Diverting intracellular trafficking of Salmonella to the lysosome through activation of the late endocytic Rab7 by intracellular delivery of muramyl dipeptide.
Previously, we showed that live Salmonella-containing phagosomes (LSP) recruit early acting Rab5 and promote fusion with early endosomes, thus avoiding transport to the lysosomes. Therefore, live Salmonella survive in a specialized compartment. Here we show that scavenger-receptor-mediated intracellular delivery of muramyl dipeptide (MDP) to macrophages leads to efficient killing of Salmonella both in vitro and in vivo. To understand the intracellular trafficking modulation of Salmonella by delivery of MDP, we investigated the levels of endocytic Rab proteins, which are the major regulators of vesicular transport. Western blot analysis reveals reduced Rab5 and enhanced Rab7 content in the maleylated bovine serum albumin-MDP (MBSA-MDP)-treated cells. The reduced content of Rab5 in the treated cells and on phagosomes inhibits the fusion of Salmonella-containing phagosomes with early endosomes, and the enhanced Rab7 content in these cells facilitated targeting of LSP to lysosomes, which contain cathepsin D and vacuolar ATPase, for killing. In vitro reconstitution of lysosomal transport demonstrated that a reduced content of Rab5 and an enhanced level of Rab7 in MBSA-MDP-treated cells is primarily responsible for targeting Salmonella to lysosomes. Intracellular delivery of MDP thus offers a general strategy against macrophage-associated infections caused by intracellular pathogens that survive in the host cell by resisting transport to lysosomes.
National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Konark
K
Mukherjee
Seetharaman
S
Parashuraman
Ganga
G
Krishnamurthy
Jolly
J
Majumdar
Ashok
A
Yadav
Ravi
R
Kumar
Sandip K
SK
Basu
Amitabha
A
Mukhopadhyay
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D006790:Host-Parasite Interactions / Q000187:drug effects / Q000502:physiology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D012480:Salmonella Infections / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000276:immunology / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D000090802:rab7 GTP-Binding Proteins; C000716465:rab7 GTP-binding proteins, mouse; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins