Stromal cell derived factor-2 (Sdf2): A novel protein expressed in mouse

Investigation of new autoantibodies in urothelial bladder cancer for biomarker discovery using immunoproteomics

BACKGROUND

Tumor-associated antigens (TAAs) lead to the production of tumor-specific autoantibodies (anti-TAA autoantibodies) by triggering the humoral immune system which can be used as candidate biomarkers. This study aims to investigate TAAs proteins eliciting humoral responses in different stages of urothelial bladder carcinoma (UBC) using an immunoproteomics approach to find novel biomarkers for the clinical management of the disease.

METHODS

Total proteins were obtained from the newly established UBC cell line, JAM-ICR, and separated by two-dimensional gel electrophoresis (2DE). These proteins were then immobilized using pooled serum samples from healthy individuals, autoimmune and UBC patients at different stages. The immunoreactive spots in UBC patient samples were identified by mass spectrometry and verified with several databases such as GEPIA and Enrichr databases.

RESULTS

Through the comparison of the immunoreactivity pattern of serums, we were able to identify eight specific proteins using LC-MS. Patients with muscle invasion showed increased expression of ENO1, VDAC2, AKR1B1, SDF2L1, PRDX6, PSME1, HSPB1 and PHB1 compared to controls. In addition, non-muscle invasive patients showed overexpression of ENO1, VDAC2, AKR1B1, and PRDX6 compared to controls. In addition to their diagnostic function, PRDX6, ENO1, VDAC2, and PHB1 have been demonstrated to possess prognostic capabilities in patients with UBC. Interestingly, these proteins were mainly associated with cellular growth and anti-apoptotic activity.

CONCLUSION

In this study, eight anti-TAA autoantibodies were identified that have the potential to serve as diagnostic and prognostic biomarkers. These could represent a valuable panel of biomarkers for the management of UBC.

Identification of stromal cell-derived factor 4 as a liquid biopsy-based diagnostic marker in solid cancers

There is a need for serum diagnostic biomarkers to improve the prognosis of solid malignant tumors. Here, we conducted a single-institutional study to evaluate the diagnostic performance of serum stromal cell-derived factor 4 (SDF4) levels in cancer patients. Serum samples were collected from a total of 582 patients with solid cancers including gastric cancer (GC) and 80 healthy volunteers. SDF4 protein levels in sera, and conditioned media or lysates of human GC cell lines were measured by enzyme-linked immunosorbent assay, and those in GC tissue by immunohistochemistry. Serum SDF4 levels were higher in patients with cancer than the healthy control in all cancer type. Regarding GC, serum SDF4 levels distinguished healthy controls from GC patients with the area under the curve value of 0.973, sensitivity of 89%, and specificity of 99%. Serum SDF4 levels were significantly elevated in patient with early stage GC. In immunohistochemistry, the frequency of SDF4-positive GC tumors did not vary significantly between GC stages. The ability of human GC cell lines to both produce and secrete SDF4 was confirmed in vitro. In conclusion, serum SDF4 levels could be a promising candidate for a novel diagnostic biomarker for GC and other malignancies.

Sevoflurane exerts protection against myocardial ischemia-reperfusion injury and pyroptosis through the circular RNA PAN3/microRNA-29b-3p/stromal cell-derived factor 4 axis

OBJECTIVE

Sevoflurane is suggested to exert protective functions against myocardial ischemia-reperfusion injury (MIRI). However, the particular mechanism remains elusive. Therefore, this research explored the mechanism of sevoflurane in MIRI-induced damage and pyroptosis.

METHODS

Subsequent to gain-or loss-of-function assays or/and sevoflurane treatment, the MIRI model was developed in rats. Cardiac function and body and heart weight of rats were evaluated, followed by measurement of apoptosis and creatine kinase MB (CK-MB), lactate dehydrogenase (LDH), and pyroptosis-related protein levels. After loss-of-function assays or/and sevoflurane treatment in human cardiomyocytes (HCMs), the hypoxia/reoxygenation (H/R) model was constructed. In HCMs, cell viability, apoptosis, and pyroptosis-related proteins were detected. Circular RNA PAN3 (circPAN3), microRNA (miR)-29b-3p, and stromal cell-derived factor 4 (SDF4) expression was determined in rat myocardial tissues and HCMs. Mechanistically, interactions among circPAN3, miR-29b-3p, and SDF4 were analyzed.

RESULTS

MIRI modeling increased miR-29b-3p expression and diminished circPAN3 and SDF4 expression in H/R-treated HCMs and MIRI rats, which was nullified by sevoflurane preconditioning. Mechanistically, circPAN3 negatively targeted miR-29b-3p to upregulate SDF4. Moreover, sevoflurane preconditioning reduced heart weight/body weight ratio, LDH, CK-MB, myocardial infarct size, left ventricular end-diastolic pressure, apoptosis, and pyroptosis, while elevating the increase and decrease of left ventricular pressure (±dp/dt _max) and left ventricular systolic pressure in MIRI rats. In addition, sevoflurane preconditioning augmented viability while diminishing apoptosis and pyroptosis in H/R-treated HCMs. Moreover, circPAN3 silencing or miR-29b-3p overexpression abrogated alleviatory effects of sevoflurane on myocardial injury and pyroptosis in vitro.

CONCLUSION

Sevoflurane treatment ameliorated myocardial injury and pyroptosis in MIRI via circPAN3/miR-29b-3p/SDF4 axis.

Stromal Cell-Derived Factor (SDF) 2 and the Endoplasmic Reticulum Stress Response of Trophoblast Cells in Gestational Diabetes Mellitus and In vitro Hyperglycaemic Condition

BACKGROUND AND AIM

The endoplasmic reticulum (ER) stress response and the unfolded protein response (UPR) are essential cellular mechanisms to ensure the proper functioning of ER in adverse conditions. However, activation of these pathways has also been associated with insulin resistance and cell death in pathological conditions such as diabetes mellitus. In the present study, we investigated whether stromal cell-derived factor 2 (SDF2)-an ER stress-responsive factor-is related to ER response in placental cells exposed to maternal gestational diabetes mellitus (GDM) or to a hyperglycaemic in vitro condition.

OBJECTIVE

The study aimed to investigate the role of SDF2 in BeWo cells , a trophoblast cell line originating from choriocarcinoma , and in placental tissue under hyperglycaemic conditions.

METHODS

Protein levels of SDF2 and UPR factors, glucose-related protein 78 (GRP78) and eukaryotic initiation factor 2 alpha (elF2 alpha) were evaluated in the placentae of pregnant women diagnosed with GDM and treated by diet-control (insulin was added when necessary). The mRNA expression of SDF2 and UPR factors CHOP and sXBP1 were assessed in cultured BeWo cells challenged with glucose and treated with or without insulin.

RESULTS

SDF2 expression was increased in the placentae of GDM women treated with diet. However, its values were similar to those of normoglycemic controls when the GDM women were treated with insulin and diet. BeWo cells cultured with high glucose and insulin showed decreased SDF2 expression, while high glucose increased CHOP and sXBP1 expression, which was then significantly reverted with insulin treatment.

CONCLUSION

Our findings extend the understanding of ER stress and SDF2 expression in placentae exposed to hyperglycaemia, highlighting the relevance of insulin in reducing the levels of ER stress factors in placental cells. Understanding the effect of ER stress partners such as SDF2 on signalling pathways involved in gestation, complicated by hyperglycaemia, is pivotal for basic biomedical research and may lead to new therapeutic possibilities.

The integrated stress response mediates necrosis in murine Mycobacterium tuberculosis granulomas

The mechanism by which only some individuals infected with Mycobacterium tuberculosis develop necrotic granulomas with progressive disease while others form controlled granulomas that contain the infection remains poorly defined. Mice carrying the sst1-suscepible (sst1S) genotype develop necrotic inflammatory lung lesions, similar to human tuberculosis (TB) granulomas, which are linked to macrophage dysfunction, while their congenic counterpart (B6) mice do not. In this study we report that (a) sst1S macrophages developed aberrant, biphasic responses to TNF characterized by superinduction of stress and type I interferon pathways after prolonged TNF stimulation; (b) the late-stage TNF response was driven via a JNK/IFN-β/protein kinase R (PKR) circuit; and (c) induced the integrated stress response (ISR) via PKR-mediated eIF2α phosphorylation and the subsequent hyperinduction of ATF3 and ISR-target genes Chac1, Trib3, and Ddit4. The administration of ISRIB, a small-molecule inhibitor of the ISR, blocked the development of necrosis in lung granulomas of M. tuberculosis-infected sst1S mice and concomitantly reduced the bacterial burden. Hence, induction of the ISR and the locked-in state of escalating stress driven by the type I IFN pathway in sst1S macrophages play a causal role in the development of necrosis in TB granulomas. Interruption of the aberrant stress response with inhibitors such as ISRIB may offer novel host-directed therapy strategies.

Location, function and role of stromal cell‑derived factors and possible implications in cancer (Review)

Despite improvements in therapy and management, cancer represents and remains a major cause of mortality and morbidity worldwide. Although genetics serve an important role in tumorigenesis and tumour progression, the tumour microenvironment (TME) in solid tumours is also important and has been indicated to contribute to these processes. Stromal cell‑derived factors (SDFs) represent an important family within the TME. The family includes SDF‑1, SDF‑2, SDF2‑like 1 (SDF2L1), SDF‑3, SDF‑4 and SDF‑5. SDF‑1 has been demonstrated to act as a positive regulator in a number of types of tumour, such as oesophago‑gastric, pancreatic, lung, breast, colorectal and ovarian cancer, while the biology and functions of other members of the SDF family, including SDF‑2, SDF2L1, SDF‑4 and SDF‑5, in cancer are different, complex and controversial, and remain mainly unknown. Full identification and understanding of the SDFs across multiple types of cancer is required to elucidate their function and establish potential key targets in cancer.

Generation of Rat Monoclonal Antibodies Specific for Human Stromal Cell-Derived Factor-2

Stromal cell-derived factor-2 (SDF-2) is reportedly involved in multiple endoplasmic reticulum (ER) functions, including the misfolded protein catabolic process, protein glycosylation, and ER protein quality control. However, the precise molecular and cellular functions of SDF-2 remain unknown. Previously, we discovered that SDF-2 mediates acquired resistance to oxaliplatin in human gastric cancer cells. In this study, we have generated SDF-2-specific monoclonal antibodies (mAbs), using the rat medial iliac lymph node method, as a tool to explore novel mechanisms of oxaliplatin resistance. The antibodies detected endogenous human SDF-2 in immunoblotting analyses. In addition, immunoprecipitation analyses revealed the availability of these antibodies for human SDF-2. Thus, these mAbs will be available to elucidate molecular and cellular functions of SDF-2 in cancer cells.

SDF2-like protein 1 (SDF2L1) regulates the endoplasmic reticulum localization and chaperone activity of ERdj3 protein

Molecular chaperones facilitate protein folding by associating with nascent polypeptides, thereby preventing protein misfolding and aggregation. Endoplasmic reticulum (ER) chaperone BiP, the sole HSP70 chaperone in the ER, is regulated by HSP40 chaperones, including ER-resident protein ERdj3 (DNAJB11). ERdj3 lacks an ER retrieval signal, is secreted under ER stress conditions, and functions as a chaperone in the extracellular space, but how its secretion is regulated remains unclear. We recently showed that ERdj3 forms a complex with ER-resident stromal cell-derived factor 2 (SDF2) and SDF2L1 (SDF2-like protein 1) and thereby prevents protein aggregation during the BiP chaperone cycle. However, the contribution of the ERdj3-SDF2L1 complex to protein quality control is poorly understood. Here, we analyzed the intracellular localization and chaperone activity of ERdj3 in complex with SDF2L1. We found that ERdj3 was retained in the ER by associating with SDF2/SDF2L1. In vitro analyses revealed that the ERdj3 dimer incorporated two SDF2L1 molecules; otherwise, ERdj3 alone formed a homotetramer. The ERdj3-SDF2L1 complex suppressed ER protein aggregation, and this suppression did not require substrate transfer to BiP. The ERdj3-SDF2L1 complex inhibited aggregation of denatured GSH S-transferase (GST) in vitro and maintained GST in a soluble oligomeric state. Both in cellulo and in vitro, the chaperone activities of the ERdj3-SDF2L1 complex were higher than those of ERdj3 alone. These findings suggest that, under normal conditions, ERdj3 functions as an ER chaperone in complex with SDF2/SDF2L1 but is secreted into the extracellular space when it cannot form this complex.

The potential contribution of stromal cell-derived factor 2 (SDF2) in endoplasmic reticulum stress response in severe preeclampsia and labor-onset

Endoplasmic reticulum (ER) stress occurs when the protein folding machinery in the cell is unable to cope with newly synthesized proteins, which results in an accumulation of misfolded proteins in the ER lumen. In response, the cell activates a cellular signaling pathway known as the Unfolded Protein Response (UPR), aiming to restore cellular homeostasis. Activation and exacerbation of the UPR have been described in several human pathologies, including cancer and neurological disorders, and in some gestational diseases such as preeclampsia and gestational diabetes. This review explores the participation of stromal cell-derived factor 2 (SDF2) in UPR pathways, shows new information and discusses its exacerbation regarding protein expression in severe preeclampsia and labor, both of which are associated with ER stress.

Three interacting genomic loci incorporating two novel mutations underlie the evolution of diet-induced diabetes

We investigated the pathophysiology of diet-induced diabetes in the Cohen diabetic rat (CDs/y) from its induction to its chronic phase, using a multi-layered integrated genomic approach. We identified by linkage analysis two diabetes-related quantitative trait loci on RNO4 and RNO13. We determined their functional contribution to diabetes by chromosomal substitution, using congenic and consomic strains. To identify within these loci genes of relevance to diabetes, we sequenced the genome of CDs/y and compared it to 25 other rat strains. Within the RNO4 locus, we detected a novel high impact deletion in the Ndufa4 gene that was unique to CDs/y. Within the RNO13 locus, we found multiple SNPs and INDELs that were unique to CDs/y but were unable to prioritize any of the genes. Genome wide screening identified a novel third locus not detected by linkage analysis that consisted of a novel high impact deletion on RNO11 that was unique to CDs/y and that involved the Sdf2l1 gene. Using co-segregation analysis, we investigated in silico the relative contribution to the diabetic phenotype and the interaction between the three genomic loci on RNO4, RNO11 and RNO13. We found that the RNO4 locus plays a major role during the induction of diabetes, whereas the genomic loci on RNO13 and RNO11, while interacting with the RNO4 locus, contribute more significantly to the diabetic phenotype during the chronic phase of the disease. The mechanisms whereby the mutations on RNO4 and 11 and the RNO13 locus contribute to the development of diabetes are under continuing investigation.

Stromal Cell-Derived Factor 2: A Novel Protein that Interferes in Endoplasmic Reticulum Stress Pathway in Human Placental Cells

Endoplasmic reticulum (ER) stress results from changes in ER homeostasis and folding of proteins. ER stress initiates cellular adaptive mechanisms to rescue cell homeostasis or, if that does not work, to elicit apoptosis. We have previously shown that mouse SDF2 is sublocalized in the ER, is ubiquitously expressed, and shows strong similarities with stromal cell-derived factor (SDF) 2L1 and SDF2-like from Arabidopsis, ER proteins involved in chaperone network and protein folding. Thus, we hypothesized that SDF2 plays a role in the ER stress and unfolded protein response. In this study, we investigated the possible role of SDF2 in the human placenta. Expression of SDF2 was present throughout gestation and was expressed by several cell types. Second-trimester cytotrophoblast cells (CTBs) in the differentiation process, monitored through chorionic gonadotropin production, showed upregulation of SDF2 protein. SDF2 expression, however, was significantly diminished in placentas from neonates small for gestational age and in hypoxic in vitro conditions (P ≤ 0.001, 2% O2), suggesting a link with cellular stress. ER stress-induced cells-CTB and BeWo-also showed SDF2 downregulation in different time points, emphasizing this relationship. SDF2 downregulation was also followed by an increase in binding immunoglobulin protein (BiP) expression, an ER protein-associated chaperone acting as a sensor for misfolded proteins and an ER stress cell survival marker. In line with this, SDF2 siRNA resulted in significant anticipation of BiP expression. Downregulation of SDF2 also interfered with C/EBP homologous protein expression, one of the highest inducible genes during ER stress. These findings suggest that SDF2 may be an important regulatory factor by which trophoblast cells can control cell survival under ER stress. In conclusion, this study identifies a novel factor with the ability to interfere with ER stress proteins, which may contribute to the understanding of ER stress associated with placental-related diseases of pregnancy.

Stromal cell-derived factor 2 is critical for Hsp90-dependent eNOS activation

Endothelial nitric oxide synthase (eNOS) catalyzes the conversion of l-arginine and molecular oxygen into l-citrulline and nitric oxide (NO), a gaseous second messenger that influences cardiovascular physiology and disease. Several mechanisms regulate eNOS activity and function, including phosphorylation at Ser and Thr residues and protein-protein interactions. Combining a tandem affinity purification approach and mass spectrometry, we identified stromal cell-derived factor 2 (SDF2) as a component of the eNOS macromolecular complex in endothelial cells. SDF2 knockdown impaired agonist-stimulated NO synthesis and decreased the phosphorylation of eNOS at Ser(1177), a key event required for maximal activation of eNOS. Conversely, SDF2 overexpression dose-dependently increased NO synthesis through a mechanism involving Akt and calcium (induced with ionomycin), which increased the phosphorylation of Ser(1177) in eNOS. NO synthesis by iNOS (inducible NOS) and nNOS (neuronal NOS) was also enhanced upon SDF2 overexpression. We found that SDF2 was a client protein of the chaperone protein Hsp90, interacting preferentially with the M domain of Hsp90, which is the same domain that binds to eNOS. In endothelial cells exposed to vascular endothelial growth factor (VEGF), SDF2 was required for the binding of Hsp90 and calmodulin to eNOS, resulting in eNOS phosphorylation and activation. Thus, our data describe a function for SDF2 as a component of the Hsp90-eNOS complex that is critical for signal transduction in endothelial cells.