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Blood. April 5, 2012; 119 (14): 3352-60.

JAM-A protects from thrombosis by suppressing integrin αIIbβ3-dependent outside-in signaling in platelets.

Naik MU , Stalker TJ , Brass LF , Naik UP .

Mounting evidence suggests that agonist-initiated signaling in platelets is closely regulated to avoid excessive responses to injury. A variety of physiologic agonists induce a cascade of signaling events termed as inside-out signaling that culminate in exposure of high-affinity binding sites on integrin α(IIb)β(3). Once platelet activation has occurred, integrin α(IIb)β(3) stabilizes thrombus formation by providing agonist-independent "outside-in" signals mediated in part by contractile signaling. Junctional adhesion molecule A (JAM-A), a member of the cortical thymocyte marker of the Xenopus (CTX) family, was initially identified as a receptor for a platelet stimulatory mAb. Here we show that JAM-A in resting platelets functions as an endogenous inhibitor of platelet function. Genetic ablation of Jam-A in mice enhances thrombotic function of platelets in vivo. The absence of Jam-A results in increase in platelet aggregation ex vivo. This gain of function is not because of enhanced inside-out signaling because granular secretion, Thromboxane A2 (TxA2) generation, as well as fibrinogen receptor activation, are normal in the absence of Jam-A. Interestingly, integrin outside-in signaling such as platelet spreading and clot retraction is augmented in Jam-A-deficient platelets. We conclude that JAM-A normally limits platelet accumulation by inhibiting integrin outside-in signaling thus preventing premature platelet activation.

PubMed ID: 22271446
PMC ID: PMC3321861
Article link: Blood.
Grant support: 2P20 16472-11 PHS HHS , 5P20 RR015588-10 NCRR NIH HHS , HL40387 NHLBI NIH HHS , HL57630 NHLBI NIH HHS , HL63960 NHLBI NIH HHS , HL63960 NHLBI NIH HHS , R01 HL119374 NHLBI NIH HHS , R29 HL057630 NHLBI NIH HHS , R01 HL063960 NHLBI NIH HHS , 2P20 16472-11 PHS HHS , R01 HL057630 NHLBI NIH HHS , P20 RR016472 NCRR NIH HHS , 5P20 RR015588-10 NCRR NIH HHS , HL57630 NHLBI NIH HHS , HL40387 NHLBI NIH HHS , P01 HL040387 NHLBI NIH HHS , P20 RR015588 NCRR NIH HHS

Genes referenced: f11r fga vsig1

Ablooglu, 2009, Pubmed[+]

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