The intraflagellar transport protein IFT20 is associated with the Golgi complex and is required for cilia assembly：（intraflagellar运输蛋白质IFT20与高尔基氏复合体和纤毛需要组装）.pdfVIP

Molecular Biology of the Cell Vol. 17, 3781–3792, September 2006 The Intraflagellar Transport Protein IFT20 Is Associated with the Golgi Complex and Is Required for Cilia Assembly□V John A. Follit,* Richard A. Tuft,† Kevin E. Fogarty,† and Gregory J. Pazour* *Program in Molecular Medicine and †Biomedical Imaging Group, Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01605 Submitted February 14, 2006; Revised May 9, 2006; Accepted June 5, 2006 Monitoring Editor: Ben Margolis Eukaryotic cilia are assembled via intraflagellar transport (IFT) in which large protein particles are motored along ciliary microtubules. The IFT particles are composed of at least 17 polypeptides that are thought to contain binding sites for various cargos that need to be transported from their site of synthesis in the cell body to the site of assembly in the cilium. We show here that the IFT20 subunit of the particle is localized to the Golgi complex in addition to the basal body and cilia where all previous IFT particle proteins had been found. In living cells, fluorescently tagged IFT20 is highly dynamic and moves between the Golgi complex and the cilium as well as along ciliary microtubules. Strong knock down of IFT20 in mammalian cells blocks ciliary assembly but does not affect Golgi structure. Moderate knockdown does not block cilia assembly but reduces the amount of polycystin-2 that is localized to the cilia. This work suggests that IFT20 functions in the delivery of ciliary membrane proteins from the Golgi complex to the cilium. INTRODUCTION been localized to the mammalian primary cilium, including the SSTR3 isoform of the somatostatin receptor (Handel et Cilia are usually thought of as motile organelles, but many al., 1999), the 5HT6 isoform of the se