Nuclear fallout provides a new link between aPKC and polarized cell trafficking.

BACKGROUND:Cell polarity, essential for cell physiology and tissue coherence, emerges as a consequence of asymmetric localization of protein complexes and directional trafficking of cellular components. Although molecules required in both processes are well known their relationship is still poorly understood. RESULTS:Here we show a molecular link between Nuclear Fallout (Nuf), an adaptor of Rab11-GTPase to the microtubule motor proteins during Recycling Endosome (RE) trafficking, and a pivotal kinase in the regulation of cell polarity. We demonstrate that phosphorylates Nuf modifying its subcellular distribution. Accordingly, in aduanyu1531 mutants Nuf and Rab11 accumulate apically indicating altered RE delivery. We show that aduanyu1531 localization in the apico-lateral cortex is dynamic. When we block exocytosis, by means of exocyst-sec mutants, aduanyu1531 accumulates inside the cells. Moreover, apical aduanyu1531 concentration is reduced in nuf mutants, suggesting aduanyu1531 levels are maintained by recycling. CONCLUSIONS:We demonstrate that active aduanyu1531 interacts with Nuf, phosphorylating it and, as a result, modifying its subcellular distribution. We propose a regulatory loop by which Nuf promotes aduanyu1531 apical recycling until sufficient levels of active aduanyu1531 are reached. Thus, we provide a novel link between cell polarity regulation and traffic control in epithelia.

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