Sven Lang
Saarland University
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Publication
Featured researches published by Sven Lang.
The EMBO Journal | 2012
Nico Schäuble; Sven Lang; Martin Jung; Sabine Cappel; Stefan Schorr; Ozlem Ulucan; Johannes Linxweiler; Johanna Dudek; Robert Blum; Volkhard Helms; Adrienne W. Paton; James C. Paton; Adolfo Cavalié; Richard Zimmermann
In mammalian cells, signal peptide‐dependent protein transport into the endoplasmic reticulum (ER) is mediated by a dynamic protein‐conducting channel, the Sec61 complex. Previous work has characterized the Sec61 channel as a potential ER Ca2+ leak channel and identified calmodulin as limiting Ca2+ leakage in a Ca2+‐dependent manner by binding to an IQ motif in the cytosolic aminoterminus of Sec61α. Here, we manipulated the concentration of the ER lumenal chaperone BiP in cells in different ways and used live cell Ca2+ imaging to monitor the effects of reduced levels of BiP on ER Ca2+ leakage. Regardless of how the BiP concentration was lowered, the absence of available BiP led to increased Ca2+ leakage via the Sec61 complex. When we replaced wild‐type Sec61α with mutant Sec61αY344H in the same model cell, however, Ca2+ leakage from the ER increased and was no longer affected by manipulation of the BiP concentration. Thus, BiP limits ER Ca2+ leakage through the Sec61 complex by binding to the ER lumenal loop 7 of Sec61α in the vicinity of tyrosine 344.
Nature Communications | 2014
Stefan Pfeffer; Johanna Dudek; Marko Gogala; Stefan Schorr; Johannes Linxweiler; Sven Lang; Thomas Becker; Roland Beckmann; Richard Zimmermann; Friedrich Förster
In mammalian cells, proteins are typically translocated across the endoplasmic reticulum (ER) membrane in a co-translational mode by the ER protein translocon, comprising the protein-conducting channel Sec61 and additional complexes involved in nascent chain processing and translocation. As an integral component of the translocon, the oligosaccharyl-transferase complex (OST) catalyses co-translational N-glycosylation, one of the most common protein modifications in eukaryotic cells. Here we use cryoelectron tomography, cryoelectron microscopy single-particle analysis and small interfering RNA-mediated gene silencing to determine the overall structure, oligomeric state and position of OST in the native ER protein translocon of mammalian cells in unprecedented detail. The observed positioning of OST in close proximity to Sec61 provides a basis for understanding how protein translocation into the ER and glycosylation of nascent proteins are structurally coupled. The overall spatial organization of the native translocon, as determined here, serves as a reliable framework for further hypothesis-driven studies.
Journal of Cell Science | 2012
Sven Lang; Julia Benedix; Sorin V. Fedeles; Stefan Schorr; Claudia Schirra; Nico Schäuble; Carolin Jalal; Markus Greiner; Sarah Haßdenteufel; Jörg Tatzelt; Birgit Kreutzer; Ludwig Edelmann; Elmar Krause; Jens Rettig; Stefan Somlo; Richard Zimmermann; Johanna Dudek
Co-translational transport of polypeptides into the endoplasmic reticulum (ER) involves the Sec61 channel and additional components such as the ER lumenal Hsp70 BiP and its membrane-resident co-chaperone Sec63p in yeast. We investigated whether silencing the SEC61A1 gene in human cells affects co- and post-translational transport of presecretory proteins into the ER and post-translational membrane integration of tail-anchored proteins. Although silencing the SEC61A1 gene in HeLa cells inhibited co- and post-translational transport of signal-peptide-containing precursor proteins into the ER of semi-permeabilized cells, silencing the SEC61A1 gene did not affect transport of various types of tail-anchored protein. Furthermore, we demonstrated, with a similar knockdown approach, a precursor-specific involvement of mammalian Sec63 in the initial phase of co-translational protein transport into the ER. By contrast, silencing the SEC62 gene inhibited only post-translational transport of a signal-peptide-containing precursor protein.
The EMBO Journal | 2011
Frank Erdmann; Nico Schäuble; Sven Lang; Martin Jung; Alf Honigmann; Mazen Ahmad; Johanna Dudek; Julia Benedix; Anke Harsman; Annika Kopp; Volkhard Helms; Adolfo Cavalié; Richard F. Wagner; Richard Zimmermann
In eukaryotes, protein transport into the endoplasmic reticulum (ER) is facilitated by a protein‐conducting channel, the Sec61 complex. The presence of large, water‐filled pores with uncontrolled ion permeability, as formed by Sec61 complexes in the ER membrane, would seriously interfere with the regulated release of calcium from the ER lumen into the cytosol, an essential mechanism for intracellular signalling. We identified a calmodulin (CaM)‐binding motif in the cytosolic N‐terminus of mammalian Sec61α that bound CaM but not Ca2+‐free apocalmodulin with nanomolar affinity and sequence specificity. In single‐channel measurements, CaM potently mediated Sec61‐channel closure in Ca2+‐dependent manner. At the cellular level, two different CaM antagonists stimulated calcium release from the ER through Sec61 channels. However, protein transport into microsomes was not modulated by Ca2+‐CaM. Molecular modelling of the ribosome/Sec61/CaM complexes supports the view that simultaneous ribosome and CaM binding to the Sec61 complex may be possible. Overall, CaM is involved in limiting Ca2+ leakage from the ER.
Journal of Cell Science | 2012
Nicholas Johnson; Fabio Vilardi; Sven Lang; Pawel Leznicki; Richard Zimmermann; Stephen High
Summary Whilst the co-translational translocation of nascent proteins across the mammalian endoplasmic reticulum (ER) is well defined, the capacity of this organelle for post-translational translocation is poorly delineated. Here we identify two human secretory protein precursors, apelin and statherin, as bona fide substrates for post-translational translocation across the ER membrane. Further studies, in combination with Hyalophora cecropia preprocecropin A (ppcecA), show that all three proteins bind to TRC40 and can utilise this component for their delivery to the ER membrane in a well-established in vitro system. However, ppcecA is not an obligate TRC40 substrate, and it can also be delivered to the ER by an alternative TRC40-independent pathway. Upon arrival at the ER membrane, these short secretory proteins appear to be ubiquitously transported across the ER membrane through the Sec61 translocon, apparently irrespective of their delivery route. We speculate that the post-translational translocation of secretory proteins in higher eukaryotes is more prevalent than previously acknowledged.
Channels | 2011
Sven Lang; Frank Erdmann; Martin Jung; Richard F. Wagner; Adolfo Cavalié; Richard Zimmermann
In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis and in calcium signalling. The heterotrimeric Sec61 complex in the ER membrane provides an aqueous pathway for transporting newly synthesized polypeptides into the ER lumen and may also allow calcium leakage from the ER into the cytosol. In this study, planar lipid bilayer experiments demonstrated that the Sec61 complex is permeable to calcium ions. We also investigated whether silencing the SEC61A1 gene affected calcium leakage from the ER. Silencing the SEC61A1 gene using two different siRNAs in HeLa cells for 96 hours had little effect on cell growth and viability. However, calcium leakage from the ER was greatly decreased in the SEC61A1-silenced cells. Thus, the Sec61 complexes that are present in the ER membrane of nucleated cells form calcium leak channels that may play a crucial role in calcium homeostasis.
The EMBO Journal | 2013
Natalie V. Pfeiffer; Daniela Dirndorfer; Sven Lang; Ulrike K. Resenberger; Lisa Michelle Restelli; Charles Hemion; Margit Miesbauer; Stephan Frank; Albert Neutzner; Richard Zimmermann; Konstanze F. Winklhofer; Jörg Tatzelt
Protein targeting to specified cellular compartments is essential to maintain cell function and homeostasis. In eukaryotic cells, two major pathways rely on N‐terminal signal peptides to target proteins to either the endoplasmic reticulum (ER) or mitochondria. In this study, we show that the ER signal peptides of the prion protein‐like protein shadoo, the neuropeptide hormone somatostatin and the amyloid precursor protein have the property to mediate alternative targeting to mitochondria. Remarkably, the targeting direction of these signal peptides is determined by structural elements within the nascent chain. Each of the identified signal peptides promotes efficient ER import of nascent chains containing α‐helical domains, but targets unstructured polypeptides to mitochondria. Moreover, we observed that mitochondrial targeting by the ER signal peptides correlates inversely with ER import efficiency. When ER import is compromised, targeting to mitochondria is enhanced, whereas improving ER import efficiency decreases mitochondrial targeting. In conclusion, our study reveals a novel mechanism of dual targeting to either the ER or mitochondria that is mediated by structural features within the nascent chain.
The Prostate | 2011
Markus Greiner; Birgit Kreutzer; Sven Lang; Volker Jung; Adolfo Cavalié; Gerhard Unteregger; Richard Zimmermann; Bernd Wullich
We previously reported that over‐expression of the SEC62 gene is a widespread phenomenon in prostate cancer. Since the use of endoplasmic reticulum (ER) stress‐inducing substances such as thapsigargin in prostate cancer therapy is widely discussed in the literature, we investigated the influence of Sec62 protein content on the cellular response to these drugs.
FEBS Letters | 2009
Frank Erdmann; Martin Jung; Susanne Eyrisch; Sven Lang; Volkhard Helms; Richard Wagner; Richard Zimmermann
Previous electrophysiological experiments characterized the Sec61 complex, which provides the aqueous path for entry of newly‐synthesized polypeptides into the mammalian endoplasmic reticulum, as a highly dynamic channel that, once activated by precursor proteins, fluctuates between main open states with mean conductances of 220 and 550 pS. Millimolar concentrations of lanthanum ions simultaneously restricted the dynamics of the Sec61 channel and inhibited translocation of polypeptides. Molecular modeling indicates that lanthanum binding sites cluster at the putative lateral gate of the Sec61 complex and suggests that structural flexibility of the lateral gate is essential for channel and protein transport activities of the Sec61 complex.
FEBS Letters | 2017
Sarah Haßdenteufel; Mark Sicking; Stefan Schorr; Naama Aviram; Claudia Fecher-Trost; Maya Schuldiner; Martin Jung; Richard Zimmermann; Sven Lang
Recently, understanding of protein targeting to the endoplasmic reticulum (ER) was expanded by the discovery of multiple pathways that function in parallel to the signal recognition particle (SRP). Guided entry of tail‐anchored proteins and SRP independent (SND) are two such targeting pathways described in yeast. So far, no human SND component is functionally characterized. Here, we report hSnd2 as the first constituent of the human SND pathway able to support substrate‐specific protein targeting to the ER. Similar to its yeast counterpart, hSnd2 is assumed to function as a membrane‐bound receptor preferentially targeting precursors carrying C‐terminal transmembrane domains. Our genetic and physical interaction studies show that hSnd2 is part of a complex network of targeting and translocation that is dynamically regulated.