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Kisaretova P, Tsybko A, Bondar N, Reshetnikov V. Molecular Abnormalities in BTBR Mice and Their Relevance to Schizophrenia and Autism Spectrum Disorders: An Overview of Transcriptomic and Proteomic Studies. Biomedicines 2023; 11:biomedicines11020289. [PMID: 36830826 PMCID: PMC9953015 DOI: 10.3390/biomedicines11020289] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
Animal models of psychopathologies are of exceptional interest for neurobiologists because these models allow us to clarify molecular mechanisms underlying the pathologies. One such model is the inbred BTBR strain of mice, which is characterized by behavioral, neuroanatomical, and physiological hallmarks of schizophrenia (SCZ) and autism spectrum disorders (ASDs). Despite the active use of BTBR mice as a model object, the understanding of the molecular features of this strain that cause the observed behavioral phenotype remains insufficient. Here, we analyzed recently published data from independent transcriptomic and proteomic studies on hippocampal and corticostriatal samples from BTBR mice to search for the most consistent aberrations in gene or protein expression. Next, we compared reproducible molecular signatures of BTBR mice with data on postmortem samples from ASD and SCZ patients. Taken together, these data helped us to elucidate brain-region-specific molecular abnormalities in BTBR mice as well as their relevance to the anomalies seen in ASDs or SCZ in humans.
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Affiliation(s)
- Polina Kisaretova
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Prospekt Akad. Lavrentyeva 10, Novosibirsk 630090, Russia
- Department of Natural Sciences, Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| | - Anton Tsybko
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Prospekt Akad. Lavrentyeva 10, Novosibirsk 630090, Russia
| | - Natalia Bondar
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Prospekt Akad. Lavrentyeva 10, Novosibirsk 630090, Russia
| | - Vasiliy Reshetnikov
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Prospekt Akad. Lavrentyeva 10, Novosibirsk 630090, Russia
- Department of Biotechnology, Sirius University of Science and Technology, 1 Olympic Avenue, Sochi 354340, Russia
- Correspondence:
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Barranco N, Plá V, Alcolea D, Sánchez-Domínguez I, Fischer-Colbrie R, Ferrer I, Lleó A, Aguado F. Dense core vesicle markers in CSF and cortical tissues of patients with Alzheimer's disease. Transl Neurodegener 2021; 10:37. [PMID: 34565482 PMCID: PMC8466657 DOI: 10.1186/s40035-021-00263-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 09/14/2021] [Indexed: 12/19/2022] Open
Abstract
Background New fluid biomarkers for Alzheimer's disease (AD) that reveal synaptic and neural network dysfunctions are needed for clinical practice and therapeutic trial design. Dense core vesicle (DCV) cargos are promising cerebrospinal fluid (CSF) indicators of synaptic failure in AD patients. However, their value as biomarkers has not yet been determined. Methods Immunoassays were performed to analyze the secretory proteins prohormone convertases PC1/3 and PC2, carboxypeptidase E (CPE), secretogranins SgIII and SgII, and Cystatin C in the cerebral cortex (n = 45, provided by Bellvitge University Hospital) and CSF samples (n = 66, provided by The Sant Pau Initiative on Neurodegeneration cohort) from AD patients (n = 56) and age-matched controls (n = 55).
Results In AD tissues, most DCV proteins were aberrantly accumulated in dystrophic neurites and activated astrocytes, whereas PC1/3, PC2 and CPE were also specifically accumulated in hippocampal granulovacuolar degeneration bodies. AD individuals displayed an overall decline of secretory proteins in the CSF. Interestingly, in AD patients, the CSF levels of prohormone convertases strongly correlated inversely with those of neurodegeneration markers and directly with cognitive impairment status. Conclusions These results demonstrate marked alterations of neuronal-specific prohormone convertases in CSF and cortical tissues of AD patients. The neuronal DCV cargos are biomarker candidates for synaptic dysfunction and neurodegeneration in AD. Supplementary Information The online version contains supplementary material available at 10.1186/s40035-021-00263-0.
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Affiliation(s)
- Neus Barranco
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.,Institute of Neurosciences, University of Barcelona, 08028, Barcelona, Spain
| | - Virginia Plá
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.,Institute of Neurosciences, University of Barcelona, 08028, Barcelona, Spain.,Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Daniel Alcolea
- Memory Unit, Department of Neurology, Sant Pau Biomedical Research Institute. Sant Pau Hospital, Autonomous University of Barcelona, 08041, Barcelona, Spain.,Center for Networked Biomedical Research on Neurodegenerative Diseases (CIBERNED), 28031, Madrid, Spain
| | - Irene Sánchez-Domínguez
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.,Institute of Neurosciences, University of Barcelona, 08028, Barcelona, Spain
| | | | - Isidro Ferrer
- Institute of Neurosciences, University of Barcelona, 08028, Barcelona, Spain.,Center for Networked Biomedical Research on Neurodegenerative Diseases (CIBERNED), 28031, Madrid, Spain.,Department of Pathology and Experimental Therapeutics, University of Barcelona, and Bellvitge University Hospital, Bellvitge Biomedical Research Institute, Hospitalet de Llobregat, Spain
| | - Alberto Lleó
- Memory Unit, Department of Neurology, Sant Pau Biomedical Research Institute. Sant Pau Hospital, Autonomous University of Barcelona, 08041, Barcelona, Spain.,Center for Networked Biomedical Research on Neurodegenerative Diseases (CIBERNED), 28031, Madrid, Spain
| | - Fernando Aguado
- Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain. .,Institute of Neurosciences, University of Barcelona, 08028, Barcelona, Spain.
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Germanos M, Gao A, Taper M, Yau B, Kebede MA. Inside the Insulin Secretory Granule. Metabolites 2021; 11:metabo11080515. [PMID: 34436456 PMCID: PMC8401130 DOI: 10.3390/metabo11080515] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022] Open
Abstract
The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.
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Ramzy A, Kieffer TJ. Altered islet prohormone processing: A cause or consequence of diabetes? Physiol Rev 2021; 102:155-208. [PMID: 34280055 DOI: 10.1152/physrev.00008.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Peptide hormones are first produced as larger precursor prohormones that require endoproteolytic cleavage to liberate the mature hormones. A structurally conserved but functionally distinct family of nine prohormone convertase enzymes (PCs) are responsible for cleavage of protein precursors of which PC1/3 and PC2 are known to be exclusive to neuroendocrine cells and responsible for prohormone cleavage. Differential expression of PCs within tissues define prohormone processing; whereas glucagon is the major product liberated from proglucagon via PC2 in pancreatic α-cells, proglucagon is preferentially processed by PC1/3 in intestinal L cells to produce glucagon-like peptides 1 and 2 (GLP-1, GLP-2). Beyond our understanding of processing of islet prohormones in healthy islets, there is convincing evidence that proinsulin, proIAPP, and proglucagon processing is altered during prediabetes and diabetes. There is predictive value of elevated circulating proinsulin or proinsulin : C-peptide ratio for progression to type 2 diabetes and elevated proinsulin or proinsulin : C-peptide is predictive for development of type 1 diabetes in at risk groups. After onset of diabetes, patients have elevated circulating proinsulin and proIAPP and proinsulin may be an autoantigen in type 1 diabetes. Further, preclinical studies reveal that α-cells have altered proglucagon processing during diabetes leading to increased GLP-1 production. We conclude that despite strong associative data, current evidence is inconclusive on the potential causal role of impaired prohormone processing in diabetes, and suggest that future work should focus on resolving the question of whether altered prohormone processing is a causal driver or merely a consequence of diabetes pathology.
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Affiliation(s)
- Adam Ramzy
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada
| | - Timothy J Kieffer
- Laboratory of Molecular and Cellular Medicine, Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada.,Department of Surgery, University of British Columbia, Vancouver, BC, Canada.,School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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Abstract
The kexin-like proprotein convertases perform the initial proteolytic cleavages that ultimately generate a variety of different mature peptide and proteins, ranging from brain neuropeptides to endocrine peptide hormones, to structural proteins, among others. In this review, we present a general introduction to proprotein convertase structure and biochemistry, followed by a comprehensive discussion of each member of the kexin-like subfamily of proprotein convertases. We summarize current knowledge of human proprotein convertase insufficiency syndromes, including genome-wide analyses of convertase polymorphisms, and compare these to convertase null and mutant mouse models. These mouse models have illuminated our understanding of the roles specific convertases play in human disease and have led to the identification of convertase-specific substrates; for example, the identification of procorin as a specific PACE4 substrate in the heart. We also discuss the limitations of mouse null models in interpreting human disease, such as differential precursor cleavage due to species-specific sequence differences, and the challenges presented by functional redundancy among convertases in attempting to assign specific cleavages and/or physiological roles. However, in most cases, knockout mouse models have added substantively both to our knowledge of diseases caused by human proprotein convertase insufficiency and to our appreciation of their normal physiological roles, as clearly seen in the case of the furin, proprotein convertase 1/3, and proprotein convertase 5/6 mouse models. The creation of more sophisticated mouse models with tissue- or temporally-restricted expression of specific convertases will improve our understanding of human proprotein convertase insufficiency and potentially provide support for the emerging concept of therapeutic inhibition of convertases.
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Affiliation(s)
- Manita Shakya
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
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Shakya M, Yildirim T, Lindberg I. Increased expression and retention of the secretory chaperone proSAAS following cell stress. Cell Stress Chaperones 2020; 25:929-941. [PMID: 32607937 PMCID: PMC7591655 DOI: 10.1007/s12192-020-01128-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 06/05/2020] [Accepted: 06/10/2020] [Indexed: 11/25/2022] Open
Abstract
The secretory pathway of neurons and endocrine cells contains a variety of mechanisms designed to combat cellular stress. These include not only the unfolded protein response pathways but also diverse chaperone proteins that collectively work to ensure proteostatic control of secreted and membrane-bound molecules. One of the least studied of these chaperones is the neural- and endocrine-specific molecule known as proSAAS. This small chaperone protein acts as a potent anti-aggregant both in vitro and in cellulo and also represents a cerebrospinal fluid biomarker in Alzheimer's disease. In the present study, we have examined the idea that proSAAS, like other secretory chaperones, might represent a stress-responsive protein. We find that exposure of neural and endocrine cells to the cell stressors tunicamycin and thapsigargin increases cellular proSAAS mRNA and protein in Neuro2A cells. Paradoxically, proSAAS secretion is inhibited by these same drugs. Exposure of Neuro2A cells to low concentrations of the hypoxic stress inducer cobalt chloride, or to sodium arsenite, an oxidative stressor, also increases cellular proSAAS content and reduces its secretion. We conclude that the cellular levels of the small secretory chaperone proSAAS are positively modulated by cell stress.
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Affiliation(s)
- Manita Shakya
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF2, S267, Baltimore, MD, 21201, USA
| | - Taha Yildirim
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF2, S267, Baltimore, MD, 21201, USA
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF2, S267, Baltimore, MD, 21201, USA.
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7
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Chaplot K, Jarvela TS, Lindberg I. Secreted Chaperones in Neurodegeneration. Front Aging Neurosci 2020; 12:268. [PMID: 33192447 PMCID: PMC7481362 DOI: 10.3389/fnagi.2020.00268] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 08/03/2020] [Indexed: 12/11/2022] Open
Abstract
Protein homeostasis, or proteostasis, is a combination of cellular processes that govern protein quality control, namely, protein translation, folding, processing, and degradation. Disruptions in these processes can lead to protein misfolding and aggregation. Proteostatic disruption can lead to cellular changes such as endoplasmic reticulum or oxidative stress; organelle dysfunction; and, if continued, to cell death. A majority of neurodegenerative diseases involve the pathologic aggregation of proteins that subverts normal neuronal function. While prior reviews of neuronal proteostasis in neurodegenerative processes have focused on cytoplasmic chaperones, there is increasing evidence that chaperones secreted both by neurons and other brain cells in the extracellular – including transsynaptic – space play important roles in neuronal proteostasis. In this review, we will introduce various secreted chaperones involved in neurodegeneration. We begin with clusterin and discuss its identification in various protein aggregates, and the use of increased cerebrospinal fluid (CSF) clusterin as a potential biomarker and as a potential therapeutic. Our next secreted chaperone is progranulin; polymorphisms in this gene represent a known genetic risk factor for frontotemporal lobar degeneration, and progranulin overexpression has been found to be effective in reducing Alzheimer’s- and Parkinson’s-like neurodegenerative phenotypes in mouse models. We move on to BRICHOS domain-containing proteins, a family of proteins containing highly potent anti-amyloidogenic activity; we summarize studies describing the biochemical mechanisms by which recombinant BRICHOS protein might serve as a therapeutic agent. The next section of the review is devoted to the secreted chaperones 7B2 and proSAAS, small neuronal proteins which are packaged together with neuropeptides and released during synaptic activity. Since proteins can be secreted by both classical secretory and non-classical mechanisms, we also review the small heat shock proteins (sHsps) that can be secreted from the cytoplasm to the extracellular environment and provide evidence for their involvement in extracellular proteostasis and neuroprotection. Our goal in this review focusing on extracellular chaperones in neurodegenerative disease is to summarize the most recent literature relating to neurodegeneration for each secreted chaperone; to identify any common mechanisms; and to point out areas of similarity as well as differences between the secreted chaperones identified to date.
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Affiliation(s)
- Kriti Chaplot
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Timothy S Jarvela
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, University of Maryland, Baltimore, Baltimore, MD, United States
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8
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Hammond MJ, Wang T, Cummins SF. Characterisation of early metazoan secretion through associated signal peptidase complex subunits, prohormone convertases and carboxypeptidases of the marine sponge (Amphimedon queenslandica). PLoS One 2019; 14:e0225227. [PMID: 31714927 PMCID: PMC6850559 DOI: 10.1371/journal.pone.0225227] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 10/30/2019] [Indexed: 01/31/2023] Open
Abstract
Efficient communication between cells requires the ability to process precursor proteins into their mature and biologically active forms, prior to secretion into the extracellular space. Eukaryotic cells achieve this via a suite of enzymes that involve a signal peptidase complex, prohormone convertases and carboxypeptidases. Using genome and transcriptome data of the demosponge Amphimedon queenslandica, a universal ancestor to metazoan multicellularity, we endeavour to bridge the evolution of precursor processing machinery from single-celled eukaryotic ancestors through to the complex multicellular organisms that compromise Metazoa. The precursor processing repertoire as defined in this study of A. queenslandica consists of 3 defined signal peptidase subunits, 6 prohormone convertases and 1 carboxypeptidase, with 2 putative duplicates identified for signal peptidase complex subunits. Analysis of their gene expression levels throughout the sponge development enabled us to predict levels of activity. Some A. queenslandica precursor processing components belong to established functional clades while others were identified as having novel, yet to be discovered roles. These findings have clarified the presence of precursor processing machinery in the poriferans, showing the necessary machinery for the removal of precursor sequences, a critical post-translational modification required by multicellular organisms, and further sets a foundation towards understanding the molecular mechanism for ancient protein processing.
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Affiliation(s)
- Michael J. Hammond
- Genecology Research Centre, University of the Sunshine Coast, Maroochydore Dc, Queensland, Australia
- * E-mail:
| | - Tianfang Wang
- Genecology Research Centre, University of the Sunshine Coast, Maroochydore Dc, Queensland, Australia
| | - Scott F. Cummins
- Genecology Research Centre, University of the Sunshine Coast, Maroochydore Dc, Queensland, Australia
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Beraki T, Hu X, Broncel M, Young JC, O'Shaughnessy WJ, Borek D, Treeck M, Reese ML. Divergent kinase regulates membrane ultrastructure of the Toxoplasma parasitophorous vacuole. Proc Natl Acad Sci U S A 2019; 116:6361-6370. [PMID: 30850550 PMCID: PMC6442604 DOI: 10.1073/pnas.1816161116] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Apicomplexan parasites replicate within a protective organelle, called the parasitophorous vacuole (PV). The Toxoplasma gondii PV is filled with a network of tubulated membranes, which are thought to facilitate trafficking of effectors and nutrients. Despite being critical to parasite virulence, there is scant mechanistic understanding of the network's functions. Here, we identify the parasite-secreted kinase WNG1 (With-No-Gly-loop) as a critical regulator of tubular membrane biogenesis. WNG1 family members adopt an atypical protein kinase fold lacking the glycine rich ATP-binding loop that is required for catalysis in canonical kinases. Unexpectedly, we find that WNG1 is an active protein kinase that localizes to the PV lumen and phosphorylates PV-resident proteins, several of which are essential for the formation of a functional intravacuolar network. Moreover, we show that WNG1-dependent phosphorylation of these proteins is required for their membrane association, and thus their ability to tubulate membranes. Consequently, WNG1 knockout parasites have an aberrant PV membrane ultrastructure. Collectively, our results describe a unique family of Toxoplasma kinases and implicate phosphorylation of secreted proteins as a mechanism of regulating PV development during parasite infection.
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Affiliation(s)
- Tsebaot Beraki
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX 75390
| | - Xiaoyu Hu
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX 75390
| | - Malgorzata Broncel
- Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, NW1 1AT London United Kingdom
| | - Joanna C Young
- Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, NW1 1AT London United Kingdom
| | - William J O'Shaughnessy
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX 75390
| | - Dominika Borek
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Moritz Treeck
- Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, NW1 1AT London United Kingdom
| | - Michael L Reese
- Department of Pharmacology, University of Texas, Southwestern Medical Center, Dallas, TX 75390;
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
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10
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Jarvela TS, Womack T, Georgiou P, Gould TD, Eriksen JL, Lindberg I. 7B2 chaperone knockout in APP model mice results in reduced plaque burden. Sci Rep 2018; 8:9813. [PMID: 29955078 PMCID: PMC6023903 DOI: 10.1038/s41598-018-28031-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 06/08/2018] [Indexed: 01/18/2023] Open
Abstract
Impairment of neuronal proteostasis is a hallmark of Alzheimer's and other neurodegenerative diseases. However, the underlying molecular mechanisms leading to pathogenic protein aggregation, and the role of secretory chaperone proteins in this process, are poorly understood. We have previously shown that the neural-and endocrine-specific secretory chaperone 7B2 potently blocks in vitro fibrillation of Aβ42. To determine whether 7B2 can function as a chaperone in vivo, we measured plaque formation and performed behavioral assays in 7B2-deficient mice in an hAPPswe/PS1dE9 Alzheimer's model mouse background. Surprisingly, immunocytochemical analysis of cortical levels of thioflavin S- and Aβ-reactive plaques showed that APP mice with a partial or complete lack of 7B2 expression exhibited a significantly lower number and burden of thioflavin S-reactive, as well as Aβ-immunoreactive, plaques. However, 7B2 knockout did not affect total brain levels of either soluble or insoluble Aβ. While hAPP model mice performed poorly in the Morris water maze, their brain 7B2 levels did not impact performance. Since 7B2 loss reduced amyloid plaque burden, we conclude that brain 7B2 can impact Aβ disposition in a manner that facilitates plaque formation. These results are reminiscent of prior findings in hAPP model mice lacking the ubiquitous secretory chaperone clusterin.
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Affiliation(s)
- Timothy S Jarvela
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Tasha Womack
- Department of Pharmacology, College of Pharmacy, University of Houston, Houston, TX, USA
| | - Polymnia Georgiou
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Todd D Gould
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Jason L Eriksen
- Department of Pharmacology, College of Pharmacy, University of Houston, Houston, TX, USA
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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11
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Böttcher-Friebertshäuser E, Garten W, Klenk HD. Characterization of Proprotein Convertases and Their Involvement in Virus Propagation. ACTIVATION OF VIRUSES BY HOST PROTEASES 2018. [PMCID: PMC7122180 DOI: 10.1007/978-3-319-75474-1_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
| | - Wolfgang Garten
- Institut für Virologie, Philipps Universität, Marburg, Germany
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12
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Li W, Webster KA, LeBlanc ME, Tian H. Secretogranin III: a diabetic retinopathy-selective angiogenic factor. Cell Mol Life Sci 2018; 75:635-647. [PMID: 28856381 PMCID: PMC5771826 DOI: 10.1007/s00018-017-2635-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 12/13/2022]
Abstract
Secretogranin III (Scg3) is a member of the granin protein family that regulates the biogenesis of secretory granules. Scg3 was recently discovered as an angiogenic factor, expanding its functional role to extrinsic regulation. Unlike many other known angiogenic factors, the pro-angiogenic actions of Scg3 are restricted to pathological conditions. Among thousands of quantified endothelial ligands, Scg3 has the highest binding activity ratio to diabetic vs. healthy mouse retinas and lowest background binding to normal vessels. In contrast, vascular endothelial growth factor binds to and stimulates angiogenesis of both diabetic and control vasculature. Consistent with its role in pathological angiogenesis, Scg3-neutralizing antibodies alleviate retinal vascular leakage in mouse models of diabetic retinopathy and retinal neovascularization in oxygen-induced retinopathy mice. This review summarizes our current knowledge of Scg3 as a regulatory protein of secretory granules, highlights its new role as a highly disease-selective angiogenic factor, and envisions Scg3 inhibitors as "selective angiogenesis blockers" for targeted therapy.
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Affiliation(s)
- Wei Li
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, FL, 33136, USA.
- Vascular Biology Institute, University of Miami School of Medicine, Miami, FL, 33136, USA.
| | - Keith A Webster
- Vascular Biology Institute, University of Miami School of Medicine, Miami, FL, 33136, USA
- Department Pharmacology, University of Miami School of Medicine, Miami, FL, 33136, USA
| | - Michelle E LeBlanc
- Schepens Eye Research Institute, Harvard Medical School, Boston, MA, 02114, USA
| | - Hong Tian
- Everglades Biopharma, Miami, FL, 33156, USA
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13
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Majerova P, Barath P, Michalicova A, Katina S, Novak M, Kovac A. Changes of Cerebrospinal Fluid Peptides due to Tauopathy. J Alzheimers Dis 2017; 58:507-520. [DOI: 10.3233/jad-170110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Petra Majerova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Bratislava, Slovak Republic
- AXON Neuroscience R&D, Bratislava, Slovak Republic
| | - Peter Barath
- Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Slovak Republic
| | - Alena Michalicova
- Institute of Neuroimmunology, Slovak Academy of Sciences, Bratislava, Slovak Republic
- AXON Neuroscience R&D, Bratislava, Slovak Republic
| | - Stanislav Katina
- AXON Neuroscience R&D, Bratislava, Slovak Republic
- Institute of Mathematics and Statistics, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Michal Novak
- Institute of Neuroimmunology, Slovak Academy of Sciences, Bratislava, Slovak Republic
- AXON Neuroscience R&D, Bratislava, Slovak Republic
| | - Andrej Kovac
- Institute of Neuroimmunology, Slovak Academy of Sciences, Bratislava, Slovak Republic
- AXON Neuroscience R&D, Bratislava, Slovak Republic
- Department of Pharmacology and Toxicology, The University of Veterinary Medicine and Pharmacy, Kosice, Slovak Republic
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14
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Baek AE, Nelson ER. The Contribution of Cholesterol and Its Metabolites to the Pathophysiology of Breast Cancer. Discov Oncol 2016; 7:219-28. [PMID: 27020054 DOI: 10.1007/s12672-016-0262-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/17/2016] [Indexed: 02/07/2023] Open
Abstract
As the most common cancer in women, one in eight will develop invasive breast cancer over their lifetime making it the second most common cause of cancer-related death among women. Of the many known risk factors for developing breast cancer, obesity stands out as prominent and modifiable. Interestingly, elevated cholesterol is highly associated with obesity and has emerged as an independent risk factor for breast cancer onset and recurrence. This indicates that cholesterol also contributes to the breast cancer pathogenicity of obesity. This review highlights our current understanding of the mechanisms by which cholesterol impacts breast cancer. Key preclinical studies have been highlighted, including the discussion of homeostatic control of cholesterol levels, signaling by cholesterol metabolites through the estrogen receptors, cholesterol formation of lipid rafts and subsequent signaling, and the potential roles of cholesterol in creating a pro-inflammatory tumor microenvironment. Future directions and avenues for therapeutic exploitation are also considered.
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Affiliation(s)
- Amy E Baek
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 407 S. Goodwin Ave (MC-114), Urbana, IL, 61801, USA
| | - Erik R Nelson
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, 407 S. Goodwin Ave (MC-114), Urbana, IL, 61801, USA. .,Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA. .,University of Illinois Cancer Center, Chicago, IL, USA.
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15
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Abstract
UNLABELLED Cellular protein homeostasis (proteostasis) maintains the integrity of the proteome and includes protein synthesis, folding, oligomerization, and turnover; chaperone proteins assist with all of these processes. Neurons appear to be especially susceptible to failures in proteostasis, and this is now increasingly recognized as a major origin of neurodegenerative disease. This review, based on a mini-symposium presented at the 2015 Society for Neuroscience meeting, describes new work in the area of neuronal proteostasis, with a specific focus on the roles and therapeutic uses of protein chaperones. We first present a brief review of protein misfolding and aggregation in neurodegenerative disease. We then discuss different aspects of chaperone control of neuronal proteostasis on topics ranging from chaperone engineering, to chaperone-mediated blockade of protein oligomerization and cytotoxicity, to the potential rescue of neurodegenerative processes using modified chaperone proteins. SIGNIFICANCE STATEMENT Aberrant protein homeostasis within neurons results in protein misfolding and aggregation. In this review, we discuss specific roles for protein chaperones in the oligomerization, assembly, and disaggregation of proteins known to be abnormally folded in neurodegenerative disease. Collectively, our goal is to identify therapeutic mechanisms to reduce the cellular toxicity of abnormal aggregates.
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16
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Nakamoto K, Aizawa F, Nishinaka T, Tokuyama S. Regulation of prohormone convertase 2 protein expression via GPR40/FFA1 in the hypothalamus. Eur J Pharmacol 2015; 762:459-63. [DOI: 10.1016/j.ejphar.2015.06.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 06/03/2015] [Accepted: 06/05/2015] [Indexed: 11/27/2022]
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17
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Lin CY, Vedin LL, Steffensen KR. The emerging roles of liver X receptors and their ligands in cancer. Expert Opin Ther Targets 2015; 20:61-71. [PMID: 26788589 DOI: 10.1517/14728222.2015.1081169] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Liver X receptors (LXRs) are nuclear receptors with well-known functions in cholesterol transport, fatty acid and glucose metabolism, and modulation of immune responses. Natural and synthetic ligands have been identified and are under development for the treatment of metabolic and inflammatory conditions and diseases. There is mounting evidence pointing to functional roles for LXRs in a variety of malignancies and the potential therapeutic efficacy of their ligands. AREAS COVERED This review summarizes the discovery and characterization of LXRs and their ligands, surveys their effects and mechanisms of action in cell-based and animal models of cancer, and proposes the future direction of basic and translational studies of LXRs and their ligands in cancer research and therapeutics. EXPERT OPINION Targeting LXRs is a promising strategy for cancer treatment, particularly for those cancers which do not have effective treatment options. Key questions remain, however, regarding the specific mechanisms of action, effects on other target cells within the tumor microenvironment, and receptor status in patient populations. Moreover, LXR ligands optimized for disease-specific functions and cancer-related endpoints are currently not available. These issues represent both challenges and significant opportunities for future research and development efforts.
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Affiliation(s)
- Chin-Yo Lin
- a 1 University of Houston, Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry , Houston, TX, USA
| | - Lise-Lotte Vedin
- b 2 Karolinska University Hospital Huddinge, Karolinska Institutet, Division of Clinical Chemistry, Department of Laboratory Medicine , SE-141 86 Stockholm, Sweden
| | - Knut R Steffensen
- b 2 Karolinska University Hospital Huddinge, Karolinska Institutet, Division of Clinical Chemistry, Department of Laboratory Medicine , SE-141 86 Stockholm, Sweden
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18
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Ramos-Molina B, Lindberg I. Phosphorylation and Alternative Splicing of 7B2 Reduce Prohormone Convertase 2 Activation. Mol Endocrinol 2015; 29:756-64. [PMID: 25811241 DOI: 10.1210/me.2014-1394] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
FAM20C is a secretory kinase responsible for the phosphorylation of multiple secreted proteins in mammalian cells; it has been shown to phosphorylate serine residues within a variety of different bone proteins. In this work we demonstrate that FAM20C also phosphorylates threonines, specifically those within the N-terminal domain of the neuroendocrine chaperone 7B2. Analysis of the primary sequence of 7B2 revealed that three threonine residues in its N-terminal domain are located within FAM20C consensus motifs: Thr73, Thr99, and Thr111. The individual substitution of Thr73 and Thr111 residues by neutral alanines caused a marked decrease in the total phosphorylation of 7B2. Furthermore, the phosphomimetic substitution of Thr111 by Glu clearly diminished the ability of 7B2 to activate pro-prohormone convertase 2 (PC2) in 7B2-lacking SK-N-MC neuroblastoma cells, suggesting that the phosphorylation of this residue critically impacts the 7B2-proPC2 interaction. However, the phosphomimetic mutation did not alter 7B2's ability to function as an antiaggregant for human islet amyloid polypeptide. FAM20C-mediated phosphorylation of a common alternatively spliced variant of human 7B2 that lacks Ala100 (thus eliminating the Thr99 phosphorylation consensus site) was similar to the Ala-containing protein, but this variant did not activate proPC2 as efficiently as the Ala-containing protein. Although threonines within 7B2 were phosphorylated efficiently, FAM20C was incapable of performing the well-known regulatory threonine phosphorylation of the molecular chaperone binding immunoglobulin protein. Taken together, these results indicate that FAM20C plays a role in 7B2-mediated proPC2 activation by phosphorylating residue Thr111; and that 7B2 function is regulated by alternative splicing.
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Affiliation(s)
- Bruno Ramos-Molina
- Department of Anatomy and Neurobiology, School of Medicine, University of Maryland-Baltimore, Baltimore, Maryland 21201
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19
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Alioui A, Celhay O, Baron S, Lobaccaro JMA. Lipids and prostate cancer adenocarcinoma. ACTA ACUST UNITED AC 2014. [DOI: 10.2217/clp.14.51] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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20
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Hoshino A, Helwig M, Rezaei S, Berridge C, Eriksen JL, Lindberg I. A novel function for proSAAS as an amyloid anti-aggregant in Alzheimer's disease. J Neurochem 2013; 128:419-30. [PMID: 24102330 DOI: 10.1111/jnc.12454] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 01/23/2023]
Abstract
Neurodegenerative diseases such as Alzheimer's disease (AD) are characterized by an abnormal aggregation of misfolded beta-sheet rich proteins such as β-amyloid (Aβ). Various ubiquitously expressed molecular chaperones control the correct folding of cellular proteins and prevent the accumulation of harmful species. We here describe a novel anti-aggregant chaperone function for the neuroendocrine protein proSAAS, an abundant secretory polypeptide that is widely expressed within neural and endocrine tissues and which has previously been associated with neurodegenerative disease in various proteomics studies. In the brains of 12-month-old APdE9 mice, and in the cortex of a human AD-affected brain, proSAAS immunoreactivity was highly colocalized with amyloid pathology. Immunoreactive proSAAS co-immunoprecipitated with Aβ immunoreactivity in lysates from APdE9 mouse brains. In vitro, proSAAS efficiently prevented the fibrillation of Aβ(1-42) at molar ratios of 1 : 10, and this anti-aggregation effect was dose dependent. Structure-function studies showed that residues 97-180 were sufficient for the anti-aggregation function against Aβ. Finally, inclusion of recombinant proSAAS in the medium of Neuro2a cells, as well as lentiviral-mediated proSAAS over-expression, blocked the neurocytotoxic effect of Aβ(1-42) in Neuro2a cells. Taken together, our results suggest that proSAAS may play a role in Alzheimer's disease pathology.
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Affiliation(s)
- Akina Hoshino
- Department of Anatomy and Neurobiology, University of Maryland-Baltimore, Baltimore, Maryland, USA
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21
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Ager-Wick E, Dirks RP, Burgerhout E, Nourizadeh-Lillabadi R, de Wijze DL, Spaink HP, van den Thillart GEEJM, Tsukamoto K, Dufour S, Weltzien FA, Henkel CV. The pituitary gland of the European eel reveals massive expression of genes involved in the melanocortin system. PLoS One 2013; 8:e77396. [PMID: 24130881 PMCID: PMC3795071 DOI: 10.1371/journal.pone.0077396] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 09/02/2013] [Indexed: 11/18/2022] Open
Abstract
Hormones secreted from the pituitary gland regulate important processes such as development, growth and metabolism, reproduction, water balance, and body pigmentation. Synthesis and secretion of pituitary hormones are regulated by different factors from the hypothalamus, but also through feedback mechanisms from peripheral organs, and from the pituitary itself. In the European eel extensive attention has been directed towards understanding the different components of the brain-pituitary-gonad axis, but little is known about the regulation of upstream processes in the pituitary gland. In order to gain a broader mechanistic understanding of the eel pituitary gland, we have performed RNA-seq transcriptome profiling of the pituitary of prepubertal female silver eels. RNA-seq reads generated on the Illumina platform were mapped to the recently assembled European eel genome. The most abundant transcript in the eel pituitary codes for pro-opiomelanocortin, the precursor for hormones of the melanocortin system. Several genes putatively involved in downstream processing of pro-opiomelanocortin were manually annotated, and were found to be highly expressed, both by RNA-seq and by qPCR. The melanocortin system, which affects skin color, energy homeostasis and in other teleosts interacts with the reproductive system, has so far received limited attention in eels. However, since up to one third of the silver eel pituitary's mRNA pool encodes pro-opiomelanocortin, our results indicate that control of the melanocortin system is a major function of the eel pituitary.
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Affiliation(s)
- Eirill Ager-Wick
- Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, Oslo, Norway
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22
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Peinado JR, Sami F, Rajpurohit N, Lindberg I. Blockade of islet amyloid polypeptide fibrillation and cytotoxicity by the secretory chaperones 7B2 and proSAAS. FEBS Lett 2013; 587:3406-11. [PMID: 24042052 DOI: 10.1016/j.febslet.2013.09.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/03/2013] [Accepted: 09/06/2013] [Indexed: 10/26/2022]
Abstract
The deposition of fibrillated human islet β-cell peptide islet amyloid polypeptide (hIAPP) into amyloid plaques is characteristic of the pathogenesis of islet cell death during type 2 diabetes. We investigated the effects of the neuroendocrine secretory proteins 7B2 and proSAAS on hIAPP fibrillation in vitro and on cytotoxicity. In vitro, 21-kDa 7B2 and proSAAS blocked hIAPP fibrillation. Structure-function studies showed that a central region within 21-kDa 7B2 is important in this effect and revealed the importance of the N-terminal region of proSAAS. Both chaperones blocked the cytotoxic effects of exogenous hIAPP on Rin5f cells; 7B2 generated by overexpression was also effective. ProSAAS and 7B2 may perform a chaperone role as secretory anti-aggregants in normal islet cell function and in type 2 diabetes.
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Affiliation(s)
- Juan R Peinado
- Department of Anatomy and Neurobiology, University of Maryland-Baltimore, Baltimore, MD 21201, United States
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23
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McVeigh P, Atkinson L, Marks NJ, Mousley A, Dalzell JJ, Sluder A, Hammerland L, Maule AG. Parasite neuropeptide biology: Seeding rational drug target selection? Int J Parasitol Drugs Drug Resist 2012; 2:76-91. [PMID: 24533265 PMCID: PMC3862435 DOI: 10.1016/j.ijpddr.2011.10.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Revised: 10/25/2011] [Accepted: 10/28/2011] [Indexed: 01/16/2023]
Abstract
The rationale for identifying drug targets within helminth neuromuscular signalling systems is based on the premise that adequate nerve and muscle function is essential for many of the key behavioural determinants of helminth parasitism, including sensory perception/host location, invasion, locomotion/orientation, attachment, feeding and reproduction. This premise is validated by the tendency of current anthelmintics to act on classical neurotransmitter-gated ion channels present on helminth nerve and/or muscle, yielding therapeutic endpoints associated with paralysis and/or death. Supplementary to classical neurotransmitters, helminth nervous systems are peptide-rich and encompass associated biosynthetic and signal transduction components - putative drug targets that remain to be exploited by anthelmintic chemotherapy. At this time, no neuropeptide system-targeting lead compounds have been reported, and given that our basic knowledge of neuropeptide biology in parasitic helminths remains inadequate, the short-term prospects for such drugs remain poor. Here, we review current knowledge of neuropeptide signalling in Nematoda and Platyhelminthes, and highlight a suite of 19 protein families that yield deleterious phenotypes in helminth reverse genetics screens. We suggest that orthologues of some of these peptidergic signalling components represent appealing therapeutic targets in parasitic helminths.
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Affiliation(s)
- Paul McVeigh
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Louise Atkinson
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Nikki J. Marks
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Angela Mousley
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Johnathan J. Dalzell
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
| | - Ann Sluder
- Scynexis Inc., P.O. Box 12878, Research Triangle Park, NC 27709-2878, USA
| | | | - Aaron G. Maule
- Molecular Biosciences–Parasitology, Institute of Agri-Food and Land Use, School of Biological Sciences, Queen’s University Belfast, Belfast BT9 7BL, UK
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24
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Helwig M, Hoshino A, Berridge C, Lee SN, Lorenzen N, Otzen DE, Eriksen JL, Lindberg I. The neuroendocrine protein 7B2 suppresses the aggregation of neurodegenerative disease-related proteins. J Biol Chem 2012; 288:1114-24. [PMID: 23172224 PMCID: PMC3542996 DOI: 10.1074/jbc.m112.417071] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Neurodegenerative diseases such as Alzheimer (AD) and Parkinson (PD) are characterized by abnormal aggregation of misfolded β-sheet-rich proteins, including amyloid-β (Aβ)-derived peptides and tau in AD and α-synuclein in PD. Correct folding and assembly of these proteins are controlled by ubiquitously expressed molecular chaperones; however, our understanding of neuron-specific chaperones and their involvement in the pathogenesis of neurodegenerative diseases is limited. We here describe novel chaperone-like functions for the secretory protein 7B2, which is widely expressed in neuronal and endocrine tissues. In in vitro experiments, 7B2 efficiently prevented fibrillation and formation of Aβ1–42, Aβ1–40, and α-synuclein aggregates at a molar ratio of 1:10. In cell culture experiments, inclusion of recombinant 7B2, either in the medium of Neuro-2A cells or intracellularly via adenoviral 7B2 overexpression, blocked the neurocytotoxic effect of Aβ1–42 and significantly increased cell viability. Conversely, knockdown of 7B2 by RNAi increased Aβ1–42-induced cytotoxicity. In the brains of APP/PSEN1 mice, a model of AD amyloidosis, immunoreactive 7B2 co-localized with aggregation-prone proteins and their respective aggregates. Furthermore, in the hippocampus and substantia nigra of human AD- and PD-affected brains, 7B2 was highly co-localized with Aβ plaques and α-synuclein deposits, strongly suggesting physiological association. Our data provide insight into novel functions of 7B2 and establish this neural protein as an anti-aggregation chaperone associated with neurodegenerative disease.
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Affiliation(s)
- Michael Helwig
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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25
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Dasgupta I, Sanglas L, Enghild JJ, Lindberg I. The neuroendocrine protein 7B2 is intrinsically disordered. Biochemistry 2012; 51:7456-64. [PMID: 22947085 PMCID: PMC3457758 DOI: 10.1021/bi300871k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
The small neuroendocrine protein 7B2 has been shown to
be required
for the productive maturation of proprotein convertase 2 (proPC2)
to an active enzyme form; this action is accomplished via its ability
to block aggregation of proPC2 into nonactivatable forms. Recent data
show that 7B2 can also act as a postfolding chaperone to block the
aggregation of a number of other proteins, for example, α-synuclein.
To gain insight into the mechanism of action of 7B2 in blocking protein
aggregation, we performed structural studies of this protein using
gel filtration chromatography, intrinsic tryptophan fluorescence,
1-anilino-8-naphthalenesulfonate (ANS) binding, circular dichroism
(CD), and nuclear magnetic resonance (NMR) spectroscopy. Gel filtration
studies indicated that 7B2 exists as an extended monomer, eluting
at a molecular mass higher than that expected for a globular protein
of similar size. However, chemical cross-linking showed that 7B2 exhibits
concentration-dependent oligomerization. CD experiments showed that
both full-length 27 kDa 7B2 and the C-terminally truncated 21 kDa
form lack appreciable secondary structure, although the longer protein
exhibited more structural content than the latter, as demonstrated
by intrinsic and ANS fluorescence studies. NMR spectra confirmed the
lack of structure in native 7B2, but a disorder-to-order transition
was observed upon incubation with one of its client proteins, α-synuclein.
We conclude that 7B2 is a natively disordered protein whose function
as an antiaggregant chaperone is likely facilitated by its lack of
appreciable secondary structure and tendency to form oligomers.
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Affiliation(s)
- Indrani Dasgupta
- Department of Anatomy and Neurobiology, School of Medicine, University of Maryland-Baltimore, Baltimore, MD 21201, USA
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26
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27
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28
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Bartolomucci A, Possenti R, Mahata SK, Fischer-Colbrie R, Loh YP, Salton SRJ. The extended granin family: structure, function, and biomedical implications. Endocr Rev 2011; 32:755-97. [PMID: 21862681 PMCID: PMC3591675 DOI: 10.1210/er.2010-0027] [Citation(s) in RCA: 228] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
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.
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Affiliation(s)
- Alessandro Bartolomucci
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, Minnesota 55455, USA
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29
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Helwig M, Lee SN, Hwang JR, Ozawa A, Medrano JF, Lindberg I. Dynamic modulation of prohormone convertase 2 (PC2)-mediated precursor processing by 7B2 protein: preferential effect on glucagon synthesis. J Biol Chem 2011; 286:42504-42513. [PMID: 22013069 DOI: 10.1074/jbc.m111.281980] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The small neuroendocrine protein 7B2 is required for the production of active prohormone convertase 2 (PC2), an enzyme involved in the synthesis of peptide hormones, such as glucagon and proopiomelanocortin-derived α-melanocyte-stimulating hormone. However, whether 7B2 can dynamically modulate peptide production through regulation of PC2 activity remains unclear. Infection of the pancreatic alpha cell line α-TC6 with 7B2-encoding adenovirus efficiently increased production of glucagon, whereas siRNA-mediated knockdown of 7B2 significantly decreased stored glucagon. Furthermore, rescue of 7B2 expression in primary pituitary cultures prepared from 7B2 null mice restored melanocyte-stimulating hormone production, substantiating the role of 7B2 as a regulatory factor in peptide biosynthesis. In anterior pituitary and pancreatic beta cell lines, however, overexpression of 7B2 affected neither production nor secretion of peptides despite increased release of active PC2. In direct contrast, 7B2 overexpression decreased the secretion and increased the activity of PC2 within α-TC6 cells; the increased intracellular concentration of active PC2 within these cells may therefore account for the enhanced production of glucagon. In line with these findings, we found elevated circulating glucagon levels in 7B2-overexpressing cast/cast mice in vivo. Surprisingly, when proopiomelanocortin and proglucagon were co-expressed in either pituitary or pancreatic alpha cell lines, proglucagon processing was preferentially decreased when 7B2 was knocked down. Taken together, these results suggest that proglucagon cleavage has a greater dependence on PC2 activity than other precursors and moreover that 7B2-dependent routing of PC2 to secretory granules is cell line-specific. The manipulation of 7B2 could therefore represent an effective way to selectively regulate synthesis of certain PC2-dependent peptides.
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Affiliation(s)
- Michael Helwig
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Sang-Nam Lee
- Research Center for Natural Human Defense System, Yonsei University College of Medicine, Seoul 120-752, Korea
| | - Jae Ryoung Hwang
- Molecular Therapy Research Center, Sungkyunkwan University, Seoul 135-710, Korea
| | - Akihiko Ozawa
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Juan F Medrano
- Department of Animal Science, University of California, Davis, California 95616-8521
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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30
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Hoshino A, Kowalska D, Jean F, Lazure C, Lindberg I. Modulation of PC1/3 activity by self-interaction and substrate binding. Endocrinology 2011; 152:1402-11. [PMID: 21303942 PMCID: PMC3060626 DOI: 10.1210/en.2010-1170] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Prohormone convertase (PC)1/3 is a eukaryotic serine protease in the subtilase family that participates in the proteolytic maturation of prohormone and neuropeptide precursors such as proinsulin and proopiomelanocortin. Despite the important role of this enzyme in peptide synthesis, how PC1/3 activity is regulated is still poorly understood. Using ion exchange chromatography and two-dimensional gel electrophoresis we found that natural PC1/3 present in AtT-20 cells and bovine chromaffin granules, as well as recombinant PC1/3 secreted from overexpressing Chinese hamster ovary cells, exists as multiple ionic forms. Gel filtration and cross-linking studies revealed that protein oligomerization and aggregation contribute greatly to variability in surface charge. The most acidic forms of PC1/3 contained both inactive aggregates as well as oligomerized 87-kDa PC1/3 that exhibited stable activity which was partially latent and could be revealed by dilution. No such latency was observed for the more basic, 66/74-kDa forms of PC1/3. Fractions containing these species were stabilized by preincubation with micromolar concentrations of either fluorogenic substrate or peptides containing pairs of basic residues. In addition, the most active form of 87-kDa PC1/3, a probable homodimer, was activated by preincubation with these same peptides. Cleavage by PC1/3 is often the initiating step in the biosynthetic pathway for peptide hormones, implying that this is a natural step for regulation. Our data suggest that enzyme oligomerization and peptide stabilization represent important contributing factors for the control of PC1/3 activity within secretory granules.
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Affiliation(s)
- Akina Hoshino
- Department of Anatomy and Neurobiology, University of Maryland-Baltimore, 20 Penn Street, HSFII Room S251, Baltimore, Maryland 21201, USA
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31
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Elson AE, Dotson CD, Egan JM, Munger SD. Glucagon signaling modulates sweet taste responsiveness. FASEB J 2010; 24:3960-9. [PMID: 20547661 PMCID: PMC2996909 DOI: 10.1096/fj.10-158105] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 05/27/2010] [Indexed: 11/11/2022]
Abstract
The gustatory system provides critical information about the quality and nutritional value of food before it is ingested. Thus, physiological mechanisms that modulate taste function in the context of nutritional needs or metabolic status could optimize ingestive decisions. We report that glucagon, which plays important roles in the maintenance of glucose homeostasis, enhances sweet taste responsiveness through local actions in the mouse gustatory epithelium. Using immunohistochemistry and confocal microscopy, we found that glucagon and its receptor (GlucR) are coexpressed in a subset of mouse taste receptor cells. Most of these cells also express the T1R3 taste receptor implicated in sweet and/or umami taste. Genetic or pharmacological disruption of glucagon signaling in behaving mice indicated a critical role for glucagon in the modulation of taste responsiveness. Scg5(-/-) mice, which lack mature glucagon, had significantly reduced responsiveness to sucrose as compared to wild-type littermates in brief-access taste tests. No significant differences were seen in responses to prototypical salty, sour, or bitter stimuli. Taste responsiveness to sucrose was similarly reduced upon acute and local disruption of glucagon signaling by the GlucR antagonist L-168,049. Together, these data indicate a role for local glucagon signaling in the peripheral modulation of sweet taste responsiveness.
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Affiliation(s)
- Amanda E.T. Elson
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; and
| | - Cedrick D. Dotson
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; and
| | - Josephine M. Egan
- National Institute on Aging/National Institutes of Health, Baltimore, Maryland, USA
| | - Steven D. Munger
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, USA; and
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Ozawa A, Peinado JR, Lindberg I. Modulation of prohormone convertase 1/3 properties using site-directed mutagenesis. Endocrinology 2010; 151:4437-45. [PMID: 20610561 PMCID: PMC2940488 DOI: 10.1210/en.2010-0296] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Prohormone convertase (PC)1/3 and PC2 cleave active peptide hormones and neuropeptides from precursor proteins. Compared with PC2, recombinant PC1/3 exhibits a very low specific activity against both small fluorogenic peptides and recombinant precursors, even though the catalytic domains in mouse PC1/3 and PC2 share 56% amino acid sequence identity. In this report, we have designed PC2-specific mutations into the catalytic domain of PC1/3 in order to investigate the molecular contributions of these sequences to PC1/3-specific properties. The exchange of residues RQG(314) with the SY sequence present in the same location within PC2 paradoxically shifted the pH optimum of PC1/3 upward into the neutral range; other mutations in the catalytic domain had no effect. Although none of the full-length PC1/3 mutants examined exhibited increased specific activity, the 66-kDa form of the RQG(314)SY mutant was two to four times more active than the 66-kDa form of wild-type PC1/3. However, stable transfection of RQG(314)SY into PC12 cells did not result in greater activity against the endogenous substrate proneurotensin, implying unknown cellular controls of PC1/3 activity. Mutation of GIVTDA(243-248) to QPFMTDI, a molecular determinant of 7B2 binding, resulted in increased zymogen expression but no propeptide cleavage or secretion, suggesting that this mutant is trapped in the endoplasmic reticulum due to an inability to cleave its own propeptide. We conclude that many convertase-specific properties are attributable less to convertase-specific catalytic cleft residues than to convertase-specific domain interactions.
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Affiliation(s)
- Akihiko Ozawa
- Department of Anatomy and Neurobiology, University of Maryland, Baltimore, 20 Penn Street, Health Sciences Facility II Room S251, Baltimore, Maryland 21201, USA
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Jansen EJR, Hafmans TGM, Martens GJM. V-ATPase-mediated granular acidification is regulated by the V-ATPase accessory subunit Ac45 in POMC-producing cells. Mol Biol Cell 2010; 21:3330-9. [PMID: 20702583 PMCID: PMC2947469 DOI: 10.1091/mbc.e10-04-0274] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The regulation of the V-ATPase, the proton pump mediating intraorganellar acidification, is still elusive. We find that excess of the neuroendocrine V-ATPase accessory subunit Ac45 reduces the intragranular pH and consequently disturbs prohormone convertase activation and prohormone processing. Thus, Ac45 represents the first V-ATPase regulator. The vacuolar (H+)-ATPase (V-ATPase) is an important proton pump, and multiple critical cell-biological processes depend on the proton gradient provided by the pump. Yet, the mechanism underlying the control of the V-ATPase is still elusive but has been hypothesized to involve an accessory subunit of the pump. Here we studied as a candidate V-ATPase regulator the neuroendocrine V-ATPase accessory subunit Ac45. We transgenically manipulated the expression levels of the Ac45 protein specifically in Xenopus intermediate pituitary melanotrope cells and analyzed in detail the functioning of the transgenic cells. We found in the transgenic melanotrope cells the following: i) significantly increased granular acidification; ii) reduced sensitivity for a V-ATPase-specific inhibitor; iii) enhanced early processing of proopiomelanocortin (POMC) by prohormone convertase PC1; iv) reduced, neutral pH–dependent cleavage of the PC2 chaperone 7B2; v) reduced 7B2-proPC2 dissociation and consequently reduced proPC2 maturation; vi) decreased levels of mature PC2 and consequently reduced late POMC processing. Together, our results show that the V-ATPase accessory subunit Ac45 represents the first regulator of the proton pump and controls V-ATPase-mediated granular acidification that is necessary for efficient prohormone processing.
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Affiliation(s)
- Eric J R Jansen
- Department of Molecular Animal Physiology, Donders Institute for Brain, Cognition, and Behaviour and Nijmegen Centre for Molecular Life Sciences (NCMLS), Faculty of Science, Radboud University Nijmegen, Nijmegen, The Netherlands
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Xie F, London SE, Southey BR, Annangudi SP, Amare A, Rodriguez-Zas SL, Clayton DF, Sweedler JV. The zebra finch neuropeptidome: prediction, detection and expression. BMC Biol 2010; 8:28. [PMID: 20359331 PMCID: PMC2873334 DOI: 10.1186/1741-7007-8-28] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 04/01/2010] [Indexed: 11/24/2022] Open
Abstract
Background Among songbirds, the zebra finch (Taeniopygia guttata) is an excellent model system for investigating the neural mechanisms underlying complex behaviours such as vocal communication, learning and social interactions. Neuropeptides and peptide hormones are cell-to-cell signalling molecules known to mediate similar behaviours in other animals. However, in the zebra finch, this information is limited. With the newly-released zebra finch genome as a foundation, we combined bioinformatics, mass-spectrometry (MS)-enabled peptidomics and molecular techniques to identify the complete suite of neuropeptide prohormones and final peptide products and their distributions. Results Complementary bioinformatic resources were integrated to survey the zebra finch genome, identifying 70 putative prohormones. Ninety peptides derived from 24 predicted prohormones were characterized using several MS platforms; tandem MS confirmed a majority of the sequences. Most of the peptides described here were not known in the zebra finch or other avian species, although homologous prohormones exist in the chicken genome. Among the zebra finch peptides discovered were several unique vasoactive intestinal and adenylate cyclase activating polypeptide 1 peptides created by cleavage at sites previously unreported in mammalian prohormones. MS-based profiling of brain areas required for singing detected 13 peptides within one brain nucleus, HVC; in situ hybridization detected 13 of the 15 prohormone genes examined within at least one major song control nucleus. Expression mapping also identified prohormone messenger RNAs in areas associated with spatial learning and social behaviours. Based on the whole-genome analysis, 40 prohormone probes were found on a commonly used zebra finch brain microarray. Analysis of these newly annotated transcripts revealed that six prohormone probes showed altered expression after birds heard song playbacks in a paradigm of song recognition learning; we partially verify this result experimentally. Conclusions The zebra finch peptidome and prohormone complement is now characterized. Based on previous microarray results on zebra finch vocal learning and synaptic plasticity, a number of these prohormones show significant changes during learning. Interestingly, most mammalian prohormones have counterparts in the zebra finch, demonstrating that this songbird uses similar biochemical pathways for neurotransmission and hormonal regulation. These findings enhance investigation into neuropeptide-mediated mechanisms of brain function, learning and behaviour in this model.
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Affiliation(s)
- Fang Xie
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA
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Nelsen SM, Christian JL. Site-specific cleavage of BMP4 by furin, PC6, and PC7. J Biol Chem 2009; 284:27157-66. [PMID: 19651771 PMCID: PMC2785643 DOI: 10.1074/jbc.m109.028506] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 07/27/2009] [Indexed: 11/06/2022] Open
Abstract
Bone morphogenetic proteins (BMPs) require proteolytic activation by members of the proprotein convertase (PC) family. Pro-BMP4 is initially cleaved at a site adjacent to the mature ligand domain (S1) and then at an upstream site (S2) within the prodomain. Cleavage at the S2 site, which appears to occur in a tissue-specific fashion, regulates the activity and signaling range of mature BMP4. To test the hypothesis that tissue-specific cleavage of pro-BMP4 is regulated by differential expression of a site-specific protease, we identified the PCs that cleave each site in vivo. In Xenopus oocytes, furin and PC6 function redundantly to cleave both the S1 and S2 sites of pro-BMP4, as evidenced by the results of antisense-mediated gene knockdown and the use of the furin- and PC6-selective inhibitor alpha(1)-PDX. By contrast, alpha(1)-PDX blocked cleavage of the S2 but not the S1 site of pro-BMP4 in embryos, suggesting the existence of a developmentally regulated S1 site-specific convertase. This protease is likely to be PC7 based on knowledge of its required substrate cleavage motif and resistance to alpha(1)-PDX. Consistent with this prediction, an alpha(1)-PDX variant engineered to target PC7, in addition to furin and PC6, completely inhibited cleavage of BMP4 in oocytes and embryos. Further studies showed that pc7 transcripts are expressed and polyadenylated, and that the PC7 precursor protein undergoes efficient autocatalytic activation in both oocytes and embryos. These results suggest that PC7, or a convertase with similar substrate specificity, functions to selectively cleave the S1 site of pro-BMP4 in a developmentally regulated fashion.
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Affiliation(s)
| | - Jan L. Christian
- Cell and Developmental Biology, Oregon Health and Science University School of Medicine, Portland, Oregon 97239-3098
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Southey BR, Rodriguez-Zas SL, Sweedler JV. Characterization of the prohormone complement in cattle using genomic libraries and cleavage prediction approaches. BMC Genomics 2009; 10:228. [PMID: 19445702 PMCID: PMC2698874 DOI: 10.1186/1471-2164-10-228] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 05/16/2009] [Indexed: 12/30/2022] Open
Abstract
Background Neuropeptides are cell to cell signalling molecules that regulate many critical biological processes including development, growth and reproduction. These peptides result from the complex processing of prohormone proteins, making their characterization both challenging and resource demanding. In fact, only 42 neuropeptide genes have been empirically confirmed in cattle. Neuropeptide research using high-throughput technologies such as microarray and mass spectrometry require accurate annotation of prohormone genes and products. However, the annotation and associated prediction efforts, when based solely on sequence homology to species with known neuropeptides, can be problematic. Results Complementary bioinformatic resources were integrated in the first survey of the cattle neuropeptide complement. Functional neuropeptide characterization was based on gene expression profiles from microarray experiments. Once a gene is identified, knowledge of the enzymatic processing allows determination of the final products. Prohormone cleavage sites were predicted using several complementary cleavage prediction models and validated against known cleavage sites in cattle and other species. Our bioinformatics approach identified 92 cattle prohormone genes, with 84 of these supported by expressed sequence tags. Notable findings included an absence of evidence for a cattle relaxin 1 gene and evidence for a cattle galanin-like peptide pseudogene. The prohormone processing predictions are likely accurate as the mammalian proprotein convertase enzymes, except for proprotein convertase subtilisin/kexin type 9, were also identified. Microarray analysis revealed the differential expression of 21 prohormone genes in the liver associated with nutritional status and 8 prohormone genes in the placentome of embryos generated using different reproductive techniques. The neuropeptide cleavage prediction models had an exceptional performance, correctly predicting cleavage in more than 86% of the prohormone sequence positions. Conclusion A substantial increase in the number of cattle prohormone genes identified and insights into the expression profiles of neuropeptide genes were obtained from the integration of bioinformatics tools and database resources and gene expression information. Approximately 20 prohormones with no empirical evidence were detected and the prohormone cleavage sites were predicted with high accuracy. Most prohormones were supported by expressed sequence tag data and many were differentially expressed across nutritional and reproductive conditions. The complete set of cattle prohormone sequences identified and the cleavage prediction approaches are available at .
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Affiliation(s)
- Bruce R Southey
- Department of Chemistry, University of Illinois, Urbana, IL, USA.
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Kudo H, Liu J, Jansen EJR, Ozawa A, Panula P, Martens GJM, Lindberg I. Identification of proSAAS homologs in lower vertebrates: conservation of hydrophobic helices and convertase-inhibiting sequences. Endocrinology 2009; 150:1393-9. [PMID: 18948394 PMCID: PMC2654743 DOI: 10.1210/en.2008-1301] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The prohormone convertases (PCs) 1/3 and 2 accomplish the major proteolytic cleavage events in neuroendocrine tissues; each of these convertases has a small associated binding protein that inhibits convertase action in the secretory pathway. The proSAAS protein binds to PC1/3, whereas the 7B2 protein binds to PC2. However, both convertase-binding proteins are more widely expressed than their cognate enzymes, suggesting that they may perform other functions as well. All known mammalian proSAASs are over 85% conserved; thus, identifying functionally important segments has been impossible. Here, we report the first identification of nonmammalian proSAAS molecules, from Xenopus and zebrafish (Danio rerio). Although these two proteins show an overall amino acid sequence identity of only 29 and 30% with mouse proSAAS, two 14-16 residue hydrophobic segments (predicted to form alpha-helices) and two, nine through 11 residue sequences containing basic convertase cleavage sites are highly conserved; therefore, these sequences may be of functional importance. Confidence that these nonmammalian molecules represent authentic proSAAS is supported by the finding that both inhibit mouse PC1/3 with nanomolar inhibition constants; human furin was not inhibited. In vitro, the two proteins were cleaved by PC2 and furin to three or more peptide products. Both zebrafish and Xenopus proSAAS exhibited neural and endocrine distributions, as assessed by in situ and PCR experiments, respectively. In summary, the identification of proSAAS molecules in lower vertebrates provides clues as to functional regions within this widely expressed neuroendocrine protein.
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Affiliation(s)
- H Kudo
- Department of Anatomy and Neurobiology, University of Maryland-Baltimore, Baltimore, Maryland 21201, USA
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Prohormone convertases 1/3 and 2 together orchestrate the site-specific cleavages of progastrin to release gastrin-34 and gastrin-17. Biochem J 2008; 415:35-43. [PMID: 18554181 DOI: 10.1042/bj20080881] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Cellular synthesis of peptide hormones requires PCs (prohormone convertases) for the endoproteolysis of prohormones. Antral G-cells synthesize the most gastrin and express PC1/3, 2 and 5/6 in the rat and human. But the cleavage sites in progastrin for each PC have not been determined. Therefore, in the present study, we measured the concentrations of progastrin, processing intermediates and alpha-amidated gastrins in antral extracts from PC1/3-null mice and compared the results with those in mice lacking PC2 and wild-type controls. The expression of PCs was examined by immunocytochemistry and in situ hybridization of mouse G-cells. Finally, the in vitro effect of recombinant PC5/6 on progastrin and progastrin fragments containing the relevant dibasic cleavage sites was also examined. The results showed that mouse G-cells express PC1/3, 2 and 5/6. The concentration of progastrin in PC1/3-null mice was elevated 3-fold. Chromatography showed that cleavage of the Arg(36)Arg(37) and Arg(73)Arg(74) sites were grossly decreased. Accordingly, the concentrations of progastrin products were markedly reduced, alpha-amidated gastrins (-34 and -17) being 25% of normal. Lack of PC1/3 was without effect on the third dibasic site (Lys(53)Lys(54)), which is the only processing site for PC2. Recombinant PC5/6 did not cleave any of the dibasic processing sites in progastrin and fragments containing the relevant dibasic processing sites. The complementary cleavages of PC1/3 and 2, however, suffice to explain most of the normal endoproteolysis of progastrin. Moreover, the results show that PCs react differently to the same dibasic sequences, suggesting that additional structural factors modulate the substrate specificity.
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