3b-2, b-3) (17). We also found that clustering of RILP in the perinuclear regions was disrupted and diffused by the expression
of Rab7T22N. Collectively, our data demonstrate that Rab7 is vital for recruiting RILP to phagosomes during the maturation process, but not for recruiting CD63. How M.tb escapes the effects of the bactericidal components within the phagosome while still acquiring nutrients for growth is very important question. It has been suggested that mycobacterial phagosomes arrest their maturation at an early stage and completely avoid fusion with lysosomes (18, 19). However, we have shown the localization of CD63 (Fig. 2) and LAMP-2 (4) on M.tb phagosomes in macrophages. It Selleck Doxorubicin has been proposed that phagolysosome biogenesis is achieved by a series of fusions with heterogeneous lysosomes (20). This model is supported by a report demonstrating the existence of sub-populations of lysosomes in macrophages (6). Our previous and current studies demonstrating the alternative localization of lysosomal markers on M.tb phagosomes further support this model. From these observations, it seems that dissociation
of Rab7 from M.tb phagosomes selectively inhibits fusion with harmful lysosomes despite continued fusion with non-microbicidal lysosomes. In conclusion, based on our findings we propose the following model for M.tb-induced inhibition of phagolysosome biogenesis: Early M.tb phagosomes are capable of recruiting Rab7 and can potentially fuse with lysosomes. RILP is also recruited to M.tb phagosomes, which form the Rab7-RILP-dynein/dynactin protein complex followed by promotion of selleck chemicals llc phagolysosome biogenesis. However, viable M.tb is able to release Rab7 from phagosomes, resulting in inhibition of further fusion with lysosomal vesicles and disassembly of the RILP-phagosome complex. This causes the blocking of subsequent phagolysosome biogenesis. over On the other hand, non-microbicidal vesicles expressing CD63 and/or LAMP-2 continuously fuse with M.tb phagosomes
despite Rab7 dissociation, and this fusion would support the acquisition of nutrients for mycobacterial proliferation within the phagosome. We thank Drs. Toshi Nagata and Masato Uchijima (Hamamatsu University School of Medicine, Hamamatsu, Japan) for their helpful discussion. M.tb strain H37Rv was kindly provided by Dr. Isamu Sugawara (Research Institute of Tuberculosis, Tokyo, Japan). This work was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science, COE Research and Scientific Research on Priority Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan, Health and Labor Science Research Grants for Research into Emerging and Reemerging Infectious Diseases from the Ministry of Health, Labor and Welfare of Japan, and the United States-Japan Cooperative Medical Science Committee.