Activation of Platelet mTORC2/Akt Pathway by Anti-β2GP1 Antibody Promotes Thrombosis in Antiphospholipid Syndrome

Abstract

BACKGROUND: Anti-β2GP1 (β2-glycoprotein 1) antibodies are the primary pathogenic antibody to promote thrombosis in antiphospholipid syndrome (APS), yet the underlying mechanism remains obscure. We aimed to explore the intracellular pathway that mediated platelet activation. METHODS: Platelets were isolated from patients with APS and subjected to RNA sequencing. Platelet aggregation, the release of platelet granules, platelet spreading, and clot retraction were detected to evaluate platelet activation. We purified anti-β2GP1 antibodies from patients with APS and the total IgG from healthy donors to stimulate platelets with/without FcγRIIA (Fcγ receptor IIA) blocking antibody or Akt inhibitor. Platelet-specific Sin1 (stress-activated protein kinase–interacting protein) deficiency mice were established. The thrombus model of inferior vena cava flow restriction, ferric chloride–induced carotid injury model, and laser-induced vessel wall injury in cremaster arterioles model were constructed after administration of anti-β2GP1 antibodies. RESULTS: Combined RNA sequencing and bioinformatics analyses suggested that APS platelets exhibit increased levels of mRNA associated with platelet activation, which was in line with the hyperactivation of APS platelets in response to stimuli. Platelet activation in APS platelets is accompanied by upregulation of the mTORC2 (mammalian target of the rapamycin complex 2)/Akt pathway and increased levels of SIN1 phosphorylation at threonine 86. Anti-β2GP1 antibody derived from patients with APS enhanced platelet activation and upregulated the mTORC2/Akt pathway. Moreover, the Akt inhibitor weakened the potentiating effect of the anti-β2GP1 antibody on platelet activation. Notably, Sin1 deficiency suppresses anti-β2GP1 antibody–enhanced platelet activation in vitro and thrombosis in all 3 models. CONCLUSIONS: This study elucidated the novel mechanism involving the mTORC2/Akt pathway, which mediates the promotion of platelet activation and induction of thrombosis by the anti-β2GP1 antibody. The findings suggest that SIN1 may be a promising therapeutic target for the treatment of APS.

CNPY2 governs PDGF‑BB‑treated vascular smooth muscle cell proliferation, migration and phenotypic transformation via the Akt/mTOR/GSK‑3β signaling pathway

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Cooling Platelets Down in Antibody-Mediated Immunothrombosis

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“…Tamam Bakchoul, Nina Wolska I n this issue of Arteriosclerosis, Thrombosis, and Vascular Biology, 2 groups reported on novel signaling pathways upregulated by antibodies directed at platelets in immune thrombotic thrombocytopenia (ITT). Renna et al 1 present an article entitled "Novel strategy to combat the procoagulant phenotype in heparin-induced thrombocytopenia using 12-LOX inhibition" and the article "Activation of platelet mTORC2/Akt pathway by anti-β2GP1 antibody promotes thrombosis in antiphospholipid syndrome" is offered by Tang et al 2 Both works elegantly demonstrate that specific inhibition of platelet activation under pathophysiological conditions can effectively prevent thromboembolic events, probably without increasing the risk for thrombocytopenia-associated bleeding.…”