title: RNA interference of signal peptide-binding protein SRP54 elicits deleterious effects and protein sorting defects in trypanosomes.
abstract: Trypanosomes are protozoan parasites that have a major impact on health. This family diverged very early from the eukaryotic lineage and possesses unique RNA processing mechanisms such as trans-splicing and RNA editing. The trypanosome signal recognition particle (SRP) has a unique composition compared with all known SRP complexes, because it contains two RNA molecules, the 7SL RNA and a tRNA-like molecule. RNA interference was utilized to elucidate the essentiality of the SRP pathway and its role in protein translocation in Trypanosoma brucei. The production of double stranded RNA specific for the signal peptide-binding protein SRP54 induced the degradation of the mRNA and a loss of the SRP54 protein. SRP54 depletion elicited inhibition in growth and cytokinesis, suggesting that the SRP pathway is essential. The translocation of four signal peptide-containing proteins was examined. Surprisingly, the proteins were translocated to the endoplasmic reticulum and properly processed. However, the surface EP procyclin, the lysosomal protein p67, and the flagellar pocket protein CRAM were mislocalized and accumulated in megavesicles, most likely because of a secondary effect on protein sorting. The translocation of these proteins to the endoplasmic reticulum under SRP54 depletion suggests that an alternative pathway for protein translocation exists in trypanosomes.
authors.affiliation: Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Xue-hai
authors.initials: XH
authors.lastname: Liang
authors.forename: Shai
authors.initials: S
authors.lastname: Uliel
authors.forename: Ron
authors.initials: R
authors.lastname: Unger
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Ullu
authors.forename: Shulamit
authors.initials: S
authors.lastname: Michaeli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002455:Cell Division; D018105:DNA, Kinetoplast; D019992:Databases as Topic; D004591:Electrophoresis, Polyacrylamide Gel; D020868:Gene Silencing; D008562:Membrane Glycoproteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D020733:RNA, Small Cytoplasmic / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014346:Trypanosoma brucei brucei
chemical_list: C115990:7SL RNA; D018105:DNA, Kinetoplast; D008562:Membrane Glycoproteins; D009841:Oligonucleotides; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D012333:RNA, Messenger; D020733:RNA, Small Cytoplasmic; D018271:Signal Recognition Particle; C053277:procyclic acidic repetitive protein, Trypanosoma