycocalicin (extramembranous part of GP1bα) with KD ~ 10.46 ± 3 μM. HbS induced phosphorylation of signaling adapter proteins, such as Lyn, PI3K, Akt and ERK in platelets, and also increased the surface expression of platelet activation markers such as P-selectin (10.7 fold) and PAC1 binding (10.4 fold) in platelet surface in a concentration-dependent manner. HbS also increased the platelet microparticle-generation (4.7 fold) and thrombus-formation (4.3 fold) in a concentration-dependent manner. An elevated level of extracellular Hb in plasma correlated directly with platelet activation markers such as P-selectin (r = 0.7947), PAC1 binding (r = 0.5914) on platelet surface and plasma levels of platelet-derived microparticles (r = 0.7834) in patients with SCD. Our study therefore suggests that the HbS-induced platelet activation may play a crucial role in intravascular clot formation observed in SCD patients characterized by high propensity to vascular occlusion and hypercoagulable states.
authors.affiliation: Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.|Department of Biotechnology, Manipal University, Karnataka, India.
authors.forename: Gowtham K
authors.initials: GK
authors.lastname: Annarapu
authors.affiliation: Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.|Department of Biotechnology, Manipal University, Karnataka, India.
authors.forename: Rashi
authors.initials: R
authors.lastname: Singhal
authors.affiliation: Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.
authors.forename: Avinash
authors.initials: A
authors.lastname: Gupta
authors.affiliation: Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.
authors.forename: Sheetal
authors.initials: S
authors.lastname: Chawla
authors.affiliation: Department of Medicine-Hematology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Harish
authors.initials: H
authors.lastname: Batra
authors.affiliation: Department of Medicine-Hematology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Tulika
authors.initials: T
authors.lastname: Seth
authors.affiliation: Disease Biology Laboratory, Regional Centre for Biotechnology, National Capital Region Biotech Science Cluster, Faridabad, India.
authors.forename: Prasenjit
authors.identifier: http://orcid.org/0000-0002-6601-6692
authors.initials: P
authors.lastname: Guchhait
mesh_terms: D000755:Anemia, Sickle Cell / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000378:metabolism*; D006451:Hemoglobin, Sickle / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D015539:Platelet Activation; D011485:Protein Binding; D020349:Surface Plasmon Resonance
chemical_list: C048566:A1BG protein, human; D006023:Glycoproteins; D006451:Hemoglobin, Sickle; D007136:Immunoglobulins