Protease trafficking in two primitive eukaryotes is mediated by a prodomain protein motif.
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.
Huete-Pérez
J A
JA
Department of Pathology, University of California, San Francisco, California 94121, USA.
Engel
J C
JC
Brinen
L S
LS
Mottram
J C
JC
McKerrow
J H
JH
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*
D004792:Enzyme Precursors; D008164:Luminescent Proteins; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins; D003546:Cysteine Endopeptidases; C074032:cruzain, Trypanosoma cruzi