Peptide products of the neurotrophin-inducible gene vgf are produced in human neuroendocrine cells from early development and increase in hyperplasia and neoplasia

VGF: A prospective biomarker and therapeutic target for neuroendocrine and nervous system disorders

Neuroendocrine regulatory polypeptide VGF (nerve growth factor inducible) was firstly found in the rapid induction of nerve growth factor on PC12 cells. It was selectively distributed in neurons and many neuroendocrine tissues. This paper reviewed the latest literatures on the gene structure, transcriptional regulation, protein processing, distribution and potential receptors of VGF. The neuroendocrine roles of VGF and its derived polypeptides in regulating energy, water electrolyte balance, circadian rhythm and reproductive activities were also summarized. Furthermore, based on the experimental evidence in vivo and in vitro, dysregulation of VGF in different neuroendocrine diseases and the possible mechanism mediated by VGF polypeptides were discussed. We next discussed the potential as the clinical diagnosis and therapy for VGF related diseases in the future.

Neuronal survival factor VGF promotes chemoresistance and predicts poor prognosis in lung cancers with neuroendocrine feature

High-grade neuroendocrine tumors (NETs) of the lung consist of small-cell lung cancer (SCLC) and large-cell neuroendocrine carcinoma (LCNEC). Both exhibit aggressive malignancy with poor prognosis. The transformation of lung adenocarcinoma (ADC) to SCLC or LCNEC also contributes to acquired resistance to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs). Despite initially being responsive to chemotherapy, high-grade NET patients inevitably develop drug resistance; thus, novel therapeutic targets are urgently needed for these patients. This study reported that VGF (nerve growth factor inducible), a factor mainly expressed in neurons during neural development, is highly expressed in SCLC and LCNEC as well as in a subset of ADCs, whereas targeting VGF attenuates cancer cell growth and tumor formation. High VGF expression was associated with advanced stage SCLC and predicted poor prognosis in lung ADC. In addition, EGFR-TKI selection enriched VGF expression in TKI-resistant ADC under epigenetic control. The VGF locus possessed the HDAC1 binding site, and treatment of ADC cells with the HDAC1 inhibitor induced VGF expression. High VGF expression was associated with chemoresistance, and silencing VGF induced BMF and BCL2L11 expression and rendered lung cancer cells sensitive to chemotherapy drugs. These findings suggested the potential of VGF as a prognostic factor and therapeutic target in lung cancers with neuroendocrine feature. This article is protected by copyright. All rights reserved.

Evaluation of VGF peptides as potential anti-obesity candidates in pre-clinical animal models

VGF is a peptide precursor expressed in neuroendocrine cells that is suggested to play a role in the regulation of energy homeostasis. VGF is proteolytically cleaved to yield multiple bioactive peptides. However, the specific actions of VGF-derived peptides on energy homeostasis remain unclear. The aim of the present work was to investigate the role of VGF-derived peptides in energy homeostasis and explore the pharmacological actions of VGF-derived peptides on body weight in preclinical animal models. VGF-derived peptides (NERP-1, NERP-2, PGH-NH₂, PGH-OH, NERP-4, TLQP-21, TLQP-30, TLQP-62, HHPD-41, AQEE-30, and LQEQ-19) were synthesized and screened for their ability to affect neuronal activity in vitro on hypothalamic brain slices and modulate food intake and energy expenditure after acute central administration in vivo. In addition, the effects of NERP-1, NERP-2, PGH-NH₂, TLQP-21, TLQP-62, and HHPD-41 on energy homeostasis were studied after chronic central infusion. NERP-1, PGH-NH₂, HHPD-41, and TLQP-62 increased the functional activity of hypothalamic neuronal networks. However, none of the peptides altered energy homeostasis after either acute or chronic ICV administration. The present data do not support the potential use of the tested VGF-derived peptides as novel anti-obesity drug candidates.

Generation and characterization of CRISPR/Cas9-mediated MEN1 knockout BON1 cells: a human pancreatic neuroendocrine cell line

Among patients with the rare diagnosis of pancreatic neuroendocrine tumor (P-NET), a substantial proportion suffer from the inherited cancer syndrome multiple endocrine neoplasia type 1 (MEN1), which is caused by germline mutations of the MEN1 suppressor gene. Somatic mutations and loss of the MEN1 protein (menin) are frequently also found in sporadic P-NETs. Thus, a human neuroendocrine pancreatic cell line with biallelic inactivation of MEN1 might be of value for studying tumorigenesis. We used the polyclonal human P-NET cell line BON1, which expresses menin, serotonin, chromogranin A and neurotensin, to generate a monoclonal stable MEN1 knockout BON1 cell line (MEN1-KO-BON1) by CRISPR/Cas9 editing. Changes in morphology, hormone secretion, and proliferation were analyzed, and proteomics were assessed using nanoLC-MS/MS and Ingenuity Pathway Analysis (IPA). The menin-lacking MEN1-KO-BON1 cells had increased chromogranin A production and were smaller, more homogenous, rounder and grew faster than their control counterparts. Proteomic analysis revealed 457 significantly altered proteins, and IPA identified biological functions related to cancer, e.g., posttranslational modification and cell death/survival. Among 39 proteins with at least a two-fold difference in expression, twelve are relevant in glucose homeostasis and insulin resistance. The stable monoclonal MEN1-KO-BON1 cell line was found to have preserved neuroendocrine differentiation, increased proliferation, and an altered protein profile.

Intricacies of the Molecular Machinery of Catecholamine Biosynthesis and Secretion by Chromaffin Cells of the Normal Adrenal Medulla and in Pheochromocytoma and Paraganglioma

The adrenal medulla is composed predominantly of chromaffin cells producing and secreting the catecholamines dopamine, norepinephrine, and epinephrine. Catecholamine biosynthesis and secretion is a complex and tightly controlled physiologic process. The pathways involved have been extensively studied, and various elements of the underlying molecular machinery have been identified. In this review, we provide a detailed description of the route from stimulus to secretion of catecholamines by the normal adrenal chromaffin cell compared to chromaffin tumor cells in pheochromocytomas. Pheochromocytomas are adrenomedullary tumors that are characterized by uncontrolled synthesis and secretion of catecholamines. This uncontrolled secretion can be partly explained by perturbations of the molecular catecholamine secretory machinery in pheochromocytoma cells. Chromaffin cell tumors also include sympathetic paragangliomas originating in sympathetic ganglia. Pheochromocytomas and paragangliomas are usually locally confined tumors, but about 15% do metastasize to distant locations. Histopathological examination currently poorly predicts future biologic behavior, thus long term postoperative follow-up is required. Therefore, there is an unmet need for prognostic biomarkers. Clearer understanding of the cellular mechanisms involved in the secretory characteristics of pheochromocytomas and sympathetic paragangliomas may offer one approach for the discovery of novel prognostic biomarkers for improved therapeutic targeting and monitoring of treatment or disease progression.

lncRNA H19 binds VGF and promotes pNEN progression via PI3K/AKT/CREB signaling

Pancreatic neuroendocrine neoplasms (pNENs) are endocrine tumors arising in pancreas and is the most common neuroendocrine tumors. Mounting evidence indicates lncRNA H19 could be a determinant of tumor progression. However, the expression and mechanism of H19 and the relevant genes mediated by H19 in pNENs remain undefined. Microarray analysis was conducted to identify the differentially expressed lncRNAs in pNENs. H19 expression was analyzed in 39 paired pNEN tissues by qPCR. The biological role of H19 was determined by functional experiments. RNA pulldown, mass spectroscopy and RNA immunoprecipitation were performed to confirm the interaction between H19 and VGF. RNA-seq assays were performed after knockdown H19 or VGF. H19 was significantly upregulated in pNEN tissues with malignant behaviors, and the upregulation predicted poor prognosis in pNENs. In vitro and in vivo data showed that H19 overexpression promoted tumor growth and metastasis, whereas H19 knockdown led to the opposite phenotypes. H19 interacted with VGF, which was significantly upregulated in pNENs, and higher VGF expression was markedly related to poor differentiation and advanced stage. Furthermore, VGF was downregulated when H19 was knocked down, and VGF promoted cell proliferation, migration and invasion. Mechanistic investigations revealed that H19 activated PI3K/AKT/CREB signaling and promoted pNEN progression by interacting with VGF. These findings indicate that H19 is a promising prognostic factor in pNENs with malignant behaviors and functions as an oncogene via the VGF-mediated PI3K/AKT/CREB pathway. In addition, our study implies that VGF may also serve as a candidate prognostic biomarker and therapeutic target in pNENs.

Perineural invasion in pancreatic cancer: proteomic analysis and in vitro modelling

Perineural invasion (PNI) is a common and characteristic feature of pancreatic ductal adenocarcinoma (PDAC) that is associated with poor prognosis, tumor recurrence, and generation of pain. However, the molecular alterations in cancer cells and nerves within PNI have not previously been comprehensively analyzed. Here, we describe our proteomic analysis of the molecular changes underlying neuro-epithelial interactions in PNI using liquid chromatography-mass spectrometry (LC-MS/MS) in microdissected PNI and non-PNI cancer, as well as in invaded and noninvaded nerves from formalin-fixed, paraffin-embedded PDAC tissues. In addition, an in vitro model of PNI was developed using a co-culture system comprising PDAC cell lines and PC12 cells as the neuronal element. The overall proteomic profiles of PNI and non-PNI cancer appeared largely similar. In contrast, upon invasion by cancer cells, nerves demonstrated widespread plasticity with a pattern consistent with neuronal injury. The up-regulation of SCG2 (secretogranin II) and neurosecretory protein VGF (nonacronymic) in invaded nerves in PDAC tissues was further validated using immunohistochemistry. The tested PDAC cell lines were found to be able to induce neuronal plasticity in PC12 cells in our in vitro established co-culture model. Changes in expression levels of VGF, as well as of two additional proteins previously reported to be overexpressed in PNI, Nestin and Neuromodulin (GAP43), closely recapitulated our proteomic findings in PDAC tissues. Furthermore, induction of VGF, while not necessary for PC12 survival, mediated neurite extension induced by PDAC cell lines. In summary, here we report the proteomic alterations underlying PNI in PDAC and confirm that PDAC cells are able to induce neuronal plasticity. In addition, we describe a novel, simple, and easily adaptable co-culture model for in vitro study of neuro-epithelial interactions.

Heat Stress and Thermal Ablation Induce Local Expression of Nerve Growth Factor Inducible (VGF) in Hepatocytes and Hepatocellular Carcinoma: Preclinical and Clinical Studies

The purposes of this study were to test the hypothesis that heat stress and hepatic thermal ablation induce nerve growth factor inducible (VGF) and to determine intrahepatic versus systemic VGF expression induced by thermal ablation in vivo and in patients. Hepatocytes and HCC cells were subjected to moderate (45°C) or physiologic (37°C) heat stress for 10 min and assessed for VGF expression at 0-72 h post-heat stress (n ≥ 3 experiments). Orthotopic N1S1 HCC-bearing rats were randomized to sham or laser thermal ablation (3 W × 90 s), and liver/serum was harvested at 0-7 days postablation for analysis of VGF expression (n ≥ 6 per group). Serum was collected from patients undergoing thermal ablation for HCC (n = 16) at baseline, 3-6, and 18-24 h postablation and analyzed for VGF expression. Data were analyzed using ordinary or repeated-measures one-way analysis of variance and post hoc pairwise comparison with Dunnett's test. Moderate heat stress induced time-dependent VGF mRNA (3- to 15-fold; p < 0.04) and protein expression and secretion (3.1- to 3.3-fold; p < 0.05). Thermal ablation induced VGF expression at the hepatic ablation margin at 1 and 3 days postablation but not remote from the ablation zone or distant intrahepatic lobe. There was no detectable serum VGF following hepatic thermal ablation in rats and no increase in serum VGF following HCC thermal ablation in patients at 3-6 and 18-24 h postablation compared to baseline (0.71- and 0.63-fold; p = 0.27 and p = 0.16, respectively). Moderate heat stress induces expression and secretion of VGF in HCC cells and hepatocytes in vitro, and thermal ablation induces local intrahepatic but not distant intrahepatic or systemic VGF expression in vivo.

A New Possible Lung Cancer Marker: VGF Detection from the Conditioned Medium of Pulmonary Large Cell Neuroendocrine Carcinoma–Derived Cells using Secretome Analysis

The prognosis of malignant neuroendocrine tumors of the lung is known to be very poor. Aiming to identify new markers of pulmonary neuroendocrine tumors in early stages and also differential diagnostic markers between large cell neuroendocrine carcinoma and small cell lung cancer, we comprehensively analyzed peptides which were secreted into conditioned medium by LCN1, a large cell neuroendocrine carcinoma cell line. Specific peaks in conditioned medium but not in used medium alone were detected using matrix-associated laser desorption/ionization time of flight mass spectrometry. Two peptide fragments of 40 and 19 amino acid residues were identified by matrix-associated laser desorption/ionization time of flight mass spectrometry. These two fragments were demonstrated to be parts of VGF nerve growth factor inducible (VGF), which is usually expressed in nerve cells or neuroendocrine cells. RT-PCR analysis of lung cancer cell lines showed that VGF mRNA was expressed only in neuroendocrine carcinoma–derived cells. Our data suggest that VGF can be used as a novel serological diagnostic marker of pulmonary neuroendocrine tumors.

The human VGF-derived bioactive peptide TLQP-21 binds heat shock 71 kDa protein 8 (HSPA8)on the surface of SH-SY5Y cells

VGF (non-acronymic)is a secreted chromogranin/secretogranin that gives rise to a number of bioactive peptides by a complex proteolysis mechanism. VGF-derived peptides exert an extensive array of biological effects in energy metabolism, mood regulation, pain, gastric secretion function, reproduction and, perhaps, cancer. It is therefore surprising that very little is known about receptors and binding partners of VGF-derived peptides and their downstream molecular mechanisms of action. Here, using affinity chromatography and mass spectrometry-based protein identification, we have identified the heat shock cognate 71 kDa protein A8 (HSPA8)as a binding partner of human TLQP-21 on the surface of human neuroblastomaSH-SY5Y cells. Binding of TLQP-21 to membrane associated HSPA8 in live SH-SY5Y cells was further supported by cross-linking to live cells. Interaction between HSPA8 and TLQP-21 was confirmed in vitro by label-free Dynamic Mass Redistribution (DMR) studies. Furthermore, molecular modeling studies show that TLQP-21 can be docked into the HSPA8 peptide binding pocket. Identification of HSPA8 as a cell surface binding partner of TLQP-21 opens new avenues to explore the molecular mechanisms of its physiological actions, and of pharmacological modulation thereof.

Expression of Neuroendocrine Factor VGF in Lung Cancer Cells Confers Resistance to EGFR Kinase Inhibitors and Triggers Epithelial-to-Mesenchymal Transition

Mutations in EGFR drive tumor growth but render tumor cells sensitive to treatment with EGFR tyrosine kinase inhibitors (TKI). Phenotypic alteration in epithelial-to-mesenchymal transition (EMT) has been linked to the TKI resistance in lung adenocarcinoma. However, the mechanism underlying this resistance remains unclear. Here we report that high expression of a neuroendocrine factor termed VGF induces the transcription factor TWIST1 to facilitate TKI resistance, EMT, and cancer dissemination in a subset of lung adenocarcinoma cells. VGF silencing resensitized EGFR-mutated lung adenocarcinoma cells to TKI. Conversely, overexpression of VGF in sensitive cells conferred resistance to TKIs and induced EMT, increasing migratory and invasive behaviors. Correlation analysis revealed a significant association of VGF expression with advanced tumor grade and poor survival in patients with lung adenocarcinoma. In a mouse xenograft model of lung adenocarcinoma, suppressing VGF expression was sufficient to attenuate tumor growth. Overall, our findings show how VGF can confer TKI resistance and trigger EMT, suggesting its potential utility as a biomarker and therapeutic target in lung adenocarcinoma. Cancer Res; 77(11); 3013-26. ©2017 AACR.

VGF Protein and Its C-Terminal Derived Peptides in Amyotrophic Lateral Sclerosis: Human and Animal Model Studies

VGF mRNA is widely expressed in areas of the nervous system known to degenerate in Amyotrophic Lateral Sclerosis (ALS), including cerebral cortex, brainstem and spinal cord. Despite certain VGF alterations are reported in animal models, little information is available with respect to the ALS patients. We addressed VGF peptide changes in fibroblast cell cultures and in plasma obtained from ALS patients, in parallel with spinal cord and plasma samples from the G93A-SOD1 mouse model. Antisera specific for the C-terminal end of the human and mouse VGF proteins, respectively, were used in immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), while gel chromatography and HPLC/ESI-MS/MS were used to identify the VGF peptides present. Immunoreactive VGF C-terminus peptides were reduced in both fibroblast and plasma samples from ALS patients in an advanced stage of the disease. In the G93A-SOD1 mice, the same VGF peptides were also decreased in plasma in the late-symptomatic stage, while showing an earlier down-regulation in the spinal cord. In immunohistochemistry, a large number of gray matter structures were VGF C-terminus immunoreactive in control mice (including nerve terminals, axons and a few perikarya identified as motoneurons), with a striking reduction already in the pre-symptomatic stage. Through gel chromatography and spectrometry analysis, we identified one form likely to be the VGF precursor as well as peptides containing the NAPP- sequence in all tissues studied, while in the mice and fibroblasts, we revealed also AQEE- and TLQP- peptides. Taken together, selective VGF fragment depletion may participate in disease onset and/or progression of ALS.

Characterization of Gonadotrope Secretoproteome Identifies Neurosecretory Protein VGF-derived Peptide Suppression of Follicle-stimulating Hormone Gene Expression

Reproductive function is controlled by the pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH), which regulates the expression of the gonadotropins luteinizing hormone and FSH in pituitary gonadotropes. Paradoxically, Fshb gene expression is maximally induced at lower frequency GnRH pulses, which provide a very low average concentration of GnRH stimulation. We studied the role of secreted factors in modulating gonadotropin gene expression. Inhibition of secretion specifically disrupted gonadotropin subunit gene regulation but left early gene induction intact. We characterized the gonadotrope secretoproteome and global mRNA expression at baseline and after Gα_s knockdown, which has been found to increase Fshb gene expression (1). We identified 1077 secreted proteins or peptides, 19 of which showed mRNA regulation by GnRH or/and Gα_s knockdown. Among several novel secreted factors implicated in Fshb gene regulation, we focused on the neurosecretory protein VGF. Vgf mRNA, whose gene has been implicated in fertility (2), exhibited high induction by GnRH and depended on Gα_s In contrast with Fshb induction, Vgf induction occurred preferentially at high GnRH pulse frequency. We hypothesized that a VGF-derived peptide might regulate Fshb gene induction. siRNA knockdown or extracellular immunoneutralization of VGF augmented Fshb mRNA induction by GnRH. GnRH stimulated the secretion of the VGF-derived peptide NERP1. NERP1 caused a concentration-dependent decrease in Fshb gene induction. These findings implicate a VGF-derived peptide in selective regulation of the Fshb gene. Our results support the concept that signaling specificity from the cell membrane GnRH receptor to the nuclear Fshb gene involves integration of intracellular signaling and exosignaling regulatory motifs.

Chronic effects of neuroendocrine regulatory peptide (NERP-1 and -2) on insulin secretion and gene expression in pancreatic β-cells

Neuroendocrine regulatory peptides (NERP-1 and -2) are novel amidated peptides derived from VGF, a polypeptide secreted from neurons and endocrine cells through a regulated pathway. Dr. Nakazato Masamitsu reported that NERP-1 and -2 may have a local modulator function on the human endocrine system, and clearly showed expression of NERP-1 and -2 in human pancreas islets. Based on these data, we investigated the alteration of insulin secretion, insulin granule-related protein, and pancreas-specific transcription factors in response to NERPs expression. We confirmed the expression of NERP-1 and -2 in the pancreas of a human diabetes patient, in addition to diabetic animal models. When INS1 cells and primary rat islets were incubated with 10nM NERPs for 3 days, glucose-stimulated insulin secretion levels were blunted by NERP-1 and -2. The number of insulin granules released from the readily releasable pool, which is associated with the first phase of glucose-stimulated insulin release, was decreased by NERP-1 and -2. Insulin granule-related proteins and mRNAs were down-regulated by NERP-2 treatment. NERP-2 decreased the expression of BETA2/NeuroD and insulin and controlled the nucleo-cytoplasmic translocation of FOXO1 and Pdx-1. We observed that NERP-2 levels were dramatically increased in diabetic pancreas. In conclusion, NERP-2 may play an important role in insulin secretion through the regulation of insulin secretory granules and β-cell transcription factors. In addition, NERP-2 expression is increased in diabetic conditions. Therefore, we suggest that NERPs may be potent endogenous suppressors of glucose-dependent insulin secretion.

Search for neuro-endocrine markers (chromogranin A, synaptophysin and VGF) in breast cancers. An integrated approach using immunohistochemistry and gene expression profiling

Discordant data are reported in the literature on the definition, incidence and clinical features of neuroendocrine (NE) carcinomas of the breast. This tumour entity is currently assessed by immunohistochemistry (IHC) detecting "general" NE markers such as chromogranin A (CHGA) and synaptophysin (SYP), but other markers have been considered as well. In the present study, in addition to CHGA and SYP, we investigated the expression of VGF, a neurotrophin-inducible gene, which is emerging as a new specific NE marker. In order to evaluate the differential expression of these neuro-endocrine markers in breast cancers, we conducted parallel immunohistochemical and gene expression analyses, using PCR, gene array and real-time quantitative PCR procedures. Data obtained in 28 cases were further validated with a meta-analysis of published datasets of 103 breast cancer cases. The value of IHC positivity (irrespective of the percentage of positive cells) was confirmed by over-expression of the related gene. However, the genetic approach emerged as more sensitive, showing over-expression of NE markers in a subset of IHC-negative carcinomas. In conclusion, the present study confirms, by a novel approach, the occurrence of NE differentiation in breast cancers. Over-expression of one or more NE marker (CHGA and/or SYP and/or VGF) characterizes a significant fraction (approximately 10 %) of infiltrative breast cancers.

Mass spectrometry identification of granins and other proteins secreted by neuroblastoma cells

We used mass spectrometry-based protein identification to determine the presence of granins and other proteins in the mouse neuroblastoma secretome. We detected polypeptides derived from four members of the granin family: chromogranin A, chromogranin B, secretogranin III, and VGF. Many of them are derived from previously described biologically active regions; however, for VGF and CgB, we detected peptides not related to known bioactivities. Along with granins, we identified 115 other proteins secreted by mouse neuroblastoma cells, belonging to different functional categories. Fifty-six out of 119 detected proteins possess the signal fragments required for translocation into endoplasmic reticulum. Sequences of remaining 63 proteins were analyzed using SecretomeP algorithm to determine probability of nonclassical secretion. Identified proteins are involved in the regulation of cell cycle, proliferation, apoptosis, angiogenesis, proteolysis, and cell adhesion.

The extended granin family: structure, function, and biomedical implications

The chromogranins (chromogranin A and chromogranin B), secretogranins (secretogranin II and secretogranin III), and additional related proteins (7B2, NESP55, proSAAS, and VGF) that together comprise the granin family subserve essential roles in the regulated secretory pathway that is responsible for controlled delivery of peptides, hormones, neurotransmitters, and growth factors. Here we review the structure and function of granins and granin-derived peptides and expansive new genetic evidence, including recent single-nucleotide polymorphism mapping, genomic sequence comparisons, and analysis of transgenic and knockout mice, which together support an important and evolutionarily conserved role for these proteins in large dense-core vesicle biogenesis and regulated secretion. Recent data further indicate that their processed peptides function prominently in metabolic and glucose homeostasis, emotional behavior, pain pathways, and blood pressure modulation, suggesting future utility of granins and granin-derived peptides as novel disease biomarkers.

VGF: an inducible gene product, precursor of a diverse array of neuro-endocrine peptides and tissue-specific disease biomarkers

The vgf gene (non-acronymic) is induced in vivo by neurotrophins including Nerve Growth Factor (NGF), Brain Derived Growth Factor (BDNF) and Glial Derived Growth Factor (GDNF), by synaptic activity and by homeostatic and other stimuli. Post-translational processing of a single VGF precursor gives raise to a varied multiplicity of neuro-endocrine peptides, some of which are secreted upon stimulation both in vitro and in vivo. Several VGF peptides, accounting for ∼20% of the VGF precursor sequence, have shown biological roles including regulation of food intake, energy balance, reproductive and homeostatic mechanisms, synaptic strengthening, long-term potentiation (LTP) and anti-depressant activity. From a further ∼50% of VGF derive multiple "fragments", largely identified in the human cerebro-spinal fluid by proteomic studies searching for disease biomarkers. These represent an important starting point for discovery of further VGF products relevant to neuronal brain functions, as well as to neurodegenerative and psychiatric disease conditions. A distinct feature of VGF peptides is their cell type specific diversity in all neuroendocrine organs studied so far. Selective differential profiles are found across the cell populations of pituitary, adrenal medulla and pancreatic islets, and in gastric neuroendocrine as well as some further mucosal cells, and are yet to be investigated in neuronal systems. At the same time, specific VGF peptide/s undergo selective modulation in response to organ or cell population relevant stimuli. Such pattern argues for a multiplicity of roles for VGF peptides, including endocrine functions, local intercellular communication, as well as the possible mediation of intracellular mechanisms.

Characterization of the mechanisms involved in the gastric antisecretory effect of TLQP-21, a vgf-derived peptide, in rats

TLQP-21, a vgf-derived peptide modulates gastric emptying and prevents ethanol-induced gastric lesions in rats. However, it remains to be studied whether or not TLQP-21 affects gastric acid secretion. In this study, we evaluated the effects of central (0.8-8 nmol/rat) or peripheral (48-240 nmol/kg, intraperitoneally) TLQP-21 administration on gastric acid secretion in pylorus-ligated rats. The mechanisms involved in such activity were also examined. Central TLQP-21 injection significantly reduced gastric acid volume and dose-dependently inhibited total acid output (ED(50) = 2.71 nmol), while peripheral TLQP-21 administration had no effect. The TLQP-21 antisecretory activity was prevented by cysteamine (300 mg/kg, subcutaneously), a depletor of somatostatin, by indomethacin (0.25 mg/rat, intracerebroventricularly), a non-selective cyclooxygenase inhibitor, and by functional ablation of sensory nerves by capsaicin. We conclude that TLQP-21 could be considered a new member of the large group of regulatory peptides affecting gastric acid secretion. The central inhibitory effect of TLQP-21 on gastric acid secretion is mediated by endogenous somatostatin and prostaglandins and requires the integrity of sensory nerve fibres.

Proteomics of dense core secretory vesicles reveal distinct protein categories for secretion of neuroeffectors for cell-cell communication

Regulated secretion of neurotransmitters and neurohumoral factors from dense core secretory vesicles provides essential neuroeffectors for cell-cell communication in the nervous and endocrine systems. This study provides comprehensive proteomic characterization of the categories of proteins in chromaffin dense core secretory vesicles that participate in cell-cell communication from the adrenal medulla. Proteomic studies were conducted by nano-HPLC Chip MS/MS tandem mass spectrometry. Results demonstrate that these secretory vesicles contain proteins of distinct functional categories consisting of neuropeptides and neurohumoral factors, protease systems, neurotransmitter enzymes and transporters, receptors, enzymes for biochemical processes, reduction/oxidation regulation, ATPases, protein folding, lipid biochemistry, signal transduction, exocytosis, calcium regulation, as well as structural and cell adhesion proteins. The secretory vesicle proteomic data identified 371 proteins in the soluble fraction and 384 membrane proteins, for a total of 686 distinct secretory vesicle proteins. Notably, these proteomic analyses illustrate the presence of several neurological disease-related proteins in these secretory vesicles, including huntingtin interacting protein, cystatin C, ataxin 7, and prion protein. Overall, these findings demonstrate that multiple protein categories participate in dense core secretory vesicles for production, storage, and secretion of bioactive neuroeffectors for cell-cell communication in health and disease.

Distribution of VGF peptides in the human cortex and their selective changes in Parkinson's and Alzheimer's diseases

VGF mRNA and its precursor-derived products are selectively expressed in certain neurons and promptly respond to neurotrophins and to neural/electrical activity. Proteomic studies have previously revealed a reduction in some VGF peptides in the cerebrospinal fluid of patients affected by Alzheimer's disease and other conditions, suggesting their potential diagnostic and clinical significance. As the presence of VGF peptides within the human cortex has been somewhat elucidated, they were studied postmortem in the frontal, parietal, and temporal cortex areas of control subjects and patients affected by Parkinson's disease, and in parietal cortex samples from patients with Alzheimer's disease. We raised antibodies to the C-/N-terminal portions of the proVGF precursor protein, to the TPGH and TLQP sequences and to the neuroendocrine regulatory peptide (NERP)-1, all used for enzyme-linked immunosorbent assay coupled with gel chromatography and for immunohistochemistry. In the control brain samples, the levels of TPGH and C-terminus peptides were about 130-200 and 700-2000 pmol g⁻¹, respectively, the N-terminus and NERP-1 peptides were less represented (about 10-30 and 4-20 pmol g⁻¹, respectively), and the TLQP peptides were below detection limits. Upon gel chromatography, the VGF antisera mainly revealed small molecular weight forms (i.e. about 0.8-1.3 kDa), whereas VGF immunolocalisation was found within different types of neuron in rat and bovine brain cortices. In the Parkinson's disease samples, a clear-cut decrease was revealed in the parietal cortex only, exclusively for TPGH and NERP-1 peptides, whereas in the Alzheimer's disease samples, a reduction in all of the VGF peptides was shown. The results suggest the involvement of VGF in the physiological or pathophysiological mechanisms occurring in the parietal cortex of patients with Parkinson's and Alzheimer's diseases.

Granins and their derived peptides in normal and tumoral chromaffin tissue: Implications for the diagnosis and prognosis of pheochromocytoma

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Typical clinical manifestations are sustained or paroxysmal hypertension, severe headaches, palpitations and sweating resulting from hormone excess. However, their presentation is highly variable and can mimic many other diseases. The diagnosis of pheochromocytomas depends mainly upon the demonstration of catecholamine excess by 24-h urinary catecholamines and metanephrines or plasma metanephrines. Occurrence of malignant pheochromocytomas can only be asserted by imaging of metastatic lesions, which are associated with a poor survival rate. The characterization of tissue, circulating or genetic markers is therefore crucial for the management of these tumors. Proteins of the granin family and their derived peptides are present in dense-core secretory vesicles and secreted into the bloodstream, making them useful markers for the identification of neuroendocrine cells and neoplasms. In this context, we will focus here on reviewing the distribution and characterization of granins and their processing products in normal and tumoral chromaffin cells, and their clinical usefulness for the diagnosis and prognosis of pheochromocytomas. It appears that, except SgIII, all members of the granin family i.e. CgA, CgB, SgII, SgIV-SgVII and proSAAS, and most of their derived peptides are present in adrenomedullary chromaffin cells and in pheochromocytes. Moreover, besides the routinely used CgA test assays, other assays have been developed to measure concentrations of tissue and/or circulating granins or their derived peptides in order to detect the occurrence of pheochromocytomas. In most cases, elevated levels of these entities were found, in correlation with tumor occurrence, while rarely discriminating between benign and malignant neoplasms. Nevertheless, measurement of the levels of granins and derived peptides improves the diagnostic sensitivity and may therefore provide a complementary tool for the management of pheochromocytomas. However, the existing data need to be substantiated in larger groups of patients, particularly in the case of malignant disease.

Granins and granin-related peptides in neuroendocrine tumours

This review focus on neuroendocrine tumours (NETs), with special reference to the immunohistochemical analysis of granins and granin-related peptides and their usefulness in identifying and characterizing the great diversity of NET types. Granins, their derived peptides, and complex protein-processing enzyme systems that cleave granins and prohormones, have to some extent cell-specific expression patterns in normal and neoplastic NE cells. The marker most commonly used in routine histopathology to differentiate between non-NETs and NETs is chromogranin (Cg) A, to some extent CgB. Other members of the granin family may also be of diagnostic value by identifying special NET types, e.g. secretogranin (Sg) VI was only found in pancreatic NETs and phaeochromocytomas. SgIII has recently arisen as an important NET marker; it was strongly expressed in NETs, with some exceptions--phaeochromocytomas expressed few cells and parathyroid adenomas none. Some expression patterns of granin-related peptides seem valuable in differentiating between some benign and malignant NETs, some may also provide prognostic information, among which: well-differentiated NET types expressed more CgA epitopes than the poorly differentiated ones, except insulinomas, where the opposite was noted; medullary thyroid carcinomas containing few cells immunoreactive to a CgB antibody were related to a bad prognosis; C-terminal secretoneurin visualized a cell type related to malignancy in phaeochromocytomas. Further research will probably establish new staining patterns with marker functions for granins in NETs which may be of histopathological diagnostic value.

Identification of Mac-2-binding protein as a putative marker of neuroendocrine tumors from the analysis of cell line secretomes

Neuroendocrine tumors (NETs) can arise from a variety of organs. They can vary widely in clinical behavior; consequently, optimizing their treatment plan can be problematic. NETs display diverse tumor biology; however, most secrete peptides such as chromogranin A into the circulation, consistent with their neuroendocrine origin. In this study, we sought to identify other potential markers for NETs by analyzing the secreted proteomes of three neuroendocrine cell lines. BON-1, NCI-H727, and SHP-77 cells were grown in serum-free media, and the secreted proteins were separated by SDS-PAGE and identified by LC-MS/MS. We identified 205 proteins of which 61 were secreted by two or more of the cell lines and 19 were secreted by all three lines. Mac-2-binding protein (Mac-2BP) was found to be secreted by all three cell lines, and this was confirmed by Western blotting. Immunohistochemical analysis found 29 of 33 NET cases from different primary sites to be positive for Mac-2BP. Serum Mac-2BP was significantly elevated in NET patients compared with healthy controls (p < 0.001). This study demonstrated that analysis of the secreted proteomes of neuroendocrine cell lines can identify potential biomarkers for NET. Initial assessment showed that serum Mac-2BP is significantly elevated in patients with NET and is expressed by the majority of NET tissues.

In vitro and in vivo pharmacological role of TLQP-21, a VGF-derived peptide, in the regulation of rat gastric motor functions

BACKGROUND AND PURPOSE

Vgf gene expression has been detected in various endocrine and neuronal cells in the gastrointestinal tract. In this study we investigated the pharmacological activity of different VGF-derived peptides. Among these, TLQP-21, corresponding to the 556-576 fragment of the protein was the unique active peptide, and its pharmacological profile was further studied.

EXPERIMENTAL APPROACH

The effects of TLQP-21 were examined in vitro by smooth muscle contraction in isolated preparations from the rat gastrointestinal tract and, in vivo, by assessing gastric emptying in rats. Rat stomach tissues were also processed for immunohistochemical and biochemical characterization.

KEY RESULTS

In rat longitudinal forestomach strips, TLQP-21 (100 nmol x L(-1)-10 micromol x L(-1)) concentration-dependently induced muscle contraction (in female rats, EC(50) = 0.47 micromol.L(-1), E(max): 85.7 +/- 7.9 and in male rats, 0.87 micromol x L(-1), E(max): 33.4 +/- 5.3; n = 8), by release of prostaglandin (PG)E(2) and PGF(2a) from the mucosal layer. This effect was significantly antagonized by indomethacin and selective inhibitors of either cyclooxygenase-1 (S560) or cyclooxygenase-2 (NS398). Immunostaining and biochemical studies confirmed the presence of VGF in the gastric neuronal cells. TLQP-21, injected i.c.v. (2-32 nmol per rat), significantly decreased gastric emptying by about 40%. This effect was significantly (P < 0.05) blocked by i.c.v. injection of indomethacin, suggesting that, also in vivo, this peptide acts in the brain stimulating PG release.

CONCLUSIONS AND IMPLICATIONS

The present results demonstrate that this VGF-derived peptide plays a central and local role in the regulation of rat gastric motor functions.

Chronic intracerebroventricular injection of TLQP-21 prevents high fat diet induced weight gain in fast weight-gaining mice

The vgf gene regulates energy homeostasis and the VGF-derived peptide TLQP-21 centrally exerts catabolic effects in mice and hamsters. Here, we investigate the effect of chronic intracerebroventricular (icv) injection of TLQP-21 in mice fed high fat diet (HFD). Fast weight-gaining mice injected with the peptide or cerebrospinal fluid were selected for physiological, endocrine, and molecular analysis. TLQP-21 selectively inhibited the increase in body weight and epididymal white adipose tissue (eWAT) weight induced by HFD in control animals despite both groups having a similar degree of hyperphagia. TLQP-21 normalized the increase in leptin and decrease in ghrelin while increasing epinephrine and epinephrine/norepinephrine ratio when compared to values in controls. Finally, HFD-TLQP-21 mice showed a selective increase of eWAT beta3-adrenergic receptor mRNA. Peroxisome-proliferator-activated-receptor-delta and hormone-sensing-lipase mRNA were also upregulated. In conclusion, chronic icv infusion of TLQP-21 prevented the early phase of diet-induced obesity despite overfeeding. These effects were paralleled by activation of catabolic pathways within the eWAT. Our results further support a role for TLQP-21 as a catabolic neuropeptide.

Large isoform of MRJ (DNAJB6) reduces malignant activity of breast cancer

Introduction

Mammalian relative of DnaJ (MRJ [DNAJB6]), a novel member of the human DnaJ family, has two isoforms. The smaller isoform, MRJ(S), is studied mainly for its possible role in Huntington's disease. There are no reports of any biologic activity of the longer isoform, MRJ(L). We investigated whether this molecule plays any role in breast cancer. Our studies were prompted by interesting observations we made regarding the expression of MRJ in breast cancer cell lines and breast cancer tissue microarrays, as described below.

Methods

Expression of MRJ(L) from several breast cancer cell lines was evaluated using real-time PCR. Relative levels of the small and large isoforms in breast cancer cell lines were studied using Western blot analysis. A breast cancer progression tissue microarray was probed using anti-MRJ antibody. MRJ(L) was ectopically expressed in two breast cancer cell lines. These cell lines were evaluated for their in vitro correlates of tumor aggressiveness, such as invasion, migration, and anchorage independence. The cell lines were also evaluated for in vivo tumor growth and metastasis. The secreted proteome of the MRJ(L) expressors was analyzed to elucidate the biochemical changes brought about by re-expression of MRJ(L).

Results

We found that MRJ(L) is expressed at a significantly lower level in aggressive breast cancer cell lines compared with normal breast. Furthermore, in clinical cases of breast cancer expression of MRJ is lost as the grade of infiltrating ductal carcinoma advances. Importantly, MRJ staining is lost in those cases that also had lymph node metastasis. We report that MRJ(L) is a protein with a functional nuclear localization sequence. Expression of MRJ(L) via an exogenous promoter in breast cancer cell line MDA-MB-231 and in MDA-MB-435 (a cell line that metastasizes from the mammary fat pad) decreases their migration and invasion, reduces their motility, and significantly reduces orthotopic tumor growth in nude mice. Moreover, the secreted proteome of the MRJ(L)-expressing cells exhibited reduced levels of tumor progression and metastasis promoting secreted proteins, such as SPP1 (osteopontin), AZGP1 (zinc binding α₂-glycoprotein 1), SPARC (osteonectin), NPM1 (nucleophosmin) and VGF (VGF nerve growth factor inducible). On the other hand, levels of the secreted metastasis-suppressor KiSS1 (melanoma metastasis suppressor) were increased in the secreted proteome of the MRJ(L)-expressing cells. We confirmed by quantitative RT-PCR analysis that the secreted profile reflected altered transcription of the respective genes.

Conclusion

Collectively, our data indicate an important role for a totally uncharacterized isoform of DNAJB6 in breast cancer. We show that MRJ(L) is a nuclear protein that is lost in breast cancer, that regulates several key players in tumor formation and metastasis, and that is functionally able to retard tumor growth.

The role of the vgf gene and VGF-derived peptides in nutrition and metabolism

Energy homeostasis is a complex physiological function coordinated at multiple levels. The issue of genetic regulation of nutrition and metabolism is attracting increasing interest and new energy homeostasis-regulatory genes are continuously identified. Among these genes, vgf is gaining increasing interest following two observations: (1) VGF-/- mice have a lean and hypermetabolic phenotype; (2) the first VGF-derived peptide involved in energy homeostasis, named TLQP-21, has been identified. The aim of this review will be to discuss the role of the vgf gene and VGF derived peptides in metabolic and nutritional functions. In particular we will: (1) provide a brief overview on the central systems regulating energy homeostasis and nutrition particularly focusing on the melanocortin system; (2) introduce the structure and molecular characteristic of vgf; (3) describe the phenotype of VGF deficient mice; (4) present recent data on the metabolic role of VGF-derived peptides, particularly focusing on one peptide named TLQP-21.