JAM-A Has Inhibitory Role in Platelets
Junctional adhesion molecule A inhibits integrin outside-in signaling, premature platelet activation
THURSDAY, May 10 (HealthDay News) -- A platelet protein, junctional adhesion molecule A (JAM-A), inhibits integrin outside-in signaling and prevents premature platelet activation, according to a study published in the April 5 issue of Blood.
Noting that JAM-A was initially identified as a receptor for platelet stimulatory monoclonal antibodies, Meghna U. Naik, M.D., of the University of Delaware in Newark, and colleagues investigated its role in resting platelets.
The researchers found that JAM-A functioned as an endogenous inhibitor of platelet function. Genetic ablation of Jam-A in mice was associated with augmented platelet thrombotic function in vivo, and its absence increased platelet aggregation ex vivo. This gain of function was not due to enhanced inside-out signaling. In Jam-A-deficient platelets, integrin outside-in signaling, such as platelet spreading and clot retraction, was enhanced.
"Here we show that JAM-A acts as a negative regulator of platelet activation and hence the process of hemostasis and thrombosis," the authors write. "Our results identify a novel function for JAM-A in suppressing platelet activation as opposed to its previously-thought stimulatory role."