title: A ternary complex comprising transportin1, Rab8 and the ciliary targeting signal directs proteins to ciliary membranes.
abstract: The sensory functions of cilia are dependent on the enrichment of cilium-resident proteins. Although it is known that ciliary targeting signals (CTSs) specifically target ciliary proteins to cilia, it is still unclear how CTSs facilitate the entry and retention of cilium-resident proteins at the molecular level. We found that non-ciliary membrane reporters can passively diffuse into cilia through the lateral transport pathway, and the translocation of membrane reporters through the ciliary diffusion barrier is facilitated by importin binding motifs and domains. Screening known CTSs of ciliary membrane residents uncovered that fibrocystin, photoreceptor retinol dehydrogenase, rhodopsin and retinitis pigmentosa 2 interact with transportin1 (TNPO1) through previously identified CTSs. We further discovered that a new ternary complex, comprising TNPO1, Rab8 and a CTS, can assemble or disassemble under the guanine nucleotide exchange activity of Rab8. Our study suggests a new mechanism in which the TNPO1-Rab8-CTS complex mediates selective entry into and retention of cargos within cilia.
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore.
authors.forename: Viswanadh
authors.initials: V
authors.lastname: Madugula
authors.affiliation: School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore lulei@ntu.edu.sg.
authors.forename: Lei
authors.identifier: 0000-0002-8192-1471
authors.initials: L
authors.lastname: Lu
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism; D020816:Amino Acid Motifs; D002462:Cell Membrane / Q000378:metabolism; D002923:Cilia / Q000378:metabolism*; D004058:Diffusion; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D006150:Guanine Nucleotides / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D000072417:Protein Domains; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction; D028961:beta Karyopherins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D006150:Guanine Nucleotides; D046912:Multiprotein Complexes; C451750:PKHD1 protein, human; D011956:Receptors, Cell Surface; C108121:TNPO1 protein, human; D028961:beta Karyopherins; D012243:Rhodopsin; D000429:Alcohol Oxidoreductases; C082377:RAB8A protein, human; D020691:rab GTP-Binding Proteins; D020931:ran GTP-Binding Protein
keywords: Cilia; Ciliary targeting signal; Rab8; Transportin1