Rab8 binding to immune cell-specific adaptor LAX facilitates formation of trans-Golgi network-proximal CTLA-4 vesicles for surface expression

Mol Cell Biol. 2014 Apr;34(8):1486-99. doi: 10.1128/MCB.01331-13. Epub 2014 Feb 10.


Despite playing a central role in tolerance, little is known regarding the mechanism by which intracellular CTLA-4 is shuttled from the trans-Golgi network to the surfaces of T cells. In this context, Ras-related GTPase Rab8 plays an important role in the intracellular transport, while we have previously shown that CTLA-4 binds to the immune cell adaptor TRIM in T cells. In this study, we demonstrate that CTLA-4 forms a multimeric complex comprised of TRIM and related LAX that in turn binds to GTP bound Rab8 for post-Golgi transport to the cell surface. LAX bound via its N terminus to active GTP-Rab8, as well as the cytoplasmic tail of CTLA-4. TRIM required LAX for binding to Rab8 in a complex. Wild-type LAX or its N terminus (residues 1 to 77) increased CTLA-4 surface expression, whereas small interfering RNAs of Rab8 or LAX or disruption of LAX/Rab8 binding reduced numbers of CTLA-4-containing vesicles and its coreceptor surface expression. LAX also promoted the polarization of CTLA-4 and the reorientation of the microtubule-organizing center to the site of T-cell receptor engagement. Our results identify a novel CTLA-4/TRIM/LAX/Rab8 effector complex in the transport of CTLA-4 to the surfaces of T cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / immunology
  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Animals
  • CTLA-4 Antigen / immunology
  • CTLA-4 Antigen / metabolism*
  • Cell Culture Techniques
  • Cell Line
  • Cell Membrane / metabolism
  • Germinal Center Kinases
  • Humans
  • Mice
  • Monomeric GTP-Binding Proteins / metabolism
  • Protein Serine-Threonine Kinases / immunology
  • Protein Serine-Threonine Kinases / metabolism*
  • Protein Transport / immunology
  • Receptors, Antigen, T-Cell / metabolism
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism
  • trans-Golgi Network / metabolism*


  • Adaptor Proteins, Vesicular Transport
  • CTLA-4 Antigen
  • Germinal Center Kinases
  • LAX1 protein, human
  • Receptors, Antigen, T-Cell
  • Protein Serine-Threonine Kinases
  • Monomeric GTP-Binding Proteins