Architecture of a Host-Parasite Interface: Complex Targeting Mechanisms Revealed Through Proteomics.
Surface membrane organization and composition is key to cellular function, and membrane proteins serve many essential roles in endocytosis, secretion, and cell recognition. The surface of parasitic organisms, however, is a double-edged sword; this is the primary interface between parasites and their hosts, and those crucial cellular processes must be carried out while avoiding elimination by the host immune defenses. For extracellular African trypanosomes, the surface is partitioned such that all endo- and exocytosis is directed through a specific membrane region, the flagellar pocket, in which it is thought the majority of invariant surface proteins reside. However, very few of these proteins have been identified, severely limiting functional studies, and hampering the development of potential treatments. Here we used an integrated biochemical, proteomic and bioinformatic strategy to identify surface components of the human parasite Trypanosoma brucei. This surface proteome contains previously known flagellar pocket proteins as well as multiple novel components, and is significantly enriched in proteins that are essential for parasite survival. Molecules with receptor-like properties are almost exclusively parasite-specific, whereas transporter-like proteins are conserved in model organisms. Validation shows that the majority of surface proteome constituents are bona fide surface-associated proteins and, as expected, most present at the flagellar pocket. Moreover, the largest systematic analysis of trypanosome surface molecules to date provides evidence that the cell surface is compartmentalized into three distinct domains with free diffusion of molecules in each, but selective, asymmetric traffic between. This work provides a paradigm for the compartmentalization of a cell surface and a resource for its analysis.
From the ‡School of Life Sciences, University of Nottingham, Nottingham, UK, NG2 7UH; §Department of Pathology, University of Cambridge, Cambridge, UK, CB2 1QP; catarina.gadelha@nottingham.ac.uk.
Catarina
C
Gadelha
¶Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, 10021;
Wenzhu
W
Zhang
From the ‡School of Life Sciences, University of Nottingham, Nottingham, UK, NG2 7UH;
James W
JW
Chamberlain
¶Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, 10021;
Brian T
BT
Chait
From the ‡School of Life Sciences, University of Nottingham, Nottingham, UK, NG2 7UH;
Bill
B
Wickstead
‖Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, UK, DD1 5EH.
Mark C
MC
Field
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D019295:Computational Biology; D054884:Host-Pathogen Interactions; D006801:Humans; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000378:metabolism; D010271:Parasites / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D020543:Proteome / Q000378:metabolism; D040901:Proteomics / Q000379:methods*; D015800:Protozoan Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D014346:Trypanosoma brucei brucei / Q000378:metabolism
D008565:Membrane Proteins; D020543:Proteome; D015800:Protozoan Proteins