title: Gα13 and Rho mediate endosomal trafficking of CXCR4 into Rab11+ vesicles upon stromal cell-derived factor-1 stimulation.
abstract: CXCR4, like other G protein-coupled receptors, signals via heterotrimeric guanine nucleotide-binding proteins (G proteins) to regulate gene transcription, migration, development, growth, and transformation. We describe a formerly uncharacterized function of a G protein: a role in receptor trafficking. We previously showed that CXCR4 and the TCR physically associate and form a heterodimer upon stromal cell-derived factor-1 or CXCL12 (SDF-1) stimulation in human T cells to prolong ERK activation and, thereby, lead to gene upregulation and cytokine secretion. The CXCR4-TCR heterodimers occur on the cell surface and in an intracellular compartment in response to SDF-1. Neither the intracellular compartment to which the CXCR4-TCR heterodimers localize nor the mechanism for localization has been elucidated. In this article, we characterize molecular mechanisms required for postendocytic trafficking of CXCR4. Upon SDF-1 stimulation, CXCR4 localizes to Rab11(+) vesicles, a recycling compartment near the microtubule organizing center and Golgi apparatus. This trafficking requires the CXCR4 C-terminal tail domain but not the CXCR4 ubiquitination sites. The TCR also constitutively localizes to this Rab11(+) compartment. Trafficking of CXCR4 into the Rab11(+), TCR-containing endosomes requires actin polymerization. Furthermore, inhibiting Rho activation or depleting Gα13 prevented trafficking of CXCR4 into the Rab11(+) endosomes without hindering the ability of CXCR4 to endocytose. These results indicated that, upon SDF-1 treatment, Gα13 and Rho mediate the actin polymerization necessary for trafficking CXCR4 into the Rab11(+), recycling endosomal compartment, which also contains constitutively recycling TCR and, thus, CXCR4-TCR heterodimers. To our knowledge, this is the first report of Gα13 as a mediator of receptor trafficking.
authors.affiliation: Department of Immunology, Mayo Clinic College of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Ashok
authors.initials: A
authors.lastname: Kumar
authors.forename: Kimberly N
authors.initials: KN
authors.lastname: Kremer
authors.forename: Daniel
authors.initials: D
authors.lastname: Dominguez
authors.forename: Madhavi
authors.initials: M
authors.lastname: Tadi
authors.forename: Karen E
authors.initials: KE
authors.lastname: Hedin
mesh_terms: D054377:Chemokine CXCL12 / Q000502:physiology*; D022162:Cytoplasmic Vesicles / Q000276:immunology / Q000378:metabolism*; D004705:Endocytosis / Q000276:immunology; D011992:Endosomes / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000276:immunology; D019718:Receptors, CXCR4 / Q000737:chemistry / Q000378:metabolism*; D016176:T-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D054875:Ubiquitination / Q000276:immunology; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000502:physiology*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D054377:Chemokine CXCL12; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019718:Receptors, CXCR4; D020691:rab GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C527276:CXCR4 protein, human