Rab5-mediated endosome-endosome fusion regulates hemoglobin endocytosis in Leishmania donovani.
To understand the trafficking of endocytosed hemoglobin (Hb) in Leishmania, we investigated the characteristics of in vitro fusion between endosomes containing biotinylated Hb (BHb) and avidin-horseradish peroxidase (AHRP). We showed that early endosome fusion in Leishmania is temperature and cytosol dependent and is inhibited by ATP depletion, ATPgammaS, GTPgammaS and N-ethylmaleimide treatment. The Rab5 homolog from Leishmania donovani, LdRab5, was cloned and expressed. Our results showed that homotypic fusion between the early endosomes in Leishmania is Rab5 dependent. Early endosomes containing BHb fused efficiently with late endosomes in a process regulated by Rab7, whereas no fusion between early and late endosomes was detected using fluid phase markers. Pre-treatment of early endosomes containing BHb with monoclonal antibody specific for the C-terminus of the Hb receptor (HbR) or the addition of the C-terminal cytoplasmic fragment of the HbR specifically inhibited the fusion with late endosomes, suggesting that signal(s) mediated through the HbR cytoplasmic tail promotes the fusion of early endosomes containing Hb with late endosomes.
National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Sudha B
SB
Singh
Ruchi
R
Tandon
Ganga
G
Krishnamurthy
Rajagopal
R
Vikram
Nimisha
N
Sharma
Sandip K
SK
Basu
Amitabha
A
Mukhopadhyay
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan; D002352:Carrier Proteins / Q000502:physiology; D004705:Endocytosis; D006454:Hemoglobins / Q000378:metabolism*; D066298:In Vitro Techniques; D007893:Leishmania donovani / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D052066:N-Ethylmaleimide-Sensitive Proteins; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000276:immunology / Q000502:physiology*
D000913:Antibodies, Protozoan; D002352:Carrier Proteins; D006454:Hemoglobins; D015800:Protozoan Proteins; D033921:Vesicular Transport Proteins; D052066:N-Ethylmaleimide-Sensitive Proteins; D020696:rab5 GTP-Binding Proteins