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A more recent version of this article appeared on August 1, 2005
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Submitted on March 1, 2005
Revised on April 15, 2005
Accepted on May 11, 2005
Howard Hughes Medical Institute and Department of Physiology and Biochemistry, University of California-San Francisco, San Francisco, CA 94143-0725
Monitoring Editor: Susan Strome
In Drosophila, asymmetric division occurs during proliferation of neural precursors of the central and peripheral nervous system (PNS), where a membrane-associated protein, Numb, is asymmetrically localized during cell division and is segregated to one of the two daughter cells (the pIIb cell) following mitosis. numb has been shown genetically to function as an antagonist of Notch signaling (Rhyu et al., 1994), and also as a negative regulator of the membrane localization of Sanpodo, a four-pass transmembrane protein required for Notch signaling during asymmetric cell division in the central nervous system (CNS) (OConnor-Giles and Skeath, 2003). Previously, we identified lethal giant larvae (lgl) as a gene required for numb-mediated inhibition of Notch in the adult PNS (Justice et al., 2003). In this study we show that Sanpodo is expressed in asymmetrically dividing precursor cells of the PNS and that Sanpodo internalization in the pIIb cell is dependent cytoskeletally-associated Lgl. Lgl specifically regulates internalization of Sanpodo, likely through endocytosis, but is not required for the endocytosis Delta, which is a required step in the Notch-mediated cell fate decision during asymmetric cell division. Conversely, the E3 ubiquitin ligase neuralized is required for both Delta endocytosis and the internalization of Sanpodo. This study identifies a hitherto unreported role for Lgl as a regulator of Sanpodo during asymmetric cell division in the adult PNS.