Localization of serum resistance-associated protein in Trypanosoma brucei rhodesiense and transgenic Trypanosoma brucei brucei.
African trypanosomes infect a broad range of mammals, but humans and some higher primates are protected by serum trypanosome lytic factors that contain apolipoprotein L1 (ApoL1). In the human-infective subspecies of Trypanosoma brucei, Trypanosoma brucei rhodesiense, a gene product derived from the variant surface glycoprotein gene family member, serum resistance-associated protein (SRA protein), protects against ApoL1-mediated lysis. Protection against trypanosome lytic factor requires the direct interaction between SRA protein and ApoL1 within the endocytic apparatus of the trypanosome, but some uncertainty remains as to the precise mechanism and location of this interaction. In order to provide more insight into the mechanism of SRA-mediated resistance to trypanosome lytic factor, we assessed the localization of SRA in T. b. rhodesiense EATRO3 using a novel monoclonal antibody raised against SRA together with a set of well-characterized endosomal markers. By three-dimensional deconvolved immunofluorescence single-cell analysis, combined with double-labelling immunoelectron microscopy, we found that ≈ 50% of SRA protein localized to the lysosome, with the remaining population being distributed through the endocytic pathway, but apparently absent from the flagellar pocket membrane. These data suggest that the SRA/trypanolytic factor interaction is intracellular, with the concentration within the endosomes potentially crucial for ensuring a high efficiency.
Instituto de Parasitología y Biomedicina 'López-Neyra', Consejo Superior de Investigaciones Científicas, Granada, Spain.|Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain.
Jean-Mathieu
JM
Bart
Instituto de Parasitología y Biomedicina 'López-Neyra', Consejo Superior de Investigaciones Científicas, Granada, Spain.
Carlos
C
Cordon-Obras
Instituto de Parasitología y Biomedicina 'López-Neyra', Consejo Superior de Investigaciones Científicas, Granada, Spain.
Isabel
I
Vidal
Department of Biochemistry, University of Cambridge, Cambridge, UK.
Jennifer
J
Reed
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
Esperanza
E
Perez-Pastrana
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
Laureano
L
Cuevas
Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, UK.
Mark C
MC
Field
Department of Biochemistry, University of Cambridge, Cambridge, UK.
Mark
M
Carrington
Instituto de Parasitología y Biomedicina 'López-Neyra', Consejo Superior de Investigaciones Científicas, Granada, Spain.
Miguel
M
Navarro
D000818:Animals; D000075944:Apolipoprotein L1; D001053:Apolipoproteins / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry*; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism; D008247:Lysosomes / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics*; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D015800:Protozoan Proteins / Q000032:analysis* / Q000235:genetics*; D014346:Trypanosoma brucei brucei / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology; D016833:Trypanosoma brucei rhodesiense / Q000737:chemistry* / Q000187:drug effects / Q000276:immunology
C108666:APOL1 protein, human; D000075944:Apolipoprotein L1; D001053:Apolipoproteins; D008075:Lipoproteins, HDL; D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; C403774:serum resistance associated protein, Trypanosoma brucei