Browsing by Author "Perrella, Gina"

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    Flow studies on human GPVI-deficient blood under coagulating and noncoagulating conditions
    (2020) Nagy, Magdolna; Perrella, Gina; Dalby, Amanda; Becerra Yañez, María Francisca Aurora del Car; García Quintanilla, Lourdes; Pike, Jeremy A.; Morgan, Neil V.; Gardiner, Elizabeth E.; Heemskerk, Johan W. M.; Azócar López, Lorena Karina; Miquel Poblete, Juan Francisco; Mezzano Abedrapo, Diego; Watson, Steve P.
    The role of glycoprotein VI (GPVI) in platelets was investigated in 3 families bearing an insertion within the GP6 gene that introduces a premature stop codon prior to the transmembrane domain, leading to expression of a truncated protein in the cytoplasm devoid of the transmembrane region. Western blotting and flow cytometry of GP6(hom) (homozygous) platelets confirmed loss of the full protein. The level of the Fc receptor -gamma-chain, which associates with GPVI in the membrane, was partially reduced, but expression of other receptors and signaling proteins was not altered. Spreading of platelets on collagen and von Willebrand factor (which supports partial spreading) was abolished in GP6(hom) platelets, and spreading on uncoated glass was reduced. Anticoagulated whole blood flowed over immobilized collagen or a mixture of von Willebrand factor, laminin, and rhodocytin (noncollagen surface) generated stable platelet aggregates that express phosphatidylserine (PS). Both responses were blocked on the 2 surfaces in GP6(hom) individuals, but adhesion was not altered. Thrombin generation was partially reduced in GP6(hom) blood. The frequency of the GP6(het) (heterozygous) variant in a representative sample of the Chilean population (1212 donors) is 2.9%, indicating that there are similar to 4000 GP6(hom) individuals in Chile. These results demonstrate that GPVI supports aggregation and PS exposure under flow on collagen and noncollagen surfaces, but not adhesion. The retention of adhesion may contribute to the mild bleeding diathesis of GP6(hom) patients and account for why so few of the estimated 4000 GP6(hom) individuals in Chile have been identified.
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    Platelet activation by charged ligands and nanoparticles: platelet glycoprotein receptors as pattern recognition receptors
    (2021) Montague, Samantha J.; Patel, Pushpa; Martin, Eleyna M.; Slater, Alexandre; Quintanilla, Lourdes Garcia; Perrella, Gina; Kardeby, Caroline; Nagy, Magdolna; Mezzano, Diego; Mendes, Paula M.; Watson, Steve P.
    Charge interactions play a critical role in the activation of the innate immune system by damage- and pathogen-associated molecular pattern receptors. The ability of these receptors to recognize a wide spectrum of ligands through a common mechanism is critical in host defense. In this article, we argue that platelet glycoprotein receptors that signal through conserved tyrosine-based motifs function as pattern recognition receptors (PRRs) for charged endogenous and exogenous ligands, including sulfated polysaccharides, charged proteins and nanoparticles. This is exemplified by GPVI, CLEC-2 and PEAR1 which are activated by a wide spectrum of endogenous and exogenous ligands, including diesel exhaust particles, sulfated polysaccharides and charged surfaces. We propose that this mechanism has evolved to drive rapid activation of platelets at sites of injury, but that under some conditions it can drive occlusive thrombosis, for example, when blood comes into contact with infectious agents or toxins. In this Opinion Article, we discuss mechanisms behind charge-mediated platelet activation and opportunities for designing nanoparticles and related agents such as dendrimers as novel antithrombotics.