title: Single GDP-dissociation Inhibitor Protein regulates endocytic and secretory pathways in Leishmania.
abstract: The role of GDP dissociation inhibitor (GDI) protein in regulation of Rab cycle in Leishmania is not known. Here, we have cloned and characterized the functions of GDI homologue in vivo in Leishmania. Our results have shown that LdGDI:WT along with GDP removes the Rab5 from purified endosomes and inhibits the homotypic fusion between early endosomes. Whereas, LdGDI:R239A, a dominant negative mutant of GDI, under the same condition neither removes the Rab5 from endosome nor inhibits fusion. To determine the role of Ld-GDI in vivo, transgenic parasites overexpressing GFP-LdGDI:WT or GFP-LdGDI:R239A, are co-expressed with RFP-LdRab5:WT, RFP-LdRab7:WT or RFP-LdRab1:WT. Our results have shown that overexpression of GFP-LdGDI:WT extracts the RFP-LdRab5, RFP-LdRab7 or RFP-LdRab1 from their discrete endomembrane predominantly into cytosol. No change in the distribution of indicated Rabs is detected with overexpression of GFP-LdGDI:R239A. To determine the functional significance, we have used hemoglobin as an endocytic marker and gp63 as a marker for secretory pathway. We have found that overexpression of GFP-LdGDI:WT enhances the lysosomal targeting of internalized hemoglobin and the secretion of gp63 in the parasites possibly by triggering Rab cycle. This is the first demonstration of a single GDI ubiquitously regulating both endocytic and secretory pathways in Leishmania.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Senthil Kumar
authors.initials: SK
authors.lastname: Shanmugam
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Kamal
authors.initials: K
authors.lastname: Kumar
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Pawan Kishor
authors.initials: PK
authors.lastname: Singh
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Ruchir
authors.initials: R
authors.lastname: Rastogi
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India.
authors.forename: Amitabha
authors.initials: A
authors.lastname: Mukhopadhyay
mesh_terms: D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism*; D007893:Leishmania donovani / Q000235:genetics / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D000074041:Microorganisms, Genetically-Modified / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D015800:Protozoan Proteins; D008666:Metalloendopeptidases; C055146:glycoprotein gp63, Leishmania; D020696:rab5 GTP-Binding Proteins