title: Protease trafficking in two primitive eukaryotes is mediated by a prodomain protein motif.
abstract: Trypanosome protozoa, an early lineage of eukaryotic cells, have proteases homologous to mammalian lysosomal cathepsins, but the precursor proteins lack mannose 6-phosphate. Utilizing green fluorescent protein as a reporter, we demonstrate that the carbohydrate-free prodomain of a trypanosome cathepsin L is necessary and sufficient for directing green fluorescent protein to the lysosome/endosome compartment. A proper prodomain/catalytic domain processing site sequence is also required to free the mature protease for delivery to the lysosome/endosome compartment. A nine-amino acid prodomain loop motif, implicated in prodomain-receptor interactions in mammalian cells, is conserved in the protozoa. Site-directed mutagenesis now confirms the importance of this loop to protease trafficking and suggests that a protein motif targeting signal for lysosomal proteases arose early in eukaryotic cell evolution.
authors.affiliation: Department of Pathology, University of California, San Francisco, California 94121, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Huete-Pérez
authors.forename: J C
authors.initials: JC
authors.lastname: Engel
authors.forename: L S
authors.initials: LS
authors.lastname: Brinen
authors.forename: J C
authors.initials: JC
authors.lastname: Mottram
authors.forename: J H
authors.initials: JH
authors.lastname: McKerrow
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004792:Enzyme Precursors / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D007894:Leishmania mexicana / Q000201:enzymology*; D008164:Luminescent Proteins; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014349:Trypanosoma cruzi / Q000201:enzymology*
chemical_list: D004792:Enzyme Precursors; D008164:Luminescent Proteins; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins; D003546:Cysteine Endopeptidases; C074032:cruzain, Trypanosoma cruzi