Down-regulation of the trypanosomatid signal recognition particle affects the biogenesis of polytopic membrane proteins but not of signal peptide-containing proteins.
Protein translocation across the endoplasmic reticulum is mediated by the signal recognition particle (SRP). In this study, the SRP pathway in trypanosomatids was down-regulated by two approaches: RNA interference (RNAi) silencing of genes encoding SRP proteins in Trypanosoma brucei and overexpression of dominant-negative mutants of 7SL RNA in Leptomonas collosoma. The biogenesis of both signal peptide-containing proteins and polytopic membrane proteins was examined using endogenous and green fluorescent protein-fused proteins. RNAi silencing of SRP54 or SRP68 in T. brucei resulted in reduced levels of polytopic membrane proteins, but no effect on the level of signal peptide-containing proteins was observed. When SRP deficiency was achieved in L. collosoma by overexpression of dominant-negative mutated 7SL RNA, a major effect was observed on polytopic membrane proteins but not on signal peptide-containing proteins. This study included two trypanosomatid species, tested various protein substrates, and induced depletion of the SRP pathway by affecting either the levels of SRP binding proteins or that of SRP RNA. Our results demonstrate that, as in bacteria but in contrast to mammalian cells, the trypanosome SRP is mostly essential for the biogenesis of membrane proteins.
Lustig
Yaniv
Y
The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel.
Vagima
Yaron
Y
Goldshmidt
Hanoch
H
Erlanger
Avigail
A
Ozeri
Vered
V
Vince
James
J
McConville
Malcolm J
MJ
Dwyer
Dennis M
DM
Landfear
Scott M
SM
Michaeli
Shulamit
S
D000818:Animals; D002460:Cell Line; D015536:Down-Regulation / Q000235:genetics*; D005799:Genes, Dominant; D008565:Membrane Proteins / Q000096:biosynthesis*; D009154:Mutation / Q000235:genetics; D021382:Protein Sorting Signals; D021381:Protein Transport; D015800:Protozoan Proteins / Q000378:metabolism*; D034622:RNA Interference; D020733:RNA, Small Cytoplasmic / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D018271:Signal Recognition Particle / Q000235:genetics* / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000378:metabolism; D014351:Trypanosomatina / Q000166:cytology / Q000378:metabolism*
C115990:7SL RNA; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D020733:RNA, Small Cytoplasmic; D011993:Recombinant Fusion Proteins; D018271:Signal Recognition Particle
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