title: The small GTPase Rab8 interacts with VAMP-3 to regulate the delivery of recycling T-cell receptors to the immune synapse.
abstract: IFT20, a component of the intraflagellar transport (IFT) system that controls ciliogenesis, regulates immune synapse assembly in the non-ciliated T-cell by promoting T-cell receptor (TCR) recycling. Here, we have addressed the role of Rab8 (for which there are two isoforms Rab8a and Rab8b), a small GTPase implicated in ciliogenesis, in TCR traffic to the immune synapse. We show that Rab8, which colocalizes with IFT20 in Rab11(+) endosomes, is required for TCR recycling. Interestingly, as opposed to in IFT20-deficient T-cells, TCR(+) endosomes polarized normally beneath the immune synapse membrane in the presence of dominant-negative Rab8, but were unable to undergo the final docking or fusion step. This could be accounted for by the inability of the vesicular (v)-SNARE VAMP-3 to cluster at the immune synapse in the absence of functional Rab8, which is responsible for its recruitment. Of note, and similar to in T-cells, VAMP-3 interacts with Rab8 at the base of the cilium in NIH-3T3 cells, where it regulates ciliary growth and targeting of the protein smoothened. The results identify Rab8 as a new player in vesicular traffic to the immune synapse and provide insight into the pathways co-opted by different cell types for immune synapse assembly and ciliogenesis.
authors.affiliation: Department of Life Sciences, University of Siena, Siena 53100, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Finetti
authors.affiliation: Department of Life Sciences, University of Siena, Siena 53100, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Patrussi
authors.affiliation: Department of Life Sciences, University of Siena, Siena 53100, Italy.
authors.forename: Donatella
authors.initials: D
authors.lastname: Galgano
authors.affiliation: Department of Life Sciences, University of Siena, Siena 53100, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Cassioli
authors.affiliation: Department of Medical, Surgical and Health Sciences, School of Dentistry, University of Trieste, Trieste 34129, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Perinetti
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Pazour
authors.affiliation: Department of Life Sciences, University of Siena, Siena 53100, Italy cosima.baldari@unisi.it.
authors.forename: Cosima T
authors.initials: CT
authors.lastname: Baldari
mesh_terms: D000818:Animals; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D006801:Humans; D054992:Immunological Synapses / Q000235:genetics / Q000378:metabolism*; D019169:Jurkat Cells; D051379:Mice; D041681:NIH 3T3 Cells; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D051040:Vesicle-Associated Membrane Protein 3 / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C521976:Rab8 protein, mouse; D011948:Receptors, Antigen, T-Cell; D050600:SNARE Proteins; C494946:VAMP3 protein, human; D051040:Vesicle-Associated Membrane Protein 3; C494953:vesicle-associated membrane protein 3, mouse; C082377:RAB8A protein, human; D020691:rab GTP-Binding Proteins
keywords: Immune synapse; Rab8; TCR recycling