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Poddar A, Ahmady F, Rao SR, Sharma R, Kannourakis G, Prithviraj P, Jayachandran A. The role of pregnancy associated plasma protein-A in triple negative breast cancer: a promising target for achieving clinical benefits. J Biomed Sci 2024; 31:23. [PMID: 38395880 PMCID: PMC10885503 DOI: 10.1186/s12929-024-01012-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 02/10/2024] [Indexed: 02/25/2024] Open
Abstract
Pregnancy associated plasma protein-A (PAPP-A) plays an integral role in breast cancer (BC), especially triple negative breast cancer (TNBC). This subtype accounts for the most aggressive BC, possesses high tumor heterogeneity, is least responsive to standard treatments and has the poorest clinical outcomes. There is a critical need to address the lack of effective targeted therapeutic options available. PAPP-A is a protein that is highly elevated during pregnancy. Frequently, higher PAPP-A expression is detected in tumors than in healthy tissues. The increase in expression coincides with increased rates of aggressive cancers. In BC, PAPP-A has been demonstrated to play a role in tumor initiation, progression, metastasis including epithelial-mesenchymal transition (EMT), as well as acting as a biomarker for predicting patient outcomes. In this review, we present the role of PAPP-A, with specific focus on TNBC. The structure and function of PAPP-A, belonging to the pappalysin subfamily, and its proteolytic activity are assessed. We highlight the link of BC and PAPP-A with respect to the IGFBP/IGF axis, EMT, the window of susceptibility and the impact of pregnancy. Importantly, the relevance of PAPP-A as a TNBC clinical marker is reviewed and its influence on immune-related pathways are explored. The relationship and mechanisms involving PAPP-A reveal the potential for more treatment options that can lead to successful immunotherapeutic targets and the ability to assist with better predicting clinical outcomes in TNBC.
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Affiliation(s)
- Arpita Poddar
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Federation University, Victoria, Australia
- RMIT University, Victoria, Australia
| | - Farah Ahmady
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Federation University, Victoria, Australia
| | - Sushma R Rao
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Revati Sharma
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Federation University, Victoria, Australia
| | - George Kannourakis
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Federation University, Victoria, Australia
| | - Prashanth Prithviraj
- Fiona Elsey Cancer Research Institute, Victoria, Australia
- Federation University, Victoria, Australia
| | - Aparna Jayachandran
- Fiona Elsey Cancer Research Institute, Victoria, Australia.
- Federation University, Victoria, Australia.
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2
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Conover CA, Oxvig C. The Pregnancy-Associated Plasma Protein-A (PAPP-A) Story. Endocr Rev 2023; 44:1012-1028. [PMID: 37267421 DOI: 10.1210/endrev/bnad017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/01/2023] [Accepted: 05/31/2023] [Indexed: 06/04/2023]
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) was first identified in the early 1970s as a placental protein of unknown function, present at high concentrations in the circulation of pregnant women. In the mid-to-late 1990s, PAPP-A was discovered to be a metzincin metalloproteinase, expressed by many nonplacental cells, that regulates local insulin-like growth factor (IGF) activity through cleavage of high-affinity IGF binding proteins (IGFBPs), in particular IGFBP-4. With PAPP-A as a cell surface-associated enzyme, the reduced affinity of the cleavage fragments results in increased IGF available to bind and activate IGF receptors in the pericellular environment. This proteolytic regulation of IGF activity is important, since the IGFs promote proliferation, differentiation, migration, and survival in various normal and cancer cells. Thus, there has been a steady growth in investigation of PAPP-A structure and function outside of pregnancy. This review provides historical perspective on the discovery of PAPP-A and its structure and cellular function, highlights key studies of the first 50 years in PAPP-A research, and introduces new findings from recent years.
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Affiliation(s)
- Cheryl A Conover
- Division of Endocrinology, Mayo Clinic, Rochester, MN 55905, USA
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
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3
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Jepsen MR, Østergaard JA, Conover CA, Wogensen L, Birn H, Krag SP, Fenton RA, Oxvig C. Increased activity of the metalloproteinase PAPP-A promotes diabetes-induced glomerular hypertrophy. Metabolism 2022; 132:155218. [PMID: 35588861 DOI: 10.1016/j.metabol.2022.155218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/19/2022] [Accepted: 05/12/2022] [Indexed: 12/27/2022]
Abstract
BACKGROUND Diabetic nephropathy (DN) is a serious complication of diabetes and a common cause of end stage renal failure. Insulin-like growth factor (IGF)-signaling has been implicated in DN, but is mechanistically poorly understood. Here, we assessed the activity of the metalloproteinase PAPP-A, an activator of IGF activity, and its possible interaction with the endogenous PAPP-A inhibitors stanniocalcin (STC)-1 and -2 in the mammalian kidney under normal and hyperglycemic conditions. METHODS AND RESULTS Immunohistochemistry demonstrated that PAPP-A, its proteolytic substrate IGF binding protein-4, STC1 and STC2 are present in the human kidney. Endogenous inhibited complexes of PAPP-A (PAPP-A:STC1 and PAPP-A:STC2) were demonstrated in media conditioned by human mesangial cells (HMCs), suggesting that PAPP-A activity is regulated by the STCs in kidney tissue. A method for the selective detection of active PAPP-A in tissue was developed and a significant increase in glomerular active PAPP-A in human diabetic kidney relative to normal was observed. In DN patients, the estimated glomerular filtration rate correlated with PAPP-A activity. In diabetic mice, glomerular growth was reduced when PAPP-A activity was antagonized by adeno-associated virus-mediated overexpression of STC2. CONCLUSION We propose that PAPP-A activity in renal tissue is precisely balanced by STC1 and STC2. An imbalance in this equilibrium causing increased PAPP-A enzymatic activity potentially contributes to the development of DN, and thus, therapeutic targeting of PAPP-A activity may represent a novel strategy for its treatment.
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Affiliation(s)
- Malene R Jepsen
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Jakob A Østergaard
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, DK-8200 Aarhus N, Denmark; Steno Diabetes Center Aarhus, Aarhus University Hospital, DK-8200 Aarhus N, Denmark
| | | | - Lise Wogensen
- Dean's Office, Faculty of Health, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Henrik Birn
- Department of Renal Medicine, Aarhus University Hospital, DK-8200 Aarhus N, Denmark; Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Søren P Krag
- Department of Histopathology, Aarhus University Hospital, DK-8200 Aarhus N, Denmark
| | - Robert A Fenton
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark.
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Mattoso Miskulin Cardoso AP, Tavares Pereira M, Dos Santos Silva R, Medeiros de Carvalho Sousa LM, Giometti IC, Kowalewski MP, de Carvalho Papa P. Global transcriptome analysis implicates cholesterol availability in the regulation of canine cyclic luteal function. Gen Comp Endocrinol 2021; 307:113759. [PMID: 33771531 DOI: 10.1016/j.ygcen.2021.113759] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 01/06/2021] [Accepted: 03/10/2021] [Indexed: 12/24/2022]
Abstract
Considering the key role of the corpus luteum in the regulation of the canine diestrus, the present study aimed to investigate changes in the luteal transcriptome of pseudopregnant dogs (n = 18) from days (D) 10, 20, 30, 40, 50 and 60 post-ovulation. After RNAsequencing was performed, data was analyzed by resorting to several informatic tools. A total of 3300 genes were differently expressed among all samples (FDR < 0.01). By comparing different time points, enriched biological processes as response to estradiol and lipids (D20 vs D10) and intracellular cholesterol transport (D40 vs D60) were observed. Moreover, LXR/RXR (liver X receptor- retinoid X receptor) signaling appeared as an overrepresented pathway in all comparisons. Thus, the expression of 19 genes involved in intracellular cholesterol availability was further evaluated; most were affected by time (P < 0.05). Adding to the deep transcriptomic analysis, presented data implies the importance of cholesterol regulation in luteal physiology of pseudopregnant dogs.
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Affiliation(s)
| | - Miguel Tavares Pereira
- Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Renata Dos Santos Silva
- School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | | | - Ines Cristina Giometti
- Faculty of Veterinary Medicine, University of Western São Paulo, Presidente Prudente, Brazil
| | | | - Paula de Carvalho Papa
- School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil; Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
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5
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Beattie J, Al-Khafaji H, Noer PR, Alkharobi HE, Alhodhodi A, Meade J, El-Gendy R, Oxvig C. Insulin- like Growth Factor-Binding Protein Action in Bone Tissue: A Key Role for Pregnancy- Associated Plasma Protein-A. Front Endocrinol (Lausanne) 2018; 9:31. [PMID: 29503631 PMCID: PMC5820303 DOI: 10.3389/fendo.2018.00031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 01/23/2018] [Indexed: 11/13/2022] Open
Abstract
The insulin-like growth factor (IGF) axis is required for the differentiation, development, and maintenance of bone tissue. Accordingly, dysregulation of this axis is associated with various skeletal pathologies including growth abnormalities and compromised bone structure. It is becoming increasingly apparent that the action of the IGF axis must be viewed holistically taking into account not just the actions of the growth factors and receptors, but also the influence of soluble high affinity IGF binding proteins (IGFBPs).There is a recognition that IGFBPs exert IGF-dependent and IGF-independent effects in bone and other tissues and that an understanding of the mechanisms of action of IGFBPs and their regulation in the pericellular environment impact critically on tissue physiology. In this respect, a group of IGFBP proteinases (which may be considered as ancillary members of the IGF axis) play a crucial role in regulating IGFBP function. In this model, cleavage of IGFBPs by specific proteinases into fragments with lower affinity for growth factor(s) regulates the partition of IGFs between IGFBPs and cell surface IGF receptors. In this review, we examine the importance of IGFBP function in bone tissue with special emphasis on the role of pregnancy associated plasma protein-A (PAPP-A). We examine the function of PAPP-A primarily as an IGFBP-4 proteinase and present evidence that PAPP-A induced cleavage of IGFBP-4 is potentially a key regulatory step in bone metabolism. We also highlight some recent findings with regard to IGFBP-2 and IGFBP-5 (also PAPP-A substrates) function in bone tissue and briefly discuss the actions of the other three IGFBPs (-1, -3, and -6) in this tissue. Although our main focus will be in bone we will allude to IGFBP activity in other cells and tissues where appropriate.
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Affiliation(s)
- James Beattie
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, University of Leeds, St James University Hospital, Leeds, United Kingdom
- *Correspondence: James Beattie,
| | - Hasanain Al-Khafaji
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, University of Leeds, St James University Hospital, Leeds, United Kingdom
| | - Pernille R. Noer
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Hanaa Esa Alkharobi
- Department of Oral Biology, Dental College, King AbdulAziz University, Jeddah, Saudi Arabia
| | - Aishah Alhodhodi
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, University of Leeds, St James University Hospital, Leeds, United Kingdom
| | - Josephine Meade
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, University of Leeds, St James University Hospital, Leeds, United Kingdom
| | - Reem El-Gendy
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, University of Leeds, St James University Hospital, Leeds, United Kingdom
- Department of Oral Pathology, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
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Conover CA, Oxvig C. PAPP-A: a promising therapeutic target for healthy longevity. Aging Cell 2017; 16:205-209. [PMID: 28035757 PMCID: PMC5334524 DOI: 10.1111/acel.12564] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2016] [Indexed: 12/16/2022] Open
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) is a proteolytic enzyme that was discovered to increase local insulin-like growth factor (IGF) availability for receptor activation through cleavage of inhibitory IGF binding proteins (IGFBPs). Reduced IGF signaling has been associated with increased lifespan and healthspan. Therefore, inhibition of PAPP-A represents a novel approach to indirectly decrease the availability of bioactive IGF. Here, we will review data in support of PAPP-A as a therapeutic target to promote healthy longevity.
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Affiliation(s)
| | - Claus Oxvig
- Department of Molecular Biology and Genetics; Aarhus Universitet; Aarhus Denmark
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7
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PAPP-A and the IGF system. ANNALES D'ENDOCRINOLOGIE 2016; 77:90-6. [DOI: 10.1016/j.ando.2016.04.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 04/11/2016] [Indexed: 01/25/2023]
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Steffensen LB, Conover CA, Bjørklund MM, Ledet T, Bentzon JF, Oxvig C. Stanniocalcin-2 overexpression reduces atherosclerosis in hypercholesterolemic mice. Atherosclerosis 2016; 248:36-43. [DOI: 10.1016/j.atherosclerosis.2016.02.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 01/29/2016] [Accepted: 02/23/2016] [Indexed: 11/26/2022]
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9
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Mikkelsen JH, Resch ZT, Kalra B, Savjani G, Kumar A, Conover CA, Oxvig C. Indirect targeting of IGF receptor signaling in vivo by substrate-selective inhibition of PAPP-A proteolytic activity. Oncotarget 2015; 5:1014-25. [PMID: 24572990 PMCID: PMC4011579 DOI: 10.18632/oncotarget.1629] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The insulin-like growth factor (IGF) signaling pathway is involved in certain human cancers, and the feasibility of directly targeting the IGF receptor has been actively investigated. However, recent evidence from clinical trials suggests that this approach can be problematic. We have developed an alternative strategy to indirectly inhibit the IGF signaling by targeting the metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A). PAPP-A associated with the cell surface cleaves IGF binding protein-4 (IGFBP-4), when IGF is bound to IGFBP-4, and thereby increases IGF bioavailability for receptor activation in an autocrine/paracrine manner. We hypothesized that inhibition of PAPP-A would suppress excessive local IGF signaling in tissues where this is caused by increased PAPP-A proteolytic activity. To test this hypothesis, we developed an inhibitory monoclonal antibody, mAb 1/41, which targets a unique substrate-binding exosite of PAPP-A. This inhibitor selectively and specifically inhibits proteolytic cleavage of IGFBP-4 with an inhibitory constant (Ki) of 135 pM. In addition, it inhibited intracellular signaling of the IGF receptor (AKT phosphorylation) in monolayers of A549 cells, an IGF-responsive lung cancer-derived cell line found to express high levels of PAPP-A. We further showed that mAb 1/41 is effective towards PAPP-A bound to cell surfaces, and that it is capable of inhibiting PAPP-A activity in vivo. Using a murine xenograft model of A549 cells, we demonstrated that mAb 1/41 administered intraperitoneally significantly inhibited tumor growth. Analysis of xenograft tumor tissue recovered from treated mice showed penetration of mAb 1/41, reduced IGFBP-4 proteolysis, and reduced AKT phosphorylation. Our study provides proof of concept that IGF signaling can be selectively reduced by targeting a regulatory proteinase that functions extracellularly, upstream of the IGF receptor. PAPP-A targeting thus represents an alternative therapeutic strategy for inhibiting IGF receptor signaling.
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Affiliation(s)
- Jakob H Mikkelsen
- Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark
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10
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The role of PAPP-A in the IGF system: location, location, location. J Cell Commun Signal 2015; 9:177-87. [PMID: 25617049 DOI: 10.1007/s12079-015-0259-9] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 01/12/2015] [Indexed: 12/15/2022] Open
Abstract
Although discovered as a placental protein present abundantly in the circulation of pregnant women, pregnancy-associated plasma protein-A (PAPP-A) is widely expressed in multiple tissues. PAPP-A is a highly specific metalloproteinase binding tightly to glycosaminoglycans present on the surface of cells. By cleaving a subset of insulin-like growth factor binding proteins (IGFBPs), PAPP-A thus functions within tissues as a growth-promoting enzyme, releasing bioactive IGF in close proximity to the IGF receptor. IGFBP-4 is believed to be the principal PAPP-A substrate, and the focus in this review is on PAPP-A enzymatic activity and its role in the PAPP-A-IGFBP-4-IGF axis, which is subject to regulation at several different levels. These include e.g., transcriptional control, competing reactions potentially sequestering IGF from IGFBP-4 and hence antagonizing PAPP-A-mediated IGF activation, and proteolytic inhibition of PAPP-A. The latter may involve the protein stanniocalcin-2 (STC2), recently found to potently inhibit PAPP-A activity by forming a covalent complex with PAPP-A. PAPP-A or complex-bound variants may escape from pathological tissues into the circulation. It is emphasized that the potential use of PAPP-A as a diagnostic or predictive biomarker in nonpregnant individuals requires precise knowledge of analyte identity and assay specificity in addition to an appropriate material for standardization. Finally, PAPP-A may serve as a therapeutic target to indirectly inhibit IGF signaling in tissues where this is driven by increased PAPP-A activity. By taking advantage of the intricate interaction between PAPP-A and IGFBP-4, highly specific and selective inhibition of PAPP-A is possible.
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Jepsen MR, Kløverpris S, Mikkelsen JH, Pedersen JH, Füchtbauer EM, Laursen LS, Oxvig C. Stanniocalcin-2 inhibits mammalian growth by proteolytic inhibition of the insulin-like growth factor axis. J Biol Chem 2014; 290:3430-9. [PMID: 25533459 DOI: 10.1074/jbc.m114.611665] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mammalian stanniocalcin-2 (STC2) is a secreted polypeptide widely expressed in developing and adult tissues. However, although transgenic expression in mice is known to cause severe dwarfism, and targeted deletion of STC2 causes increased postnatal growth, its precise biological role is still unknown. We found that STC2 potently inhibits the proteolytic activity of the growth-promoting metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A). Proteolytic inhibition requires covalent binding of STC2 to PAPP-A and is mediated by a disulfide bond, which involves Cys-120 of STC2. Binding of STC2 prevents PAPP-A cleavage of insulin-like growth factor-binding protein (IGFBP)-4 and hence release within tissues of bioactive IGF, required for normal growth. Concordantly, we show that STC2 efficiently inhibits PAPP-A-mediated IGF receptor signaling in vitro and that transgenic mice expressing a mutated variant of STC2, STC2(C120A), which is unable to inhibit PAPP-A, grow like wild-type mice. Our work identifies STC2 as a novel proteinase inhibitor and a previously unrecognized extracellular component of the IGF system.
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Affiliation(s)
- Malene R Jepsen
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Søren Kløverpris
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Jakob H Mikkelsen
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Josefine H Pedersen
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Ernst-Martin Füchtbauer
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Lisbeth S Laursen
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Claus Oxvig
- From the Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
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Abstract
Pregnancy-associated plasma protein A (PAPP-A) is a key regulator of insulin-like growth factor bioavailability essential for normal fetal development. In maternal blood, this protein increases with gestational age and then rapidly decreases after delivery. It is routinely used for Down syndrome screening in the first trimester of pregnancy, and its decrease compared to a normal pregnancy indicates an increased risk for both chromosomal anomalies and adverse pregnancy outcomes. It belongs to a group of biomarkers that predict later preeclampsia development, primarily early onset preeclampsia; however, it should be combined with a Doppler ultrasonography of the uterine artery (pulsatile index) and other biochemical and maternal factors to achieve a higher detection rate with an acceptable false positivity rate. Some studies have demonstrated an even more pronounced decrease of PAPP-A in the early second trimester of pregnancy in women who subsequently develop preeclampsia compared with women who do not develop preeclampsia. Conversely, during the last trimester of pregnancy, its concentration increases even more in patients with preeclampsia than in patients without. It is also detectable at very low levels in nonpregnant individuals, and a higher concentration indicates an adverse effect in patients with acute coronary syndromes or stable atherosclerotic disease and in patients with end-stage renal disease who are being treated with hemodialysis.
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13
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Kjaer-Sorensen K, Engholm DH, Kamei H, Morch MG, Kristensen AO, Zhou J, Conover CA, Duan C, Oxvig C. Pregnancy-associated plasma protein A (PAPP-A) modulates the early developmental rate in zebrafish independently of its proteolytic activity. J Biol Chem 2013; 288:9982-9992. [PMID: 23430244 DOI: 10.1074/jbc.m112.426304] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) is a large metalloproteinase specifically cleaving insulin-like growth factor (IGF) binding proteins, causing increased IGF bioavailability and, hence, local regulation of IGF receptor activation. We have identified two highly conserved zebrafish homologs of the human PAPP-A gene. Expression of zebrafish Papp-a, one of the two paralogs, begins during gastrulation and persists throughout the first week of development, and analyses demonstrate highly conserved patterns of expression between adult zebrafish, humans, and mice. We show that the specific knockdown of zebrafish papp-a limits the developmental rate beginning during gastrulation without affecting the normal patterning of the embryo. This phenotype is different from those resulting from deficiency of Igf receptor or ligand in zebrafish, suggesting a function of Papp-a outside of the Igf system. Biochemical analysis of recombinant zebrafish Papp-a demonstrates conservation of proteolytic activity, specificity, and the intrinsic regulatory mechanism. However, in vitro transcribed mRNA, which encodes a proteolytically inactive Papp-a mutant, recues the papp-a knockdown phenotype as efficiently as wild-type Papp-a. Thus, the developmental phenotype of papp-a knockdown is not a consequence of lacking Papp-a proteolytic activity. We conclude that Papp-a possesses biological functions independent of its proteolytic activity. Our data represent the first evidence for a non-proteolytic function of PAPP-A.
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Affiliation(s)
- Kasper Kjaer-Sorensen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Ditte H Engholm
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Hiroyasu Kamei
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48105
| | - Maria G Morch
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Anisette O Kristensen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Jianfeng Zhou
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48105
| | - Cheryl A Conover
- Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905
| | - Cunming Duan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48105
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark.
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14
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Conover CA. Key questions and answers about pregnancy-associated plasma protein-A. Trends Endocrinol Metab 2012; 23:242-9. [PMID: 22463950 PMCID: PMC3348390 DOI: 10.1016/j.tem.2012.02.008] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 02/20/2012] [Accepted: 02/26/2012] [Indexed: 11/26/2022]
Abstract
Twenty-five years after it was identified as a circulating protein of unknown function derived from the placenta, pregnancy-associated plasma protein-A (PAPP-A) was discovered to be a novel zinc metalloproteinase expressed by a variety of cell types. Great progress has been made in understanding the biology of PAPP-A and its regulation during recent years, especially in regard to physiological and pathophysiological inflammatory injury responses. However, much remains to be learned about this complex protein and its potential clinical implications outside pregnancy. In this article we address some of the outstanding questions about PAPP-A, in particular about its newly emerging role in the insulin-like growth factor (IGF) system.
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Affiliation(s)
- Cheryl A Conover
- Division of Endocrinology and Metabolism, Endocrine Research Unit, Mayo Clinic, Rochester, MN 55905, USA.
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Weyer K, Glerup S. Placental Regulation of Peptide Hormone and Growth Factor Activity by proMBP1. Biol Reprod 2011; 84:1077-86. [DOI: 10.1095/biolreprod.110.090209] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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Wagner PK, Christians JK. Altered placental expression of PAPPA2 does not affect birth weight in mice. Reprod Biol Endocrinol 2010; 8:90. [PMID: 20642865 PMCID: PMC2913990 DOI: 10.1186/1477-7827-8-90] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 07/20/2010] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Pregnancy-associated plasma protein A2 (PAPPA2) is an insulin-like growth factor binding protein (IGFBP) protease expressed in the placenta and upregulated in pregnancies complicated by pre-eclampsia. The mechanism linking PAPPA2 expression and pre-eclampsia and the consequences of altered PAPPA2 expression remain unknown. We previously identified PAPPA2 as a candidate gene for a quantitative trait locus (QTL) affecting growth in mice and in the present study examined whether this QTL affects placental PAPPA2 expression and, in turn, placental or embryonic growth. METHODS Using a line of mice that are genetically homogenous apart from a 1 megabase QTL region containing the PAPPA2 gene, we bred mice homozygous for alternate QTL genotypes and collected and weighed placentae and embryos at E12.5. We used quantitative RT-PCR to measure the mRNA levels of PAPPA2, as well as mRNA levels of IGFBP-5 (PAPPA2's substrate), and PAPPA (a closely related IGFBP protease) to examine potential feedback and compensation effects. Western blotting was used to quantify PAPPA2 protein. Birth weight was measured in pregnancies allowed to proceed to parturition. RESULTS PAPPA2 mRNA and protein expression levels in the placenta differed by a factor of 2.5 between genotypes, but we did not find a significant difference between genotypes in embryonic PAPPA2 mRNA levels. Placental IGFBP-5 and PAPPA mRNA expression levels were not altered in response to PAPPA2 levels, and we could not detect IGFBP-5 protein in the placenta by Western blotting. The observed difference in placental PAPPA2 expression had no significant effect on placental or embryonic mass at mid-gestation, birth weight or litter size. CONCLUSIONS Despite a significant difference between genotypes in placental PAPPA2 expression similar in magnitude to the difference between pre-eclamptic and normal placentae previously reported, we observed no difference in embryonic, placental or birth weight. Our results suggest that elevated PAPPA2 levels are a consequence, rather than a cause, of pregnancy complications.
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Affiliation(s)
- Pamela K Wagner
- Simon Fraser University, Biological Sciences, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Julian K Christians
- Simon Fraser University, Biological Sciences, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
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17
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Pregnancy-associated plasma protein-A in the pathophysiology, diagnosis, and prognosis of coronary heart disease. COR ET VASA 2010. [DOI: 10.33678/cor.2010.120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Conover CA, Mason MA, Bale LK, Harrington SC, Nyegaard M, Oxvig C, Overgaard MT. Transgenic overexpression of pregnancy-associated plasma protein-A in murine arterial smooth muscle accelerates atherosclerotic lesion development. Am J Physiol Heart Circ Physiol 2010; 299:H284-91. [PMID: 20472761 DOI: 10.1152/ajpheart.00904.2009] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) increases local IGF-I bioavailability through cleavage of inhibitory IGF binding protein (IGFBP)-4 in a variety of systems, including the cardiovascular system. To test the hypothesis that expression of PAPP-A promotes the development of atherosclerotic lesions, we generated transgenic mice that express human PAPP-A in arterial smooth muscle. Four founder lines were characterized for transgenic human PAPP-A mRNA and protein expression, IGFBP-4 protease activity, and tissue specificity. In study I, apolipoprotein E knockout (ApoE KO) mice, a well-characterized mouse model of atherosclerosis, and ApoE KO mice expressing the human PAPP-A transgene at relatively high levels (ApoE KO/Tg) were fed a high-fat diet. At harvest, aortas were dissected and opened longitudinally for en face staining of lipid-rich lesions. Lesion area was increased 3.5-fold in aortas from ApoE KO/Tg compared with ApoE KO mice (P < 0.001), but no significant difference was seen in lesion number. In study II, replacement of PAPP-A expression in arterial smooth muscle of double ApoE KO/PAPP-A KO mice resulted in a 2.5-fold increase in lesion area (P = 0.002), without an effect on lesion number. PAPP-A transgene expression was associated with a significant increase in an IGF-responsive gene (P < 0.001), suggesting increased local IGF-I action. We therefore conclude that expression of human PAPP-A localized to arterial smooth muscle accelerates lesion progression in a mouse model of atherosclerosis. These data provide further evidence for the importance of PAPP-A in the cardiovascular system and suggest PAPP-A as a potential therapeutic target in the control of atherosclerosis.
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Affiliation(s)
- Cheryl A Conover
- Division of Endocrinology, Metabolism and Nutrition, Department of Internal Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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19
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Nyegaard M, Overgaard MT, Su YQ, Hamilton AE, Kwintkiewicz J, Hsieh M, Nayak NR, Conti M, Conover CA, Giudice LC. Lack of functional pregnancy-associated plasma protein-A (PAPPA) compromises mouse ovarian steroidogenesis and female fertility. Biol Reprod 2010; 82:1129-38. [PMID: 20130263 DOI: 10.1095/biolreprod.109.079517] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The insulin-like growth factor (IGF) system plays an important role in regulating ovarian follicular development and steroidogenesis. IGF binding proteins (IGFBP) mostly inhibit IGF actions, and IGFBP proteolysis is a major mechanism for regulating IGF bioavailability. Pregnancy-associated plasma protein-A (PAPPA) is a secreted metalloprotease responsible for cleavage of IGFBP4 in the ovary. The aim of this study was to investigate whether PAPPA plays a role in regulating ovarian functions and female fertility by comparing the reproductive phenotype of wild-type (WT) mice with mice heterozygous or homozygous for a targeted Pappa gene deletion (heterozygous and PAPP-A knockout [KO] mice, respectively). When mated with WT males, PAPP-A KO females demonstrated an overall reduction in average litter size. PAPP-A KO mice had a reduced number of ovulated oocytes, lower serum estradiol levels following equine chorionic gonadotropin administration, lower serum progesterone levels after human chorionic gonadotropin injection, and reduced expression of ovarian steroidogenic enzyme genes, compared to WT controls. In PAPP-A KO mice, inhibitory IGFBP2, IGFBP3, and IGFBP4 ovarian gene expression was reduced postgonadotropin stimulation, suggesting some compensation within the ovarian IGF system. Expression levels of follicle-stimulating hormone receptor, luteinizing hormone receptor, and genes required for cumulus expansion were not affected. Analysis of preovulatory follicular fluid showed complete loss of IGFBP4 proteolytic activity in PAPP-A KO mice, demonstrating no compensation for loss of PAPPA proteolytic activity by other IGFBP proteases in vivo in the mouse ovary. Taken together, these data demonstrate an important role of PAPPA in modulating ovarian function and female fertility by control of the bioavailability of ovarian IGF.
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Affiliation(s)
- Mette Nyegaard
- Department of Ob/Gyn., Stanford University School of Medicine, Stanford, CA, USA
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20
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Mikkelsen JH, Gyrup C, Kristensen P, Overgaard MT, Poulsen CB, Laursen LS, Oxvig C. Inhibition of the proteolytic activity of pregnancy-associated plasma protein-A by targeting substrate exosite binding. J Biol Chem 2008; 283:16772-80. [PMID: 18434323 DOI: 10.1074/jbc.m802429200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The metalloproteinase pregnancy-associated plasma protein-A (PAPP-A) cleaves both insulin-like growth factor (IGF)-binding protein 4 (IGFBP-4) and -5 at a single site in their central domain causing the release of bioactive IGF. Inhibition of IGF signaling is relevant in human disease, and several drugs in development target the IGF receptor. However, inhibition of PAPP-A activity may be a valuable alternative. We have generated monoclonal phage-derived single chain fragment variable (scFv) antibodies which selectively inhibit the cleavage of IGFBP-4 by PAPP-A, relevant under conditions where cleavage of IGFBP-4 represents the final step in the delivery of IGF to the IGF receptor. None of the antibodies inhibited the homologous proteinase PAPP-A2, which allowed mapping of antibody binding by means of chimeras between PAPP-A and PAPP-A2 to the C-terminal Lin12-Notch repeat module, separated from the proteolytic domain by almost 1000 amino acids. Hence, the antibodies define a substrate binding exosite that can be targeted for the selective inhibition of PAPP-A proteolytic activity against IGFBP-4. In addition, we show that the Lin12-Notch repeat module reversibly binds a calcium ion and that bound calcium is required for antibody binding, providing a strategy for the further development of selective inhibitory compounds. To our knowledge these data represent the first example of differential inhibition of cleavage of natural proteinase substrates by exosite targeting. Generally, exosite inhibitors are less likely to affect the activity of related proteolytic enzymes with similar active site environments. In the case of PAPP-A, selective inhibition of IGFBP-4 cleavage by interference with exosite binding is a further advantage, as the activity against other known or unknown PAPP-A substrates, whose cleavage may not depend on binding to the same exosite, is not targeted.
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Affiliation(s)
- Jakob H Mikkelsen
- Department of Molecular Biology, University of Aarhus, DK-8000 Aarhus, Denmark
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21
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Beattie J, Phillips K, Shand JH, Szymanowska M, Flint DJ, Allan GJ. Molecular interactions in the insulin-like growth factor (IGF) axis: a surface plasmon resonance (SPR) based biosensor study. Mol Cell Biochem 2007; 307:221-36. [PMID: 17899320 DOI: 10.1007/s11010-007-9601-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Accepted: 08/24/2007] [Indexed: 12/18/2022]
Abstract
This review describes a comprehensive analysis of a surface plasmon resonance (SPR)-based biosensor study of molecular interactions in the insulin-like growth factor (IGF) molecular axis. In this study, we focus on the interaction between the polypeptide growth factors IGF-I and IGF-II with six soluble IGF binding proteins (IGFBP 1-6), which occur naturally in various biological fluids. We have describe the conditions required for the accurate determination of kinetic rate constants for these interactions and highlight the experimental and theoretical pitfalls, which may be encountered in the early stages of such a study. We focus on IGFBP-5 and describe a site-directed mutagenesis study, which examines the contribution of various residues in the protein to high affinity interaction with IGF-I and -II. We analyse the interaction of IGFBP-5 (and IGFBP-3) with heparin and other biomolecules and describe experiments, which were designed to monitor multi-protein complex formation in this molecular axis.
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Affiliation(s)
- James Beattie
- Strathclyde Institute of Pharmacy & Biomedical Science, Royal College Building, University of Strathclyde, Glasgow, UK.
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22
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Boldt HB, Conover CA. Pregnancy-associated plasma protein-A (PAPP-A): a local regulator of IGF bioavailability through cleavage of IGFBPs. Growth Horm IGF Res 2007; 17:10-18. [PMID: 17218136 DOI: 10.1016/j.ghir.2006.11.003] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Pregnancy-associated plasma protein-A (PAPP-A) was originally isolated in 1974, as one of four proteins of placental origin found in high concentrations in the blood of pregnant women. In the early 1990s several laboratories reported novel protease activity against insulin-like growth factor binding protein-4 (IGFBP-4) in media conditioned by several cell types. This activity was unique, as it appeared to require the presence of IGF to cleave IGFBP-4. In 1999, this IGF-dependent IGFBP-4 protease activity was isolated from human fibroblast conditioned media and identified as PAPP-A. Subsequently, PAPP-A was shown to be expressed by a variety of cell types, and thus no longer could be considered to be just "pregnancy-associated". This review will describe what is currently known about the structure of PAPP-A and about its function as an IGFBP protease, with a focus on new insights obtained through study of a PAPP-A knock-out mouse model and on potential clinical applications.
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Affiliation(s)
- Henning B Boldt
- Division of Endocrinology, Metabolism, and Nutrition, Department of Internal Medicine, Mayo Clinic College of Medicine, 200 First Street SW, 5-194 Joseph, Rochester, MN 55905, USA
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23
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Beattie J, Allan GJ, Lochrie JD, Flint DJ. Insulin-like growth factor-binding protein-5 (IGFBP-5): a critical member of the IGF axis. Biochem J 2006; 395:1-19. [PMID: 16526944 PMCID: PMC1409685 DOI: 10.1042/bj20060086] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Accepted: 01/30/2006] [Indexed: 11/17/2022]
Abstract
The six members of the insulin-like growth factor-binding protein family (IGFBP-1-6) are important components of the IGF (insulin-like growth factor) axis. In this capacity, they serve to regulate the activity of both IGF-I and -II polypeptide growth factors. The IGFBPs are able to enhance or inhibit the activity of IGFs in a cell- and tissue-specific manner. One of these proteins, IGFBP-5, also has an important role in controlling cell survival, differentiation and apoptosis. In this review, we report on the structural and functional features of the protein which are important for these effects. We also examine the regulation of IGFBP-5 expression and comment on its potential role in tumour biology, with special reference to work with breast cancer cells.
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Key Words
- extracellular matrix (ecm)
- glycosaminoglycan
- insulin-like growth factor-i (igf-i)
- insulin-like growth factor-binding protein 5 (igfbp-5)
- mammary gland
- proteolysis
- adam, adisintegrin and metalloprotease
- ap-2, activator protein 2
- cat, chloramphenicol acetyltransferase
- cbp-4, c-terminus of insulin-like growth factor-binding protein 4 (residues 151–232)
- c/ebp, ccaat/enhancer-binding protein
- ecm, extracellular matrix
- er, oestrogen receptor
- erk1/2, extracellular-signal-regulated protein kinase 1/2
- fhl-2, four-and-a-half lim domain 2
- gag, glycosaminoglycan
- gh, growth hormone
- igf, insulin-like growth factor
- igfbp, igf-binding protein
- igf-ir, igf-i receptor
- igf-iir, igf-ii receptor
- ir, insulin receptor
- irs, ir substrate
- mapk, mitogen-activated protein kinase
- nbp-4, n-terminus of igfbp-4 (residues 3–82)
- oe2, oestradiol
- op-1, osteogenic protein-1
- opn, osteopontin
- pai-1, plasminogen activator inhibitor-1
- papp, pregnancy-associated plasma protease
- pge2, prostaglandin e2
- psmc, porcine smooth-muscle cell
- ra, retinoic acid
- rassf1c, isoform c of the ras association family 1 protein group
- rt, reverse transcription
- spr, surface plasmon resonance
- tpa, tissue plasminogen activator
- tsp-1, thrombospondin-1
- vn, vitronectin
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Affiliation(s)
- James Beattie
- Hannah Research Institute, Ayr KA6 5HL, Scotland, UK.
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24
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Bunn RC, Green LD, Overgaard MT, Oxvig C, Fowlkes JL. IGFBP-4 degradation by pregnancy-associated plasma protein-A in MC3T3 osteoblasts. Biochem Biophys Res Commun 2005; 325:698-706. [PMID: 15541345 DOI: 10.1016/j.bbrc.2004.10.092] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2004] [Indexed: 11/20/2022]
Abstract
Insulin-like growth factor (IGF) signaling is critical for osteoblast development and IGF binding protein (IGFBP)-4 is one of the principle IGFBPs expressed by osteoblasts. Release of bound IGF via proteolytic degradation of IGFBP-4 is likely to be critical for osteoblast development. We have investigated whether IGF-sensitive, IGFBP-4 degradation in mouse MC3T3-E1 osteoblasts is due to the metzincin pregnancy-associated plasma protein (PAPP)-A. Degradation of IGFBP-4 by PAPP-A or MC3T3-E1 conditioned medium was enhanced by IGF-II but inhibited by mutation of basic residues at or near the PAPP-A cleavage site in IGFBP-4. Furthermore, immunodepletion of PAPP-A from MC3T3-E1 conditioned medium abolished IGFBP-4 degradation. We also found that PAPP-A messenger RNA was expressed throughout differentiation of MC3T3-E1 cells. These results demonstrate for the first time that PAPP-A is the IGFBP-4 protease in MC3T3-E1 cells, a widely used model for osteoblast development, and that PAPP-A may regulate IGF release throughout osteoblast differentiation.
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Affiliation(s)
- R Clay Bunn
- Department of Pediatrics, University of Arkansas for Medical Sciences, Arkansas Children's Hospital Research Institute, Little Rock, AR 72202, USA.
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Conover CA, Bale LK, Overgaard MT, Johnstone EW, Laursen UH, Füchtbauer EM, Oxvig C, van Deursen J. Metalloproteinase pregnancy-associated plasma protein A is a critical growth regulatory factor during fetal development. Development 2004; 131:1187-94. [PMID: 14973274 DOI: 10.1242/dev.00997] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Pregnancy-associated plasma protein A (PAPPA) is a metzincin superfamily metalloproteinase in the insulin-like growth factor (IGF) system. PAPPA increases IGF bioavailability and mitogenic effectiveness in vitro through regulated cleavage of IGF-binding protein 4 (IGFBP4). To determine its function in vivo, we generated PAPPA-null mice by gene targeting. Mice homozygous for targeted disruption of the PAPPA gene were viable but 60% the size of wild-type littermates at birth. The impact of the mutation was exerted during the early embryonic period prior to organogenesis, resulting in proportional dwarfism. PAPPA, IGF2 and IGFBP4 transcripts co-localized in wild-type embryos, and expression of IGF2 and IGFBP4 mRNA was not altered in PAPPA-deficient embryos. However,IGFBP4 proteolytic activity was completely lacking in fibroblasts derived from PAPPA-deficient embryos, and IGFBP4 effectively inhibited IGF-stimulated mitogenesis in these cells. These results provide the first direct evidence that PAPPA is an essential growth regulatory factor in vivo, and suggest a novel mechanism for regulated IGF bioavailability during early fetal development.
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Affiliation(s)
- Cheryl A Conover
- The Division of Endocrinology, Metabolism and Nutrition, Endocrine Research Unit, Mayo Clinic and Mayo Foundation, 200 First Street SW, Rochester, MN 55905, USA.
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Schwartz RS, Bayes-Genis A, Lesser JR, Sangiorgi M, Henry TD, Conover CA. Detecting vulnerable plaque using peripheral blood: inflammatory and cellular markers. J Interv Cardiol 2003; 16:231-42. [PMID: 12800402 DOI: 10.1034/j.1600-0854.2003.8025.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The concept of the vulnerable patient has arrived. Enhanced diagnostic methods will eventually permit accurately finding and treating these patients and their disease. Clinical Cardiologists now recognize that coronary atherosclerosis is two pathophysiologically distinct syndromes: stable and unstable. Stable coronary syndromes result from fixed, severe stenoses limiting blood flow and causing secondary myocardial ischemia. The unstable acute coronary syndromes are frequently catastrophic and are pathophysiologically distinct. They result from different cell subsets causing vascular inflammatory syndromes rather than gradual lumen constriction by plaque. Though pathophysiologically distinct, they may show common pathophysiology when a ruptured plaque heals and progressively becomes a critical stenosis. For the present hs-CRP measurement is the strongest correlative factor for future clinical events due to arterial inflammation: myocardial infarction, unstable angina, stroke, and peripheral vascular disease in both diseased and apparently healthy, asymptomatic patients. The CRP plasma level also is the best risk assessment in patients with either stable or unstable angina, long term after myocardial infarction, and in patients undergoing revascularization therapies. One study showed the only independent cardiovascular risk indicators using multivariate, age adjusted and traditional risk analysis were CRP and Total/HDL cholesterol ratio. If CRP, IL-6, and ICAM-1 levels are added to lipid levels, risk assessment can be improved over lipids alone. The prevalence of high-risk subjects in the general population is low, amplifying diagnostic problems for vulnerable plaque. Since no test yet has high sensitivity or specificity, diagnostic errors are high, with many false positives and negatives. Sensitivity or specificity must be increased by developing a risk marker panel, or by simultaneously finding other markers that themselves are highly sensitive and specific for vulnerable plaque.
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Affiliation(s)
- Robert S Schwartz
- Minnesota Cardiovascular Research Institute, Minneapolis Heart Institute Foundation, Minneapolis, MN 55407, USA.
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