18 research outputs found
Hidden spin-texture at topological domain walls drive exchange bias in a Weyl semimetal
Exchange bias is a phenomenon critical to solid-state technologies that
require spin valves or non-volatile magnetic memory. The phenomenon is usually
studied in the context of magnetic interfaces between antiferromagnets and
ferromagnets, where the exchange field of the former acts as a means to pin the
polarization of the latter. In the present study, we report an unusual instance
of this phenomenon in the topological Weyl semimetal Co3Sn2S2, where the
magnetic interfaces associated with domain walls suffice to bias the entire
ferromagnetic bulk. Remarkably, our data suggests the presence of a hidden
order parameter whose behavior can be independently tuned by applied magnetic
fields. For micron-size samples, the domain walls are absent, and the exchange
bias vanishes, suggesting the boundaries are a source of pinned uncompensated
moment arising from the hidden order. The novelty of this mechanism suggests
exciting opportunities lie ahead for the application of topological materials
in spintronic technologies.Comment: Main text: 11 pages, 4 figures. Supplementary information: 7 pages, 6
figures. Supplementary videos:
Polarized Secretion of Drosophila EGFR Ligand from Photoreceptor Neurons Is Controlled by ER Localization of the Ligand-Processing Machinery
Trafficking within the endoplasmic reticulum and specialized localization of the intra-membrane protease Rhomboid regulate EGF ligand-dependent signaling in Drosophila photoreceptor axon termini
Exosome-Related Multi-Pass Transmembrane Protein TSAP6 Is a Target of Rhomboid Protease RHBDD1-Induced Proteolysis
We have previously reported that rhomboid domain containing 1 (RHBDD1), a mammalian rhomboid protease highly expressed in the testis, can cleave the Bcl-2 protein Bik. In this study, we identified a multi-pass transmembrane protein, tumor suppressor activated pathway-6 (TSAP6) as a potential substrate of RHBDD1. RHBDD1 was found to induce the proteolysis of TSAP6 in a dose- and activity-dependent manner. The cleavage of TSAP6 was not restricted to its glycosylated form and occurred in three different regions. In addition, mass spectrometry and mutagenesis analyses both indicated that the major cleavage site laid in the C-terminal of the third transmembrane domain of TSAP6. A somatic cell knock-in approach was used to genetically inactivate the endogenous RHBDD1 in HCT116 and RKO colon cancer cells. Exosome secretion was significantly elevated when RHBDD1 was inactivated in the two cells lines. The increased exosome secretion was verfied through the detection of certain exosomal components, including Tsg101, Tf-R, FasL and Trail. In addition, the elevation of exosome secretion by RHBDD1 inactivation was reduced when TSAP6 was knocked down, indicating that the role of RHBDD1 in regulating exosomal trafficking is very likely to be TSAP6-dependent. We found that the increase in FasL and Trail increased exosome-induced apoptosis in Jurkat cells. Taken together, our findings suggest that RHBDD1 is involved in the regulation of a nonclassical exosomal secretion pathway through the restriction of TSAP6
Rhomboid cleaves Star to regulate the levels of secreted Spitz
Intracellular trafficking of the precursor of Spitz (Spi), the major Drosophila EGF receptor (EGFR) ligand, is facilitated by the chaperone Star, a type II transmembrane protein. This study identifies a novel mechanism for modulating the activity of Star, thereby influencing the levels of active Spi ligand produced. We demonstrate that Star can efficiently traffic Spi even when present at sub-stoichiometric levels, and that in Drosophila S(2)R(+) cells, Spi is trafficked from the endoplasmic reticulum to the late endosome compartment, also enriched for Rhomboid, an intramembrane protease. Rhomboid, which cleaves the Spi precursor, is now shown to also cleave Star within its transmembrane domain both in cell culture and in flies, expanding the repertoire of known Rhomboid substrates to include both type I and type II transmembrane proteins. Cleavage of Star restricts the amount of Spi that is trafficked, and may explain the exceptional dosage sensitivity of the Star locus in flies
Mitochondrial membrane remodelling regulated by a conserved rhomboid protease.
Rhomboid proteins are intramembrane serine proteases that activate epidermal growth factor receptor (EGFR) signalling in Drosophila. Rhomboids are conserved throughout evolution, and even in eukaryotes their existence in species with no EGFRs implies that they must have additional roles. Here we report that Saccharomyces cerevisiae has two rhomboids, which we have named Rbd1p and Rbd2p. RBD1 deletion results in a respiratory defect; consistent with this, Rbd1p is localized in the inner mitochondrial membrane and mutant cells have disrupted mitochondria. We have identified two substrates of Rbd1p: cytochrome c peroxidase (Ccp1p); and a dynamin-like GTPase (Mgm1p), which is involved in mitochondrial membrane fusion. Rbd1p mutants are indistinguishable from Mgm1p mutants, indicating that Mgm1p is a key substrate of Rbd1p and explaining the rbd1Delta mitochondrial phenotype. Our data indicate that mitochondrial membrane remodelling is regulated by cleavage of Mgm1p and show that intramembrane proteolysis by rhomboids controls cellular processes other than signalling. In addition, mitochondrial rhomboids are conserved throughout eukaryotes and the mammalian homologue, PARL, rescues the yeast mutant, suggesting that these proteins represent a functionally conserved subclass of rhomboid proteases
Sec61Ξ², a subunit of the Sec61 protein translocation channel at the Endoplasmic Reticulum, is involved in the transport of Gurken to the plasma membrane.
<p>Abstract</p> <p>Background</p> <p>Protein translocation across the membrane of the Endoplasmic Reticulum (ER) is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER by the Sec61 translocon, a proteinaceous channel composed of three subunits, Ξ±, Ξ² and Ξ³. While it is known that Sec61Ξ± forms the actual channel, the function of the other two subunits remains to be characterized.</p> <p>Results</p> <p>In the present study we have investigated the function of Sec61Ξ² in <it>Drosophila melanogaster</it>. We describe its role in the plasma membrane traffic of Gurken, the ligand for the Epidermal Growth Factor (EGF) receptor in the oocyte. Germline clones of the mutant allele of Sec61Ξ² show normal translocation of Gurken into the ER and transport to the Golgi complex, but further traffic to the plasma membrane is impeded. The defect in plasma membrane traffic due to absence of Sec61Ξ² is specific for Gurken and is not due to a general trafficking defect.</p> <p>Conclusion</p> <p>Based on our study we conclude that Sec61Ξ², which is part of the ER protein translocation channel affects a post-ER step during Gurken trafficking to the plasma membrane. We propose an additional role of Sec61Ξ² beyond protein translocation into the ER.</p