Fusiogenic endogenous-retroviral syncytin-1 exerts anti-apoptotic functions in staurosporine-challenged CHO cells

Knerr, Ina; Schnare, Markus; Hermann, Kathrin; Kausler, S.; Lehner, Manfred; Vogler, Tina; Rascher, Wolfgang; Meißner, Udo

doi:10.1007/s10495-006-0329-9

Cited by 26 publications

(23 citation statements)

References 24 publications

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“…Basically, fusiogenic syncytin-1 is involved in human trophoblastic cell differentiation and, consequently, fusion [7] . The underlying processes in syncytiotrophoblast formation may comprise elements of the molecular machinery of early apoptosis, including the phosphatidylserine flip [29,31] . In a recent study, we were able to demonstrate cell-cell fusion along with antiapoptotic properties in a cell model of syncytin-1-transfected CHO cells [29] .…”

Section: Discussionmentioning

confidence: 99%

“…The underlying processes in syncytiotrophoblast formation may comprise elements of the molecular machinery of early apoptosis, including the phosphatidylserine flip [29,31] . In a recent study, we were able to demonstrate cell-cell fusion along with antiapoptotic properties in a cell model of syncytin-1-transfected CHO cells [29] . Connexin 43, which exerts its main effects on gap junctional communication, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…After approval by the local ethics committee, term placentas of patients who underwent cesarean section were collected for the isolation of primary trophoblasts according to a standard method using trypsin-DNAse I Percoll gradient centrifugation [27,28] [14,29] . Briefly, apoptotic cells were detected using fluorescein isothiocyanateconjugated annexin V and propidium iodide double staining.…”

Section: Cell Culturementioning

confidence: 99%

“…This was followed by an Alexa 488-conjugated goat antimouse IgG (dilution 1: 250). Cell nuclei were labeled with DAPI as reported earlier [29] . Antibodies were obtained from Chemicon (Temecula, Calif., USA) or MoBiTec (Vienna, Austria).…”

Section: Immunocytochemistrymentioning

confidence: 99%

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Syncytin-1 and Glial Cells Missing a: Hypoxia-Induced Deregulated Gene Expression along with Disordered Cell Fusion in Primary Term Human Trophoblasts

Wich¹,

Kausler²,

Dötsch³

et al. 2009

Gynecol Obstet Invest

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Background/Aims: Pre-eclampsia, a major cause of perinatal morbidity, is characterized by alterations in placental oxygen availability and trophoblast differentiation. We investigated how different levels of hypoxia alter the expression of syncytin-1, glial cells missing a (GCMa) and syncytin-1 receptor ASCT2 and affect syncytialization in primary term human trophoblasts. Methods: Cells were incubated at 1, 3, 6 and 21% O₂ for 24, 48 and 72 h with or without cyclic adenosine monophosphate (cAMP). Gene expression was analyzed by real-time PCR. Syncytialization was assessed using β-human chorionic gonadotropin measurement and desmoplakin immunostaining. Results: Following incubation with cAMP at 21% O₂, peak gene expression of syncytin-1 and GCMa was found after 24 h along with syncytium formation at 72 h. Conversely, incubation at 1% O₂ led to a time-dependent reduction of GCMa and syncytin-1 at the transcriptional level. Cell fusion occurred at 21 and 6% O₂ and was suppressed at 1% O₂. ASCT2 mRNA levels were preserved at normoxia and downregulated at 1% O₂ after 48 h. Conclusion: Our data support the premise that the expression of GCMa and syncytin-1 precedes syncytialization of trophoblasts, e.g. at 6% O₂, which is assumed to resemble physiological conditions. Severe hypoxia is associated with reduced GCMa and syncytin-1 transcripts and altered fusion of primary trophoblasts.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Cell Culturementioning

confidence: 99%

Section: Immunocytochemistrymentioning

confidence: 99%

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Syncytin-1 and Glial Cells Missing a: Hypoxia-Induced Deregulated Gene Expression along with Disordered Cell Fusion in Primary Term Human Trophoblasts

Wich¹,

Kausler²,

Dötsch³

et al. 2009

Gynecol Obstet Invest

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“…As a positive control for annexin V binding and PI staining by fluorescence microscopy, cells were treated with 0.05% Triton X-100 for 30 min on ice to allow access to the interior of the cells. Incubation with staurosporine (Sigma; 1 M) for 6 h, which induces apoptosis (32), as well as 0.05% Triton X-100 (30 min on ice), was used as a positive control for flow cytometry analysis (fluorescence-activated cell sorting [FACS]). The addition of Triton X-100 enhanced PI staining.…”

Section: Methodsmentioning

confidence: 99%

Thiol/Disulfide Exchange Is Required for Membrane Fusion Directed by the Newcastle Disease Virus Fusion Protein

Jain

McGinnes

Morrison

2007

J Virol

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Newcastle disease virus (NDV), an avian paramyxovirus, initiates infection with attachment of the viral hemagglutinin-neuraminidase (HN) protein to sialic acid-containing receptors, followed by fusion of viral and cell membranes, which is mediated by the fusion (F) protein. Like all class 1 viral fusion proteins, the paramyxovirus F protein is thought to undergo dramatic conformational changes upon activation. How the F protein accomplishes extensive conformational rearrangements is unclear. Since several viral fusion proteins undergo disulfide bond rearrangement during entry, we asked if similar rearrangements occur in NDV proteins during entry. We found that inhibitors of cell surface thiol/disulfide isomerase activity-55-dithio-bis(2-nitrobenzoic acid) (DTNB), bacitracin, and anti-protein disulfide isomerase antibody-inhibited cell-cell fusion and virus entry but had no effect on cell viability, glycoprotein surface expression, or HN protein attachment or neuraminidase activities. These inhibitors altered the conformation of surface-expressed F protein, as detected by conformation-sensitive antibodies. Using biotin maleimide (MPB), a reagent that binds to free thiols, free thiols were detected on surface-expressed F protein, but not HN protein. The inhibitors DTNB and bacitracin blocked the detection of these free thiols. Furthermore, MPB binding inhibited cell-cell fusion. Taken together, our results suggest that one or several disulfide bonds in cell surface F protein are reduced by the protein disulfide isomerase family of isomerases and that F protein exists as a mixture of oxidized and reduced forms. In the presence of HN protein, only the reduced form may proceed to refold into additional intermediates, leading to the fusion of membranes.Cell entry by enveloped viruses requires fusion of the viral envelope with host cell membranes, a step in infection that is mediated by viral fusion proteins. Viral fusion proteins have been categorized into two and possibly three groups based on their structures and mechanisms for mediating fusion (22,58,70). Class 1 fusion proteins, which fold as trimers, include paramyxovirus F proteins, influenza virus hemagglutinin (HA) proteins, and retrovirus envelope (Env) proteins. These proteins, synthesized as inactive precursors, are cleaved into two subunits, F 1 and F 2 in the case of paramyxoviruses. The sequence at the new amino terminus generated by this cleavage is the fusion peptide (FP), which inserts into the target membrane upon fusion activation (reviewed in references 12, 23, 49, and 70). These proteins also contain two important heptad repeat (HR) domains. The F protein HR domains are located just carboxyl terminal to the fusion peptide (HR1) and adjacent to the transmembrane (TM) domain (HR2). The HR1 and HR2 peptides have a strong affinity and form a very stable six-stranded coiled coil, with HR1 forming an interior trimer and HR2 binding in the grooves of the trimer in an antiparallel orientation (3). Inhibition of fusion with either the HR1 or HR2 peptide su...

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Response of HEK293 and CHO cells overexpressing fusiogenic syncytin‐1 to mitochondrion‐mediated apoptosis induced by antimycin A

Knerr¹,

Söder²,

Licha³

et al. 2008

J of Cellular Biochemistry

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Apoptosis is essential for the regulation of cellular homeostasis in the placenta and is also involved in the pathophysiology of pregnancy-related diseases such as pre-eclampsia and intrauterine growth restriction (IUGR). Syncytin-1, a fusiogenic glycoprotein of endogenous-retroviral origin expressed in human trophoblasts, facilitates placental syncytium formation and is found reduced in pre-eclamptic placentas. We focus here on the mitochondrial apoptotic pathway and investigate whether the overexpression of syncytin-1 in HEK293-52 (human embryonic kidney cells) and CHO-52 cells influences the apoptotic response to the mitochondrial inhibitor antimycin A (AA). After the induction of apoptosis by 5 microM AA and incubation for up to 36 h in the absence of serum, the mean apoptotic rate was reduced by 15-30% in syncytin-1 transfected cells compared with mock-transfectants. After 12 h of challenge with AA we found lower cytochrome c levels in the cytoplasmic protein fraction and higher amounts in the mitochondrial fraction in syncytin-1 transfectants compared with mock-transfectants. We observed a decreased Mitotracker Red staining of mitochondria following AA challenge for 24 h in mock-treated CHO cells, in particular, compared with syncytin-1 transfectants. Moreover, we found a reduced activation of caspase 9 in syncytin-1 transfected HEK293-52 cells after 48 h of apoptotic challenge compared to mock-transfectants. However, a high expression of anti-apoptotic Bcl-x(L) was found in both cell types. Using syncytin-1 transfected HEK293-52 cells and CHO-52 cells, we provide initial evidence that syncytin-1 may exert its anti-apoptotic function at the mitochondrial level. A reduced release of cytochrome c followed by a diminished activation of caspase 9 is a possible mechanism.

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Fusiogenic endogenous-retroviral syncytin-1 exerts anti-apoptotic functions in staurosporine-challenged CHO cells

Cited by 26 publications

References 24 publications

Syncytin-1 and Glial Cells Missing a: Hypoxia-Induced Deregulated Gene Expression along with Disordered Cell Fusion in Primary Term Human Trophoblasts

Syncytin-1 and Glial Cells Missing a: Hypoxia-Induced Deregulated Gene Expression along with Disordered Cell Fusion in Primary Term Human Trophoblasts

Thiol/Disulfide Exchange Is Required for Membrane Fusion Directed by the Newcastle Disease Virus Fusion Protein

Response of HEK293 and CHO cells overexpressing fusiogenic syncytin‐1 to mitochondrion‐mediated apoptosis induced by antimycin A

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