DNA sequences encoding enolase are remarkably conserved from yeast to mammals

Muscle transcriptome analysis provides new insights into the growth gap between fast- and slow-growing Sinocyclocheilus grahami

Sinocyclocheilus grahami is an economically valuable and famous fish in Yunnan Province, China. However, given its slow growth (40 g/2 years) and large growth differences among individuals, its growth performance needs to be improved for sustainable future use, in which molecular breeding technology can play an important role. In the current study, we conducted muscle transcriptomic analysis to investigate the growth gaps among individuals and the mechanism underlying growth within 14 fast- and 14 slow-growth S. grahami. In total, 1,647 differentially expressed genes (DEGs) were obtained, including 947 up-regulated and 700 down-regulated DEGs in fast-growth group. Most DEGs were significantly enriched in ECM-receptor interaction, starch and sucrose metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, amino acids biosynthesis and metabolism, peroxisome, and PPAR signaling pathway. Some genes related to glycogen degradation, glucose transport, and glycolysis (e.g., adipoq, prkag1, slc2a1, agl, pygm, pgm1, pfkm, gapdh, aldoa, pgk1, pgam2, bpgm, and eno3) were up-regulated, while some genes related to fatty acid degradation and transport (e.g., acox1, acaa1, fabp1b.1, slc27a1, and slc27a2) and amino acid metabolism (e.g., agxt, shmt1, glula, and cth) were down-regulated in the fast-growth group. Weighted gene co-expression network analysis identified col1a1, col1a2, col5a1, col6a2, col10a1, col26a1, bglap, and krt15 as crucial genes for S. grahami growth. Several genes related to bone and muscle growth (e.g., bmp2, bmp3, tgfb1, tgfb2, gdf10, and myog) were also up-regulated in the fast-growth group. These results suggest that fast-growth fish may uptake adequate energy (e.g., glucose, fatty acid, and amino acids) from fodder, with excess energy substances used to synthesize collagen to accelerate bone and muscle growth after normal life activities are maintained. Moreover, energy uptake may be the root cause, while collagen synthesis may be the direct reason for the growth gap between fast- and slow-growth fish. Hence, improving food intake and collagen synthesis may be crucial for accelerating S. grahami growth, and further research is required to fully understand and confirm these associations.

Enolase 1 differentially contributes to cell transformation in lung cancer but not in esophageal cancer

Enolase transforms 2-phospho-D-glycerate into phosphoenolpyruvate during glycolysis. The human enolase (ENO) family comprises three members named ENO3, which is restricted to muscle tissues, ENO2, which is neuron- and neuroendocrine tissue-specific, and ENO1, which is expressed in almost all tissues. ENO1 is involved in various types of human cancer, including retinoblastoma, hepatocellular carcinoma, pancreatic cancer, renal cell carcinoma, cholangiocarcinoma and gastric cancer. Furthermore, ENO1 enhances cell transformation in numerous cancer cell lines. It has been reported that ENO1 is involved in various activities that are detrimental to cell transformation, including apoptosis and differentiation. However, a few studies demonstrated that ENO1 can be down- or upregulated in various types of lung cancer, which suggests that ENO1 has an ambiguous role in the development of lung cancer. The present study aimed to investigate the differential influences of ENO1 on various types of cancer, and to clarify the role of ENO1 in lung cancer in particular. Western blotting was performed to assess ENO1 protein expression levels in lung cancer and esophageal cancer tissues. Furthermore, exogenous ENO1 was overexpressed in cell lines derived from various tissues and single cell proliferation, flowcytometric analysis, and western blotting were performed to determine the cell proliferation rate, cell transformation status, cell cycle progression and the expression of cell cycle regulators, such as cyclins and cyclin-dependent kinases, and survival factors, such as MAPK and AKT. The results demonstrated that ENO1 was upregulated in collected panels of lung cancer tissues, but not in esophageal cancer tissues. In addition, overexpression of ectopic ENO1 promoted cell proliferation and survival in lung cancer cell lines, which was not the case in other cells, including an esophageal cell line. Furthermore, mechanistic analyses revealed that ENO1 enhanced cell proliferation by accelerating G₁ progression and upregulating G₁ phase cyclin-dependent kinase 6 (CDK6), and improved cell survival by upregulating p38 in the MAPK cascade and increasing p-AKT in the AKT cascade, in particular in lung cancer cell lines. Overall, the results from the present study demonstrated that ENO1 may contribute to the development of lung cancers, but not esophageal cancers.

Strain-transcending neutralization of malaria parasite by antibodies against Plasmodium falciparum enolase

Background

Plasmodium enolase is a target for the growth neutralizing antibodies. Interestingly, the three invasive stages i.e. sporozoites, merozoites, and ookinetes express this protein on their cell surface. Polyclonal anti-Plasmodium falciparum enolase (Pfeno) antibodies disrupt traversal of ookinete through mosquito mid-gut wall as well as have inhibitory effect on parasite growth at erythrocytic stage. In a recent study, it was observed that immunization with a unique epitope of parasite enolase (EWGWS) could confer partial protection against mouse malaria. Further validation is needed for the protective potential of this unique epitope in otherwise highly conserved enolase.

Methods

In order to investigate the efficacy of growth inhibitory potential of the epitope of P falciparum enolase, a monoclonal antibody specific to EWGWS is generated. In vitro parasite growth inhibition assays and passive immunization of Plasmodium yoelii (or Plasmodium berghei) infected mice were used to assess the parasite growth neutralizing activity of the antibody.

Results

Screening a panel of monoclonal antibodies raised against recombinant Pfeno that were specific to EWGWS resulted in isolation of H12E1. This antibody recognized only EWGWS epitope containing enolases. H12E1 strongly inhibited parasite growth in culture. This inhibition was strain transcending. Passive infusion of this antibody in P. yoelii or P. berghei infected mice showed significant reduction in parasitemia as compared to controls (p < 0.001). Surface Plasmon Resonance measurements indicated high affinity binding of H12E1 to P. falciparum enolase (K_D ~ 7.6 × 10⁻⁹M).

Conclusions

A monoclonal antibody directed against EWGWS epitope of Pfeno was shown to inhibit the growth of blood stage malarial parasites. This inhibition was species/strain transcending and is likely to arise due to blockade of enolase on the surface of merozoites, functionally implicating Pfeno in invasion related events. Presence of enolase on the cell surface of merozoites and ookinetes could potentially result in inhibition of host cell invasions at erythrocytic and transmission stages in the parasite life cycle. It is suggested that antibodies against EWGWS epitope have the potential to confer dual stage, species and strain transcending protection against malaria.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2455-6) contains supplementary material, which is available to authorized users.

A comprehensive narrative review of diagnostic biomarkers in human primary membranous nephropathy

Membranous nephropathy (MN) is relatively major cause of nephrotic syndrome in adults which is recognized as an organ-specific autoimmune disease. The etiology of most cases is idiopathic, whereas the secondary MN is caused by systemic autoimmune diseases, infections, medications and malignancies. The idiopathic disease is developed by the formation of sub-epithelial immune complex deposits most likely due to binding the circulating auto-antibodies to intrinsic antigen on podocytes. The major auto antibody is the anti-phospholipase A2 receptor (anti-PLA2R), however, it is not enough sensitive. Several attempts for diagnostic biomarker identification by modern analytical technologies have been devoted recently. This article reviews the biomarker candidates for primary type of MN that are detected by different approaches on human subjects.

Proteomic analysis to identify biomarker proteins in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the fifth most common cause of death from cancer in Korea. PDAC is difficult to diagnose at an early stage and even more difficult to cure. Thus, there is an urgent need to identify molecular targets for early diagnosis and effective treatment. The objectives of this study were to identify differentially expressed biomarker proteins of PDAC using proteomic analysis, to validate the identified biomarker proteins associated with carcinogenesis using western blot analysis and to evaluate clinical factors influencing expression of candidate biomarker proteins.

METHODS

In the present study, we carried out proteomic analysis in 10 pairs of PDAC specimens with matching adjacent normal tissues to clarify the different patterns of protein expression. The proteins were separated by high-resolution 2-D polyacrylamide gel electrophoresis (2D PAGE) and the differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Differential expression of candidate biomarker proteins associated with carcinogenesis was further validated using western blot analysis. Standard statistical analysis was carried out in an attempt to establish a correlation between clinical variables and expression of candidate biomarker proteins.

RESULTS

Analysis of PDAC and the adjacent normal tissues showed reproducibly similar proteomic patterns for each group. Approximately 700 spots each were seen by silver-stained gels from both PDAC and normal tissues. Differentially expressed protein spots were gel digested and identified by MALDI-TOF MS. Twenty-five proteins were identified, of which five proteins (galectin-1, enolase-2, alpha-1-antitrypsin, N-myc interactor, peroxiredoxin-4) were previously reported as being differentially expressed either at the mRNA level or protein level in human cancer. The five proteins were selected for candidate biomarker proteins related to carcinogenesis. These proteins were further validated by western blot analysis. Among the candidate biomarker proteins, galectin-1 expression was highly correlated to histology (P = 0.019), T stage (P = 0.047), N stage (P = 0.033) and American Joint Committee on Cancer stage (P = 0.011).

CONCLUSION

Differentially expressed 25 proteins in PDAC were identified using proteomic analysis and five proteins related to carcinogenesis were validated by western blot analysis. Galectin-1 expression was highly correlated to tumour histology and stage.

Anti-alpha-enolase antibodies in patients with inflammatory Bowel disease

BACKGROUND

Patients with inflammatory bowel disease (IBD) carry autoantibodies such as perinuclear antineutrophil cytoplasmic antibodies (pANCA). alpha-Enolase has been proposed as a target antigen in IBD. We evaluated the prevalence and diagnostic value of anti-alpha-enolase antibodies in IBD and related disorders.

METHODS

We used a classic proteomic approach with extracts from granulocytes and pANCA-positive ulcerative colitis (UC) sera to confirm alpha-enolase as a target antigen. By means of Western blot analysis, we screened a cohort of 525 subjects for the presence of anti-alpha-enolase antibodies. We performed GeneArray experiments on RNA extracted from colonic mucosal biopsies from 35 IBD and 6 control patients.

RESULTS

We detected anti-alpha-enolase antibodies 49.0% of patients with UC, 50.0% of patients with Crohn's disease, 30.5% of patients with primary sclerosing cholangitis, 37.8% of patients with autoimmune hepatitis, 34.0% of patients with ANCA-positive vasculitis, 31.0% of non-IBD gastrointestinal controls, and 8.5% of healthy controls. Gene array experiments showed a significant upregulation of alpha-enolase mRNA in colonic mucosal biopsies from patients with IBD, but not from controls. There was no association between the presence of pANCA and anti-alpha-enolase antibodies. Preabsorption with alpha-enolase did not eliminate the pANCA pattern on indirect immunofluorescence.

CONCLUSIONS

Anti-alpha-enolase antibodies are present in a substantial proportion of patients with IBD, patients with various inflammatory/autoimmune disorders, and non-IBD gastrointestinal controls. Therefore, anti-alpha-enolase antibodies are of limited diagnostic value for the diagnosis of IBD.

Characterization of protein kinase C isoforms in primary cultured cerebellar granule cells

Protein kinase C (PKC) is a family of serine/threonine kinases comprised of 10 isoforms. Although commercial antibodies are available for all 10 isoforms, the specificity of these antibodies has been questioned. We have identified immunoblot conditions in which commercially purchased PKC antibodies are specific for their respective isoform. We then used these conditions to determine that PKC isoforms alpha, betaI, betaII, delta, epsilon, gamma, lambda, theta, and zeta are present in rat primary cultured cerebellar granule cells (CGCs) 6-14 days in vitro (DIV). This PKC profile is identical to that observed in cerebellar homogenates taken from 6-, 14- and 21-day-old rats. Western blot analysis indicated that the classical and the atypical PKC isoforms were more prevalent in the cytosolic subcellular fraction compared to the particulate fraction under basal conditions. Immunoreactivity for the novel isoforms tended to be higher in the particulate fraction under basal conditions. Phorbol 12-myristate 13-acetate (PMA) treatment resulted in translocated immunoreactivity from the cytosolic to the particulate fraction for all of the classical and novel PKC isoforms, but not for the atypical isoforms. However, the degree of translocation as well as the speed of translocation varied among the isoforms. The stability of the individual isoforms after PMA-induced activation also varied among the isoforms. Differences in these parameters were dependent upon culture batches and PKC isoform groups. We have identified experimental conditions in which reproducible results can be obtained with primary cultured CGCs in the study of PKC. We discuss possible solutions for problems encountered when utilizing primary cultured neurons to study PKC-mediated signal transduction.

Anti-alpha-enolase antibodies in pituitary disease

A previous study reported a high prevalence of autoantibodies to alpha-enolase in lymphocytic hypophysitis and these antibodies efficiently distinguished lymphocytic hypophysitis from pituitary tumors. To confirm this, we examined autoantibodies to alpha-enolase in patients with lymphocytic hypophysitis (n = 17), pituitary non-functioning adenoma (n = 13), other pituitary diseases (n = 17) and other autoimmune diseases (n = 30), and compared to healthy controls (n = 46). Autoantibodies were found in 41.2%, 46.2%, 23.5%, 20.0% and 4.3%, respectively. Our findings indicate that detection of anti-alpha-enolase antibodies is not suitable for specific diagnosis of lymphocytic hypophysitis.

Proteomic analysis of human brain identifies α-enolase as a novel autoantigen in Hashimoto's encephalopathy

Hashimoto's encephalopathy (HE) is a rare autoimmune disease associated with Hashimoto's thyroiditis (HT). To identify the HE-related autoantigens, we developed a human brain proteome map using two-dimensional electrophoresis and applied it to the immuno-screening of brain proteins that react with autoantibodies in HE patients. After sequential MALDI-TOF-MASS analysis, immuno-positive spots of 48 kDa (pI 7.3-7.8) detected from HE patient sera were identified as a novel autoimmuno-antigen, alpha-enolase, harboring several modifications. Specific high reactivities against human alpha-enolase were significant in HE patients with excellent corticosteroid sensitivity, whereas the patients with fair or poor sensitivity to the corticosteroid treatment showed less reactivities than cut-off level. Although a few HT patients showed faint reactions to alpha-enolase, 95% of HT patients, patients with other neurological disorders, and healthy subjects tested were all negative. These results suggest that the detection of anti-alpha-enolase antibody is useful for defining HE-related pathology, and this proteomic strategy is a powerful method for identifying autoantigens of various central nervous system diseases with unknown autoimmune etiologies.

Disease association, origin, and clinical relevance of autoantibodies to the glycolytic enzyme enolase

Serum autoantibodies to the glycolytic enzyme enolase have been reported in a diverse range of inflammatory, degenerative, and psychiatric disorders. Diseases in which these antibodies have been reported in high incidence include autoimmune polyglandular syndrome type 1 (80%, 35 of 44), primary (69%, 60 of 87), and secondary (58%, 14 of 24) membranous nephropathy, cancer-associated retinopathy (68.8%, 11 of 16), autoimmune hepatitis type 1 (60%, 12 of 20), mixed cryoglobulinemia with renal involvement (63.6%, seven of 11), cystoid macular edema (60%, six of 10), and endometriosis (50%, 21 of 41). In autoimmune polyglandular syndrome type 1 patients, all had chronic mucocutaneous candidiasis with demonstrated antibody reactivity to candida enolase, which is suggestive of cross reactivity or epitope mimicry. Formation of autoantibodies to enolase may be a normal process, with reported incidence in apparently healthy subjects ranging from 0% (zero of 91) to 11.7% (seven of 60). Nonetheless, we suggest that excessive production of these autoantibodies, which are generated as a consequence of uptake of enolase by antigen-presenting cells and subsequent B cell activation, can potentially initiate tissue injury as a result of immune complex deposition.

Neuroendocrine marker expression in thyroid epithelial tumors

Tissue sections from 50 cases with thyroid tumors, composed of 11 follicular adenomas, 10 follicular carcinomas, 14 papillary carcinomas, 10 anaplastic carcinomas, and 5 medullary carcinomas, were immunohistochemically analyzed for representative neuroendocrine markers. Immunoexpression ratios of these neuroendocrine markers were as follows: Follicular adenomas, neuron-specific enolase (NSE)63.6%, synaptophysin (SynP) 45.5%, Leu7 27.3%, NCAM 45.5%, chromogranin A (CgA) 0%, SNAP25 0%; follicular carcinomas, NSE 90.0%, SynP 80.0%, Leu7 80.0%, NCAM 0%, CgA 0%, SNAP25 0%; papillary carcinomas, NSE 85.7%, SynP 78.6%, Leu7 100%, NCAM 7.0%, CgA 0%, SNAP25.0%; anaplastic carcinomas, NSE 10.0%, SynP 0%, Leu7 0%, NCAM 0%, CgA 0%, SNAP25 0%; medullary carcinomas, NSE 100%, SynP100%, Leu7 80.0%, NCAM 40.0%, CgA 100%, SNAP25 100%. The two follicular carcinomas, which were morphologically characterized by "insular" (or "alveolar") arrangements, showed distinct immunoexpression of NSE and SynP at the same time. By in situ hybridization (ISH), expression of mRNA for NSE was confirmed in cases with marked immunoexpression of NSE. Although no endocrine granules were found, our results suggested that a specific type of follicular carcinoma, i.e., insular variant, may be immaturely neuroendocrine-differentiated.

The glycolytic enzyme enolase is present in sperm tail and displays nucleotide-dependent association with microtubules

We examined the expression and localisation of enolase (2-phospho-D-glycerate hydrolase) in differentiating rat spermatogenic cells. We found that enolase is most abundant in mature spermatozoa and in residual cytoplasmic bodies detached from elongating spermatids with little to no enolase detected in meiotic primary spermatocytes and round spermatids. We localised enolase mostly to the tail of mature spermatozoa by immunoblotting and by immunofluorescence. RT-PCR analysis of differentiating spermatogenic cells detected only the alpha isoform of enolase. As several glycolytic enzymes are known to associate with microtubules prepared from brain, we investigated the association of enolase with brain and testis microtubules. We found that only a small fraction of testis and brain-derived cytosolic enolase (4.9% and 11.2%, respectively) co-sediments with microtubules stabilised in the presence of taxol. In the presence of certain nucleotides in excess (3 mM ATP, CTP, GTP and ITP) the association of enolase with microtubules was disrupted, however, this was not the case for UTP. This observation is consistent with the finding that in the presence of 0.5 mM AMP-PNP, a nonhydrolysable analogue of ATP, there is an increased association of enolase with microtubules. We propose that the nucleotide-dependent association of enolase with microtubules regulates enzyme activity by linking energy production to utilisation.

Circulating antibodies against alpha-enolase in patients with primary membranous nephropathy (MN)

MN is characterized by the glomerular deposition of IgG4 immune complexes. This suggests that nephritogenic immune responses in MN are of the Th2 T helper cell type; however, the pathogenesis of MN is still unknown. In this study we examined sera from patients with primary MN for antibodies to renal proteins. A 47-kD protein in both human and porcine renal extracts was found by immunoblotting to react specifically with serum IgG from some patients. This protein was purified from porcine kidney and identified as alpha-enolase on the basis of its partial amino acid sequences. Sera from 87 patients with primary MN, 24 patients with secondary MN (15 rheumatoid arthritis patients, nine systemic lupus erythematosus patients), and 16 healthy subjects were examined by ELISA using purified alpha-enolase. In 60 (69%) patients with primary MN and 14 (58%) patients with secondary MN, the measured optical density values, and hence serum anti-alpha-enolase antibody levels, were greater than the mean + 2 s.d. of healthy subjects. Immunoblot analysis showed that IgG1 or IgG3 was the predominant subclass (Th1 T helper cell type subclass) of antibodies against alpha-enolase in patients with primary and secondary MN. Since circulating antibodies against alpha-enolase have recently been reported in patients with various autoimmune disorders, our results suggest that a number of patients with presumed primary MN may also have abnormalities in Th1 T helper cell-mediated immune responses.

Autoantibodies to evolutionarily conserved epitopes of enolase in a patient with discoid lupus erythematosus

Although the pathology of discoid lupus erythematosus is well documented the causative agents are not known. Here, we report the identity of the target antigen of an autoantibody present in high titre in the serum of a patient with discoid lupus erythematosus. We have demonstrated that the antigen is enolase; first, because it has properties consistent with this glycolytic enzyme (47,000 MW, cytosolic localization and ubiquitous tissue distribution). Secondly, limited amino acid sequence determination after trypsin digestion shows identity with alpha-enolase. Finally, the autoimmune serum immunoblots rabbit and yeast enolase and predominantly one isoelectric form of enolase (PI approximately 6.1). These results indicate that the reactive autoepitopes are highly conserved from man to yeast. The results also suggest that the autoantibodies are most reactive to the alpha-isoform of enolase, although it is possible that they may also be reactive with gamma-enolase, and have least reactivity to beta-enolase. The anti-enolase autoantibodies belong to the immunoglobulin G1 (IgG1) isotype. This is the first report of IgG1 autoantibodies to evolutionarily conserved autoepitopes of enolase in the serum of a patient with discoid lupus erythematosus. Previous reports of autoantibodies to enolase have suggested associations with autoimmune polyglandular syndrome type I and cancer-associated retinopathy. This report and an earlier report of what is likely to be enolase autoantibodies in two patients without systemic disease suggest that enolase autoantibodies have a broad association and are not restricted to any particular disease.

Nucleotide sequence of the Treponema pallidum eno gene

We determined the nucleotide sequence of the enolase (eno) gene of Treponema pallidum, the noncultivable agent of syphilis. The deduced amino acid sequence of T. pallidum enolase (Eno) is 432 amino acids long with a predicted molecular mass of 46.7 kDa. The Eno amino acid sequence has a high degree of homology to the amino acid sequences of prokaryotic and eukaryotic Eno. This is the first eno sequence reported for a bacterium in the order Spirochaetales.