Killing of Trypanosoma brucei by concanavalin A: structural basis of resistance in glycosylation mutants.
Concanavalin A (Con A) kills procyclic (insect) forms of Trypanosoma brucei by binding to N-glycans on EP-procyclin, a major surface glycosyl phosphatidylinositol (GPI)-anchored protein which is rich in Glu-Pro repeats. We have previously isolated and studied two procyclic mutants (ConA 1-1 and ConA 4-1) that are more resistant than wild-type (WT) to Con A killing. Although both mutants express the same altered oligosaccharides compared to WT cells, ConA 4-1 is considerably more resistant to lectin killing than is ConA 1-1. Thus, we looked for other alterations to account for the differences in sensitivity. Using mass spectrometry, together with chemical and enzymatic treatments, we found that both mutants express types of EP-procyclin that are either poorly expressed or not found at all in WT cells. ConA 1-1 expresses mainly EP1-3, a novel procyclin that contains 18 EP repeats, is partially N-glycosylated, and bears hybrid-type glycans. On the other hand, ConA 4-1 cells express almost exclusively EP2-3, a novel non-glycosylated procyclin isoform with 23 EP repeats and no site for glycosylation. The predominance of EP2-3 in ConA 4-1 cells explains their high resistance to ConA killing. Thus, switching the procyclin repertoire, a process that could be relevant to parasite development in the insect vector, modulates the sensitivity of trypanosomes to cytotoxic lectins.
Acosta-Serrano
A
A
Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Cole
R N
RN
Englund
P T
PT
D000595:Amino Acid Sequence; D000606:Amino Sugars / Q000378:metabolism; D000818:Animals; D003208:Concanavalin A / Q000378:metabolism* / Q000633:toxicity*; D004351:Drug Resistance / Q000235:genetics; D019143:Evolution, Molecular; D006031:Glycosylation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010455:Peptides / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D016415:Sequence Alignment; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014346:Trypanosoma brucei brucei / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development
D000606:Amino Sugars; D008562:Membrane Glycoproteins; D010455:Peptides; D020033:Protein Isoforms; D015800:Protozoan Proteins; C053277:procyclic acidic repetitive protein, Trypanosoma; D003208:Concanavalin A; C000458:N-acetyllactosamine