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Vesicle-Associated Membrane Protein-8/Endobrevin Negatively Regulates Phagocytosis of Bacteria in Dendritic Cells¹

Yong Hou Sunny Ho^*, Deyu Tarika Cai^*, Cheng-Chun Wang, Dachuan Huang^* and Siew Heng Wong^2,*

^* Laboratory of Membrane Trafficking and Immunoregulation Research, Department of Microbiology, Immunology Program, Yong Loo Lin School of Medicine, National University of Singapore and Membrane Biology Laboratory, Institute of Molecular and Cell Biology, Proteos, Singapore, Republic of Singapore

Phagocytosis is a specialized mechanism used by mammalian cells, particularly the cells of the immune system, such as dendritic cells (DC) and macrophages, to protect the host against infection. The process involves a complex cascade of pathways, from the ligation of surface receptors of phagocytes with components of the microorganism’s surface, formation of phagosomes and subsequently phagolysosomes, to the eventual presentation of foreign Ags. Vesicle-associated membrane protein (VAMP)-8/endobrevin has been shown previously to function in the endocytic pathways. Our results showed that VAMP-8 colocalized with lysosome-associated membrane protein-2, and a significant amount of VAMP-8 was recruited to the phagosomes during bacterial ingestion. However, overexpression of VAMP-8 significantly inhibited phagocytosis in DC. We also found that the phagocytic activity of VAMP-8^–/– DC was significantly higher than wild-type VAMP-8^+/+ DC, thus further confirming that VAMP-8 negatively regulates phagocytosis in immature DC.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ This work was supported by Grant R182-005-067-731 from the Microbiology Vaccine Initiative (to S.H.W.) and by the Academic Research Council, Singapore Ministry of Education (R182-000-099-112 to S.H.W.).

² Address correspondence and reprint requests to Dr. Siew Heng Wong, Laboratory of Membrane Trafficking and Immunoregulation Research, Department of Microbiology, Immunology Program, Yong Loo Lin School of Medicine, National University of Singapore, Block MD4, 5 Science Drive 2, Singapore 117597, Republic of Singapore. E-mail address: micwsh{at}nus.edu.sg

³ Abbreviations used in this paper: DC, dendritic cell; VAMP, vesicle-associated membrane protein; LAMP, lysosome-associated membrane protein; ER, endoplasmic reticulum; NSF, N-ethylmaleimide-sensitive factor; siRNA, small interfering RNA.