IFT20 is subunit 20 of the intraflagellar transport complex B [1]. The intraflagellar transport complex assembles and maintains eukaryotic cilia and flagella. IFT20 is localised to the Golgi complex and is anchored there by the Golgi polypeptide, GMAP210, whereas all other subunits except IFT172 localise to cilia and the peri-basal body or centrosomal region at the base of cilia [1,2,3]. IFT20 accompanies Golgi-derived vesicles to the point of exocytosis near the basal bodies where the other IFT polypeptides are present, and where the intact IFT particle is assembled in association with the inner surface of the cell membrane. Passage of the IFT complex then follows, through the flagellar pore recognition site at the transition region, into the ciliary compartment. There also appears to be a role of intraflagellar transport (IFT) polypeptides in the formation of the immune synapse in non ciliated cells. The flagellum, in addition to being a sensory and motile organelle, is also a secretory organelle [5]. A number of IFT components are expressed in haematopoietic cells, which have no cilia, indicating an unexpected role of IFT proteins in immune synapse-assembly and intracellular membrane trafficking in T lymphocytes; this suggests that the immune synapse could represent the functional homologue of the primary cilium in these cells [6,7].

1: IFT20 links kinesin II with a mammalian intraflagellar transport complex that is conserved in motile flagella and sensory cilia. Baker SA, Freeman K, Luby-Phelps K, Pazour GJ, Besharse JC; J Biol Chem. 2003;278:34211-34218. PMID:12821668

2: Cloning and characterization of the human IFT20 gene. Yin G, Dai J, Ji C, Ni X, Shu G, Ye X, Dai J, Wu Q, Gu S, Xie Y, Zhao RC, Mao Y; Mol Biol Rep. 2003;30:255-260. PMID:14672413

3: Pericentrin forms a complex with intraflagellar transport proteins and polycystin-2 and is required for primary cilia assembly. Jurczyk A, Gromley A, Redick S, San Agustin J, Witman G, Pazour GJ, Peters DJ, Doxsey S; J Cell Biol. 2004;166:637-643. PMID:15337773

4: The intraflagellar transport protein IFT20 is associated with the Golgi complex and is required for cilia assembly. Follit JA, Tuft RA, Fogarty KE, Pazour GJ; Mol Biol Cell. 2006;17:3781-3792. PMID:16775004

5: Characterization of mouse IFT complex B. Follit JA, Xu F, Keady BT, Pazour GJ; Cell Motil Cytoskeleton. 2009;66:457-468. PMID:19253336

6: Intraflagellar transport: it's not just for cilia anymore. Baldari CT, Rosenbaum J; Curr Opin Cell Biol. 2010;22:75-80. PMID:19962875

7: Intraflagellar transport: a new player at the immune synapse. Finetti F, Paccani SR, Rosenbaum J, Baldari CT; Trends Immunol. 2011;32:139-145. PMID:21388881