Role of protein translocation pathways across the endoplasmic reticulum in Trypanosoma brucei

Goldshmidt, Hanoch; Sheiner, Lilach; Bütikofer, Peter; Roditi, Isabel; Uliel, Shai; Günzel, Mark; Engstler, Markus; Michaeli, Shulamit (2008). Role of protein translocation pathways across the endoplasmic reticulum in Trypanosoma brucei. Journal of biological chemistry, 283(46), pp. 32085-32098. Bethesda, Md.: American Society for Biochemistry and Molecular Biology 10.1074/jbc.M801499200

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The translocation of secretory and membrane proteins across the endoplasmic reticulum (ER) membrane is mediated by co-translational (via the signal recognition particle (SRP)) and post-translational mechanisms. In this study, we investigated the relative contributions of these two pathways in trypanosomes. A homologue of SEC71, which functions in the post-translocation chaperone pathway in yeast, was identified and silenced by RNA interference. This factor is essential for parasite viability. In SEC71-silenced cells, signal peptide (SP)-containing proteins traversed the ER, but several were mislocalized, whereas polytopic membrane protein biogenesis was unaffected. Surprisingly trypanosomes can interchangeably utilize two of the pathways to translocate SP-containing proteins except for glycosylphosphatidylinositol-anchored proteins, whose level was reduced in SEC71-silenced cells but not in cells depleted for SRP68, an SRP-binding protein. Entry of SP-containing proteins to the ER was significantly blocked only in cells co-silenced for the two translocation pathways (SEC71 and SRP68). SEC63, a factor essential for both translocation pathways in yeast, was identified and silenced by RNA interference. SEC63 silencing affected entry to the ER of both SP-containing proteins and polytopic membrane proteins, suggesting that, as in yeast, this factor is essential for both translocation pathways in vivo. This study suggests that, unlike bacteria or other eukaryotes, trypanosomes are generally promiscuous in their choice of mechanism for translocating SP-containing proteins to the ER, although the SRP-independent pathway is favored for glycosylphosphatidylinositol-anchored proteins, which are the most abundant surface proteins in these parasites.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine
08 Faculty of Science > Department of Biology > Institute of Cell Biology

UniBE Contributor:

Bütikofer, Peter and Roditi, Isabel

ISSN:

0021-9258

Publisher:

American Society for Biochemistry and Molecular Biology

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 15:03

Last Modified:

17 Mar 2015 22:16

Publisher DOI:

10.1074/jbc.M801499200

PubMed ID:

18768469

Web of Science ID:

000260760800090

URI:

https://boris.unibe.ch/id/eprint/27318 (FactScience: 106020)

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