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Yadati T, Houben T, Bitorina A, Shiri-Sverdlov R. The Ins and Outs of Cathepsins: Physiological Function and Role in Disease Management. Cells 2020; 9:cells9071679. [PMID: 32668602 PMCID: PMC7407943 DOI: 10.3390/cells9071679] [Citation(s) in RCA: 188] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 07/10/2020] [Accepted: 07/11/2020] [Indexed: 12/14/2022] Open
Abstract
Cathepsins are the most abundant lysosomal proteases that are mainly found in acidic endo/lysosomal compartments where they play a vital role in intracellular protein degradation, energy metabolism, and immune responses among a host of other functions. The discovery that cathepsins are secreted and remain functionally active outside of the lysosome has caused a paradigm shift. Contemporary research has unraveled many versatile functions of cathepsins in extralysosomal locations including cytosol and extracellular space. Nevertheless, extracellular cathepsins are majorly upregulated in pathological states and are implicated in a wide range of diseases including cancer and cardiovascular diseases. Taking advantage of the differential expression of the cathepsins during pathological conditions, much research is focused on using cathepsins as diagnostic markers and therapeutic targets. A tailored therapeutic approach using selective cathepsin inhibitors is constantly emerging to be safe and efficient. Moreover, recent development of proteomic-based approaches for the identification of novel physiological substrates offers a major opportunity to understand the mechanism of cathepsin action. In this review, we summarize the available evidence regarding the role of cathepsins in health and disease, discuss their potential as biomarkers of disease progression, and shed light on the potential of extracellular cathepsin inhibitors as safe therapeutic tools.
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Luziga C. Potential role of cytotoxic T-lymphocyte antigen 2 alpha in secretory activity of endocrine cells in mouse adenohypophysis. Open Vet J 2019; 9:114-119. [PMID: 31360649 PMCID: PMC6626156 DOI: 10.4314/ovj.v9i2.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 03/10/2019] [Indexed: 11/18/2022] Open
Abstract
The peptide hormones of the adenohypophysis are produced by proteolytic processing of their prohormone precursors. Cathepsin L is known to function as a major proteolytic enzyme involved in the production of the peptide hormones. The structure of the propeptide region of cathepsin L is identical to cytotoxic T-lymphocyte antigen-2 alpha (CTLA-2α) which is also shown to exhibit selective inhibitory activities against cathepsin L. However, the specific cell types synthesizing CTLA-2α in mouse adenohypophysis and its functional implications as relevant in vivo have not been demonstrated. In this study, CTLA-2α expression in the adenohypophysis was evaluated by immunohistochemistry. In both male and female mice, strong immunoreactivity was specifically detected in folliculostellate (FS) cells surrounding endocrine cells which were delineated by CTLA-2α. These findings suggest that the CTLA-2α may be involved in the proteolytic processing and secretion of the hormones in the adenohypophysis through regulation of cathepsin L.
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Affiliation(s)
- Claudius Luziga
- Department of Veterinary Anatomy and Pathology, Sokoine University of Agriculture, Morogoro, Tanzania
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3
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Sudhan DR, Siemann DW. Cathepsin L targeting in cancer treatment. Pharmacol Ther 2015; 155:105-16. [PMID: 26299995 DOI: 10.1016/j.pharmthera.2015.08.007] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/17/2015] [Indexed: 12/14/2022]
Abstract
Proteolytic enzymes may serve as promising targets for novel therapeutic treatment strategies seeking to impede cancer progression and metastasis. One such enzyme is cathepsin L (CTSL), a lysosomal cysteine protease. CTSL upregulation, a common occurrence in a variety of human cancers, has been widely correlated with metastatic aggressiveness and poor patient prognosis. In addition, CTSL has been implicated to contribute to cancer-associated osteolysis, a debilitating morbidity affecting both life expectancy and the quality of life. In this review, we highlight the mechanisms by which CTSL contributes to tumor progression and dissemination and discuss the therapeutic utility of CTSL intervention strategies aimed at impeding metastatic progression and bone resorption.
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Affiliation(s)
- Dhivya R Sudhan
- Department of Radiation Oncology, University of Florida Health Cancer Center, Gainesville, FL, USA
| | - Dietmar W Siemann
- Department of Radiation Oncology, University of Florida Health Cancer Center, Gainesville, FL, USA; Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, USA.
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Podvin S, Bundey R, Toneff T, Ziegler M, Hook V. Profiles of secreted neuropeptides and catecholamines illustrate similarities and differences in response to stimulation by distinct secretagogues. Mol Cell Neurosci 2015; 68:177-85. [PMID: 26092702 DOI: 10.1016/j.mcn.2015.06.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 05/12/2015] [Accepted: 06/01/2015] [Indexed: 12/20/2022] Open
Abstract
The goal of this study was to define profiles of secreted neuropeptide and catecholamine neurotransmitters that undergo co-release from sympathoadrenal chromaffin cells upon stimulation by distinct secretagogues. Chromaffin cells of the adrenal medulla participate in the dynamic responses to stress, especially that of 'fight and flight', and, thus, analyses of the co-release of multiple neurotransmitters is necessary to gain knowledge of how the stress response regulates cell-cell communication among physiological systems. Results of this study demonstrated that six different secretagogues stimulated the co-release of the neuropeptides Met-enkephalin, galanin, NPY, and VIP with the catecholamines dopamine, norepinephrine, and epinephrine. Importantly, the quantitative profiles of the secreted neurotransmitters showed similarities and differences upon stimulation by the different secretagogues evaluated, composed of KCl depolarization, nicotine, carbachol, PACAP, bradykinin, and histamine. The rank-orders of the secreted profiles of the neurotransmitters were generally similar among these secretagogues, but differences in the secreted amounts of each neurotransmitter occurred with different secretagogues. Epinephrine among the catecholamines showed the highest level of secretion. (Met)enkephalin showed the largest levels of secretion compared to the other neuropeptides examined. Levels of secreted catecholamines were greater than that of the neuropeptides. These data support the hypothesis that profiles of secreted neuropeptide and catecholamine neurotransmitters show similarities and differences upon stimulation by distinct secretagogues. These results illustrate the co-release of concerted neurotransmitter profiles that participate in the stress response of the sympathoadrenal nervous system.
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Affiliation(s)
- Sonia Podvin
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Richard Bundey
- Dept. of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Thomas Toneff
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Michael Ziegler
- Dept. of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States
| | - Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States; Dept. of Neuroscience and Dept. of Pharmacology, School of Medicine, Univ. of Calif.-San Diego, La Jolla, CA 92093, United States.
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5
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Cynis H, Funkelstein L, Toneff T, Mosier C, Ziegler M, Koch B, Demuth HU, Hook V. Pyroglutamate-amyloid-β and glutaminyl cyclase are colocalized with amyloid-β in secretory vesicles and undergo activity-dependent, regulated secretion. NEURODEGENER DIS 2014; 14:85-97. [PMID: 24943989 DOI: 10.1159/000358430] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 01/07/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND AIMS N-truncated pyroglutamate (pGlu)-amyloid-β [Aβ(3-40/42)] peptides are key components that promote Aβ peptide accumulation, leading to neurodegeneration and memory loss in Alzheimer's disease. Because Aβ deposition in the brain occurs in an activity-dependent manner, it is important to define the subcellular organelle for pGlu-Aβ(3-40/42) production by glutaminyl cyclase (QC) and their colocalization with full-length Aβ(1-40/42) peptides for activity-dependent, regulated secretion. Therefore, the objective of this study was to investigate the hypothesis that pGlu-Aβ and QC are colocalized with Aβ in dense-core secretory vesicles (DCSV) for activity-dependent secretion with neurotransmitters. METHODS Purified DCSV were assessed for pGlu-Aβ(3-40/42), Aβ(1-40/42), QC, and neurotransmitter secretion. Neuron-like chromaffin cells were analyzed for cosecretion of pGlu-Aβ, QC, Aβ, and neuropeptides. The cells were treated with a QC inhibitor, and pGlu-Aβ production was measured. Human neuroblastoma cells were also examined for pGlu-Aβ and QC secretion. RESULTS Isolated DCSV contain pGlu-Aβ(3-40/42), QC, and Aβ(1-40/42) with neuropeptide and catecholamine neurotransmitters. Cellular pGlu-Aβ and QC undergo activity-dependent cosecretion with Aβ and enkephalin and galanin neurotransmitters. The QC inhibitor decreased the level of secreted pGlu-Aβ. The human neuroblastoma cells displayed regulated secretion of pGlu-Aβ that was colocalized with QC. CONCLUSIONS pGlu-Aβ and QC are present with Aβ in DCSV and undergo activity-dependent, regulated cosecretion with neurotransmitters.
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Medina Benavente JJ, Mogami H, Sakurai T, Sawada K. Evaluation of silicon nitride as a substrate for culture of PC12 cells: an interfacial model for functional studies in neurons. PLoS One 2014; 9:e90189. [PMID: 24587271 PMCID: PMC3937378 DOI: 10.1371/journal.pone.0090189] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 01/30/2014] [Indexed: 12/24/2022] Open
Abstract
Silicon nitride is a biocompatible material that is currently used as an interfacial surface between cells and large-scale integration devices incorporating ion-sensitive field-effect transistor technology. Here, we investigated whether a poly-L-lysine coated silicon nitride surface is suitable for the culture of PC12 cells, which are widely used as a model for neural differentiation, and we characterized their interaction based on cell behavior when seeded on the tested material. The coated surface was first examined in terms of wettability and topography using contact angle measurements and atomic force microscopy and then, conditioned silicon nitride surface was used as the substrate for the study of PC12 cell culture properties. We found that coating silicon nitride with poly-L-lysine increased surface hydrophilicity and that exposing this coated surface to an extracellular aqueous environment gradually decreased its roughness. When PC12 cells were cultured on a coated silicon nitride surface, adhesion and spreading were facilitated, and the cells showed enhanced morphological differentiation compared to those cultured on a plastic culture dish. A bromodeoxyuridine assay demonstrated that, on the coated silicon nitride surface, higher proportions of cells left the cell cycle, remained in a quiescent state and had longer survival times. Therefore, our study of the interaction of the silicon nitride surface with PC12 cells provides important information for the production of devices that need to have optimal cell culture-supporting properties in order to be used in the study of neuronal functions.
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Affiliation(s)
- Johan Jaime Medina Benavente
- Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Japan
- Core Research for Evolutional Science and Technology Program, Japan Science and Technology Agency, Tokyo, Japan
- * E-mail:
| | - Hideo Mogami
- Core Research for Evolutional Science and Technology Program, Japan Science and Technology Agency, Tokyo, Japan
- Faculty of Health Promotional Sciences, Hamamatsu University, Hamamatsu, Japan
| | - Takashi Sakurai
- Core Research for Evolutional Science and Technology Program, Japan Science and Technology Agency, Tokyo, Japan
- Electronics-Inspired Interdisciplinary Research Institute, Toyohashi University of Technology, Toyohashi, Japan
| | - Kazuaki Sawada
- Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Japan
- Core Research for Evolutional Science and Technology Program, Japan Science and Technology Agency, Tokyo, Japan
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Gu WW, Ao GZ, Zhu YM, Sun SC, Zhou Q, Fan JH, Nobuhiko K, Ishidoh K, Zhang HL, Gao XM. Autophagy and cathepsin L are involved in the antinociceptive effect of DMBC in a mouse acetic acid-writhing model. Acta Pharmacol Sin 2013; 34:1007-12. [PMID: 23912553 DOI: 10.1038/aps.2013.30] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/06/2013] [Indexed: 12/19/2022] Open
Abstract
AIM 2-(3',5'-Dimethoxybenzylidene) cyclopentanone (DMBC) is a novel synthetic compound with antinociceptive activities. The aim of this study was to investigate the roles of the autophagic-lysosomal pathway in the antinociceptive effect of DMBC in a mouse acetic acid-writhing model. METHODS Mouse acetic acid-writhing test and hotplate test were used to assess the antinociceptive effects of DMBC, 3-MA (autophagy inhibitor) and Clik148 (cathepsin L inhibitor). The drugs were administered peripherally (ip) or centrally (icv). RESULTS Peripheral administration of 3-MA (7.5-30 mg/kg) or Clik148 (10-80 mg/kg) produced potent antinociceptive effect in acetic acid-writhing test. Central administration of 3-MA or Clik148 (12.5-50 nmol/L) produced comparable antinociceptive effect in acetic acid-writhing test. Peripheral administration of DMBC (25-50 mg/kg) produced potent antinociceptive effects in both acetic acid-writhing and hotplate tests. Furthermore, the antinociceptive effect produced by peripheral administration of DMBC (50 mg/kg) in acetic acid-writhing test was antagonized by low doses of 3-MA (3.75 mg/kg) or Clik148 (20 mg/kg) peripherally administered, but was not affected by 3-MA or Clik148 (25 nmol/L) centrally administered. CONCLUSION Activation of central autophagy and cathepsin L is involved in nociception in mice, whereas peripheral autophagy and cathepsin L contributes, at least in part, to the antinociceptive effect of DMBC in mice.
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Cheng XW, Shi GP, Kuzuya M, Sasaki T, Okumura K, Murohara T. Role for cysteine protease cathepsins in heart disease: focus on biology and mechanisms with clinical implication. Circulation 2012; 125:1551-62. [PMID: 22451605 DOI: 10.1161/circulationaha.111.066712] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Xian Wu Cheng
- Department of Cardiology, Nagoya University Graduate School of Medicine, 65 Tsuruma-cho, Nagoya, Japan.
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Funkelstein L, Lu WD, Koch B, Mosier C, Toneff T, Taupenot L, O'Connor DT, Reinheckel T, Peters C, Hook V. Human cathepsin V protease participates in production of enkephalin and NPY neuropeptide neurotransmitters. J Biol Chem 2012; 287:15232-41. [PMID: 22393040 PMCID: PMC3346103 DOI: 10.1074/jbc.m111.310607] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 02/23/2012] [Indexed: 12/11/2022] Open
Abstract
Proteases are required for processing precursors into active neuropeptides that function as neurotransmitters for cell-cell communication. This study demonstrates the novel function of human cathepsin V protease for producing the neuropeptides enkephalin and neuropeptide Y (NPY). Cathepsin V is a human-specific cysteine protease gene. Findings here show that expression of cathepsin V in neuroendocrine PC12 cells and human neuronal SK-N-MC cells results in production of (Met)enkephalin from proenkephalin. Gene silencing of cathepsin V by siRNA in human SK-N-MC cells results in reduction of (Met)enkephalin by more than 80%, illustrating the prominent role of cathepsin V for neuropeptide production. In vitro processing of proenkephalin by cathepsin V occurs at dibasic residue sites to generate enkephalin-containing peptides and an ∼24-kDa intermediate present in human brain. Cathepsin V is present in human brain cortex and hippocampus where enkephalin and NPY are produced and is present in purified human neuropeptide secretory vesicles. Colocalization of cathepsin V with enkephalin and NPY in secretory vesicles of human neuroblastoma cells was illustrated by confocal microscopy. Furthermore, expression of cathepsin V with proNPY results in NPY production. These findings indicate the unique function of human cathepsin V for producing enkephalin and NPY neuropeptides required for neurotransmission in health and neurological diseases.
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Affiliation(s)
- Lydiane Funkelstein
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093
| | - W. Douglas Lu
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093
| | - Britta Koch
- the Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs Universitat, Freiburg, Germany D-79104 Freiburg
| | - Charles Mosier
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093
| | - Thomas Toneff
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093
| | - Laurent Taupenot
- the Department of Medicine, University of California, San Diego, California 92093
| | - Daniel T. O'Connor
- the Department of Medicine, University of California, San Diego, California 92093
| | - Thomas Reinheckel
- the Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs Universitat, Freiburg, Germany D-79104 Freiburg
- BIOSS Centre for Biological Signaling Studies, D-79104 Freiburg, Germany, and
| | - Christoph Peters
- the Institut für Molekulare Medizin und Zellforschung, Albert-Ludwigs Universitat, Freiburg, Germany D-79104 Freiburg
- BIOSS Centre for Biological Signaling Studies, D-79104 Freiburg, Germany, and
| | - Vivian Hook
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92093
- the Department of Medicine, University of California, San Diego, California 92093
- the Departments of of Neurosciences, Pharmacology, and Medicine, University of California, San Diego, La Jolla, California 92093
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Lu WD, Liu T, Li S, Woods VL, Hook V. The prohormone proenkephalin possesses differential conformational features of subdomains revealed by rapid H-D exchange mass spectrometry. Protein Sci 2012; 21:178-87. [PMID: 22102294 DOI: 10.1002/pro.2000] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 10/19/2011] [Accepted: 10/22/2011] [Indexed: 11/11/2022]
Abstract
Active enkephalin and related peptide hormones or neurotransmitters are generated by proteolytic processing of inactive prohormone precursors. Little is known about the relative accessibilities of prohormone cleavage sites and conformations of subdomains that undergo proteolytic processing. Therefore, this study investigated the conformational features of the prohormone proenkephalin (PE) by rapid hydrogen-deuterium exchange mass spectrometry (DXMS). DXMS analyzes rates of hydrogen exchange of the polypeptide backbone of PE with deuterium from D(2) O (heavy water) by mass spectrometry, accomplished at sub-second and multisecond time periods. Results showed differential accessibilities of cleavage sites and adjacent subdomains of PE to the aqueous environment. Importantly, protease cleavage sites of PE with greater relative accessibilities correspond to sites most readily cleaved by processing proteases to generate active peptide neurotransmitters. For comparison, peptides derived from PE (by pepsin digestion) displayed greater accessibility to the solvent environment, illustrated by their higher rates of H-D exchange compared to that of intact PE protein. The more limited H-D exchange accessibilities of PE protein, compared to peptides derived from PE, indicate that PE possesses tertiary conformation. These results demonstrate that differential tertiary conformations of PE subdomains undergo ordered proteolytic processing to generate active enkephalin peptides for cell-cell communication in the nervous and endocrine systems.
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Affiliation(s)
- Weiya D Lu
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Hook V, Funkelstein L, Wegrzyn J, Bark S, Kindy M, Hook G. Cysteine Cathepsins in the secretory vesicle produce active peptides: Cathepsin L generates peptide neurotransmitters and cathepsin B produces beta-amyloid of Alzheimer's disease. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:89-104. [PMID: 21925292 DOI: 10.1016/j.bbapap.2011.08.015] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 08/26/2011] [Accepted: 08/29/2011] [Indexed: 12/01/2022]
Abstract
Recent new findings indicate significant biological roles of cysteine cathepsin proteases in secretory vesicles for production of biologically active peptides. Notably, cathepsin L in secretory vesicles functions as a key protease for proteolytic processing of proneuropeptides (and prohormones) into active neuropeptides that are released to mediate cell-cell communication in the nervous system for neurotransmission. Moreover, cathepsin B in secretory vesicles has been recently identified as a β-secretase for production of neurotoxic β- amyloid (Aβ) peptides that accumulate in Alzheimer's disease (AD), participating as a notable factor in the severe memory loss in AD. These secretory vesicle functions of cathepsins L and B for production of biologically active peptides contrast with the well-known role of cathepsin proteases in lysosomes for the degradation of proteins to result in their inactivation. The unique secretory vesicle proteome indicates proteins of distinct functional categories that provide the intravesicular environment for support of cysteine cathepsin functions. Features of the secretory vesicle protein systems insure optimized intravesicular conditions that support the proteolytic activity of cathepsins. These new findings of recently discovered biological roles of cathepsins L and B indicate their significance in human health and disease. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.
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Affiliation(s)
- Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, Dept. of Neurosciences, Univ. of Calif., San Diego, USA.
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VGF: an inducible gene product, precursor of a diverse array of neuro-endocrine peptides and tissue-specific disease biomarkers. J Chem Neuroanat 2011; 42:249-61. [PMID: 21621608 DOI: 10.1016/j.jchemneu.2011.05.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 05/10/2011] [Accepted: 05/12/2011] [Indexed: 12/13/2022]
Abstract
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.
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Funkelstein L, Hook V. The novel role of cathepsin L for neuropeptide production illustrated by research strategies in chemical biology with protease gene knockout and expression. Methods Mol Biol 2011; 768:107-125. [PMID: 21805239 DOI: 10.1007/978-1-61779-204-5_5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Neuropeptides are essential for cell-cell communication in the nervous and endocrine systems. Production of active neuropeptides requires proteolytic processing of proneuropeptide precursors in secretory vesicles that produce, store, and release neuropeptides that regulate physiological functions. This review describes research strategies utilizing chemical biology combined with protease gene knockout and expression to demonstrate the key role of cathepsin L for production of neuropeptides in secretory vesicles. Cathepsin L was discovered using activity-based probes and mass spectrometry to identify proenkephalin cleaving activity as cathepsin L. Significantly, in vivo protease gene knockout and expression approaches illustrate the key role of cathepsin L for neuropeptide production. Notably, cathepsin L is colocalized with neuropeptide secretory vesicles, the major site of proteolytic processing of proneuropeptides to generate active neuropeptides. Cathepsin L participates in producing opioid neuropeptides consisting of enkephalin, β-endorphin, and dynorphin, as well as in generating the POMC-derived peptide hormones ACTH and α-MSH. In addition, NPY, CCK, and catestatin neuropeptides utilize cathepsin L for their biosynthesis. The role of cathepsin L for neuropeptide production indicates its unique biological role in secretory vesicles, which contrasts with its role in lysosomes for protein degradation. Interesting evaluations of protease gene knockout studies in mice that lack cathepsin L compared to the PC1/3 and PC2 (PC, prohormone convertase) indicate the significant role of cathepsin L in neuropeptide production. Thus, dual cathepsin L and prohormone convertase protease pathways participate in neuropeptide production. These recent new findings indicate cathepsin L as a novel 'proprotein convertase' for production of neuropeptides that mediate cell-cell communication in health and disease.
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Affiliation(s)
- Lydiane Funkelstein
- Department of Neuroscience, Pharmacology, and Medicine, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, CA 93093, USA.
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15
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Funkelstein L, Beinfeld M, Minokadeh A, Zadina J, Hook V. Unique biological function of cathepsin L in secretory vesicles for biosynthesis of neuropeptides. Neuropeptides 2010; 44:457-66. [PMID: 21047684 PMCID: PMC3058267 DOI: 10.1016/j.npep.2010.08.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 08/05/2010] [Accepted: 08/30/2010] [Indexed: 11/18/2022]
Abstract
Neuropeptides are essential for cell-cell communication in the nervous and neuroendocrine systems. Production of active neuropeptides requires proteolytic processing of proneuropeptide precursors in secretory vesicles that produce, store, and release neuropeptides that regulate physiological functions. This review describes recent findings indicating the prominent role of cathepsin L in secretory vesicles for production of neuropeptides from their protein precursors. The role of cathepsin L in neuropeptide production was discovered using the strategy of activity-based probes for proenkephalin-cleaving activity for identification of the enzyme protein by mass spectrometry. The novel role of cathepsin L in secretory vesicles for neuropeptide production has been demonstrated in vivo by cathepsin L gene knockout studies, cathepsin L gene expression in neuroendocrine cells, and notably, cathepsin L localization in neuropeptide-containing secretory vesicles. Cathepsin L is involved in producing opioid neuropeptides consisting of enkephalin, β-endorphin, and dynorphin, as well as in generating the POMC-derived peptide hormones ACTH and α-MSH. In addition, NPY, CCK, and catestatin neuropeptides utilize cathepsin L for their biosynthesis. The neuropeptide-synthesizing functions of cathepsin L represent its unique activity in secretory vesicles, which contrasts with its role in lysosomes. Interesting evaluations of protease gene knockout studies in mice that lack cathepsin L compared to those lacking PC1/3 and PC2 (PC, prohormone convertase) indicate the key role of cathepsin L in neuropeptide production. Therefore, dual cathepsin L and prohormone convertase protease pathways participate in neuropeptide production. Significantly, the recent new findings indicate cathepsin L as a novel 'proprotein convertase' for production of neuropeptides that mediate cell-cell communication in health and disease.
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Affiliation(s)
- Lydiane Funkelstein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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Mahata SK, Mahata M, Fung MM, O'Connor DT. Reprint of: Catestatin: a multifunctional peptide from chromogranin A. REGULATORY PEPTIDES 2010; 165:52-62. [PMID: 20965217 PMCID: PMC10838673 DOI: 10.1016/j.regpep.2010.09.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In 1997, we identified a novel peptide, catestatin (CST: bovine chromogranin A [CHGA]₃₄₄₋₃₆₄: RSMRLSFRARGYGFRGPGLQL; human CHGA₃₅₂₋₃₇₂: SSMKLSFRARGYGFRGPGPQL), which is a potent inhibitor of nicotinic-cholinergic-stimulated catecholamine secretion. CST shows characteristic inhibitory effects on nicotinic cationic (Na+, Ca²+) signal transduction, which are specific to the neuronal nicotinic receptor. Utilizing systematic polymorphism discovery at the human CHGA locus we discovered three human variants of CST: G³⁶⁴S, P³⁷⁰L, and R³⁷⁴Q that showed differential potencies towards the inhibition of catecholamine secretion. In humans, CHGA is elevated and its processing to CST is diminished in hypertension. Diminished CST is observed not only in hypertensive individuals but also in the early-normotensive offspring of patients with hypertension, suggesting that an early deficiency of CST might play a pathogenic role in the subsequent development of the disease. Consistent with human findings, prevention of endogenous CST expression by targeted ablation (knockout) of the mouse Chga locus (Chga-KO) resulted in severe hypertension that can be "rescued" specifically by replacement of the CST peptide. CST acts directly on the heart to inhibit the inotropic and lusitropic properties of the rodent heart and also acts as a potent vasodilator in rats and humans. While the G³⁶⁴S CST variant caused profound changes in human autonomic activity and seemed to reduce the risk of developing hypertension, CST replacement rescued Chga-KO mice from dampened baroreflex sensitivity. In addition, CST has been shown to induce chemotaxis and acts as an antimicrobial as well as an antimalarial peptide. The present review summarizes these multiple actions of CST.
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Affiliation(s)
- Sushil K Mahata
- Department of Medicine (0838), University of California at San Diego, and Veterans Affairs San Diego Healthcare System, 9500 Gilman Drive, La Jolla, CA 92093-0838, USA.
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Wu S, Ma C, Li G, Mai M, Wu Y. Intrathecal implantation of microencapsulated PC12 cells reduces cold allodynia in a rat model of neuropathic pain. Artif Organs 2010; 35:294-300. [PMID: 21114677 DOI: 10.1111/j.1525-1594.2010.01059.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The transplantation of cells into the central nervous system provides a constant and replenishable source of analgesic substances for the alleviation of chronic pain. In the present study, PC12 cells were microencapsulated in a semipermeable membrane that protected the cells from the host's immune system. A chronic neuropathic pain model was induced by chronic constriction injury (CCI) of the sciatic nerve in rats. Thirty Sprague-Dawley rats with CCI were divided randomly into two groups: the cell-loaded group received microencapsulated PC12 cells (n = 15) and the control group received empty capsules (n = 15). The microcapsules were implanted into the lumbar subarachnoid space. After implantation, a significant reduction of cold allodynia was observed in the rats of the cell-loaded group at 7, 14, 21, and 28 days compared to the control group with the empty capsules (P < 0.05). Furthermore, the levels of catecholamines and met-enkephalin in the cerebrospinal fluid of rats in the cell-loaded group were higher than the levels in the controls (P < 0.05). These results suggest that intrathecal microencapsulated PC12 cells could be a useful method for chronic neuropathic pain management.
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Affiliation(s)
- Shaoling Wu
- Pain Treatment Centre of the Department of Rehabilitation Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, China
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18
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Gupta N, Bark SJ, Lu WD, Taupenot L, O'Connor DT, Pevzner P, Hook V. Mass spectrometry-based neuropeptidomics of secretory vesicles from human adrenal medullary pheochromocytoma reveals novel peptide products of prohormone processing. J Proteome Res 2010; 9:5065-75. [PMID: 20704348 DOI: 10.1021/pr100358b] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neuropeptides are required for cell-cell communication in the regulation of physiological and pathological processes. While selected neuropeptides of known biological activities have been studied, global analyses of the endogenous profile of human peptide products derived from prohormones by proteolytic processing in vivo are largely unknown. Therefore, this study utilized the global, unbiased approach of mass spectrometry-based neuropeptidomics to define peptide profiles in secretory vesicles, isolated from human adrenal medullary pheochromocytoma of the sympathetic nervous system. The low molecular weight pool of secretory vesicle peptides was subjected to nano-LC-MS/MS with ion trap and QTOF mass spectrometry analyzed by different database search tools (InsPecT and Spectrum Mill). Peptides were generated by processing of prohormones at dibasic cleavage sites as well as at nonbasic residues. Significantly, peptide profiling provided novel insight into newly identified peptide products derived from proenkephalin, pro-NPY, proSAAS, CgA, CgB, and SCG2 prohormones. Previously unidentified intervening peptide domains of prohormones were observed, thus providing new knowledge of human neuropeptidomes generated from precursors. The global peptidomic approach of this study demonstrates the complexity of diverse neuropeptides present in human secretory vesicles for cell-cell communication.
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Affiliation(s)
- Nitin Gupta
- Bioinformatics Graduate Program, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA
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19
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Wegrzyn JL, Bark SJ, Funkelstein L, Mosier C, Yap A, Kazemi-Esfarjani P, La Spada AR, Sigurdson C, O'Connor DT, Hook V. Proteomics of dense core secretory vesicles reveal distinct protein categories for secretion of neuroeffectors for cell-cell communication. J Proteome Res 2010; 9:5002-24. [PMID: 20695487 DOI: 10.1021/pr1003104] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
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.
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Affiliation(s)
- Jill L Wegrzyn
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, USA
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20
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Reiser J, Adair B, Reinheckel T. Specialized roles for cysteine cathepsins in health and disease. J Clin Invest 2010; 120:3421-31. [PMID: 20921628 DOI: 10.1172/jci42918] [Citation(s) in RCA: 430] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Cathepsins were originally identified as proteases that act in the lysosome. Recent work has uncovered nontraditional roles for cathepsins in the extracellular space as well as in the cytosol and nucleus. There is strong evidence that subspecialized and compartmentalized cathepsins participate in many physiologic and pathophysiologic cellular processes, in which they can act as both digestive and regulatory proteases. In this review, we discuss the transcriptional and translational control of cathepsin expression, the regulation of intracellular sorting of cathepsins, and the structural basis of cathepsin activation and inhibition. In particular, we highlight the emerging roles of various cathepsin forms in disease, particularly those of the cardiac and renal systems.
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Affiliation(s)
- Jochen Reiser
- Department of Medicine, Leonard Miller School of Medicine, University of Miami, Miami, Florida, USA.
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21
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Mahata SK, Mahata M, Fung MM, O'Connor DT. Catestatin: a multifunctional peptide from chromogranin A. ACTA ACUST UNITED AC 2010; 162:33-43. [PMID: 20116404 DOI: 10.1016/j.regpep.2010.01.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2009] [Revised: 01/11/2010] [Accepted: 01/21/2010] [Indexed: 12/16/2022]
Abstract
In 1997, we identified a novel peptide, catestatin (CST: bovine chromogranin A [CHGA](344-364): RSMRLSFRARGYGFRGPGLQL; human CHGA(352-372): SSMKLSFRARGYGFRGPGPQL), which is a potent inhibitor of nicotinic-cholinergic-stimulated catecholamine secretion. CST shows characteristic inhibitory effects on nicotinic cationic (Na(+), Ca(2+)) signal transduction, which are specific to the neuronal nicotinic receptor. Utilizing systematic polymorphism discovery at the human CHGA locus we discovered three human variants of CST: G(364)S, P(370)L, and R(374)Q that showed differential potencies towards the inhibition of catecholamine secretion. In humans, CHGA is elevated and its processing to CST is diminished in hypertension. Diminished CST is observed not only in hypertensive individuals but also in the early-normotensive offspring of patients with hypertension, suggesting that an early deficiency of CST might play a pathogenic role in the subsequent development of the disease. Consistent with human findings, prevention of endogenous CST expression by targeted ablation (knockout) of the mouse Chga locus (Chga-KO) resulted in severe hypertension that can be "rescued" specifically by replacement of the CST peptide. CST acts directly on the heart to inhibit the inotropic and lusitropic properties of the rodent heart and also acts as a potent vasodilator in rats and humans. While the G(364)S CST variant caused profound changes in human autonomic activity and seemed to reduce the risk of developing hypertension, CST replacement rescued Chga-KO mice from dampened baroreflex sensitivity. In addition, CST has been shown to induce chemotaxis and acts as an antimicrobial as well as an antimalarial peptide. The present review summarizes these multiple actions of CST.
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Affiliation(s)
- Sushil K Mahata
- Department of Medicine (0838), University of California at San Diego, and Veterans Affairs San Diego Healthcare System, 9500 Gilman Drive, La Jolla, CA 92093-0838, USA.
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Zhang X, Pan H, Peng B, Steiner DF, Pintar JE, Fricker LD. Neuropeptidomic analysis establishes a major role for prohormone convertase-2 in neuropeptide biosynthesis. J Neurochem 2009; 112:1168-79. [PMID: 19968759 DOI: 10.1111/j.1471-4159.2009.06530.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Prohormone convertase 2 (PC2) functions in the generation of neuropeptides from their precursors. A quantitative peptidomics approach was used to evaluate the role of PC2 in the processing of peptides in a variety of brain regions. Altogether, 115 neuropeptides or other peptides derived from secretory pathway proteins were identified. These peptides arise from 28 distinct secretory pathway proteins, including proenkephalin, proopiomelanocortin, prodynorphin, protachykinin A and B, procholecystokinin, and many others. Forty one of the peptides found in wild-type (WT) mice were not detectable in any of the brain regions of PC2 knockout mice, and another 24 peptides were present at levels ranging from 20% to 79% of WT levels. Most of the other peptides were not substantially affected by the mutation, with levels ranging from 80% to 120% of WT levels, and only three peptides were found to increase in one or more brain regions of PC2 knockout mice. Taken together, these results are consistent with a broad role for PC2 in neuropeptide processing, but with functional redundancy for many of the cleavages. Comparison of the cleavage sites affected by the absence of PC2 confirms previous suggestions that sequences with a Trp, Tyr, and/or Pro in the P1' or P2' position are preferentially cleaved by PC2 and not by other enzymes present in the secretory pathway.
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Affiliation(s)
- Xin Zhang
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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23
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Minokadeh A, Funkelstein L, Toneff T, Hwang SR, Beinfeld M, Reinheckel T, Peters C, Zadina J, Hook V. Cathepsin L participates in dynorphin production in brain cortex, illustrated by protease gene knockout and expression. Mol Cell Neurosci 2009; 43:98-107. [PMID: 19837164 DOI: 10.1016/j.mcn.2009.10.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 09/15/2009] [Accepted: 10/05/2009] [Indexed: 02/08/2023] Open
Abstract
Dynorphin opioid neuropeptides mediate neurotransmission for analgesia and behavioral functions. Dynorphin A, dynorphin B, and alpha-neoendorphin are generated from prodynorphin by proteolytic processing. This study demonstrates the significant role of the cysteine protease cathepsin L for producing dynorphins. Cathepsin L knockout mouse brains showed extensive decreases in dynorphin A, dynorphin B, and alpha-neoendorphin that were reduced by 75%, 83%, and 90%, respectively, compared to controls. Moreover, cathepsin L in brain cortical neurons was colocalized with dynorphins in secretory vesicles, the primary site of neuropeptide production. Cellular coexpression of cathepsin L with prodynorphin in PC12 cells resulted in increased production of dynorphins A and B. Comparative studies of PC1/3 and PC2 convertases showed that PC1/3 knockout mouse brains had a modest decrease in dynorphin A, and PC2 knockout mice showed a minor decrease in alpha-neoendorphin. Overall, these results demonstrate a prominent role for cathepsin L, jointly with PC1/3 and PC2, for production of dynorphins in brain.
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Affiliation(s)
- Ardalan Minokadeh
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
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24
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Beinfeld MC, Funkelstein L, Foulon T, Cadel S, Kitagawa K, Toneff T, Reinheckel T, Peters C, Hook V. Cathepsin L plays a major role in cholecystokinin production in mouse brain cortex and in pituitary AtT-20 cells: protease gene knockout and inhibitor studies. Peptides 2009; 30:1882-91. [PMID: 19589362 PMCID: PMC2755599 DOI: 10.1016/j.peptides.2009.06.030] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/23/2009] [Accepted: 06/25/2009] [Indexed: 01/08/2023]
Abstract
Cholecystokinin (CCK) is a peptide neurotransmitter whose production requires proteolytic processing of the proCCK precursor to generate active CCK8 neuropeptide in brain. This study demonstrates the significant role of the cysteine protease cathepsin L for CCK8 production. In cathepsin L knockout (KO) mice, CCK8 levels were substantially reduced in brain cortex by an average of 75%. To evaluate the role of cathepsin L in producing CCK in the regulated secretory pathway of neuroendocrine cells, pituitary AtT-20 cells that stably produce CCK were treated with the specific cathepsin L inhibitor, CLIK-148. CLIK-148 inhibitor treatment resulted in decreased amounts of CCK secreted from the regulated secretory pathway of AtT-20 cells. CLIK-148 also reduced cellular levels of CCK9 (Arg-CCK8), consistent with CCK9 as an intermediate product of cathepsin L, shown by the decreased ratio of CCK9/CCK8. The decreased CCK9/CCK8 ratio also suggests a shift in the production to CCK8 over CCK9 during inhibition of cathepsin L. During reduction of the PC1/3 processing enzyme by siRNA, the ratio of CCK9/CCK8 was increased, suggesting a shift to the cathepsin L pathway for the production of CCK9. The changes in ratios of CCK9 compared to CCK8 are consistent with dual roles of the cathepsin L protease pathway that includes aminopeptidase B to remove NH2-terminal Arg or Lys, and the PC1/3 protease pathway. These results suggest that cathepsin L functions as a major protease responsible for CCK8 production in mouse brain cortex, and participates with PC1/3 for CCK8 production in pituitary cells.
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Affiliation(s)
- Margery C. Beinfeld
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111
| | - Lydiane Funkelstein
- Skaggs School of Pharmacy and Pharmaceutical Sciences and Depts. of Neuroscience, Pharmacology, and Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Thierry Foulon
- Universite Pierre et Marie Curie-Paris 6, FRE 2852 CNRS, Protéines: Biochimie Structurale et Fonctionnelle, Paris, F-75005 France
| | - Sandrine Cadel
- Universite Pierre et Marie Curie-Paris 6, FRE 2852 CNRS, Protéines: Biochimie Structurale et Fonctionnelle, Paris, F-75005 France
| | - Kouki Kitagawa
- Faculty of Pharmaceutical Sciences, Niigata University of Pharmacy and Applied Life Sciences, 5-13-2 Kaminshin'eicho, Niigata 950-2081, Japan
| | - Thomas Toneff
- Skaggs School of Pharmacy and Pharmaceutical Sciences and Depts. of Neuroscience, Pharmacology, and Medicine, University of California, San Diego, La Jolla, CA 92093
| | - Thomas Reinheckel
- Institut fur Molekulare Medizin und Zellforschung, Albert-Ludwigs Universitat, Freiburg, Germany
| | - Christoph Peters
- Institut fur Molekulare Medizin und Zellforschung, Albert-Ludwigs Universitat, Freiburg, Germany
| | - Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences and Depts. of Neuroscience, Pharmacology, and Medicine, University of California, San Diego, La Jolla, CA 92093
- Corresponding author: Vivian Hook, Ph.D., Skaggs School of Pharmacy, Univ. of Calif, San Diego, 9500 Gilman Dr. MC 0744, La Jolla, CA 92093, phone (858) 822-6682, E-mail:
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25
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26
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Biswas N, Rodriguez-Flores JL, Courel M, Gayen JR, Vaingankar SM, Mahata M, Torpey JW, Taupenot L, O'Connor DT, Mahata SK. Cathepsin L colocalizes with chromogranin a in chromaffin vesicles to generate active peptides. Endocrinology 2009; 150:3547-57. [PMID: 19372204 PMCID: PMC2717865 DOI: 10.1210/en.2008-1613] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chromogranin A (CgA), the major soluble protein in chromaffin granules, is proteolytically processed to generate biologically active peptides including the catecholamine release inhibitory peptide catestatin. Here we sought to determine whether cysteine protease cathepsin L (CTSL), a novel enzyme for proteolytic processing of neuropeptides, acts like the well-established serine proteases [prohormone convertase (PC)1/3 or PC2] to generate catestatin by proteolytic processing of CgA. We found that endogenous CTSL colocalizes with CgA in the secretory vesicles of primary rat chromaffin cells. Transfection of PC12 cells with an expression plasmid encoding CTSL directed expression of CTSL toward secretory vesicles. Deconvolution fluorescence microscopy suggested greater colocalization of CTSL with CgA than the lysosomal marker LGP110. The overexpression of CTSL in PC12 cells caused cleavage of full-length CgA. CTSL also cleaved CgA in vitro, in time- and dose-dependent fashion, and specificity of the process was documented through E64 (thiol reagent) inhibition. Mass spectrometry on CTSL-digested recombinant CgA identified a catestatin-region peptide, corresponding to CgA(360-373). The pool of peptides generated from the CTSL cleavage of CgA inhibited nicotine-induced catecholamine secretion from PC12 cells. CTSL processing in the catestatin region was diminished by naturally occurring catestatin variants, especially Pro370Leu and Gly364Ser. Among the CTSL-generated peptides, a subset matched those found in the catestatin region in vivo. These findings indicate that CgA can be a substrate for the cysteine protease CTSL both in vitro and in cella, and their colocalization within chromaffin granules in cella suggests the likelihood of an enzyme/substrate relationship in vivo.
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Affiliation(s)
- Nilima Biswas
- Department of Medicine (0838), University of California, San Diego, La Jolla, California 92093-0838, USA
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27
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Hook V, Funkelstein L, Toneff T, Mosier C, Hwang SR. Human pituitary contains dual cathepsin L and prohormone convertase processing pathway components involved in converting POMC into the peptide hormones ACTH, alpha-MSH, and beta-endorphin. Endocrine 2009; 35:429-37. [PMID: 19343278 PMCID: PMC2731682 DOI: 10.1007/s12020-009-9163-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 01/16/2009] [Accepted: 02/23/2009] [Indexed: 01/30/2023]
Abstract
The production of the peptide hormones ACTH, alpha-MSH, and beta-endorphin requires proteolytic processing of POMC which is hypothesized to utilize dual cysteine- and subtilisin-like protease pathways, consisting of the secretory vesicle cathepsin L pathway and the well-known subtilisin-like prohormone convertase (PC) pathway. To gain knowledge of these protease components in human pituitary where POMC-derived peptide hormones are produced, this study investigated the presence of these protease pathway components in human pituitary. With respect to the cathepsin L pathway, human pituitary contained cathepsin L of 27-29 kDa and aminopeptidase B of approximately 64 kDa, similar to those in secretory vesicles of related neuroendocrine tissues. The serpin inhibitor endopin 2, a selective inhibitor of cathepsin L, was also present. With respect to the PC pathway, human pituitary expresses PC1/3 and PC2 of approximately 60-65 kDa, which represent active PC1/3 and PC2; peptide hormone production then utilizes carboxypeptidase E (CPE) which is present as a protein of approximately 55 kDa. Analyses of POMC products in human pituitary showed that they resemble those in mouse pituitary which utilizes cathepsin L and PC2 for POMC processing. These findings suggest that human pituitary may utilize the cathepsin L and prohormone convertase pathways for producing POMC-derived peptide hormones.
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Affiliation(s)
- Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, La Jolla, San Diego, CA 92093-0744, USA.
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28
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Lu WD, Asmus K, Hwang SR, Li S, Woods VL, Hook V. Differential accessibilities of dibasic prohormone processing sites of proenkephalin to the aqueous environment revealed by H-D exchange mass spectrometry. Biochemistry 2009; 48:1604-12. [PMID: 19173595 DOI: 10.1021/bi801888j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proenkephalin (PE) is a prohormone containing dibasic sites that are cleaved by proteases to generate peptide neurotransmitters and hormones. Little is known about the conformational features of such protease cleavage sites within prohormone substrates. Therefore, the goal of this study was to investigate the relative accessibilities of multiple dibasic processing sites of PE by peptide amide hydrogen-deuterium exchange mass spectrometry (DXMS). DXMS demonstrated differences in the relative accessibilities of the KR, KK, and RR cleavage sites of PE to the aqueous environment. DXMS assesses relative rates of exchange of hydrogens of the polypeptide backbone of PE with deuterium atoms from D(2)O (heavy water) in solvent. Analyses of peptides spanning each of the 12 dibasic PE cleavage sites illustrated differences in H-D exchange rates that reflect relative solvent accessibility. The mid-domain cleavage sites (dibasic sites 4-8) exhibited greater accessibility to the aqueous solvent compared to regions of the NH(2) and COOH domains (dibasic sites 2, 3, and 9-11, respectively). The NH(2)- and COOH-terminal domains both exhibited relatively high H-D exchange rates. The hydrogen exchange rate profile of PE, as well as its circular dichroism (CD) features for secondary structure, was modified in trifluoroethanol, an organic solvent that represents a more hydrophobic environment. These findings suggest that the dibasic protease cleavage sites of the PE prohormone with differences in accessibility to the aqueous environment undergo proteolytic processing to generate active neuropeptides for cell-cell communication in neuroendocrine systems.
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Affiliation(s)
- Weiya D Lu
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, 9500 Gilman Dr., MC 0744, La Jolla, CA 92093-0744, USA
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29
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Crivellato E, Nico B, Ribatti D. The chromaffin vesicle: advances in understanding the composition of a versatile, multifunctional secretory organelle. Anat Rec (Hoboken) 2009; 291:1587-602. [PMID: 19037853 DOI: 10.1002/ar.20763] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Chromaffin vesicles (CV) are highly sophisticated secretory organelles synthesized in adrenal medullary chromaffin cells. They contain a complex mixture of structural proteins, catecholamine neurotransmitters, peptide hormones, and the relative processing enzymes, as well as protease inhibitors. In addition, CV store ATP, ascorbic acid, and calcium. During the last decades, extensive studies have contributed to increase our understanding of the molecular composition of CV. Yet, the recent development of biochemical and imaging procedures has greatly increased the list of CV-soluble constituents and opened new horizons as to the complexity of CV involvement in acute stress responses. Thus, a coherent picture of CV molecular composition is still to be drawn. This review article will provide a detailed account of the content of CV soluble molecules as it emerges from the most recent analytical studies. Moreover, this review article will attempt at focussing on the physiological and pathophysiological implications of the products released by CV.
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Affiliation(s)
- Enrico Crivellato
- Department of Medical and Morphological Research, Section of Anatomy, University of Udine School of Medicine, Udine, Italy.
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30
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Hwang SR, Bundey R, Toneff T, Hook V. Endopin serpin protease inhibitors localize with neuropeptides in secretory vesicles and neuroendocrine tissues. Neuroendocrinology 2009; 89:210-6. [PMID: 18840998 PMCID: PMC2731708 DOI: 10.1159/000162916] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 07/02/2008] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS The endopin serpin protease inhibitors have been identified by molecular studies as components of secretory vesicles that produce neuropeptides. Endopin 1 inhibits trypsin-like serine proteases, and endopin 2 inhibits cathepsin L that produces neuropeptides in secretory vesicles. To assess the secretory vesicle and neuroendocrine tissue distribution of these endopins, the goal of this study was to define specific antisera for each endopin isoform and to examine their localization with neuropeptides and in neuroendocrine tissues. METHODS This study utilized methods consisting of Western blots, immunoelectron microscopy, and immunofluorescence microscopy for evaluation of the localization of endopin protease inhibitors in neuroendocrine tissues. RESULTS Immunoelectron microscopy with these selective antisera demonstrated the localization of endopins 1 and 2 within secretory vesicles of adrenal medulla (bovine). Cellular immunofluorescence confocal microscopy illustrated the high level of colocalization of endopins 1 and 2 with enkephalin and NPY neuropeptides that are present in secretory vesicles of adrenal medullary chromaffin cells in primary culture. Tissue distribution studies (by Western blots) showed the expression of endopins 1 and 2 in bovine brain, pituitary, adrenal medulla, and other neuroendocrine tissues. CONCLUSIONS These results implicate endopins 1 and 2 as endogenous protease inhibitors in neuropeptide-containing secretory vesicles and neuroendocrine tissues.
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Affiliation(s)
- Shin-Rong Hwang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093-0744, USA
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31
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Abstract
This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd.,Flushing, NY 11367, United States.
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Zhang X, Che FY, Berezniuk I, Sonmez K, Toll L, Fricker LD. Peptidomics of Cpe(fat/fat) mouse brain regions: implications for neuropeptide processing. J Neurochem 2008; 107:1596-613. [PMID: 19014391 DOI: 10.1111/j.1471-4159.2008.05722.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Quantitative peptidomics was used to compare levels of peptides in wild type (WT) and Cpe(fat/fat) mice, which lack carboxypeptidase E (CPE) activity because of a point mutation. Six different brain regions were analyzed: amygdala, hippocampus, hypothalamus, prefrontal cortex, striatum, and thalamus. Altogether, 111 neuropeptides or other peptides derived from secretory pathway proteins were identified in WT mouse brain extracts by tandem mass spectrometry, and another 47 peptides were tentatively identified based on mass and other criteria. Most secretory pathway peptides were much lower in Cpe(fat/fat) mouse brain, relative to WT mouse brain, indicating that CPE plays a major role in their biosynthesis. Other peptides were only partially reduced in the Cpe(fat/fat) mice, indicating that another enzyme (presumably carboxypeptidase D) contributes to their biosynthesis. Approximately 10% of the secretory pathway peptides were present in the Cpe(fat/fat) mouse brain at levels similar to those in WT mouse brain. Many peptides were greatly elevated in the Cpe(fat/fat) mice; these peptide processing intermediates with C-terminal Lys and/or Arg were generally not detectable in WT mice. Taken together, these results indicate that CPE contributes, either directly or indirectly, to the production of the majority of neuropeptides.
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Affiliation(s)
- Xin Zhang
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Funkelstein L, Toneff T, Mosier C, Hwang SR, Beuschlein F, Lichtenauer UD, Reinheckel T, Peters C, Hook V. Major role of cathepsin L for producing the peptide hormones ACTH, beta-endorphin, and alpha-MSH, illustrated by protease gene knockout and expression. J Biol Chem 2008; 283:35652-9. [PMID: 18849346 DOI: 10.1074/jbc.m709010200] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The pituitary hormones adrenocorticotropic hormone (ACTH), beta-endorphin, and alpha-melanocyte stimulating hormone (alpha-MSH) are synthesized by proteolytic processing of their common proopiomelanocortin (POMC) precursor. Key findings from this study show that cathepsin L functions as a major proteolytic enzyme for the production of POMC-derived peptide hormones in secretory vesicles. Specifically, cathepsin L knock-out mice showed major decreases in ACTH, beta-endorphin, and alpha-MSH that were reduced to 23, 18, and 7% of wild-type controls (100%) in pituitary. These decreased peptide levels were accompanied by increased levels of POMC consistent with proteolysis of POMC by cathepsin L. Immunofluorescence microscopy showed colocalization of cathepsin L with beta-endorphin and alpha-MSH in the intermediate pituitary and with ACTH in the anterior pituitary. In contrast, cathepsin L was only partially colocalized with the lysosomal marker Lamp-1 in pituitary, consistent with its extralysosomal function in secretory vesicles. Expression of cathepsin L in pituitary AtT-20 cells resulted in increased ACTH and beta-endorphin in the regulated secretory pathway. Furthermore, treatment of AtT-20 cells with CLIK-148, a specific inhibitor of cathepsin L, resulted in reduced production of ACTH and accumulation of POMC. These findings demonstrate a prominent role for cathepsin L in the production of ACTH, beta-endorphin, and alpha-MSH peptide hormones in the regulated secretory pathway.
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Affiliation(s)
- Lydiane Funkelstein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, USA
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Funkelstein L, Toneff T, Hwang SR, Reinheckel T, Peters C, Hook V. Cathepsin L participates in the production of neuropeptide Y in secretory vesicles, demonstrated by protease gene knockout and expression. J Neurochem 2008; 106:384-91. [PMID: 18410501 DOI: 10.1111/j.1471-4159.2008.05408.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neuropeptide Y (NPY) functions as a peptide neurotransmitter and as a neuroendocrine hormone. The active NPY peptide is generated in secretory vesicles by proteolytic processing of proNPY. Novel findings from this study show that cathepsin L participates as a key proteolytic enzyme for NPY production in secretory vesicles. Notably, NPY levels in cathepsin L knockout (KO) mice were substantially reduced in brain and adrenal medulla by 80% and 90%, respectively. Participation of cathepsin L in producing NPY predicts their colocalization in secretory vesicles, a primary site of NPY production. Indeed, cathepsin L was colocalized with NPY in brain cortical neurons and in chromaffin cells of adrenal medulla, demonstrated by immunofluorescence confocal microscopy. Immunoelectron microscopy confirmed the localization of cathepsin L with NPY in regulated secretory vesicles of chromaffin cells. Functional studies showed that coexpression of proNPY with cathepsin L in neuroendocrine PC12 cells resulted in increased production of NPY. Furthermore, in vitro processing indicated cathepsin L processing of proNPY at paired basic residues. These findings demonstrate a role for cathepsin L in the production of NPY from its proNPY precursor. These studies illustrate the novel biological role of cathepsin L in the production of NPY, a peptide neurotransmitter, and neuroendocrine hormone.
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Affiliation(s)
- Lydiane Funkelstein
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093-0744, USA
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Hwang SR, Hook V. Zinc regulation of aminopeptidase B involved in neuropeptide production. FEBS Lett 2008; 582:2527-31. [PMID: 18571504 DOI: 10.1016/j.febslet.2008.06.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Revised: 06/05/2008] [Accepted: 06/12/2008] [Indexed: 11/28/2022]
Abstract
Aminopeptidase B (AP-B) is a metallopeptidase that removes basic residues from the N-termini of neuropeptide substrates in secretory vesicles. This study assessed zinc regulation of AP-B activity, since secretory vesicles contain endogenous zinc. AP-B was inhibited by zinc at concentrations typically present in secretory vesicles. Zinc effects were dependent on concentration, incubation time, and the molar ratio of zinc to enzyme. AP-B activity was recovered upon removal of zinc. AP-B with zinc became susceptible to degradation by trypsin, suggesting that zinc alters enzyme conformation. Zinc regulation demonstrates the metallopeptidase property of AP-B.
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Affiliation(s)
- Shin-Rong Hwang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093-0744, United States
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Liu J, Hong Z, Ding J, Liu J, Zhang J, Chen S. Predominant release of lysosomal enzymes by newborn rat microglia after LPS treatment revealed by proteomic studies. J Proteome Res 2008; 7:2033-49. [PMID: 18380473 DOI: 10.1021/pr7007779] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Growing evidence suggest that microglia may play an important role in the pathogenesis of neurodegenerative disease including Parkinson's disease, Alzheimer's disease, and so forth. The activation of microglia may cause neuronal damage through the release of reactive oxygen species and proinflammatory cytokines. However, the early response of microglial cells remains unclear before cells can secrete the proinflammatory cytokines. Here, a time course analysis showed the earliest expression of inducible nitric oxide synthase and cyclooxygenase-2 at 3 and 24 h following lipopolysaccharide (LPS) treatment. To further define initial response proteins of microglia after LPS treatment, we utilized a novel mass spectrometry-based quantitative proteomic technique termed SILAC (for stable isotope labeling by amino acids in cell culture) to compare the protein profiles of the cell culture-conditioned media of 1 h LPS-treated microglia as compared with controls. The proteomic analysis identified 77 secreted proteins using SignalP; of these, 28 proteins were associated with lysosome of cells and 13 lysosome-related proteins displayed significant changes in the relative abundance after 1 h LPS treatment. Four proteins were further evaluated with Western blot, demonstrating good agreement with quantitative proteomic data. These results suggested that microglia first released some lysosomal enzymes which may be involved in neuronal damage process. Furthermore, ammonium chloride, which inhibits microglia lysosomal enzyme activity, could prevent microglia from causing neuronal injury. Hence, in addition to the numerous novel proteins that are potentially important in microglial activation-mediated neurodegeneration revealed by the search, the study has indicated that the early release of lysosomal enzymes in microglial cells would contribute to LPS-activated inflammatory response.
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Affiliation(s)
- Jun Liu
- Department of Neurology & Institute of Neurology, Ruijin Hospital, Shanghai Jiatong University School of Medicine, Shanghai, China
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Hook V, Funkelstein L, Lu D, Bark S, Wegrzyn J, Hwang SR. Proteases for processing proneuropeptides into peptide neurotransmitters and hormones. Annu Rev Pharmacol Toxicol 2008; 48:393-423. [PMID: 18184105 PMCID: PMC2731677 DOI: 10.1146/annurev.pharmtox.48.113006.094812] [Citation(s) in RCA: 185] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Peptide neurotransmitters and peptide hormones, collectively known as neuropeptides, are required for cell-cell communication in neurotransmission and for regulation of endocrine functions. Neuropeptides are synthesized from protein precursors (termed proneuropeptides or prohormones) that require proteolytic processing primarily within secretory vesicles that store and secrete the mature neuropeptides to control target cellular and organ systems. This review describes interdisciplinary strategies that have elucidated two primary protease pathways for prohormone processing consisting of the cysteine protease pathway mediated by secretory vesicle cathepsin L and the well-known subtilisin-like proprotein convertase pathway that together support neuropeptide biosynthesis. Importantly, this review discusses important areas of current and future biomedical neuropeptide research with respect to biological regulation, inhibitors, structural features of proneuropeptide and protease interactions, and peptidomics combined with proteomics for systems biological approaches. Future studies that gain in-depth understanding of protease mechanisms for generating active neuropeptides will be instrumental for translational research to develop pharmacological strategies for regulation of neuropeptide functions. Pharmacological applications for neuropeptide research may provide valuable therapeutics in health and disease.
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Affiliation(s)
- Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, and Department of Neuroscience, Pharmacology, and Medicine, School of Medicine, University of California-San Diego, La Jolla, CA 92093-0744, USA.
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Prohormone convertases 1/3, 2, furin and protein 7B2 (Secretogranin V) in endocrine cells of the human pancreas. ACTA ACUST UNITED AC 2007; 146:117-24. [PMID: 17959263 DOI: 10.1016/j.regpep.2007.09.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 07/12/2007] [Accepted: 09/02/2007] [Indexed: 11/24/2022]
Abstract
Prohormone convertases (PCs) are proteinases that cleave inactive prohormones to biologically active peptides. Seven PCs have been identified; two of them, PC1/3 and PC2, have only been localized in neuroendocrine (NE) tissues; a third, furin, in both endocrine and exocrine tissues. We have studied the immunoreactivity of PC1/3, PC2 and furin in the four major NE cell types of the human pancreas by using double immunofluorescence techniques. The study also included the expression of NE secretory protein 7B2 (secretogranin V), a member of the granin family, which influences the function of PC2. The results showed that the three PCs and 7B2 were expressed only in endocrine pancreas, furin also in exocrine cells. Insulin (B) cells harboured PC1/3 and PC2, but not furin. Glucagon (A) cells were immunoreactive to all three PCs; all glucagon cells expressed PC2, but one subpopulation showed PC1/3 immunoreactivity and another furin. Only a few somatostatin (D) cells contained PC2, but no other proconvertase. Pancreatic polypeptide (PP) cells were non-reactive to all three PCs. 7B2 occurred only in insulin and glucagon cells. A varying co-localization pattern was observed between PCs and between PCs and 7B2, with the exception of PC1/3 and furin which were not co-localized. In conclusion, our study shows that PCs are localized in insulin and glucagon cells and do seem to be important in these cell types for processing of hormone and other protein precursors, especially chromogranins, but for the two other major cell types probably other enzymes are of importance.
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