Abstract
EB1 is key factor in the organization of the microtubule cytoskeleton by binding to the plus-ends of microtubules and serving as a platform for a number of interacting proteins (termed +TIPs) that control microtubule dynamics. Together with its direct binding partner adenomatous polyposis coli (APC), EB1 can stabilize microtubules. Here, we show that Amer2 (APC membrane recruitment 2), a previously identified membrane-associated APC-binding protein, is a direct interaction partner of EB1 and acts as regulator of microtubule stability together with EB1. Amer2 binds to EB1 via specific (S/T)xIP motifs and recruits it to the plasma membrane. Coexpression of Amer2 and EB1 generates stabilized microtubules at the plasma membrane, whereas knockdown of Amer2 leads to destabilization of microtubules. Knockdown of Amer2, APC, or EB1 reduces cell migration, and morpholino-mediated down-regulation of Xenopus Amer2 blocks convergent extension cell movements, suggesting that the Amer2-EB1-APC complex regulates cell migration by altering microtubule stability.
Highlights
Amer2 localizes to the plasma membrane, interacts with adenomatous polyposis coli, and regulates Wnt signaling
Amer2 Interacts with EB1 via (S/T)xIP Motifs—In a yeast two-hybrid screen using a C-terminal fragment of Amer2 as bait, we isolated several interacting clones covering the C-terminal part of EB1 (Fig. 1, A and B) [3]
A minor fraction of Amer2 and EB1 was present at filamentous structures possibly representing microtubules, which would point to recruitment of Amer2 to microtubules by EB1 (Fig. 1F)
Summary
Amer localizes to the plasma membrane, interacts with adenomatous polyposis coli, and regulates Wnt signaling. Results: Amer recruits the microtubule-associated protein EB1 to the plasma membrane and affects the stabilization of microtubules and cell migration. We show that Amer (APC membrane recruitment 2), a previously identified membraneassociated APC-binding protein, is a direct interaction partner of EB1 and acts as regulator of microtubule stability together with EB1. EB1 recruits a variety of proteins to the microtubule plus-ends that control microtubule dynamics, suggesting that it represents a platform for microtubule regulators Because of their association with growing microtubule ends, EB1 and its binding partners are. We reveal a role for Amer in regulating microtubule stability presumably by providing a platform for the microtubule-binding proteins APC and EB1 to promote cell migration
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