FIG 6.

Model of Syk and SFK signaling in B. burgdorferi internalization. B. burgdorferi internalization is mediated by multiple phagocytic receptors, including the scavenger receptor MARCO and integrin β1. In our study, we investigated the roles of these two receptors in activating signaling pathways that lead to phagocytosis. We found that β1 integrin, via its NPxY motif, participates in the activation of Syk, while both MARCO and β1 integrin participate in the activation of the SFK pathway. These pathways have been shown in other systems to lead to the activation of small GTPases such as Rac1 and Cdc42. The small GTPases are important for the phagocytosis of B. burgdorferi via the activation of Wiskott-Aldrich syndrome protein (WASP) and Arp2/3, leading to F-actin polymerization and rearrangement.