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Mol Biol Cell. 2013 Dec;24(23):3721-35. doi: 10.1091/mbc.E13-05-0259. Epub 2013 Oct 2.

Arf-like GTPase Arl8b regulates lytic granule polarization and natural killer cell-mediated cytotoxicity.

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Division of Rheumatology, Immunology and Allergy, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115 Division of Cell Biology and Immunology, Institute of Microbial Technology, Chandigarh 160036, India Program in Cellular and Molecular Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115 Institut National de la Santé et de la Recherche Médicale, Unité 753, Institut Gustave Roussy, Villejuif 75654, France Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104 Department of Biological Sciences, Indian Institute of Science Education and Research, Mohali 140306, India Immunology, Allergy and Rheumatology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030.


Natural killer (NK) lymphocytes contain lysosome-related organelles (LROs), known as lytic granules, which upon formation of immune synapse with the target cell, polarize toward the immune synapse to deliver their contents to the target cell membrane. Here, we identify a small GTP-binding protein, ADP-ribosylation factor-like 8b (Arl8b), as a critical factor required for NK cell-mediated cytotoxicity. Our findings indicate that Arl8b drives the polarization of lytic granules and microtubule-organizing centers (MTOCs) toward the immune synapse between effector NK lymphocytes and target cells. Using a glutathione S-transferase pull-down approach, we identify kinesin family member 5B (KIF5B; the heavy chain of kinesin-1) as an interaction partner of Arl8b from NK cell lysates. Previous studies showed that interaction between kinesin-1 and Arl8b is mediated by SifA and kinesin-interacting protein (SKIP) and the tripartite complex drives the anterograde movement of lysosomes. Silencing of both KIF5B and SKIP in NK cells, similar to Arl8b, led to failure of MTOC-lytic granule polarization to the immune synapse, suggesting that Arl8b and kinesin-1 together control this critical step in NK cell cytotoxicity.

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