Chromogranin B Research Articles

Regulation of circulating chromogranin B levels in heart failure

Background: Chromogranin B (CGB) regulates B-type natriuretic peptide (BNP) production. Circulating CGB levels are elevated in heart failure (HF) animal models and HF patients, but also increase in healthy individuals in response to physical activity. Therefore, CGB seems to integrate information from myocardial stress and systemic neuro-endocrine activation. Substantial gaps remain in our understanding of CGB regulation in HF.Methods and results: We conducted a retrospective registry study including 372 patients. CGB and N-terminal pro-BNP (NT-proBNP) plasma levels were assessed in acute HF and chronic valvular HF patients and controls. CGB levels were significantly increased in acute HF and chronic valvular HF, but significantly higher in the latter. Patients in chronic valvular HF with severe mitral regurgitation (cHF-MR) showed significantly higher CGB levels than patients in chronic valvular HF with severe aortic stenosis. CGB levels progressively increased with worsening NYHA functional status and were moderately correlated to NT-proBNP, but independent of left ventricular (LV) ejection fraction (LVEF), LV mass, age and body weight. Finally, cHF-MR patients showed significant reductions of CGB levels after interventional mitral valve repair.Conclusion: CGB is a promising emerging biomarker in HF patients with unique potential to integrate information from myocardial stress and neuro-endocrine activation.

The role of variant chromogranin b as disease modifier in japanese female amyotrophic lateral sclerosis

Background: Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease that is characterized by selective loss of central and peripheral motor neurons. Recent genetic studies yielded conflicting results regarding a role for the variant chromogranin B (CHGB) P413L allele as a disease modifier in ALS.

Advances of circulating biomarkers in gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplam (GEP-NEN) is a rare group of tumors with its incidence rising significantly in recent decades. Because of the late presentation of the disease and limitations in conventional biomarkers, about 50% of GEP-NEN patients manifests advanced disease when diagnosed. Therefore, it is vital to identify circulating biomarkers which can not only be used for early diagnosis but also accurately evaluating the biological behavior of GEP-NEN. This review summarizes the advances of circulating biomarkers in diagnosing and evaluating efficacy of treatment in GEP-NEN. Well-known circulating biomarkers include chromogranin A (CgA), pancreastatin (PST), chromogranin B (CgB), neuron-specific enolase (NSE) and pancreatic peptide(PP). Novel biomarkers including circulating tumor cell(CTC), microRNA and NETest are promising biomarkers with potential clinical benefit, but further researches are needed before their clinical applications.

Chromogranin B Serves the Long-Sought-After Anion Conductance in Regulated Secretion

Regulated secretion is an intracellular pathway that empowers stimulus-controlled release of bioactive molecules in all endocrine cells. An anion channel has been known to be required for acidification and maturation of the secretory granules for forty years. But the identity of this anion conductance remains elusive. We now show that chromogranin B (CHGB), a well-conserved protein in the regulated secretory pathway, forms the long-sought-after anion-selective channel in the membranes of secretory granules. In planar lipid bilayers and lipid vesicles CHGB alone forms a pH- and Ca2+-sensitive anion channel with anion selectivity higher than other known chloride channels. Two amphipathic helical domains mediate membrane insertion and channel formation. Expression of channel-defective mutants in CHGB knockdown cells separates its role in granule maturation from that in granule biogenesis and demonstrates the necessity of the CHGB anion conductance to granule acidification and cargo maturation. Together our data demonstrate that phylogenetically conserved CHGBs constitute a new family of organelle chloride channels in endocrine cells.

Gender-Specific Associations betweenCHGBGenetic Variants and Schizophrenia in a Korean Population

PurposeSchizophrenia is a devastating mental disorder and is known to be affected by genetic factors. The chromogranin B (CHGB), a member of the chromogranin gene family, has been proposed as a candidate gene associated with the risk of schizophrenia. The secretory pathway for peptide hormones and neuropeptides in the brain is regulated by chromogranin proteins. The aim of this study was to investigate the potential associations between genetic variants of CHGB and schizophrenia susceptibility.Materials and MethodsIn the current study, 15 single nucleotide polymorphisms of CHGB were genotyped in 310 schizophrenia patients and 604 healthy controls.ResultsStatistical analysis revealed that two genetic variants (non-synonymous rs910122; rs2821 in 3′-untranslated region) were associated with schizophrenia [minimum p=0.002; odds ratio (OR)=0.72], even after correction for multiple testing (pcorr=0.02). Since schizophrenia is known to be differentially expressed between sexes, additional analysis for sex was performed. As a result, these two genetic variants (rs910122 and rs2821) and a haplotype (ht3) showed significant associations with schizophrenia in male subjects (pcorr=0.02; OR=0.64), whereas the significance disappeared in female subjects (p>0.05).ConclusionAlthough this study has limitations including a small number of samples and lack of functional study, our results suggest that genetic variants of CHGB may have sex-specific effects on the risk of schizophrenia and provide useful preliminary information for further study.

Identification of novel loci affecting circulating chromogranins and related peptides

Chromogranins are pro-hormone secretory proteins released from neuroendocrine cells, with effects on control of blood pressure. We conducted a genome-wide association study for plasma catestatin, the catecholamine release inhibitory peptide derived from chromogranin A (CHGA), and other CHGA- or chromogranin B (CHGB)-related peptides, in 545 US and 1252 Australian subjects. This identified loci on chromosomes 4q35 and 5q34 affecting catestatin concentration (P = 3.40 × 10-30 for rs4253311 and 1.85 × 10-19 for rs2731672, respectively). Genes in these regions include the proteolytic enzymes kallikrein (KLKB1) and Factor XII (F12). In chromaffin cells, CHGA and KLKB1 proteins co-localized in catecholamine storage granules. In vitro, kallikrein cleaved recombinant human CHGA to catestatin, verified by mass spectrometry. The peptide identified from this digestion (CHGA360-373) selectively inhibited nicotinic cholinergic stimulated catecholamine release from chromaffin cells. A proteolytic cascade involving kallikrein and Factor XII cleaves chromogranins to active compounds both in vivo and in vitro.

Sex-dependent effects of chromogranin B P413L allelic variant as disease modifier in amyotrophic lateral sclerosis.

Recent genetic studies yielded conflicting results regarding a role for the variant chromogranin B (CHGB)P413L allele as a disease modifier in ALS. Moreover, potential deleterious effects of the CHGBP413L variant in ALS pathology have not been investigated. Here we report that in transfected cultured cells, the variant CHGBL413 protein exhibited aberrant properties including mislocalization, failure to interact with mutant superoxide dismutase 1 (SOD1) and defective secretion. The CHGBL413 transgene in SOD1G37R mice precipitated disease onset and pathological changes related to misfolded SOD1 specifically in female mice. However, the CHGBL413 variant also slowed down disease progression in SOD1G37R mice, which is in line with a very slow disease progression that we report for a Swedish woman with ALS who is carrier of two mutant SOD1D90A alleles and two variant CHGBP413L and CHGBR458Q alleles. In contrast, overexpression of the common CHGBP413 allele in SOD1G37R mice did not affect disease onset but significantly accelerated disease progression and pathological changes. As in transgenic mice, the CHGBP413L allele conferred an earlier ALS disease onset in women of Japanese and French Canadian origins with less effect in men. Evidence is presented that the sex-dependent effects of CHGBL413 allelic variant in ALS may arise from enhanced neuronal expression of CHGB in females because of a sex-determining region Y element in the gene promoter. Thus, our results suggest that CHGB variants may act as modifiers of onset and progression in some ALS populations and especially in females because of higher expression levels compared to males.

Abstract 15325: Chromogranin B Levels are Increased in Myocardial Tissue in the Dyssynchronous Left Ventricle and Relate to Abnormalities in Regional Myocardial Deformation

Introduction: Left bundle branch block (LBBB) induces abnormal activation and deformation of the LV wall. Chromogranin B (CgB) levels are increased in myocardium and plasma of heart failure patients and are linked to cardiomyocyte Ca 2+ handling. Hypothesis: That CgB expression is increased in distinct LV regions during LBBB and may be related to regional deformation abnormalities. Methods: CgB and pro-B-type natriuretic peptide (proBNP) protein levels were measured in biopsies from septum and LV lateral wall in 6 dogs with chronic LBBB (16 weeks), 8 control animals, and in 8 dogs with LBBB that received cardiac resynchronization therapy (CRT) between 8 and 16 weeks after creation of LBBB. Regional myocardial strain was assessed by speckle tracking echocardiography, LV volumes by MRI, and hemodynamics were assessed by invasive pressure measurements (LV dP/dt max and min, tau , LVP max and min, and LV end-diastolic pressure). Results: LBBB animals had increased end-diastolic volumes (55±1 vs.45±4 mL, p=0.038) but normal LV ejection fraction (50±3 vs. 55±4 %, p=0.42) compared to control animals. CgB levels were increased in both septum (p<0.001) and LV lateral wall (p=0.01) in LBBB compared to controls, despite no changes in LV proBNP levels, and with the most prominent increment found in the septum (Figure). In LBBB+CRT animals, CgB levels were 36±18% (septum) and 50±11% (LV later wall) lower compared to LBBB animals, but this difference was not statistically significant. Septal CgB levels correlated with septal early systolic rebound stretch (r=0.76, p=0.017) and lateral wall CgB levels with lateral wall pre-ejection stretch (r=0.76, p=0.018), while no correlations were found with LV dimensions or indices of global hemodynamic function. Conclusion: Myocardial CgB expression was increased in the absence of elevated proBNP levels in LBBB animals with preserved systolic function. Local CgB levels appear to relate to abnormal local early-systolic mechanical loading.

PWE-215 An isolated abnormal chromogranin B is associated with pancreato-duodenal nets and the presence of liver metastases

Introduction Chromogranin B (CgB) is a soluble secretory protein like chromogranin A (CgA) that has been reported to be elevated in patients with neuroendocrine tumours (NETs) but is not routinely assessed. This study explores whether an abnormal CgB paired with a normal CgA provides any useful clinical information in NET patients. Method A prospective NET database (01/2007–11/2014) was interrogated for paired radioimmunoassay CgA (two assays; normal Results 1161 paired CgA and CgB results (479 patients) were retrieved. 51 patients had an isolated abnormal paired CgB (79 results; mean CgB result=2.68xULN); 2 patients were excluded as coding error. Primary sites were 24 pancreas, 9 small bowel, 4 rectal, 3 duodenal, 3 unknown, 2 duodenal-jejunal, 2 pre-sacral, 1 caecal and 1 lung. In 8/9 small bowel NETs, the CgB was raised in isolation on only one occasion on longitudinal testing. The tumour grades were 24 G1, 18 G2, 4 G3 and 3 unknown. Liver metastases were present in 38/49 patients. Conclusion An isolated abnormal paired CgB was observed in 11% of NET patients. In 59% of patients it was associated with a pancreatic or duodenal primary NET. In 78% liver metastases were present. Further assessment is required to establish the role of CgB when paired with CgA as a biomarker of clinical utility in the diagnosis, prognosis and therapeutic monitoring of NETs. Disclosure of interest None Declared.

Proteomic analyses reveal that loss of TDP-43 affects RNA processing and intracellular transport

Transactive response DNA-binding protein 43 (TDP-43) is a predominantly nuclear, ubiquitously expressed RNA and DNA-binding protein. It recognizes and binds to UG repeats and is involved in pre-mRNA splicing, mRNA stability and microRNA metabolism. TDP-43 is essential in early embryonic development but accumulates in cytoplasmic aggregates in amyotrophic lateral sclerosis (ALS) and tau-negative frontotemporal lobar degeneration (FTLD). It is not known yet whether cytoplasmic aggregates of TDP-43 are toxic or protective but they are often associated with a loss of TDP-43 from the nucleus and neurodegeneration may be caused by a loss of normal TDP-43 function or a gain of toxic function. Here we present a proteomic study to analyze the effect of loss of TDP-43 on the proteome. MS data are available via ProteomeXchange with identifier PXD001668. Our results indicate that TDP-43 is an important regulator of RNA metabolism and intracellular transport. We show that Ran-binding protein 1 (RanBP1), DNA methyltransferase 3 alpha (Dnmt3a) and chromogranin B (CgB) are downregulated upon TDP-43 knockdown. Subsequently, transportin 1 level is increased as a result of RanBP1 depletion. Improper regulation of these proteins and the subsequent disruption of cellular processes may play a role in the pathogenesis of the TDP-43 proteinopathies ALS and FTLD.

Genetic analysis of the cardiac methylome at single nucleotide resolution in a model of human cardiovascular disease.

Epigenetic marks such as cytosine methylation are important determinants of cellular and whole-body phenotypes. However, the extent of, and reasons for inter-individual differences in cytosine methylation, and their association with phenotypic variation are poorly characterised. Here we present the first genome-wide study of cytosine methylation at single-nucleotide resolution in an animal model of human disease. We used whole-genome bisulfite sequencing in the spontaneously hypertensive rat (SHR), a model of cardiovascular disease, and the Brown Norway (BN) control strain, to define the genetic architecture of cytosine methylation in the mammalian heart and to test for association between methylation and pathophysiological phenotypes. Analysis of 10.6 million CpG dinucleotides identified 77,088 CpGs that were differentially methylated between the strains. In F1 hybrids we found 38,152 CpGs showing allele-specific methylation and 145 regions with parent-of-origin effects on methylation. Cis-linkage explained almost 60% of inter-strain variation in methylation at a subset of loci tested for linkage in a panel of recombinant inbred (RI) strains. Methylation analysis in isolated cardiomyocytes showed that in the majority of cases methylation differences in cardiomyocytes and non-cardiomyocytes were strain-dependent, confirming a strong genetic component for cytosine methylation. We observed preferential nucleotide usage associated with increased and decreased methylation that is remarkably conserved across species, suggesting a common mechanism for germline control of inter-individual variation in CpG methylation. In the RI strain panel, we found significant correlation of CpG methylation and levels of serum chromogranin B (CgB), a proposed biomarker of heart failure, which is evidence for a link between germline DNA sequence variation, CpG methylation differences and pathophysiological phenotypes in the SHR strain. Together, these results will stimulate further investigation of the molecular basis of locally regulated variation in CpG methylation and provide a starting point for understanding the relationship between the genetic control of CpG methylation and disease phenotypes.

Chromogranins can be measured in samples from cats and dogs.

BackgroundMethods for objective evaluation of stress in animals are important, but clinically difficult. An alternative method to study the sympathetic activity may be to investigate Chromogranin A (CGA), Chromogranin B (CGB) and Secretogranin II (SG2). The aim of this study was to investigate the cross-reactivity of CGA, CGB and SG2 between man, cat and dog and to explore possibilities to measure these proteins in samples from cats and dogs.ResultsAdrenal gland extracts from feline and canine species were measured by region-specific radioimmunoassays in different dilution steps to explore possible inter species cross reactivity. High cross reactivity was found for cats in the CGA17-38, CGA324-337, CGA361-372, CGB and SG2 assays. High cross reactivity was found for dogs in the CGA17-38, CGA361-372, CGB and SN assays. The method measuring the intact CGA was not useful for measurements in cats and dogs.ConclusionsRegion-specific assays measuring defined parts of CGA, CGB and SG2 can be used for measurements in samples from cats and dogs. These results are promising and will allow for further studies of these proteins as possible clinical biomarkers in cats and dogs.

Co-expression network analysis of differentially expressed genes associated with metastasis in prolactin pituitary tumors.

The aim of the present study was to construct a co‑expression network of differently expressed genes (DEGs) in prolactin pituitary (PRL) tumor metastasis. The gene expression profile, GSE22812 was downloaded from the Gene Expression Omnibus database, and including five non‑invasive, twoinvasive and six aggressive‑invasive PRL tumor samples. Compared with non‑invasive samples, DEGs were identified in invasive and aggressive‑invasive samples using a limma package in Rlanguage. The expression values of DEGs were hierarchically clustered. Next, Gene Ontology (GO) function enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis of DEGs were performed via The Database for Annotation, Visualization and Integrated Discovery. Finally, gene pairs of DEGs between non‑invasive and aggressive‑invasive samples were identified using the Spearman cor() function in Rlanguage. Compared with the non‑invasive samples, 61 and 89 DEGs were obtained from invasive and aggressive‑invasive samples, respectively. Cluster analysis showed that fourgenes were shared by the two samples, including upregulated solute carrier family 2, facilitated glucose transporter member 11 (SLC2A11) and teneurin transmembrane protein 1 (TENM1) and downregulated importin 7 (IPO7) and chromogranin B (CHGB). In the invasive samples, the most significant GO terms responded to cyclic adenosine monophosphate and a glucocorticoid stimulus. However, this occurred in the cell cycle, and was in response to hormone stimulation in aggressive‑invasive samples. The co‑expression network of DEGs showed different gene pairs and modules, and SLC2A11 and CHGB occurred in two co‑expression networks within different co‑expressed pairs. In the present study, the co‑expression network was constructed using bioinformatics methods. SLC2A11, TENM1, IPO7 and CHGB are hypothesized to be closely associated with metastasis of PRL. Furthermore, CHGB and SLC2A11 may be significant in PRL tumor progression and serve as molecular biomarkers for PRL tumors. However, further investigation is required to confirm the current results.

The granin VGF promotes genesis of secretory vesicles, and regulates circulating catecholamine levels and blood pressure

Secretion of proteins and neurotransmitters from large dense core vesicles (LDCVs) is a highly regulated process. Adrenal LDCV formation involves the granin proteins chromogranin A (CgA) and chromogranin B (CgB); CgA- and CgB-derived peptides regulate catecholamine levels and blood pressure. We investigated function of the granin VGF (nonacronymic) in LDCV formation and the regulation of catecholamine levels and blood pressure. Expression of exogenous VGF in nonendocrine NIH 3T3 fibroblasts resulted in the formation of LDCV-like structures and depolarization-induced VGF secretion. Analysis of germline VGF-knockout mouse adrenal medulla revealed decreased LDCV size in noradrenergic chromaffin cells, increased adrenal norepinephrine and epinephrine content and circulating plasma epinephrine, and decreased adrenal CgB. These neurochemical changes in VGF-knockout mice were associated with hypertension. Germline knock-in of human VGF1-615 into the mouse Vgf locus rescued the hypertensive knockout phenotype, while knock-in of a truncated human VGF1-524 that lacks several C-terminal peptides, including TLQP-21, resulted in a small but significant increase in systolic blood pressure compared to hVGF1-615 mice. Finally, acute and chronic administration of the VGF-derived peptide TLQP-21 to rodents decreased blood pressure. Our studies establish a role for VGF in adrenal LDCV formation and the regulation of catecholamine levels and blood pressure.

Chromogranin B: intra‐ and extra‐cellular mechanisms to regulate catecholamine storage and release, in catecholaminergic cells and organisms

Chromogranin B (CHGB) is the major matrix protein in human catecholamine storage vesicles. CHGB genetic variation alters catecholamine secretion and blood pressure. Here, effective Chgb protein under-expression was achieved by siRNA in PC12 cells, resulting in ~ 48% fewer secretory granules on electron microscopy, diminished capacity for catecholamine uptake (by ~ 79%), and a ~ 73% decline in stores available for nicotinic cholinergic-stimulated secretion. In vivo, loss of Chgb in knockout mice resulted in a ~ 35% decline in chromaffin granule abundance and ~ 44% decline in granule diameter, accompanied by unregulated catecholamine release into plasma. Over-expression of CHGB was achieved by transduction of a CHGB-expressing lentivirus, resulting in ~ 127% elevation in CHGB protein, with ~ 122% greater abundance of secretory granules, but only ~ 14% increased uptake of catecholamines, and no effect on nicotinic-triggered secretion. Human CHGB protein and its proteolytic fragments inhibited nicotinic-stimulated catecholamine release by ~ 72%. One conserved-region CHGB peptide inhibited nicotinic-triggered secretion by up to ~ 41%, with partial blockade of cationic signal transduction. We conclude that bi-directional quantitative derangements in CHGB abundance result in profound changes in vesicular storage and release of catecholamines. When processed and released extra-cellularly, CHGB proteolytic fragments exert a feedback effect to inhibit catecholamine secretion, especially during nicotinic cholinergic stimulation.

The biochemical utility of chromogranin A, chromogranin B and cocaine- and amphetamine-regulated transcript for neuroendocrine neoplasia

Neuroendocrine neoplasia (NEN) is a heterogeneous group of tumours and often represents a therapeutic challenge to clinicians. The peptides chromogranin A (CgA), chromogranin B (CgB) and cocaine- and amphetamine-regulated transcript (CART) are widely distributed throughout the neuroendocrine system. CgA and CgB have been used as general NEN biomarkers for many years, while CART has only recently been identified. Of these biomarkers, CgA is the most commonly used. However, circulating CgA concentrations exhibit considerable intra-individual biological variation, are altered by proton pump inhibitors (PPIs) and somatostatin analogues and are elevated in non-NEN malignancies. Therefore, interpretation of CgA results must be in the context of these confounding factors. The effects of treatment and non-NEN conditions on circulating CgB and CART concentrations are less well understood. CgB is less affected by impaired renal function and PPIs than CgA; while, circulating CART concentrations lack a diurnal variation in humans and are more reliable markers of pancreatic NEN malignancy than CgA. The utility of circulating CgA measurements in NEN prognosis, surveillance and disease recurrence has been widely investigated. However, the utility of CgB and CART in NEN management is yet to be elucidated. Further studies are needed to establish whether CgB and CART are useful alternatives to CgA.

Genetic variation at the delta‐sarcoglycan (SGCD) locus elevates heritable sympathetic nerve activity in human twin pairs

The Syrian Cardiomyopathic Hamster (BIO-14.6/53.58 strains) model of cardiac failure, resulting from naturally occurring deletion at the SGCD (delta-sarcoglycan) locus, displays widespread disturbances in catecholamine metabolism. Rare Mendelian myopathy disorders of human SGCD occur, although common naturally occurring SGCD genetic variation has not been evaluated for effects on human norepinephrine (NE) secretion. This study investigated the effect of SGCD genetic variation on control of NE secretion in healthy twin pairs. Genetic associations profiled SNPs across the SGCD locus. Trait heritability (h(2)) and genetic covariance (pleiotropy; shared h(2)) were evaluated. Sympathochromaffin exocytosis in vivo was probed in plasma by both catecholamines and Chromogranin B (CHGB). Plasma NE is substantially heritable (p = 3.19E-16, at 65.2 ± 5.0% of trait variance), sharing significant (p < 0.05) genetic determination with circulating and urinary catecholamines, CHGB, eGFR, and several cardio-metabolic traits. Participants with higher pNE showed significant (p < 0.05) differences in several traits, including increased BP and hypertension risk factors. Peak SGCD variant rs1835919 predicted elevated systemic vascular compliance, without changes in specifically myocardial traits. We used a chimeric-regulated secretory pathway photoprotein (CHGA-EAP) to evaluate the effect of SGCD on the exocytotic pathway in transfected PC12 cells; in transfected cells, expression of SGCD augmented CHGA trafficking into the exocytotic regulated secretory pathway. Thus, our investigation determined human NE secretion to be a highly heritable trait, influenced by common genetic variation within the SGCD locus. Circulating NE aggregates with BP and hypertension risk factors. In addition, coordinate NE and CHGB elevation by rs1835919 implicates exocytosis as the mechanism of release.

The role of chromogranin B in an animal model of multiple sclerosis

Chromogranin B (CGB) is a high capacity, low affinity calcium binding protein in the endoplasmic reticulum (ER) that binds to the inositol 1,4,5 trisphosphate receptor (InsP3R) and amplifies calcium release from ER stores. Recently, it was discovered that levels of CGB-derived peptides are decreased in the cerebrospinal fluid of multiple sclerosis (MS) patients. One of the mechanisms by which neurodegeneration in MS is thought to occur is through increased levels of intra-axonal calcium. The combination of excess intracellular calcium and dysregulated levels of CGB in MS led us to hypothesize that CGB may be involved in MS pathophysiology. Here, we show in a mouse model of MS that CGB levels are elevated in neurons prior to onset of symptoms. Once symptoms develop, CGB protein levels increase with disease severity. Additionally, we show that elevated levels of CGB may have a role in the pathophysiology of MS and suggest that the initial elevation of CGB, prior to symptom onset, is due to inflammatory processes. Upon development of symptoms, CGB accumulation in neurons results from decreased ubiquitination and decreased secretion. Furthermore, we show that calpain activity is increased and levels of InsP3R are decreased. From these results, we suggest that the elevated levels of CGB and altered InsP3R levels may contribute to the axonal/neuronal damage and dysregulated calcium homeostasis observed in MS. Additionally, we propose that CGB can be a biomarker that predicts the onset and severity of disease in patients with MS.

Large-scale Identification of Endogenous Secretory Peptides Using Electron Transfer Dissociation Mass Spectrometry

Mass spectrometry-based unbiased analysis of the full complement of secretory peptides is expected to facilitate the identification of unknown biologically active peptides. However, tandem MS sequencing of endogenous peptides in their native form has proven difficult because they show size heterogeneity and contain multiple internal basic residues, the characteristics not found in peptide fragments produced by in vitro digestion. Endogenous peptides remain largely unexplored by electron transfer dissociation (ETD), despite its widespread use in bottom-up proteomics. We used ETD, in comparison to collision induced dissociation (CID), to identify endogenous peptides derived from secretory granules of a human endocrine cell line. For mass accuracy, both MS and tandem MS were analyzed on an Orbitrap. CID and ETD, performed in different LC-MS runs, resulted in the identification of 795 and 569 unique peptides (ranging from 1000 to 15000 Da), respectively, with an overlap of 397. Peptides larger than 3000 Da accounted for 54% in CID and 46% in ETD identifications. Although numerically outperformed by CID, ETD provided more extensive fragmentation, leading to the identification of peptides that are not reached by CID. This advantage was demonstrated in identifying a new antimicrobial peptide from neurosecretory protein VGF (non-acronymic), VGF[554-577]-NH2, or in differentiating nearly isobaric peptides (mass difference less than 2 ppm) that arise from alternatively spliced exons of the gastrin-releasing peptide gene. CID and ETD complemented each other to add to our knowledge of the proteolytic processing sites of proteins implicated in the regulated secretory pathway. An advantage of the use of both fragmentation methods was also noted in localization of phosphorylation sites. These findings point to the utility of ETD mass spectrometry in the global study of endogenous peptides, or peptidomics.

Increased Fecal Levels of Chromogranin A, Chromogranin B, and Secretoneurin in Collagenous Colitis

Interactions between the enteric nervous system and the immune system are suggested to play an important role in the pathophysiology of inflammatory bowel disease (IBD). This study aims to determine if chromogranin A (CgA), chromogranin B (CgB), and secretoneurin (SN) are detectable in feces (F) from patients with collagenous colitis (CC) and to compare the levels found in patients with ulcerative colitis (UC) and Crohn's disease (CD) before and during treatment. Patients with CC (n = 12) were studied before and after 3, 7, 28, and 56 days of treatment. Patients with IBD (UC, n = 21; CD, n = 11) were studied before and after 28 and 56 days of treatment. Clinical data were recorded, and fecal samples were collected at each occasion. F-CgA, F-CgB, and F-SN were measured by RIA. Eleven patients with CC, 21 with UC, and 10 with CD achieved remission. On inclusion, CC patients had higher levels of F-CgA, F-CgB, and F-SN than patients with IBD and controls. Patients with IBD expressed markedly lower levels of F-SN than controls. During treatment, F-SN in CC patients decreased to control levels but remained low in IBD patients. No change was found in F-CgA or F-CgB in any of the groups. In conclusion, CgA, CgB, and SN are detectable in feces, and CC patients express higher values than patients with IBD and controls. During treatment, F-SN decreased to control levels in CC. These findings suggest that the enteric nervous system is clearly involved in the pathophysiology of CC.