Identification of Proteasome Components Required for Apical Localization of Chaoptin Using Functional Genomics

Abstract

Abstract: the distinct localization of membrane proteins with regard to cell polarity is crucial for the structure and function of various organs in multicellular organisms. However, the molecules and mechanisms that regulate protein localization to particular subcellular domains are still largely unknown. To identify the genes involved in regulation of protein localization, the authors performed a large-scale screen using a Drosophila RNA interference (RNAi) library, by which Drosophila genes could be knocked down in a tissue- and stage-specific manner. Drosophila photoreceptor cells have a morphologically distinct apicobasal polarity, along which Chaoptin (Chp), a glycosylphosphatidylinositol (GPI)-anchored membrane protein, and the Na ⁺ , K⁺ -ATPase are localized to the apical and basolateral domains, respectively. By examining the subcellular localization of these proteins, the authors identified 106 genes whose knockdown resulted in mislocalization of Chp and Na⁺ , K⁺ -ATPase. Gene ontology analysis revealed that the knockdown of proteasome components resulted in mislocalization of Chp to the basolateral plasma membrane. These results suggest that the proteasome is involved, directly or indirectly, in selective localization of Chp to the apical plasma membrane of Drosophila photoreceptor cells.

Keywords::

• apical-basal polarity
• Chaoptin
• Drosophila
• Na⁺, K⁺-ATPase
• proteasome

ACKNOWLEDGMENTS

We thank members of the S.G. and Ryu Ueda (NIG) laboratories for helpful discussions and fly stocks. This work was supported by a Grant-in-Aid for Scientific Research to S.G. from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.