| 1. |
- Alkhori, Liza, et al.
(författare)
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The corepressor Atrophin specifies odorant receptor expression in Drosophila
- 2014
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Ingår i: The FASEB Journal. - : Federation of American Societies for Experimental Biology. - 0892-6638 .- 1530-6860. ; 28:3, s. 1355-1364
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Tidskriftsartikel (refereegranskat)abstract
- In both insects and vertebrates, each olfactory sensory neuron (OSN) expresses one odorant receptor (OR) from a large genomic repertoire. How a receptor is specified is a tantalizing question addressing fundamental aspects of cell differentiation. Here, we demonstrate that the corepressor Atrophin (Atro) segregates OR gene expression between OSN classes in Drosophila. We show that the knockdown of Atro result in either loss or gain of a broad set of ORs. Each OR phenotypic group correlated with one of two opposing Notch fates, Notch responding, Nba (N(on)), and nonresponding, Nab (N(off)) OSNs. Our data show that Atro segregates ORs expressed in the Nba OSN classes and helps establish the Nab fate during OSN development. Consistent with a role in recruiting histone deacetylates, immunohistochemistry revealed that Atro regulates global histone 3 acetylation (H3ac) in OSNs and requires Hdac3 to segregate OR gene expression. We further found that Nba OSN classes exhibit variable but higher H3ac levels than the Nab OSNs. Together, these data suggest that Atro determines the level of H3ac, which ensures correct OR gene expression within the Nba OSNs. We propose a mechanism by which a single corepressor can specify a large number of neuron classes.-Alkhori, L., Öst, A., Alenius, M. The corepressor Atrophin specifies odorant receptor expression in Drosophila.
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| 4. |
- Bett, Cyrus, et al.
(författare)
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Structure of the beta 2-alpha 2 loop and interspecies prion transmission
- 2012
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Ingår i: The FASEB Journal. - : Federation of American Society of Experimental Biology (FASEB). - 0892-6638 .- 1530-6860. ; 26:7, s. 2868-2876
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Tidskriftsartikel (refereegranskat)abstract
- Prions are misfolded, aggregated conformers of the prion protein that can be transmitted between species. The precise determinants of interspecies transmission remain unclear, although structural similarity between the infectious prion and host prion protein is required for efficient conversion to the misfolded conformer. The beta 2-alpha 2 loop region of endogenous prion protein, PrPC, has been implicated in barriers to prion transmission. We recently discovered that conversion was efficient when incoming and host prion proteins had similar beta 2-alpha 2 loop structures; however, the roles of primary vs. secondary structural homology could not be distinguished. Here we uncouple the effect of primary and secondary structural homology of the beta 2-alpha 2 loop on prion conversion. We inoculated prions from animals having a disordered or an ordered beta 2-alpha 2 loop into mice having a disordered loop or an ordered loop due to a single residue substitution (D167S). We found that prion conversion was driven by a homologous primary structure and occurred independently of a homologous secondary structure. Similarly, cell-free conversion using PrPC from mice with disordered or ordered loops and prions from 5 species correlated with primary but not secondary structural homology of the loop. Thus, our findings support a model in which efficient interspecies prion conversion is determined by small stretches of the primary sequence rather than the secondary structure of PrP.
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| 5. |
- Bratengeier, Cornelia, et al.
(författare)
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High shear stress amplitude in combination with prolonged stimulus duration determine induction of osteoclast formation by hematopoietic progenitor cells
- 2020
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Ingår i: The FASEB Journal. - : FEDERATION AMER SOC EXP BIOL. - 0892-6638 .- 1530-6860. ; 34:3, s. 3755-3772
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Tidskriftsartikel (refereegranskat)abstract
- To date, it is unclear how fluid dynamics stimulate mechanosensory cells to induce an osteoprotective or osteodestructive response. We investigated how murine hematopoietic progenitor cells respond to 2 minutes of dynamic fluid flow stimulation with a precisely controlled sequence of fluid shear stresses. The response was quantified by measuring extracellular adenosine triphosphate (ATP), immunocytochemistry of Piezo1, and sarcoplasmic/endoplasmic Ca2+ reticulum ATPase 2 (SERCA2), and by the ability of soluble factors produced by mechanically stimulated cells to modulate osteoclast differentiation. We rejected our initial hypothesis that peak wall shear stress rate determines the response of hematopoietic progenitor cells to dynamic fluid shear stress, as it had only a minor correlation with the abovementioned parameters. Low stimulus amplitudes corresponded to activation of Piezo1, SERCA2, low concentrations of extracellular ATP, and inhibition of osteoclastogenesis and resorption area, while high amplitudes generally corresponded to osteodestructive responses. At a given amplitude (3 Pa) and waveform (square), the duration of individual stimuli (duty cycle) showed a strong correlation with the release of ATP and osteoclast number and resorption area. Collectively, our data suggest that hematopoietic progenitor cells respond in a viscoelastic manner to loading, since a combination of high shear stress amplitude and prolonged duty cycle is needed to trigger an osteodestructive response. Plain Language Summary In case of painful joints or missing teeth, the current intervention is to replace them with an implant to keep a high-quality lifestyle. When exercising or chewing, the cells in the bone around the implant experience mechanical loading. This loading generally supports bone formation to strengthen the bone and prevent breaking, but can also stimulate bone loss when the mechanical loading becomes too high around orthopedic and dental implants. We still do not fully understand how cells in the bone can distinguish between mechanical loading that strengthens or weakens the bone. We cultured cells derived from the bone marrow in the laboratory to test whether the bone loss response depends on (i) how fast a mechanical load is applied (rate), (ii) how intense the mechanical load is (amplitude), or (iii) how long each individual loading stimulus is applied (duration). We mimicked mechanical loading as it occurs in the body, by applying very precisely controlled flow of fluid over the cells. We found that a mechanosensitive receptor Piezo1 was activated by a low amplitude stimulus, which usually strengthens the bone. The potential inhibitor of Piezo1, namely SERCA2, was only activated by a low amplitude stimulus. This happened regardless of the rate of application. At a constant high amplitude, a longer duration of the stimulus enhanced the bone-weakening response. Based on these results we deduce that a high loading amplitude tends to be bone weakening, and the longer this high amplitude persists, the worse it is for the bone.
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| 6. |
- Bratengeier, Cornelia, et al.
(författare)
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Mechanical loading intensities affect the release of extracellular vesicles from mouse bone marrow-derived hematopoietic progenitor cells and change their osteoclast-modulating effect
- 2024
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Ingår i: The FASEB Journal. - : WILEY. - 0892-6638 .- 1530-6860. ; 38:1
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Tidskriftsartikel (refereegranskat)abstract
- Low-intensity loading maintains or increases bone mass, whereas lack of mechanical loading and high-intensity loading decreases bone mass, possibly via the release of extracellular vesicles by mechanosensitive bone cells. How different loading intensities alter the biological effect of these vesicles is not fully understood. Dynamic fluid shear stress at low intensity (0.7 +/- 0.3 Pa, 5 Hz) or high intensity (2.9 +/- 0.2 Pa, 1 Hz) was used on mouse hematopoietic progenitor cells for 2 min in the presence or absence of chemical compounds that inhibit release or biogenesis of extracellular vesicles. We used a Receptor activator of nuclear factor kappa-Beta ligand-induced osteoclastogenesis assay to evaluate the biological effect of different fractions of extracellular vesicles obtained through centrifugation of medium from hematopoietic stem cells. Osteoclast formation was reduced by microvesicles (10 000x g) obtained after low-intensity loading and induced by exosomes (100 000x g) obtained after high-intensity loading. These osteoclast-modulating effects could be diminished or eliminated by depletion of extracellular vesicles from the conditioned medium, inhibition of general extracellular vesicle release, inhibition of microvesicle biogenesis (low intensity), inhibition of ESCRT-independent exosome biogenesis (high intensity), as well as by inhibition of dynamin-dependent vesicle uptake in osteoclast progenitor cells. Taken together, the intensity of mechanical loading affects the release of extracellular vesicles and change their osteoclast-modulating effect. The intensity of mechanical loading strongly affects bone remodeling by either formation of bone or resorption of bone. Low-intensity loading on bone cells releases microvesicles that reduce formation of bone-resorbing osteoclasts, while high-intensity loading on bone cells releases exosomes that induce formation of bone-resorbing osteoclasts. The graphical abstract was created with image
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| 7. |
- Eskilsson, Anna, et al.
(författare)
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The generation of immune-induced fever and emotional stress-induced hyperthermia in mice does not involve brown adipose tissue thermogenesis
- 2020
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Ingår i: FASEB Journal. - : WILEY. - 0892-6638 .- 1530-6860. ; 34:4, s. 5863-5876
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Tidskriftsartikel (refereegranskat)abstract
- We examined the role of brown adipose tissue (BAT) for fever and emotional stress-induced hyperthermia. Wild-type and uncoupling protein-1 (UCP-1) knockout mice were injected with lipopolysaccharide intraperitoneally or intravenously, or subjected to cage exchange, and body temperature monitored by telemetry. Both genotypes showed similar febrile responses to immune challenge and both displayed hyperthermia to emotional stress. Neither procedure resulted in the activation of BAT, such as the induction of UCP-1 or peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1 alpha) mRNA, or reduced BAT weight and triglyceride content. In contrast, in mice injected with a beta (3) agonist, UCP-1 and PGC-1 alpha were strongly induced, and BAT weight and triglyceride content reduced. Both lipopolysaccharide and the beta (3) agonist, and emotional stress, induced UCP-3 mRNA in skeletal muscle. A beta (3) antagonist did not attenuate lipopolysaccharide-induced fever, but augmented body temperature decrease and inhibited BAT activation when mice were exposed to cold. An alpha (1)/alpha (2b) antagonist or a 5HT(1A) agonist, which inhibit vasoconstriction, abolished lipopolysaccharide-induced fever, but had no effect on emotional stress-induced hyperthermia. These findings demonstrate that in mice, UCP-1-mediated BAT thermogenesis does not take part in inflammation-induced fever, which is dependent on peripheral vasoconstriction, nor in stress-induced hyperthermia. However, both phenomena may involve UCP-3-mediated muscle thermogenesis.
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| 8. |
- Fernandez-Gonzalo, Rodrigo, et al.
(författare)
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Three months of bed rest induce a residual transcriptomic signature resilient to resistance exercise countermeasures
- 2020
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Ingår i: The FASEB Journal. - : WILEY. - 0892-6638 .- 1530-6860. ; 34:6, s. 7958-7969
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Tidskriftsartikel (refereegranskat)abstract
- This study explored the muscle genome-wide response to long-term unloading (84-day bed rest) in 21 men. We hypothesized that a part of the bed rest-induced gene expression signature would be resilient to a concurrent flywheel resistance exercise (RE) countermeasure. Using DNA microarray technology analyzing 35 345 gene-level probe-sets, we identified 335 annotated probe-sets that were downregulated, and 315 that were upregulated after bed rest (P < .01). Besides a predictable differential expression of genes and pathways related to mitochondria (downregulation; false-discovery rates (FDR) <1E-04), ubiquitin system (upregulation; FDR = 3E-02), and skeletal muscle energy metabolism and structure (downregulation; FDR <= 3E-03), 84-day bed rest also altered circadian rhythm regulation (upregulation; FDR = 3E-02). While most of the bed rest-induced changes were counteracted by RE, 209 transcripts were resilient to the exercise countermeasure. Genes upregulated after bed rest were particularly resistant to training (P < .001 vs downregulated, non-reversed genes). Specifically, "Translation Factors," "Proteasome Degradation," "Cell Cycle," and "Nucleotide Metabolism" pathways were not normalized by RE. This study provides an unbiased high-throughput transcriptomic signature of one of the longest unloading periods in humans to date. Classical disuse-related changes in structural and metabolic genes/pathways were identified, together with a novel upregulation of circadian rhythm transcripts. In the context of previous bed rest campaigns, the latter seemed to be related to the duration of unloading, suggesting the transcriptomic machinery continues to adapt throughout extended disuse periods. Despite that the RE training offset most of the bed rest-induced muscle-phenotypic and transcriptomic alterations, we contend that the human skeletal muscle also displays a residual transcriptomic signature of unloading that is resistant to an established exercise countermeasure.
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| 9. |
- Gunnarsson, Peter, et al.
(författare)
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The acute-phase protein alpha 1-acid glycoprotein (AGP) induces rises in cytosolic Ca2+ in neutrophil granulocytes via sialic acid binding immunoglobulin-like lectins (siglecs)
- 2007
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Ingår i: The FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860. ; 21:14, s. 4059-4069
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Tidskriftsartikel (refereegranskat)abstract
- We studied whether the acute-phase protein alpha1-acid glycoprotein (AGP) induces rises in [Ca2+]i in neutrophils and sought to identify the corresponding AGP receptor (or receptors). We found that AGP elicited a minimal rise in [Ca2+]i in Fura-2-loaded neutrophils, and this response was markedly enhanced by pretreatment with anti-L-selectin antibodies. (The EC50 value of the AGP-induced Ca2+ response was 9 microg/ml.) Activation of phospholipase-C, Src tyrosine kinases, and PI3 kinases proved to be essential for the AGP-mediated increase in [Ca2+]i, whereas the p38 MAPK and SYK signaling pathways were not involved. Furthermore, antibodies against sialic acid binding, immunoglobulin-like lectin 5 (Siglec-5) and oligosaccharide 3'-sialyl-lactose both antagonized the AGP-induced response and caused an immediate increase in [Ca2+]i in anti-L-selectin-treated neutrophils, which indicates a signaling capacity of Siglec-5. We used modified forms of AGP (treated with mild periodate or neuraminidase) to establish the importance of sialic acid residues. The modified forms of AGP caused a much smaller rise in [Ca2+]i than did unaltered AGP. Affinity chromatography confirmed that unchanged AGP, but not neuraminidase-treated AGP, bound to Siglec-5. Our report provides the first evidence for a signaling capacity by AGP through a defined receptor. Pre-engagement of L-selectin significantly enhanced this signaling capacity.
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| 10. |
- Gustavsson, Johanna, 1956-, et al.
(författare)
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Localization of the insulin receptor in caveolae of adipocyte plasma membrane
- 1999
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 13:14, s. 1961-1971
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Tidskriftsartikel (refereegranskat)abstract
- The insulin receptor is a transmembrane protein of the plasma membrane, where it recognizes extracellular insulin and transmits signals into the cellular signaling network. We report that insulin receptors are localized and signal in caveolae microdomains of adipocyte plasma membrane. Immunogold electron microscopy and immunofluorescence microscopy show that insulin receptors are restricted to caveolae and are colocalized with caveolin over the plasma membrane. Insulin receptor was enriched in a caveolae-enriched fraction of plasma membrane. By extraction with β-cyclodextrin or destruction with cholesterol oxidase, cholesterol reduction attenuated insulin receptor signaling to protein phosphorylation or glucose transport. Insulin signaling was regained by spontaneous recovery or by exogenous replenishment of cholesterol. β-Cyclodextrin treatment caused a nearly complete annihilation of caveolae invaginations as examined by electron microscopy. This suggests that the receptor is dependent on the caveolae environment for signaling. Insulin stimulation of cells prior to isolation of caveolae or insulin stimulation of the isolated caveolae fraction increased tyrosine phosphorylation of the insulin receptor in caveolae, demonstrating that insulin receptors in caveolae are functional. Our results indicate that insulin receptors are localized to caveolae in the plasma membrane of adipocytes, are signaling in caveolae, and are dependent on caveolae for signaling.
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