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Courrol DDS, da Silva CCF, Prado LG, Chura-Chambi RM, Morganti L, de Souza GO, Heinemann MB, Isaac L, Conte FP, Portaro FCV, Rodrigues-da-Silva RN, Barbosa AS. Leptolysin, a Leptospira secreted metalloprotease of the pappalysin family with broad-spectrum activity. Front Cell Infect Microbiol 2022; 12:966370. [PMID: 36081769 PMCID: PMC9445424 DOI: 10.3389/fcimb.2022.966370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Accepted: 08/03/2022] [Indexed: 11/22/2022] Open
Abstract
Extracellular proteolytic enzymes are produced by a variety of pathogenic microorganisms, and contribute to host colonization by modulating virulence. Here, we present a first characterization of leptolysin, a Leptospira metalloprotease of the pappalysin family identified in a previous exoproteomic study. Comparative molecular analysis of leptolysin with two other pappalysins from prokaryotes, ulilysin and mirolysin, reveals similarities regarding calcium, zinc, and arginine -binding sites conservation within the catalytic domain, but also discloses peculiarities. Variations observed in the primary and tertiary structures may reflect differences in primary specificities. Purified recombinant leptolysin of L. interrogans was obtained as a ~50 kDa protein. The protease exhibited maximal activity at pH 8.0 and 37°C, and hydrolytic activity was observed in the presence of different salts with maximum efficiency in NaCl. Substrate specificity was assessed using a small number of FRET peptides, and showed a marked preference for arginine residues at the P1 position. L. interrogans leptolysin proteolytic activity on proteinaceous substrates such as proteoglycans and plasma fibronectin was also evaluated. All proteins tested were efficiently degraded over time, confirming the protease´s broad-spectrum activity in vitro. In addition, leptolysin induced morphological alterations on HK-2 cells, which may be partially attributed to extracellular matrix (ECM) degradation. Hemorrhagic foci were observed in the dorsal skin of mice intradermally injected with leptolysin, as a plausible consequence of ECM disarray and vascular endothelium glycocalyx damage. Assuming that leptospiral proteases play an important role in all stages of the infectious process, characterizing their functional properties, substrates and mechanisms of action is of great importance for therapeutic purposes.
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Affiliation(s)
| | | | - Luan Gavião Prado
- Laboratory of Bacteriology, Butantan Institute, São Paulo, Brazil
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Rosa Maria Chura-Chambi
- Laboratory of Bacteriology, Butantan Institute, São Paulo, Brazil
- Center of Biotechnology, Energy and Nuclear Research Institute (IPEN)-CNEN/SP), São Paulo, Brazil
| | - Ligia Morganti
- Center of Biotechnology, Energy and Nuclear Research Institute (IPEN)-CNEN/SP), São Paulo, Brazil
| | - Gisele Oliveira de Souza
- Department of Preventive Veterinary Medicine and Animal Health, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Marcos Bryan Heinemann
- Department of Preventive Veterinary Medicine and Animal Health, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Lourdes Isaac
- Department of Immunology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Fernando Paiva Conte
- Pilot Plant Implementation Project, Immunobiological Technology Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
| | | | | | - Angela Silva Barbosa
- Laboratory of Bacteriology, Butantan Institute, São Paulo, Brazil
- *Correspondence: Angela Silva Barbosa,
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Bale LK, Schafer MJ, Atkinson EJ, Le Brasseur NK, Haak AJ, Oxvig C, Conover CA. Pregnancy‐associated plasma protein‐A (PAPP‐A) is a key component of an interactive cellular mechanism promoting pulmonary fibrosis. J Cell Physiol 2022; 237:2220-2229. [PMID: 35098542 PMCID: PMC9050837 DOI: 10.1002/jcp.30687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 12/21/2021] [Accepted: 01/10/2022] [Indexed: 12/25/2022]
Abstract
Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with few effective treatment options. We found a highly significant correlation between pregnancy-associated plasma protein (PAPP)-A expression in IPF lung tissue and disease severity as measured by various pulmonary and physical function tests. PAPP-A is a metalloproteinase that enhances local insulin-like growth factor (IGF) activity. We used primary cultures of normal adult human lung fibroblasts (NHLF) to test the hypothesis that PAPP-A plays an important role in the development of pulmonary fibrosis. Treatment of NHLF with pro-fibrotic transforming growth factor (TGF)-β stimulated marked increases in IGF-I mRNA expression (>20-fold) and measurable IGF-I levels in 72-h conditioned medium (CM). TGF-β treatment also increased PAPP-A levels in CM fourfold (p = 0.004) and proteolytic activity ~2-fold. There was an indirect effect of TGF-β to stimulate signaling through the PI3K/Akt pathway, which was significantly inhibited by both IGF-I-inactivating and PAPP-A inhibitory antibodies. Induction of senescence in NHLF increased PAPP-A levels in CM 10-fold (p = 0.006) with attendant increased proteolytic activity. Thus, PAPP-A is a novel component of the senescent lung fibroblast secretome. In addition, NHLF secreted extracellular vehicles (EVs) with surface-bound active PAPP-A that were increased fivefold with senescence. Regulation of PAPP-A and IGF signaling by TGF-β and cell senescence suggests an interactive cellular mechanism underlying the resistance to apoptosis and the progression of fibrosis in IPF. Furthermore, PAPP-A-associated EVs may be a means of pro-fibrotic, pro-senescent communication with other cells in the lung and, thus, a potential therapeutic target for IPF.
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Affiliation(s)
- Laurie K. Bale
- Division of Endocrinology Metabolism and Nutrition, Endocrine Research Unit Rochester Minnesota USA
| | - Marissa J. Schafer
- Department of Physiology and Biomedical Engineering Rochester Minnesota USA
| | | | | | - Andrew J. Haak
- Department of Physiology and Biomedical Engineering Rochester Minnesota USA
| | - Claus Oxvig
- Department of Molecular Biology and Genetics University of Aarhus Aarhus Denmark
| | - Cheryl A. Conover
- Division of Endocrinology Metabolism and Nutrition, Endocrine Research Unit Rochester Minnesota USA
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Mazziotti G, Frara S, Giustina A. Pituitary Diseases and Bone. Endocr Rev 2018; 39:440-488. [PMID: 29684108 DOI: 10.1210/er.2018-00005] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 04/16/2018] [Indexed: 12/12/2022]
Abstract
Neuroendocrinology of bone is a new area of research based on the evidence that pituitary hormones may directly modulate bone remodeling and metabolism. Skeletal fragility associated with high risk of fractures is a common complication of several pituitary diseases such as hypopituitarism, Cushing disease, acromegaly, and hyperprolactinemia. As in other forms of secondary osteoporosis, pituitary diseases generally affect bone quality more than bone quantity, and fractures may occur even in the presence of normal or low-normal bone mineral density as measured by dual-energy X-ray absorptiometry, making difficult the prediction of fractures in these clinical settings. Treatment of pituitary hormone excess and deficiency generally improves skeletal health, although some patients remain at high risk of fractures, and treatment with bone-active drugs may become mandatory. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary diseases.
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Affiliation(s)
| | - Stefano Frara
- Institute of Endocrinology, Università Vita-Salute San Raffaele, Milan, Italy
| | - Andrea Giustina
- Institute of Endocrinology, Università Vita-Salute San Raffaele, Milan, Italy
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Lindsey RC, Rundle CH, Mohan S. Role of IGF1 and EFN-EPH signaling in skeletal metabolism. J Mol Endocrinol 2018; 61:T87-T102. [PMID: 29581239 PMCID: PMC5966337 DOI: 10.1530/jme-17-0284] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 03/26/2018] [Indexed: 01/11/2023]
Abstract
Insulin-like growth factor 1(IGF1) and ephrin ligand (EFN)-receptor (EPH) signaling are both crucial for bone cell function and skeletal development and maintenance. IGF1 signaling is the major mediator of growth hormone-induced bone growth, but a host of different signals and factors regulate IGF1 signaling at the systemic and local levels. Disruption of the Igf1 gene results in reduced peak bone mass in both experimental animal models and humans. Additionally, EFN-EPH signaling is a complex system which, particularly through cell-cell interactions, contributes to the development and differentiation of many bone cell types. Recent evidence has demonstrated several ways in which the IGF1 and EFN-EPH signaling pathways interact with and depend upon each other to regulate bone cell function. While much remains to be elucidated, the interaction between these two signaling pathways opens a vast array of new opportunities for investigation into the mechanisms of and potential therapies for skeletal conditions such as osteoporosis and fracture repair.
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Affiliation(s)
- Richard C Lindsey
- Musculoskeletal Disease CenterVA Loma Linda Healthcare System, Loma Linda, California, USA
- Division of BiochemistryDepartment of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California, USA
- Center for Health Disparities and Molecular MedicineDepartment of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California, USA
| | - Charles H Rundle
- Musculoskeletal Disease CenterVA Loma Linda Healthcare System, Loma Linda, California, USA
- Department of MedicineLoma Linda University, Loma Linda, California, USA
| | - Subburaman Mohan
- Musculoskeletal Disease CenterVA Loma Linda Healthcare System, Loma Linda, California, USA
- Division of BiochemistryDepartment of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California, USA
- Center for Health Disparities and Molecular MedicineDepartment of Basic Sciences, School of Medicine, Loma Linda University, Loma Linda, California, USA
- Department of MedicineLoma Linda University, Loma Linda, California, USA
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Lindsey RC, Mohan S. Skeletal effects of growth hormone and insulin-like growth factor-I therapy. Mol Cell Endocrinol 2016; 432:44-55. [PMID: 26408965 PMCID: PMC4808510 DOI: 10.1016/j.mce.2015.09.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/21/2015] [Accepted: 09/22/2015] [Indexed: 10/23/2022]
Abstract
The growth hormone/insulin-like growth factor (GH/IGF) axis is critically important for the regulation of bone formation, and deficiencies in this system have been shown to contribute to the development of osteoporosis and other diseases of low bone mass. The GH/IGF axis is regulated by a complex set of hormonal and local factors which can act to regulate this system at the level of the ligands, receptors, IGF binding proteins (IGFBPs), or IGFBP proteases. A combination of in vitro studies, transgenic animal models, and clinical human investigations has provided ample evidence of the importance of the endocrine and local actions of both GH and IGF-I, the two major components of the GH/IGF axis, in skeletal growth and maintenance. GH- and IGF-based therapies provide a useful avenue of approach for the prevention and treatment of diseases such as osteoporosis.
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Affiliation(s)
- Richard C Lindsey
- Musculoskeletal Disease Center, Loma Linda VA Healthcare System, Loma Linda, CA 92357, USA; Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA; Department of Biochemistry, Loma Linda University, Loma Linda, CA 92354, USA
| | - Subburaman Mohan
- Musculoskeletal Disease Center, Loma Linda VA Healthcare System, Loma Linda, CA 92357, USA; Department of Medicine, Loma Linda University, Loma Linda, CA 92354, USA; Department of Biochemistry, Loma Linda University, Loma Linda, CA 92354, USA.
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Protein secretion is required for pregnancy-associated plasma protein-A to promote lung cancer growth in vivo. PLoS One 2012; 7:e48799. [PMID: 23152806 PMCID: PMC3494721 DOI: 10.1371/journal.pone.0048799] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 10/01/2012] [Indexed: 12/15/2022] Open
Abstract
Pregnancy-associated plasma protein-A (PAPPA) has been reported to regulate the activity of insulin-like growth factor (IGF) signal pathway through proteolytic degradation of IGF binding proteins (IGFBPs) thereby increasing the local concentration of free IGFs available to receptors. In this study we found that PAPPA is secreted from two out of seven lung cancer cell lines examined. None of immortalized normal bronchial epithelial cells (HBE) tested secrets PAPPA. There is no correlation between expression level and secretion of PAPPA in these cells. A cell line over-expressing PAPPA accompanied with secretion shows no notable changes in proliferation under cell culture conditions in vitro, but displays significantly augmentation of tumor growth in vivo in a xenograft model. In contrast, a cell line over-expressing PAPPA without secretion exhibits reduction of tumor growth both in vitro and in vivo. Down-regulation of PAPPA expression and secretion by RNAi knockdown decreases tumor growth after implanted in vivo. The tumor promoting activity of PAPPA appears to be mediated mainly through augmentation of the IGF signaling pathway as indicated by notable increases in downstream Akt kinase phosphorylation in tumor samples. Our results indicate that PAPPA secretion may play an important role in lung cancer growth and progression.
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Perks CM, Holly JMP. IGF binding proteins (IGFBPs) and regulation of breast cancer biology. J Mammary Gland Biol Neoplasia 2008; 13:455-69. [PMID: 19031049 DOI: 10.1007/s10911-008-9106-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Accepted: 11/11/2008] [Indexed: 01/13/2023] Open
Abstract
The IGFBP family comprises six proteins with high affinity for the IGFs. Changes in the balance of the components of the IGF system may contribute to the progression of breast cancer. In tumours the abundance of IGFBPs relates to the estrogen receptor status and their production in the breast is controlled by hormones, principally estrogen and progesterone. Important interactions occur between IGFBPs and key growth regulators such as TGF-beta, PTEN and EGF which are reviewed. The conflicting observations between the effects of IGFBPs on the risk of breast cancer, in particular IGFBP-3, obtained from epidemiology studies in comparison to in vivo observations are highlighted and potential explanations provided. The functional activity of IGFBPs can also be affected by proteolysis, phosphorylation and glycosylation and the implications of these are described. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of their cellular actions. IGFBPs can affect cell function in an IGF-dependent or independent manner. The key mechanisms underlying the intrinsic actions of the IGFBPs are still in debate. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs and IGFBP proteases, but also by these factors delivered from the circulation. Finally, the therapeutic potential of IGFBPs-2 and -3 are considered together with key questions that still need to be addressed.
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Affiliation(s)
- Claire M Perks
- Department of Clinical Sciences North Bristol, IGFs and Metabolic Endocrinology Group, University of Bristol, Southmead Hospital, The Medical School Unit, Bristol, BS10 5NB, UK.
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Giustina A, Mazziotti G, Canalis E. Growth hormone, insulin-like growth factors, and the skeleton. Endocr Rev 2008; 29:535-59. [PMID: 18436706 PMCID: PMC2726838 DOI: 10.1210/er.2007-0036] [Citation(s) in RCA: 548] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 04/03/2008] [Indexed: 12/18/2022]
Abstract
GH and IGF-I are important regulators of bone homeostasis and are central to the achievement of normal longitudinal bone growth and bone mass. Although GH may act directly on skeletal cells, most of its effects are mediated by IGF-I, which is present in the systemic circulation and is synthesized by peripheral tissues. The availability of IGF-I is regulated by IGF binding proteins. IGF-I enhances the differentiated function of the osteoblast and bone formation. Adult GH deficiency causes low bone turnover osteoporosis with high risk of vertebral and nonvertebral fractures, and the low bone mass can be partially reversed by GH replacement. Acromegaly is characterized by high bone turnover, which can lead to bone loss and vertebral fractures, particularly in patients with coexistent hypogonadism. GH and IGF-I secretion are decreased in aging individuals, and abnormalities in the GH/IGF-I axis play a role in the pathogenesis of the osteoporosis of anorexia nervosa and after glucocorticoid exposure.
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Affiliation(s)
- Andrea Giustina
- Department of Medical and Surgical Sciences, University of Brescia, Brescia, Italy.
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10
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Abstract
INTRODUCTION The metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A) functions to enhance local insulin-like growth factor (IGF)-I bioavailability through cleavage of inhibitory IGF binding proteins. Because IGF-I is an important regulator of skeletal growth and remodeling and PAPP-A is highly expressed by osteoblastic cells, we hypothesized that, in the absence of PAPP-A, bone physiology would be compromised because of a blunting of local IGF-I action even in the presence of normal circulating IGF-I levels. MATERIALS AND METHODS pQCT, muCT, histomorphometry, and mechanical strength testing were performed on bones from PAPP-A knockout (KO) mice and wildtype (WT) littermates at 2-12 mo of age. IGF-I levels and bone formation and resorption markers were determined in sera from these animals. RESULTS Volumetric BMD in PAPP-A KO mice measured by pQCT at the femoral midshaft, which is primarily cortical bone, was 10% less than WT at 2 mo. This difference was maintained at 4, 6, and 12 mo. Cortical thickness at this site was similarly decreased. On the other hand, trabecular bone at the distal femur (pQCT) and in the tibia (muCT) showed age-progressive decreases in bone volume fraction in PAPP-A KO compared with WT mice. Tibial muCT indicated a 46% relative decrease in trabecular bone volume/total volume (BV/TV) and a 28% relative decrease in trabecular thickness in PAPP-A KO compared with WT mice at 6 mo. These trabecular deficiencies in PAPP-A KO mice corresponded to a weakening of the bone. Serum markers and bone histomorphometry indicated that the primary impact of PAPP-A is on skeletal remodeling resulting in a state of low-turnover osteopenia in adult PAPP-A KO mice. Circulating IGF-I levels were not altered in PAPP-A KO mice. CONCLUSIONS PAPP-A is a bone growth regulatory factor in vivo and, in its absence, mice show skeletal insufficiency in mass, density, architecture, and strength. The data suggest a primary role for PAPP-A in modulating local IGF bioavailability for trabecular bone remodeling.
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Viereck V, Siggelkow H, Pannem R, Braulke T, Scharf JG, Kübler B. Alteration of the insulin-like growth factor axis during in vitro differentiation of the human osteosarcoma cell line HOS 58. J Cell Biochem 2007; 102:28-40. [PMID: 17372931 DOI: 10.1002/jcb.21274] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The insulin-like growth factors I and II (IGF-I, IGF-II), their receptors, and high affinity binding proteins (IGFBPs) represent a family of cellular modulators that play essential roles in the development and differentiation of cells and tissues including the skeleton. Recently, the human osteosarcoma cell line HOS 58 cells were used as an in vitro model of osteoblast differentiation characterized by (i) a rapid proliferation rate in low-density cells that decreased continuously with time of culture and (ii) an increasing secretion of matrix proteins during their in vitro differentiation. In the present paper, HOS 58 cells with low cell density at early time points of the in vitro differentiation (i) displayed a low expression of IGF-I and -II; (ii) synthesized low levels of IGFBP-2, -3, -4, and -5, but (iii) showed high expression levels of both the type I and II IGF receptors. During the in vitro differentiation of HOS 58 cells, IGF-I and -II expressions increased continuously in parallel with an upregulation of IGFBP-2, -3, -4, and -5 whereas the IGF-I receptor and IGF-II/M6P receptor mRNA were downregulated. In conclusion, the high proliferative activity in low cell density HOS 58 cells was associated with high mRNA levels of the IGF-IR, but low concentrations of IGFBP-2. The rate of proliferation of HOS 58 cells continuously decreased during cultivation in parallel with a decline in IGF-IR expression, but increase of mitoinhibitory IGFBP-2. These data are indicative for a role of the IGF axis during the in vitro differentiation of HOS 58 cells.
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Affiliation(s)
- Volker Viereck
- Department of Obstetrics and Gynecology, Georg-August-Universität, Göttingen, Germany
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12
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Rivera GM, Chandrasekher YA, Evans AC, Giudice LC, Fortune JE. A potential role for insulin-like growth factor binding protein-4 proteolysis in the establishment of ovarian follicular dominance in cattle. Biol Reprod 2001; 65:102-11. [PMID: 11420229 DOI: 10.1095/biolreprod65.1.102] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A critical transition in ovarian follicular development is the selection of a dominant follicle, capable of ovulating, from a cohort of synchronously growing antral follicles. However, little is known about mechanisms and factors that regulate the selection and growth of dominant ovarian follicles. We have investigated whether a component of the insulin-like growth factor (IGF) system, namely IGFBP-4 protease, is associated with the establishment of follicular dominance in cattle. IGFBP proteases degrade IGFBPs, freeing IGFs to interact with their receptors. In experiment 1, follicular fluid from preovulatory follicles (n = 4) degraded about 80% of the added recombinant human (rh) IGFBP-4 within 18 h of incubation. The IGFBP-4 protease exhibited optimal activity at neutral/basic pH and its sensitivity to various protease inhibitors suggested a metalloprotease. The decline in the intensity of the band corresponding to intact rhIGFBP-4 was accompanied by the appearance of immunoreactive fragments of molecular weights approximately 18 and 14 kDa, which were not detectable by ligand blot analysis. In experiment 2, follicular fluid samples were collected from dominant and subordinate follicles on Day 2 or 3 of the first follicular wave, after ovariectomy (experiment 2a, n = 3/day) or by ultrasound-guided follicular aspiration (experiment 2b, n = 4-5/day). Estradiol concentrations in follicular fluid from dominant vs. subordinate follicles confirmed their identities and indicated that the dominant follicle had been selected by Day 2 of the follicular wave. In both experiments 2a and 2b, IGFBP-4 proteolytic activity was 2- to 3.5-fold (P < 0.05) and 5-fold (P < 0.01) higher in follicular fluid from dominant than subordinate follicles on Days 2 and 3 of the follicular wave, respectively. The finding that IGFBP-4 proteolytic activity is higher in dominant, estrogen-active follicles than in subordinate follicles of the same cohort, as early as Day 2 of the follicular wave, strongly suggests a role for IGFBP-4 protease in the establishment of ovarian follicular dominance.
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Affiliation(s)
- G M Rivera
- Department of Biomedical Sciences, Cornell University, Ithaca, New York 14853, USA
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Bayes-Genis A, Schwartz RS, Lewis DA, Overgaard MT, Christiansen M, Oxvig C, Ashai K, Holmes DR, Conover CA. Insulin-like growth factor binding protein-4 protease produced by smooth muscle cells increases in the coronary artery after angioplasty. Arterioscler Thromb Vasc Biol 2001; 21:335-41. [PMID: 11231911 DOI: 10.1161/01.atv.21.3.335] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Insulin-like growth factor (IGF)-I stimulates vascular smooth muscle cell (VSMC) migration and proliferation, which are fundamental to neointimal hyperplasia in postangioplasty restenosis. IGF-I action is modulated by several high-affinity IGF binding proteins (IGFBPs). IGFBP-4 is the predominant IGFBP produced by VSMCs and is a potent inhibitor of IGF-I action. However, specific IGFBP-4 proteases can cleave IGFBP-4 and liberate active IGF-I. In this study, we document IGFBP-4 protease produced by human and porcine coronary artery VSMCs in culture as pregnancy-associated plasma protein-A (PAPP-A). This was shown by a distinctive IGFBP-4 cleavage pattern, specific inhibition of IGFBP-4 protease activity with PAPP-A polyclonal antibodies, and immunorecognition of PAPP-A by monoclonal antibodies. Furthermore, we found a 2-fold increase in IGFBP-4 protease activity in injured porcine VSMC cultures in vitro (P<0.05). We also evaluated IGFBP-4 protease/PAPP-A expression in vivo after coronary artery balloon injury. Twenty-five immature female pigs underwent coronary overstretch balloon injury, and vessels were examined at defined time points after the procedure. Abundant PAPP-A expression was observed in the cytoplasm of medial and neointimal cells 7, 14, and 28 days after angioplasty (P<0.01 vs control). The highest PAPP-A labeling indices were located in the neointima (36.1+/-2.1%) and the media (31.7+/-1.2%) 28 days after injury. Western blot analysis confirmed increased PAPP-A in injured vessels. PAPP-A, a regulator of IGF-I bioavailability through proteolysis of IGFBP-4, is thus expressed by VSMCs in vitro and in restenotic lesions in vivo. These results suggest a possible role for PAPP-A in neointimal hyperplasia.
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Affiliation(s)
- A Bayes-Genis
- Division of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, Minnesota, USA
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Renner C, Holak T. NMR 15N relaxation of the insulin-like growth factor (IGF)-binding domain of IGF binding protein-5 (IGFBP-5) determined free in solution and in complex with IGF-II. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:1058-65. [PMID: 11179972 DOI: 10.1046/j.1432-1327.2001.01965.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
15N NMR relaxation rates of mini-IGFBP-5, an N-terminal insulin-like growth factor binding domain of the insulin-like growth factor binding protein 5 (IGFBP-5), were analysed at three field strengths using the Lipari-Szabo procedure (see below) and reduced spectral density methods. Isotropic and anisotropic Lipari-Szabo models were analysed and an analytical formula for the overall correlation time for anisotropic molecules is presented. Mini-IGFBP-5 was found to be mainly rigid on fast ps time scales except for 11 unstructured flexible residues at the C-terminus. The insulin-like growth factor binding loop in the apo-protein exhibits small amounts of flexibility on fast time scales (ps to ns) but several loop residues show significant exchange broadening. These loop residues display no exchange broadening in the complex of IGF-II/mini-IGFBP-5. The isotropic overall tumbling time in solution at 31 degrees C of mini-IGFBP-5 complexed to IGF-II is tauc = 18.4 +/- 0.2 ns indicating a strong tendency for aggregation.
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Affiliation(s)
- C Renner
- Max Planck Institute for Biochemistry, Martinsried, Germany
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15
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Dubaquié Y, Mortensen DL, Intintoli A, Hogue DA, Nakamura G, Rancatore P, Lester P, Sadick MD, Filvaroff E, Fielder PJ, Lowman HB. Binding protein-3-selective insulin-like growth factor I variants: engineering, biodistributions, and clearance. Endocrinology 2001; 142:165-73. [PMID: 11145579 DOI: 10.1210/endo.142.1.7864] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin-like growth factor I (IGF-I) is a potent anabolic peptide that mediates most of its pleiotropic effects through association with the IGF type I receptor. Biological availability and plasma half-life of IGF-I are modulated by soluble binding proteins (IGFBPs), which sequester free IGF-I into high affinity complexes. Elevated levels of specific IGFBPs have been observed in several pathological conditions, resulting in inhibition of IGF-I activity. Administration of IGF-I variants that are unable to bind to the up-regulated IGFBP species could potentially counteract this effect. We engineered two IGFBP-selective variants that demonstrated 700- and 80,000-fold apparent reductions in affinity for IGFBP-1 while preserving low nanomolar affinity for IGFBP-3, the major carrier of IGF-I in plasma. Both variants displayed wild-type-like potency in cellular receptor kinase assays, stimulated human cartilage matrix synthesis, and retained their ability to associate with the acid-labile subunit in complex with IGFBP-3. Furthermore, pharmacokinetic parameters and tissue distribution of the IGF-I variants in rats differed from those of wild-type IGF-I as a function of their IGFBP affinities. These IGF-I variants may potentially be useful for treating disease conditions associated with up-regulated IGFBP-1 levels, such as chronic or acute renal and hepatic failure or uncontrolled diabetes. More generally, these results suggest that the complex biology of IGF-I may be clarified through in vivo studies of IGFBP-selective variants.
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Affiliation(s)
- Y Dubaquié
- Departments of Protein Engineering Genentech, Inc., South San Francisco, California 94080, USA
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Chelius D, Conover CA, Baldwin MA, Spencer EM. Characterization of the enzymatic specificity of the IGF-dependent insulin-like growth factor binding protein-4 (IGFBP-4) protease. Growth Horm IGF Res 2000; 10:360-366. [PMID: 11161967 DOI: 10.1054/ghir.2000.0177] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The insulin-like growth factor (IGF)-dependent IGF binding protein-4 protease secreted by cultured adult human fibroblasts was recently identified as pregnancy-associated plasma protein-A (PAPP-A). In this study we showed that in addition to human IGFBP-4 the IGF-dependent IGFBP-4 protease also digests recombinant rat IGFBP-4 into two fragments by specifically cleaving at the carboxyl-terminal side of methionine at position 131 for rat IGFBP-4. Thus the cleavage site is at the KMKV site, which is not represented in other IGFBPs. While kallikrein may cleave at this site, its action is not specific.
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Affiliation(s)
- D Chelius
- Laboratory of Growth and Development, California Pacific Medical Center Research Institute, San Francisco, CA 94114, USA
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17
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Imai Y, Moralez A, Andag U, Clarke JB, Busby WH, Clemmons DR. Substitutions for hydrophobic amino acids in the N-terminal domains of IGFBP-3 and -5 markedly reduce IGF-I binding and alter their biologic actions. J Biol Chem 2000; 275:18188-94. [PMID: 10766744 DOI: 10.1074/jbc.m000070200] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin-like growth factor-binding protein-3 and -5 (IGFBP-3 and -5) have been shown to bind insulin-like growth factor-I and -II (IGF-I and -II) with high affinity. Previous studies have proposed that the N-terminal region of IGFBP-5 contains a hydrophobic patch between residues 49 and 74 that is required for high affinity binding. These studies were undertaken to determine if mutagenesis of several of these residues resulted in a reduction of the affinity of IGFBP-3 and -5 for IGF-I. Substitutions for residues 68, 69, 70, 73, and 74 in IGFBP-5 (changing one charged residue, Lys(68), to a neutral one and the four hydrophobic residues to nonhydrophobic residues) resulted in an approximately 1000-fold reduction in the affinity of IGFBP-5 for IGF-I. Substitutions for homologous residues in IGFBP-3 also resulted in a >1000-fold reduction in affinity. The physiologic consequence of this reduction was that IGFBP-3 and -5 became very weak inhibitors of IGF-I-stimulated cell migration and DNA synthesis. Likewise, the ability of IGFBP-5 to inhibit IGF-I-stimulated receptor phosphorylation was attenuated. These changes did not appear to be because of alterations in protein folding induced by mutagenesis, because the IGFBP-5 mutant was fully susceptible to proteolytic cleavage by a specific IGFBP-5 protease. In summary, residues 68, 69, 70, 73, and 74 in IGFBP-5 appear to be critical for high affinity binding to IGF-I. Homologous residues in IGFBP-3 are also required, suggesting that they form a similar binding pocket and that for both proteins these residues form an important component of the core binding site. The availability of these mutants will make it possible to determine if there are direct, non-IGF-I-dependent effects of IGFBP-3 and -5 on cellular physiologic processes in cell types that secrete IGF-I.
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Affiliation(s)
- Y Imai
- Division of Endocrinology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7170, USA
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18
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Abstract
Insulin-like growth factor I (IGF-I) stimulates osteoblastic cells in culture to proliferate and to synthesize bone matrix proteins. However, local IGF-I action is modulated by a family of IGF-binding proteins (IGFBPs) that, in turn, are modified by specific IGFBP proteases. All these components of the IGF-I regulatory system are present and operative in bone cells in vitro.
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Affiliation(s)
- C A Conover
- Endocrine Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA.
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19
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Bayes-Genis A, Conover CA, Schwartz RS. The insulin-like growth factor axis: A review of atherosclerosis and restenosis. Circ Res 2000; 86:125-30. [PMID: 10666406 DOI: 10.1161/01.res.86.2.125] [Citation(s) in RCA: 287] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Insulin-like growth factors I and II (IGF-I and -II) and their regulatory proteins are secreted by cells of the cardiovascular system. They are growth promoters for arterial cells and mediators of cardiovascular disease. IGFs are bound to IGF binding proteins (IGFBPs), which modulate IGF ligand-receptor interaction and consequently to IGF action. IGFBPs are in turn posttranslationally modulated by specific proteases. This dynamic balance (IGFs, IGFBPs, and IGFBP proteases) constitutes the IGF axis and ultimately determines the extent of IGF-dependent cellular effects. Dysregulated actions of this axis influence coronary atherosclerosis through effects on vascular smooth muscle cell growth, migration, and extracellular matrix synthesis in the atherosclerotic plaque. IGF-I promotes macrophage chemotaxis, excess LDL cholesterol uptake, and release of proinflammatory cytokines. Endothelial cells also receive the effects of IGFs stimulating their migration and organization forming capillary networks. Neointimal hyperplasia of restenosis after coronary artery injury is also modulated by the IGF axis. IGFs stimulate vascular smooth muscle cell proliferation and migration to form the neointima and upregulate tropoelastin synthesis after disruption of the elastic layer. Understanding IGF axis regulation establishes a scientific basis for strategies directed to limit or reverse plaque growth and vulnerability in atherosclerosis and in the neointimal hyperplasia of restenosis.
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Affiliation(s)
- A Bayes-Genis
- Division of Cardiovascular Diseases, Mayo Clinic and Foundation, Rochester, MN 55905, USA
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20
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Abstract
According to the somatomedin model, growth hormone (GH)-dependent hepatic synthesis is responsible for maintaining circulating insulin-like growth factor (IGF)-I levels. On the other hand, the local autocrine/paracrine IGF-I expression in peripheral tissue is generally GH-independent and reflects the effects of various and tissue-specific trophic hormones. Circulating IGF-I levels undergo important age-related variations increasing at puberty and decreasing, thereafter, to low levels in the elderly. Low IGF-I levels in the elderly mainly reflect impaired somatotroph secretion but the decline in gonadal sex steroid levels, some protein and micronutrients malnutrition as well as age-dependent variations in IGF-binding proteins may also play a role in the age-related decrease in IGF-I activity. This, in turn, partially accounts for age-related changes in bones, muscles, cardiovascular system, central nervous system and the immune system. However, it is currently unclear whether treatment with exogenous IGF-I can retard or reverse age-related changes in body structure and function.
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Affiliation(s)
- E Arvat
- Division of Endocrinology, Department of Internal Medicine, University of Turin, Italy
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21
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Ji C, Chen Y, Centrella M, McCarthy TL. Activation of the insulin-like growth factor-binding protein-5 promoter in osteoblasts by cooperative E box, CCAAT enhancer-binding protein, and nuclear factor-1 deoxyribonucleic acid-binding sequences. Endocrinology 1999; 140:4564-72. [PMID: 10499512 DOI: 10.1210/endo.140.10.7061] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) has IGF-dependent and -independent actions. PGE2 rapidly increases IGFBP-5 expression by osteoblasts through cAMP-dependent processes. A minimal DNA sequence required for basal and PGE2-stimulated IGFBP-5 promoter activity spans -69 to -35 bp. This region adjoins a functional TATA box and contains E box, CCAAT enhancer-binding protein (C/EBP), nuclear factor-1 (NF-1), and activator protein-2 (AP-2) transcription factor related binding motifs. In this study we compared minimal promoter sequences of -74 to +120 bp, without or with mutations in each potential regulatory element, by reporter gene expression and electrophoretic mobility shift assays. Mutation of the E box-related element reduced basal promoter activity by 50% and eliminated the 2-fold stimulatory effect of PGE2. In contrast, mutations in the C/EBP- or NF-1-related elements also reduced basal promoter activity without fully eliminating the PGE2 effect. Overexpression of C/EBPdelta stimulated basal IGFBP-5 promoter activity, and this effect was eliminated by mutating the C/EBP-binding site. However, mutation of the AP-2-binding site or overexpression of AP-2 did not correlate with basal or PGE2-induced promoter activation. By electrophoretic mobility shift assay, prominent gel shift complexes occurred with osteoblast nuclear extracts and 32P-labeled probes spanning the E box-, C/EBP-, and NF-1-related motifs. These gel shift complexes were depleted by specific binding site mutations and were enhanced by PGE2. Increased binding by extracts from PGE2-treated cultures was blocked by cycloheximide treatment. These results identify several elements as integral binding sequences for both basal and PGE2-stimulated IGFBP-5 promoter activity. They further reveal that multiple sequences within this cluster form a basic transcription unit where nuclear factors can accumulate in a protein synthesis-dependent way and enhance IGFBP-5 expression by osteoblasts in response to PGE2.
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Affiliation(s)
- C Ji
- Yale University School of Medicine, Section of Plastic Surgery, New Haven, Connecticut 06520-8041, USA
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22
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Lawrence JB, Oxvig C, Overgaard MT, Sottrup-Jensen L, Gleich GJ, Hays LG, Yates JR, Conover CA. The insulin-like growth factor (IGF)-dependent IGF binding protein-4 protease secreted by human fibroblasts is pregnancy-associated plasma protein-A. Proc Natl Acad Sci U S A 1999; 96:3149-53. [PMID: 10077652 PMCID: PMC15910 DOI: 10.1073/pnas.96.6.3149] [Citation(s) in RCA: 507] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteolytic cleavage of the six known insulin-like growth factor binding proteins (IGFBPs) is a powerful means of rapid structure and function modification of these important growth-regulatory proteins. Intact IGFBP-4 is a potent inhibitor of IGF action in vitro, and cleavage of IGFBP-4 has been shown to abolish its ability to inhibit IGF stimulatory effects in a variety of systems, suggesting that IGFBP-4 proteolysis acts as a positive regulator of IGF bioavailability. Here we report the isolation of an IGF-dependent IGFBP-4-specific protease from human fibroblast-conditioned media and its identification by mass spectrometry microsequencing as pregnancy-associated plasma protein-A (PAPP-A), a protein of unknown function found in high concentrations in the maternal circulation during pregnancy. Antibodies raised against PAPP-A both inhibited and immunodepleted IGFBP-4 protease activity in human fibroblast-conditioned media. Moreover, PAPP-A purified from pregnancy sera had IGF-dependent IGFBP-4 protease activity. PAPP-A mRNA was expressed by the human fibroblasts and osteoblasts, and PAPP-A protein was secreted into the culture medium. In conclusion, we have identified an IGF-dependent IGFBP protease and at the same time assigned a function to PAPP-A. This represents an unanticipated union of two areas of research that were not linked in any way before this report.
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Affiliation(s)
- J B Lawrence
- Endocrine Research Unit, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA
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23
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Lawrence JB, Bale LK, Haddad TC, Clarkson JT, Conover CA. Characterization and partial purification of the insulin-like growth factor (IGF)-dependent IGF binding protein-4-specific protease from human fibroblast conditioned media. Growth Horm IGF Res 1999; 9:25-34. [PMID: 10207505 DOI: 10.1054/ghir.1998.0083] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Insulin-like growth factors (IGFs) are one of the most potent stimulators of cell growth. IGFs are modulated by six high affinity binding proteins (IGFBPs) which are, in turn, regulated through post-translational modifications such as proteolysis. In the conditioned media of human fibroblasts, IGFBP-4 is cleaved by an apparently novel IGFBP-4-specific protease that requires IGF for functional activity. We have used several biochemical manipulations, including size exclusion chromatography, native gel electrophoresis, chaotropic salt precipitation, hydrophobic interaction chromatography, ion exchange chromatography, isoelectric focusing, lectin affinity chromatography, and metal chelating affinity chromatography to both characterize and partially purify the IGF-dependent IGFBP-4 protease. Our results indicate that this protease is a highly glycosylated, Zn+2 binding metalloprotease with a native molecular weight greater than 200 kDa.
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24
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Chen Y, Shu H, Ji C, Casinghino S, Kim K, Gundberg CM, Centrella M, McCarthy TL. Insulin-like growth factor binding proteins localize to discrete cell culture compartments in periosteal and osteoblast cultures from fetal rat bone. J Cell Biochem 1998. [DOI: 10.1002/(sici)1097-4644(19981201)71:3<351::aid-jcb4>3.0.co;2-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Kalus W, Zweckstetter M, Renner C, Sanchez Y, Georgescu J, Grol M, Demuth D, Schumacher R, Dony C, Lang K, Holak TA. Structure of the IGF-binding domain of the insulin-like growth factor-binding protein-5 (IGFBP-5): implications for IGF and IGF-I receptor interactions. EMBO J 1998; 17:6558-72. [PMID: 9822601 PMCID: PMC1171003 DOI: 10.1093/emboj/17.22.6558] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Binding proteins for insulin-like growth factors (IGFs) IGF-I and IGF-II, known as IGFBPs, control the distribution, function and activity of IGFs in various cell tissues and body fluids. Insulin-like growth factor-binding protein-5 (IGFBP-5) is known to modulate the stimulatory effects of IGFs and is the major IGF-binding protein in bone tissue. We have expressed two N-terminal fragments of IGFBP-5 in Escherichia coli; the first encodes the N-terminal domain of the protein (residues 1-104) and the second, mini-IGFBP-5, comprises residues Ala40 to Ile92. We show that the entire IGFBP-5 protein contains only one high-affinity binding site for IGFs, located in mini-IGFBP-5. The solution structure of mini-IGFBP-5, determined by nuclear magnetic resonance spectroscopy, discloses a rigid, globular structure that consists of a centrally located three-stranded anti-parallel beta-sheet. Its scaffold is stabilized further by two inside packed disulfide bridges. The binding to IGFs, which is in the nanomolar range, involves conserved Leu and Val residues localized in a hydrophobic patch on the surface of the IGFBP-5 protein. Remarkably, the IGF-I receptor binding assays of IGFBP-5 showed that IGFBP-5 inhibits the binding of IGFs to the IGF-I receptor, resulting in reduction of receptor stimulation and autophosphorylation. Compared with the full-length IGFBP-5, the smaller N-terminal fragments were less efficient inhibitors of the IGF-I receptor binding of IGFs.
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Affiliation(s)
- W Kalus
- Max Planck Institute for Biochemistry, D-82152 Martinsried
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26
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Rajaram S, Baylink DJ, Mohan S. Insulin-like growth factor-binding proteins in serum and other biological fluids: regulation and functions. Endocr Rev 1997; 18:801-31. [PMID: 9408744 DOI: 10.1210/edrv.18.6.0321] [Citation(s) in RCA: 212] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- S Rajaram
- Mineral Metabolism Laboratory, Jerry L. Pettis Memorial Veterans Administration Medical Center, Loma Linda, California 92357, USA
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27
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Fowlkes JL. Insulinlike growth factor-binding protein proteolysis an emerging paradigm in insulinlike growth factor physiology. Trends Endocrinol Metab 1997; 8:299-306. [PMID: 18406818 DOI: 10.1016/s1043-2760(97)00112-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In biologic fluids, insulinlike growth factors (IGF-I and IGF-II) are bound to high-affinity insulinlike growth factor binding proteins (IGFBPs) of which seven have now been identified (IGFBPs 1-7). In a variety of biologic fluids, several IGFBPs undergo proteolytic degradation. Such degradation can lead to increased IGF bioavailability at the cell surface, facilitating receptor interactions. Herein, recent data identifying several IGFBP-degrading proteinases and their effects on IGF bioactivity is reviewed, and how IGFBP proteolysis is regulated by IGFs and IGFBPs, as well as how IGFBP cleavage analysis provides insights into the structure and function of IGFBPs, is explored. (Trends Endocrinol Metab 1997;8:299-306). (c) 1997, Elsevier Science Inc.
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Affiliation(s)
- J L Fowlkes
- Department of Pediatrics, University of Kentucky College of Medicine, Lexington, KY 40536-0284, USA
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28
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Affiliation(s)
- E Canalis
- Saint Francis Hospital and Medical Center, Hartford, CT, USA
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29
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Mohan S, Baylink DJ. Serum insulin-like growth factor binding protein (IGFBP)-4 and IGFBP-5 levels in aging and age-associated diseases. Endocrine 1997; 7:87-91. [PMID: 9449039 DOI: 10.1007/bf02778070] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Because impaired bone formation is a major contributor to the pathogenesis of senile (type II) osteoporosis, and because insulin-like growth factors (IGFs) have been shown to be important stimulators of bone formation in vitro and in vivo, studies have been focused towards clarifying the role of IGF system in the age-related impairment in bone formation. To evaluate if changes in circulating and bone cell production of IGF binding protein (IGFBP)-4 and IGFBP-5 could contribute to age-related impairment in bone formation, the authors measured serum and skeletal levels of IGFBP-5, and serum levels of IGFBP-4 during aging. Circulating levels of IGFBP-4 increased with age, whereas that of IGFBP-5 declined with age. Serum IGFBP-4 and IGFBP-5 levels showed significant positive correlations with serum levels of parathyroid hormone (PTH) and IGFs, respectively. In addition, skeletal content of IGFBP-5 declined with age. The age-related changes in IGFBP-4 and IGFBP-5 production could contribute, in part, to the decrease in osteoblast cell proliferation and deficiency in bone formation.
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Affiliation(s)
- S Mohan
- Jerry L Pettis Veterans Medical Center, Department of Medicine, Loma Linda, CA 92357, USA.
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