Trypanosoma cruziCalreticulin Is a Lectin That Binds Monoglucosylated Oligosaccharides but Not Protein Moieties of Glycoproteins

Trypanosoma cruzi is a protozoan parasite that belongs to an early branch in evolution. Although it lacks several features of the pathway of protein N-glycosylation and oligosaccharide processing present in the endoplasmic reticulum of higher eukaryotes, it displays UDP-Glc:glycoprotein glucosyltransferase and glucosidase II activities. It is herewith reported that this protozoan also expresses a calreticulin-like molecule, the third component of the quality control of glycoprotein folding. No calnexin-encoding gene was detected. Recombinant T. cruzi calreticulin specifically recognized free monoglucosylated high-mannose-type oligosaccharides. Addition of anti-calreticulin serum to extracts obtained from cells pulse–chased with [35S]Met plus [35S]Cys immunoprecipitated two proteins that were identified as calreticulin and the lysosomal proteinase cruzipain (a major soluble glycoprotein). The latter but not the former protein disappeared from immunoprecipitates upon chasing cells. Contrary to what happens in mammalian cells, addition of the glucosidase II inhibitor 1-deoxynojirimycin promoted calreticulin–cruzipain interaction. This result is consistent with the known pathway of proteinN-glycosylation and oligosaccharide processing occurring in T. cruzi. A treatment of the calreticulin-cruzipain complexes with endo-β-N-acetylglucosaminidase H either before or after addition of anti-calreticulin serum completely disrupted calreticulin–cruzipain interaction. In addition, mature monoglucosylated but not unglucosylated cruzipain isolated from lysosomes was found to interact with recombinant calreticulin. It was concluded that the quality control of glycoprotein folding appeared early in evolution, and that T. cruzi calreticulin binds monoglucosylated oligosaccharides but not the protein moiety of cruzipain. Furthermore, evidence is presented indicating that glucosyltransferase glucosylated cruzipain at its last folding stages.

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Faculty Opinions recommendation of Characterization of rapidly degraded polypeptides in mammalian cells reveals a novel layer of nascent protein quality control.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1029300.343663 ◽

2005 ◽

Author(s):

Peter Van Endert

Keyword(s):

Quality Control ◽

Mammalian Cells ◽

Protein Quality ◽

Protein Quality Control

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The structural mechanics of cell division in Trypanosoma brucei

Biochemical Society Transactions ◽

10.1042/bst0360421 ◽

2008 ◽

Vol 36 (3) ◽

pp. 421-424 ◽

Cited By ~ 30

Author(s):

Sue Vaughan ◽

Keith Gull

Keyword(s):

Cell Division ◽

Trypanosoma Brucei ◽

Mammalian Cells ◽

Reverse Genetics ◽

Protozoan Parasite ◽

Cell Types ◽

Single Copy ◽

Structural Mechanics ◽

Sub Saharan Africa ◽

Mammalian Host

Undoubtedly, there are fundamental processes driving the structural mechanics of cell division in eukaryotic organisms that have been conserved throughout evolution and are being revealed by studies on organisms such as yeast and mammalian cells. Precision of structural mechanics of cytokinesis is however probably no better illustrated than in the protozoa. A dramatic example of this is the protozoan parasite Trypanosoma brucei, a unicellular flagellated parasite that causes a devastating disease (African sleeping sickness) across Sub-Saharan Africa in both man and animals. As trypanosomes migrate between and within a mammalian host and the tsetse vector, there are periods of cell proliferation and cell differentiation involving at least five morphologically distinct cell types. Much of the existing cytoskeleton remains intact during these processes, necessitating a very precise temporal and spatial duplication and segregation of the many single-copy organelles. This structural precision is aiding progress in understanding these processes as we apply the excellent reverse genetics and post-genomic technologies available in this system. Here we outline our current understanding of some of the structural aspects of cell division in this fascinating organism.

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Miga-mediated endoplasmic reticulum–mitochondria contact sites regulate neuronal homeostasis

eLife ◽

10.7554/elife.56584 ◽

2020 ◽

Vol 9 ◽

Author(s):

Lingna Xu ◽

Xi Wang ◽

Jia Zhou ◽

Yunyi Qiu ◽

Weina Shang ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Mammalian Cells ◽

Mitochondrial Dynamics ◽

Molecular Organization ◽

Lipid Transport ◽

Cellular Processes ◽

Contact Sites ◽

Neuronal Homeostasis ◽

Higher Eukaryotes ◽

Lateral Sclerosis

Endoplasmic reticulum (ER)–mitochondria contact sites (ERMCSs) are crucial for multiple cellular processes such as calcium signaling, lipid transport, and mitochondrial dynamics. However, the molecular organization, functions, regulation of ERMCS, and the physiological roles of altered ERMCSs are not fully understood in higher eukaryotes. We found that Miga, a mitochondrion located protein, markedly increases ERMCSs and causes severe neurodegeneration upon overexpression in fly eyes. Miga interacts with an ER protein Vap33 through its FFAT-like motif and an amyotrophic lateral sclerosis (ALS) disease related Vap33 mutation considerably reduces its interaction with Miga. Multiple serine residues inside and near the Miga FFAT motif were phosphorylated, which is required for its interaction with Vap33 and Miga-mediated ERMCS formation. The interaction between Vap33 and Miga promoted further phosphorylation of upstream serine/threonine clusters, which fine-tuned Miga activity. Protein kinases CKI and CaMKII contribute to Miga hyperphosphorylation. MIGA2, encoded by the miga mammalian ortholog, has conserved functions in mammalian cells. We propose a model that shows Miga interacts with Vap33 to mediate ERMCSs and excessive ERMCSs lead to neurodegeneration.

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UDP-GlC:glycoprotein glucosyltransferase-glucosidase II, the ying-yang of the ER quality control

Seminars in Cell and Developmental Biology ◽

10.1016/j.semcdb.2009.12.014 ◽

2010 ◽

Vol 21 (5) ◽

pp. 491-499 ◽

Cited By ~ 107

Author(s):

Cecilia D’Alessio ◽

Julio J. Caramelo ◽

Armando J. Parodi

Keyword(s):

Quality Control ◽

Er Quality Control ◽

Glucosidase Ii

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Role for ribosome-associated quality control in sampling proteins for MHC class I-mediated antigen presentation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1914401117 ◽

2020 ◽

Vol 117 (8) ◽

pp. 4099-4108 ◽

Cited By ~ 8

Author(s):

Débora Broch Trentini ◽

Matteo Pecoraro ◽

Shivani Tiwary ◽

Jürgen Cox ◽

Matthias Mann ◽

...

Keyword(s):

Quality Control ◽

Antigen Presentation ◽

Mammalian Cells ◽

Adaptive Immune System ◽

Messenger Rnas ◽

Mhc I ◽

Adaptive Immune ◽

Ribosome Stalling ◽

Endogenous Substrates ◽

Insight Into

Mammalian cells present a fingerprint of their proteome to the adaptive immune system through the display of endogenous peptides on MHC-I complexes. MHC-I−bound peptides originate from protein degradation by the proteasome, suggesting that stably folded, long-lived proteins could evade monitoring. Here, we investigate the role in antigen presentation of the ribosome-associated quality control (RQC) pathway for the degradation of nascent polypeptides that are encoded by defective messenger RNAs and undergo stalling at the ribosome during translation. We find that degradation of model proteins by RQC results in efficient MHC-I presentation, independent of their intrinsic folding properties. Quantitative profiling of MHC-I peptides in wild-type and RQC-deficient cells by mass spectrometry showed that RQC substantially contributes to the composition of the immunopeptidome. Our results also identify endogenous substrates of the RQC pathway in human cells and provide insight into common principles causing ribosome stalling under physiological conditions.

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Role of ABC Transporters in Aureobasidin A Resistance

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.4.755 ◽

1998 ◽

Vol 42 (4) ◽

pp. 755-761 ◽

Cited By ~ 23

Author(s):

Atsuko Ogawa ◽

Takashi Hashida-Okado ◽

Masahiro Endo ◽

Hirofumi Yoshioka ◽

Takashi Tsuruo ◽

...

Keyword(s):

Abc Transporters ◽

Mammalian Cells ◽

Northern Hybridization ◽

Significant Similarity ◽

Genetic Studies ◽

Multiple Copies ◽

Recessive Mutant ◽

Encoding Gene ◽

Aureobasidin A

ABSTRACT Aureobasidin A (AbA) has strong antifungal effects arising from an unusual mechanism. We show that AbA interacts with ATP-binding cassette (ABC) transporters in yeast and mammalian cells. We isolated a gene ofSaccharomyces cerevisiae that conferred resistance to AbA when the gene was present in multiple copies. The gene was identical toYOR1/YRS1, which confers resistance to oligomycin, reveromycin, and organic anions, none of which have structures similar to that of AbA. We also isolated an aur3 Rrecessive mutant of S. cerevisiae with increased resistance to AbA. Northern hybridization showed that theaur3 R mutant expressed not onlyYOR1 but also the ABC transporter-encoding genePDR5 at high levels. Genetic studies showed that theaur3 R mutant had a mutation in thePDR1 gene, which encodes a transcriptional regulator ofPDR5 and YOR1. Analysis of a yor1disruptant of the aur3/pdr1 mutant showed that both the functional YOR1 gene and the mutation in PDR1were necessary for AbA resistance. These results suggest thatYOR1 is more important than PDR5 for AbA resistance. We found in Candida albicans a novel gene whose sequence was similar to the sequence of YOR1 in S. cerevisiae. The amino acid sequence of the C. albicans YOR1 homolog showed no significant similarity to the sequences ofCDR1 and CDR2, which are ABC transporters ofC. albicans. Furthermore, AbA inhibited the efflux of the anticancer agent vincristine through P glycoproteins in cancer cells with multidrug resistance.

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On the characteristics of ASCAT wind direction ambiguities

Atmospheric Measurement Techniques ◽

10.5194/amt-6-1053-2013 ◽

2013 ◽

Vol 6 (4) ◽

pp. 1053-1060 ◽

Cited By ~ 7

Author(s):

W. Lin ◽

M. Portabella ◽

A. Stoffelen ◽

A. Verhoef

Keyword(s):

Quality Control ◽

Maximum Likelihood ◽

Wind Speed ◽

Wind Direction ◽

Maximum Likelihood Estimators ◽

High Rank ◽

Low Rank ◽

The Third ◽

Low Probability

Abstract. The inversion of the Advanced Scatterometer (ASCAT) backscatter measurement triplets generally leads to two wind ambiguities with similar wind speed values and opposite wind directions. However, for up-, down- and crosswind (with respect to the mid-beam azimuth direction) cases, the inversion often leads to three or four wind solutions. In most of such cases, the inversion residuals or maximum likelihood estimators (MLEs) of the third and fourth solutions (i.e. high-rank solutions) are substantially higher than those of the first two (low-rank) ambiguities. This indicates a low probability for the high-rank solutions and thus essentially dual ambiguity. This paper investigates the characteristics of ASCAT high-rank wind solutions under different conditions with the objective of developing a method for rejecting the spurious high-rank solutions. The implementation of this rejection procedure improves the effectiveness of the ASCAT wind quality control (QC) and ambiguity removal procedures.

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