NOGO-A/RTN4A and NOGO-B/RTN4B are simultaneously expressed in epithelial, fibroblast and neuronal cells and maintain ER morphology

Rämö, O. J.; Kumar, Darshan; Gucciardo, Erika; Joensuu, Merja; Saarekas, Maiju; Vihinen, Helena; Belevich, Ilya; Smolander, Olli‐Pekka; Qian, Keping; Auvinen, Petri; Jokitalo, Eija

doi:10.1038/srep35969

Cited by 34 publications

(39 citation statements)

References 53 publications

(81 reference statements)

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“…Apart from the nervous system, Nogo-A was shown to be expressed in the heart tissue, testis and liver, although in the latter the signal was considered unspecific[42]. Furthermore, a recent study by Ramo et al[43] has reported that Nogo-A and Nogo-B are simultaneously expressed in human hepatoma, fibroblast and neuronal cells, concluding than none of the isoforms should be considered a cell type specific isoform and revealed a wider range of functions for Nogo-A outside the nervous system. Another study addressing the expression of Nogo-A in the liver was performed by Hao et al[24], where the authors reported that Nogo-A was highly expressed in four liver cancer cell lines in vitro and the depletion of Nogo-A protein suppressed cancer cell proliferation.…”

Section: Discussionmentioning

confidence: 99%

Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis

Gelman

Šaltenienė

Pranculis

et al. 2019

WJG

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BACKGROUND Clinically significant portal hypertension (CSPH) and severe portal hypertension (SPH) increase the risk for decompensation and life-threatening complications in liver cirrhosis. Pathologic angiogenesis might contribute to the formation of these conditions. Placental growth factor (PlGF) and Nogo-A protein are biomarkers of pathological angiogenesis, but data on their role in liver cirrhosis and portal hypertension is scarce. AIM To determine plasma levels of PlGF and Nogo-A in patients with liver cirrhosis, CSPH, SPH and potential to predict portal hypertension. METHODS A cohort of 122 patients with hepatitis C virus and/or alcohol-induced liver cirrhosis with characterized hepatic venous pressure gradient (HVPG) were included in the study. Demographic data, medical history, Child-Turcotte-Pugh and Model of End Stage liver disease score, clinical chemistry, liver stiffness values were recorded on the day of the procedure prior HVPG measurement. The degree of portal hypertension was determined by the invasive HVPG measurement. Nogo-A and PlGF plasma levels were evaluated using enzyme linked immunosorbent assay. The control group consisted of 30 healthy age- and sex- matched individuals. RESULTS Peripheral PlGF levels were higher and Nogo-A levels were lower in patients with liver cirrhosis (23.20 vs 9.85; P < 0.0001 and 2.19 vs 3.12; P = 0.004 respectively). There was a positive linear correlation between peripheral levels of PlGF and HVPG ( r = 0.338, P = 0.001) and negative linear correlation between the peripheral Nogo-A levels and HVPG ( r = -0.267, P = 0.007). PlGF levels were higher in CSPH and SPH ( P = 0.006; P < 0.0001) whereas Nogo-A levels were lower ( P = 0.01; P < 0.033). Area under the curve for the diagnosis of CSPH for PlGF was 0.68 ( P = 0.003) and for Nogo-A - 0.67 ( P = 0.01); for SPH 0.714 ( P < 0.0001) and 0.65 ( P = 0.014) respectively. PlGF levels were higher and Nogo-A levels were lower in patients with esophageal varices ( P < 0.05). PlGF cut-off value of 25 pg/mL distinguished patients with CSPH at 55.7% sensitivity and 76.7% specificity; whereas Nogo-A cut-off value of 1.12 ng/mL was highly specific (93.1%) for the diagnosis of CSPH. CONCLUSION Plasma PlGF levels were higher while Nogo-A levels were lower in patients with liver cirrhosis and portal hypertension. Biomarkers showed moderate predictive value in determining CSPH and SPH.

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Section: Discussionmentioning

confidence: 99%

Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis

Gelman

Šaltenienė

Pranculis

et al. 2019

WJG

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“…Quantification was performed with Image Studio software (Li-COR). The antibody against RTN4A and RTN4B recognized only a band of about 50 kDa, indicating that the detected protein was RTN4B (49), and the result was confirmed using sheep polyclonal antibody against RTN4B (MRC-PPU Reagents).…”

Section: Discussionmentioning

confidence: 73%

“…To further examine ER distribution, two additional markers for ER were included. CLIMP-63 (cytoskeleton-linking membrane protein 63), also known as CKAP-4 (cytoskeleton-associated protein 4), is predominantly found in ER sheets (48), and reticulon 4B (RTN4B), also known as neurite outgrowth inhibitor B (Nogo-B), localizes to ER tubules and sheet edges (49). CLIMP-63 showed a distribution similar to that of calnexin, although an additional band was detected in fr.…”

Section: Isolated Sfv Rcs Are Stablementioning

confidence: 99%

Purification of Highly Active Alphavirus Replication Complexes Demonstrates Altered Fractionation of Multiple Cellular Membranes

Pietilä

Hemert

Ahola

2018

J Virol

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Positive-strand RNA viruses replicate their genomes in membrane-associated structures; alphaviruses and many other groups induce membrane invaginations called spherules. Here, we established a protocol to purify these membranous replication complexes (RCs) from cells infected with Semliki Forest virus (SFV). We isolated SFV spherules located on the plasma membrane and further purified them using two consecutive density gradients. This revealed that SFV infection strongly modifies cellular membranes. We removed soluble proteins, the Golgi and most of the mitochondria, but plasma membrane, endoplasmic reticulum (ER) and late endosome markers enriched in the membrane fraction that contained viral RNA synthesizing activity, replicase proteins and minus- and plus-strand RNA. Electron microscopy revealed that the purified membranes displayed spherule-like structures with a narrow neck. This membrane enrichment was specific to viral replication as such a distribution of membrane markers was only observed after infection. Besides the plasma membrane, SFV infection remodeled the ER, and the co-fractionation of the RC-carrying plasma membrane and ER suggests that SFV may recruit ER proteins or membrane to the site of replication. The purified RCs were highly active in synthesizing both genomic and subgenomic RNA. Detergent solubilization destroyed the replication activity demonstrating that the membrane association of the complex is essential. Most of the newly made RNA was in double-stranded replicative molecules but the purified complexes also produced single-stranded RNA as well as released newly made RNA. This indicates that the purification established here maintained the functionality of RCs and thus enables further structural and functional studies of active RCs. Similar to all positive-strand RNA viruses, the arthropod-borne alphaviruses induce membranous genome factories but little is known about the arrangement of viral replicase proteins and the presence of host proteins in these replication complexes. To improve our knowledge of alphavirus RNA-synthesizing complexes, we isolated and purified them from infected mammalian cells. Detection of viral RNA and replication assays revealed that these complexes are abundant and highly active when located on the plasma membrane. After multiple purification steps, they remain functional in synthesizing and releasing viral RNA. Besides the plasma membrane, markers for the endoplasmic reticulum and late endosomes enriched with the replication complexes demonstrating that alphavirus infection modified cellular membranes beyond inducing replication spherules on the plasma membrane. We have here developed a gentle purification method to obtain large quantities of highly active replication complexes, and similar methods can be applied to other positive-strand RNA viruses.

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“…They are known to be involved in forming and maintaining ER tubules as their over‐expression alters the balance strongly towards tubules and causes the deformation of the cell shape. On the contrary, depletion of RTN4 proteins induces formation of large peripheral ER sheets . Therefore, it is plausible to suggest that functional depletion of reticulons from the ER in aggregate‐containing cells can affect ER structure and other aspects of cellular physiology where their functions are essential.…”

Section: Discussionmentioning

confidence: 99%

Cytosolic aggregates in presence of non‐translocated proteins perturb endoplasmic reticulum structure and dynamics

Mookherjee

Majumder

Mukherjee

et al. 2019

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Presence of cytosolic protein aggregates and membrane damage are two common attributes of neurodegenerative diseases. These aggregates delay degradation of non‐translocated protein precursors leading to their persistence and accumulation in the cytosol. Here, we find that cells with intracellular protein aggregates (of cytosolic prion protein or huntingtin) destabilize the endoplasmic reticulum (ER) morphology and dynamics when non‐translocated protein load is high. This affects trafficking of proteins out from the ER, relative distribution of the rough and smooth ER and three‐way junctions that are essential for the structural integrity of the membrane network. The changes in ER membranes may be due to high aggregation tendency of the ER structural proteins—reticulons, and altered distribution of those associated with the three‐way ER junctions—Lunapark. Reticulon4 is seen to be enriched in the aggregate fractions in presence of non‐translocated protein precursors. This could be mitigated by improving signal sequence efficiencies of the proteins targeted to the ER. These were observed using PrP variants and the seven‐pass transmembrane protein (CRFR1) with different signal sequences that led to diverse translocation efficiencies. This identifies a previously unappreciated consequence of cytosolic aggregates on non‐translocated precursor proteins—their persistent presence affects ER morphology and dynamics. This may be one of the ways in which cytosolic aggregates can affect endomembranes during neurodegenerative disease.

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NOGO-A/RTN4A and NOGO-B/RTN4B are simultaneously expressed in epithelial, fibroblast and neuronal cells and maintain ER morphology

Cited by 34 publications

References 53 publications

Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis

Plasma Nogo-A and placental growth factor levels are associated with portal hypertension in patients with liver cirrhosis

Purification of Highly Active Alphavirus Replication Complexes Demonstrates Altered Fractionation of Multiple Cellular Membranes

Cytosolic aggregates in presence of non‐translocated proteins perturb endoplasmic reticulum structure and dynamics

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