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ADAP restraint of STAT1 signaling regulates macrophage phagocytosis in immune thrombocytopenia.

ABSTRACT: Heightened platelet phagocytosis by macrophages accompanied by an increase in IFN-γ play key roles in the etiology of immune thrombocytopenia (ITP); however, it remains elusive how macrophage-mediated platelet clearance is regulated in ITP. Here, we report that adhesion and degranulation-protein adaptor protein (ADAP) restrains platelet phagocytosis by macrophages in ITP via modulation of signal transducer and activator of transcription 1 (STAT1)-FcγR signaling. We show that ITP was associated with the underexpression of ADAP in splenic macrophages. Furthermore, macrophages from Adap^-/- mice exhibited elevated platelet phagocytosis and upregulated proinflammatory signaling, and thrombocytopenia in Adap^-/- mice was mitigated by the depletion of macrophages. Mechanistically, ADAP interacted and competed with STAT1 binding to importin α5. ADAP deficiency potentiated STAT1 nuclear entry, leading to a selective enhancement of FcγRI/IV transcription in macrophages. Moreover, pharmacological inhibition of STAT1 or disruption of the STAT1-importin α5 interaction relieved thrombocytopenia in Adap^-/- mice. Thus, our findings not only reveal a critical role for ADAP as an intracellular immune checkpoint for shaping macrophage phagocytosis in ITP but also identify the ADAP-STAT1-importin α5 module as a promising therapeutic target in the treatment of ITP.

SUBMITTER: Xiong Y

PROVIDER: S-EPMC9149338 | biostudies-literature |

REPOSITORIES: biostudies-literature

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ADAP-STAT1 module maintains platelet homeostasis via restraint of macrophage phagocytic in ITP

Project description:Heightened platelet phagocytosis by macrophages accompanied with an increase in IFN-γ is often attributed to the etiology of immune thrombocytopenia (ITP), an autoimmune disease characterized by low platelet counts. While deletion of the hematopoietic cell adaptor protein ADAP predisposes to ITP in mice, the mechanisms that underlie the functional role of ADAP during ITP remains largely unknown. Here we report that ADAP restrains platelet clearance by macrophages via modulation of STAT1-FcγR signaling axis. We show that under-expression of ADAP in splenic macrophage was associated with low platelet counts in patients with ITP. Further, macrophages from Adap−/− mice had an elevated phagocytosis capacity and exhibited upregulated pro-inflammatory signaling, and the thrombocytopenia in Adap−/− mice was mitigated in vivo by depletion of macrophages. Mechanically, ADAP interacted and competed with STAT1 binding to importin a5, a nuclear shuttling receptor for activated STAT1. While having no effect on STAT1 tyrosine phosphorylation, loss of ADAP increased the assembly of STAT1-importin a5 complex and facilitated STAT1 nuclear entry, leading to a selective enhancement of transcription of FcγRI/IV in macrophages. Moreover, pharmacological inhibition of STAT1 or disruption of STAT1-importin a5 interaction relieved the thrombocytopenia in Adap−/− mice. Thus, our findings reveal a critical role for ADAP as an intracellular immune checkpoint for shaping macrophage phagocytic ability in homeostatic maintenance of platelets.

2022-06-21 | GSE183385 | GEO

ADAP-STAT1 module maintains platelet homeostasis via restraint of macrophage phagocytic in ITP

Project description:ADAP-STAT1 module maintains platelet homeostasis via restraint of macrophage phagocytic in ITP

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