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Fang PW, Lin YC, Fan SY, Panja A, Xu SQ, Lee SH, Tan KT. Protein-Labeling Fluorescent Probe for Folate Receptor α. Anal Chem 2023; 95:11535-11541. [PMID: 37479992 DOI: 10.1021/acs.analchem.3c02215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
GPI-anchored folate receptor α (FRα) is an attractive anticancer drug target and diagnosis marker in fundamental biology and medical research due to its significant expression on many cancer cells. Currently, analyses of FRα expression levels are usually achieved using immunological methods. Due to the continual FRα synthesis and degradation, immunological methods are not suitable for studying real-time dynamic activities of FRα in living cells. In this paper, we introduce a rapid and specific FRα protein-labeling fluorescent probe, FR1, to facilitate the study of the dynamics of expression and degradation processes of endogenous FRα in living cells. With this labeling probe, insights on FRα protein lifetime and shedding from the cell surface can be obtained using fluorescence live-cell imaging and electrophoresis techniques. We revealed that FRα undergoes soluble domain release and endocytosis degradation simultaneously. Imaging results showed that most of the membrane FRα are transported to the lysosomes after 2 h of incubation. Furthermore, we also showed that the secretion of a FRα soluble domain into the environment is most likely accomplished by phospholipase. We believe that this protein-labeling approach can be an important tool for analyzing various dynamic processes involving FRα.
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Affiliation(s)
- Pin-Wen Fang
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Yu-Chun Lin
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Syuan-Yun Fan
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Avijit Panja
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Shun-Qiang Xu
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Szu-Hsien Lee
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
| | - Kui-Thong Tan
- Department of Chemistry, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
- Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, 101 Section 2, Kuang-Fu Road, Hsinchu 300044, Taiwan, Republic of China
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan, Republic of China
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Conjugates of small targeting molecules to non-viral vectors for the mediation of siRNA. Acta Biomater 2016; 36:21-41. [PMID: 27045350 DOI: 10.1016/j.actbio.2016.03.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 03/29/2016] [Accepted: 03/31/2016] [Indexed: 01/08/2023]
Abstract
UNLABELLED To use siRNA (small interfering RNA) for gene therapy, a gene delivery system is often necessary to overcome several challenging requirements including rapid excretion, low stability in blood serum, non-specific accumulation in tissues, poor cellular uptake and inefficient intracellular release. Active and/or passive targeting should help the delivery system to reach the desired tissue or cell, to be internalized, and to deliver siRNA to the cytoplasm so that siRNA can inhibit protein synthesis. This review covers conjugates of small targeting molecules and non-viral delivery systems for the mediation of siRNA, with a focus on their transfection properties in order to help the development of new and efficient siRNA delivery systems, as the therapeutic solutions of tomorrow. STATEMENT OF SIGNIFICANCE The delivery of siRNA into cells or tissues remains to be a challenge for its applications, an alternative strategy for siRNA delivery systems is direct conjugation of non-viral vectors with targeting moieties for cellular delivery. In comparison to macromolecules, small targeting molecules have attracted great attention due to their many potential advantages including significant simplicity and ease of production, good repeatability and biodegradability. This review will focus on the most recent advances in the delivery of siRNA using conjugates of small targeting molecules and non-viral delivery systems. Based the editor's suggestions, we hope the revised manuscript could provide more profound understanding to the conjugates of targeting molecules to vectors for mediation of siRNA.
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LDAI-Based Chemical Labeling of Intact Membrane Proteins and Its Pulse-Chase Analysis under Live Cell Conditions. ACTA ACUST UNITED AC 2014; 21:1013-22. [DOI: 10.1016/j.chembiol.2014.07.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/11/2014] [Accepted: 07/30/2014] [Indexed: 11/21/2022]
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4
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Yuan Z, Li WT, Ye XD, Liu SY, Xiao XS. Folate receptor-mediated targeted polymeric gadolinium complexes for magnetic resonance imaging in pulmonary tumor xenografts. Exp Ther Med 2012; 3:903-907. [PMID: 22969991 DOI: 10.3892/etm.2012.504] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 02/06/2012] [Indexed: 11/05/2022] Open
Abstract
Targeted delivery is a highly desirable strategy for diagnostic imaging due to enhanced efficacy and reduced dosage/toxicity. The need to develop target-specific magnetic resonance imaging (MRI) contrast agents to aid in disease characterization is highly essential. In this study, a specific contrast agent, Gd-DTPA-poly-L-lysine (PL-Gd-DTPA)-folate, was synthesized and evaluated for its efficacy as a targeted agent for the imaging of tumors that overexpress the folate receptor. Folic acid was conjugated to PL-Gd-DTPA via the ε-amino groups. The receptor binding properties of folate-PL-Gd-DTPA were studied in cultured tumor cells that overexpressed the folate receptor. The tumor-selecting properties of folate-PL-Gd-DTPA were then evaluated in BALB/c mice bearing subcutaneously implanted folate receptor-positive tumors. Tissue MR signal intensities were measured at six different time-points. In the in vitro study, the folate-PL-Gd-DTPA was able to bind to these cells, which overexpressed the folate receptor, as with free folic acid. Excellent tumor selectivity was also shown in the animal model; after the success of injection of folate-PL-Gd-DTPA, a maximum intensity increase of 125.4% was observed from pre-injection compared to post-injection images of the tumor at the 48 h time-point. The liver enhancement was non-specific and the muscle signal intensity at any time-point after injection showed no statistical difference with that observed before injection. Folate-PL-Gd-DTPA is a promising, novel receptor-specific MRI contrast agent with potential applications in the imaging of human folate receptor-positive tumors.
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Affiliation(s)
- Zheng Yuan
- Department of Radiology, Fudan University Shanghai Cancer Center, Shanghai 200032
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5
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Zheng Y, Cai Z, Song X, Chen Q, Bi Y, Li Y, Hou S. Preparation and characterization of folate conjugated N-trimethyl chitosan nanoparticles as protein carrier targeting folate receptor: in vitro studies. J Drug Target 2010; 17:294-303. [PMID: 19255895 DOI: 10.1080/10611860902737920] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Folate conjugated N-trimethyl chitosan (folate-TMC) was synthesized and characterized using Fourier transform infrared (FTIR) and (1)H spectroscopy. The fluorescein isothiocyanate conjugated bovine serum albumin (FITC-BSA) loaded TMC-nanoparticle (FB-TMC-NP) and FITC-BSA loaded folate-TMC-nanoparticle (FB-f-TMC-NP) were prepared by ionic cross-linking of TMC or folate-TMC with sodium alginate. Single factor analysis method was used to optimize the formulation of nanoparticles. The encapsulating efficiencies of FB-TMC-NP and FB-f-TMC-NP produced by optimal formulation were 98.3 +/- 1.9% and 98.7 +/- 2.7% (n=3), respectively. In addition, the mean diameters of FB-TMC-NP and FB-f-TMC-NP were 184.3 +/- 8.3 nm and 176.1 +/- 5.0 nm (n = 3), respectively. Transmission electron microscope (TEM) showed that the nanoparticles were of spherical shapes. The intracellular uptake of FB-f-TMC-NP by SKOV3 cells (folate receptor overexpressing cells) was 3.7-fold more than that of FB-TMC-NP and could be inhibited by the presence of 1 mM folate in the culture medium, although there was no significant difference between the intracellular uptake of FB-f-TMC-NP in A549 cells (folate receptor-deficient cells) and that of FB-TMC-NP in the same cells. In conclusion, the enhancement of cellular uptake of FB-f-TMC-NP by SKOV3 cells in a specific way was attributed to the folate receptor-mediated endocytosis. FB-TMC-NP was a promising carrier for protein.
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Affiliation(s)
- Yu Zheng
- West China Pharmacy School, Sichuan University, Chengdu, China
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6
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Zhang S, Zhao Y, Zhao B, Wang B. Hybrids of Nonviral Vectors for Gene Delivery. Bioconjug Chem 2010; 21:1003-9. [DOI: 10.1021/bc900261c] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Shubiao Zhang
- SEAC-ME Key Laboratory of Biotechnology and Bioresources Utilization, College of Life Science, Dalian Nationalities University, Dalian 116600, Liaoning, China
| | - Yinan Zhao
- SEAC-ME Key Laboratory of Biotechnology and Bioresources Utilization, College of Life Science, Dalian Nationalities University, Dalian 116600, Liaoning, China
| | - Budiao Zhao
- SEAC-ME Key Laboratory of Biotechnology and Bioresources Utilization, College of Life Science, Dalian Nationalities University, Dalian 116600, Liaoning, China
| | - Bing Wang
- SEAC-ME Key Laboratory of Biotechnology and Bioresources Utilization, College of Life Science, Dalian Nationalities University, Dalian 116600, Liaoning, China
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Li S, Huang L. Targeted Delivery of Antisense Oligodeoxynucleotides Formulated in a Novel Lipidic Vector. J Liposome Res 2008. [DOI: 10.3109/08982109809035529] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Gosselin MA, Lee RJ. Folate receptor-targeted liposomes as vectors for therapeutic agents. BIOTECHNOLOGY ANNUAL REVIEW 2003; 8:103-31. [PMID: 12436917 DOI: 10.1016/s1387-2656(02)08006-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The folate receptor is a cell surface protein that has recently been identified as a tumor marker, due to its differential overexpression in several malignancies. Current research indicates that folate can be covalently attached to the surface of liposomes to mediate their selective internalization by tumor cells through the folate receptor-mediated endocytic pathway. Optimized liposome formulations, characterized by improvements in drug loading, extended residence times in the circulation and improved drug release, have been developed to improve the biodistribution of therapeutic molecules. Theoretically, folate receptor-targeting can be combined with liposome encapsulation to synergistically affect disease outcome by enhancing the delivery of chemotherapeutic agents to neoplastic cells, while reducing systemic toxicities to normal tissues. The purpose of this chapter is to characterize the components of folate receptor-targeted liposomes, and summarize their applications in gene and drug delivery.
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Affiliation(s)
- Michael A Gosselin
- Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, Ohio State University, Columbus, OH 43210, USA
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10
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Magnetic resonance imaging contrast agents: Theory and the role of dendrimers. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1874-5229(02)80006-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
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11
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Konda SD, Aref M, Wang S, Brechbiel M, Wiener EC. Specific targeting of folate-dendrimer MRI contrast agents to the high affinity folate receptor expressed in ovarian tumor xenografts. MAGMA (NEW YORK, N.Y.) 2001; 12:104-13. [PMID: 11390265 DOI: 10.1007/bf02668091] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The need to develop target-specific MRI contrast agents to aid in disease characterization remains highly essential. In this study, we present a generation four polyamidoamine (PAMAM) folate-dendrimer that specifically targets the high affinity folate receptor (hFR) overexpressed on more than 80% of ovarian tumors. In vitro, mouse erythroleukemia cells expressing the hFR bind the radiolabeled folate-dendrimer chelate resulting in over 2700% increase in binding compared with untreated cells. The binding was inhibited by free folic acid to levels observed on folate-receptor-negative cells. In vivo, ovarian tumor xenografts resulted in a 33% contrast enhancement, following the folate-dendrimer chelate administration, that was significantly different compared with results obtained with a non-specific, extracellular fluid space agent, Gd-HP-DO3A. In addition, this contrast enhancement was absent in saline-treated animals, folate-receptor-negative tumors, and was inhibited by free folic acid. Results suggest that a macromolecular, dendrimeric MRI agent with high molecular relaxivities (1646 mM(-1) s(-1)) can be used in specifically targeting the hFR on tumor cells and ovarian tumors.
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Affiliation(s)
- S D Konda
- Biomedical Magnetic Resonance Laboratory, College of Medicine, University of Illinois, Urbana, IL 61801, USA
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Drummond DC, Hong K, Park JW, Benz CC, Kirpotin DB. Liposome targeting to tumors using vitamin and growth factor receptors. VITAMINS AND HORMONES 2001; 60:285-332. [PMID: 11037627 DOI: 10.1016/s0083-6729(00)60022-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Liposome-encapsulated anticancer drugs reveal their potential for increased therapeutic efficacy and decreased nonspecific toxicities due to their ability to enhance the delivery of chemotherapeutic agents to solid tumors. Advances in liposome technology have resulted in the development of ligand-targeted liposomes capable of selectively increasing the efficacy of carried agents against receptor-bearing tumor cells. Receptors for vitamins and growth factors have become attractive targets for ligand-directed liposomal therapies due to their high expression levels on various forms of cancer and their ability to internalize after binding to the liposomes conjugated to receptors' natural ligands (vitamins) or synthetic agonists (receptor-specific antibodies and synthetic peptides). This chapter summarizes various strategies and advances in targeting liposomes to vitamin and growth factor receptors in vitro and in vivo with special emphasis on two extensively studied liposome-targeting systems utilizing folate receptor and HER2/neu growth factor receptor.
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Affiliation(s)
- D C Drummond
- Liposome Research Laboratory, California Pacific Medical Center Research Institute, San Francisco 94115, USA
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Abstract
This paper reviews the chemistry, metabolism, and molecular biology of folic acid, with a particular emphasis on how it is, or may be, involved in many disease processes. Folic acid prevents neural tube defects like spina bifida, while its ability to lower homocysteine suggests it might have a positive influence on cardiovascular disease. A role for this B vitamin in maintaining good health may, in fact, extend beyond these clinical conditions to encompass other birth defects, several types of cancer, dementia, affective disorders, Down's syndrome, and serious conditions affecting pregnancy outcome. The effect of folate in these conditions can be explained largely within the context of folate-dependent pathways leading to methionine and nucleotide biosynthesis, and genetic variability resulting from a number of common polymorphisms of folate-dependent enzymes involved in the homocysteine remethylation cycle. Allelic variants of folate genes that have a high frequency in the population, and that may play a role in disease formation include 677C --> T-MTHFR, 1298A --> C-MTHFR, 2756A --> G-MetSyn, and 66A --> G-MSR. Future work will probably uncover further polymorphisms of folate metabolism, and lead to a wider understanding of the interaction between this essential nutrient and the many genes which underpin its enzymatic utilization in a plethora of critical biosynthetic reactions, and which, under adverse nutritional conditions, may promote disease.
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Affiliation(s)
- M Lucock
- Academic Unit of Paediatrics and Obstetrics and Gynaecology, University of Leeds, D Floor, Clarendon Wing, Leeds General Infirmary, West Yorkshire, Leeds, LS2 9NS, United Kingdom
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15
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Honscha W, Dötsch KU, Thomsen N, Petzinger E. Cloning and functional characterization of the bile acid-sensitive methotrexate carrier from rat liver cells. Hepatology 2000; 31:1296-304. [PMID: 10827155 DOI: 10.1053/jhep.2000.7478] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
We have cloned two complementary DNAs (cDNAs), RL-Mtx-1 and RL-Mtx-2, corresponding to the bile acid- sensitive methotrexate carrier from rat liver by direct full-length rapid amplification of cDNA ends polymerase chain reaction (RACE-PCR) using degenerated primers that were deduced from published sequences of tumor cell methotrexate transporters. When expressed in Xenopus laevis oocytes and cosM6 cells, both clones mediate methotrexate and bumetanide transport. RL-Mtx-1 consists of 2,445 bp with an open reading frame of 1,536 bp. The corresponding protein with 512 amino acids has a molecular weight of 58 kd. RL-Mtx-2 (2,654 bp) differs by an additional insert of 203 bp. This insert is located in frame at position 1,196 of the RL-Mtx-1 and contains the typical splice junction sites at the 5' and 3' end, indicating that the RL-Mtx-2 messenger RNA (mRNA) is generated by alternative splicing. The insert contains a stop codon that shortens the RL-Mtx-2 protein to 330 amino acids (38 kd). Both cDNAs contain the binding site sequence for the dioxin/nuclear translocator responsive element (Ah/Arnt-receptor) in conjunction with a barbiturate recognition sequence (Barbie box). Preliminary results show that the Barbie box acts as a negative regulatory element. The two liver cDNA clones show homologies to the published sequences of folate and the reduced folate carriers, but no homology is found to the transport systems for organic anions like the Ntcp1, oatp1, OAT-K1, and OAT1. Expression of the mRNA for the methotrexate carrier is found in liver, kidney, heart, brain, spleen, lung, and skeletal muscle, but not in the testis as revealed by Northern blot analysis. The highest abundance of the mRNA is found in the kidney.
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Affiliation(s)
- W Honscha
- Institute of Pharmacology and Toxicology, Giessen, Germany.
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Konda SD, Aref M, Brechbiel M, Wiener EC. Development of a tumor-targeting MR contrast agent using the high-affinity folate receptor: work in progress. Invest Radiol 2000; 35:50-7. [PMID: 10639036 DOI: 10.1097/00004424-200001000-00006] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
RATIONALE AND OBJECTIVES Macromolecular contrast agents enhance tumors by means of active or passive targeting. Active targeting requires surface receptors. Many tumors of epithelial origin express the high-affinity folate receptor (hFR), including ovarian tumors. The objective of this research was to enhance tumors that express hFR using macromolecular contrast agents conjugated to folic acid. METHODS The authors prepared a folate-conjugated dendrimer polychelate by attaching folic acid to a fourth-generation ammonia-core polyamidoamine dendrimer. The remaining amines were reacted with 2-(4-isothiocyanatobenzyl)-6-methyldiethylenetriamine pentaacetic acid. Relaxivity measurements (r1 and r2) and MRI were conducted at 4.7 T. RESULTS The dendrimer r2 exceeded that of Gd-HP-DO3A by 8.2 times at 4.7 T. It increased the tumor percentage contrast enhancement, 24 hours after injection, of T2-weighted images by 33%. CONCLUSIONS This new agent accumulates in tumors expressing hFR. These results do not differentiate between active and passive targeting mechanisms. Receptor-negative tumors suggest a mechanism other than a nonspecific blood pool effect.
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Affiliation(s)
- S D Konda
- Biomedical Magnetic Resonance Laboratory, College of Medicine, and the Beckman Institute, University of Illinois, Urbana-Champaign, USA
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17
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Abstract
The high affinity folate binding protein (FBP) is overexpressed in ovarian cancers. However, its role in the pathogenesis and biological behaviour of these neoplasms is not clearly understood. Using the monoclonal antibody (MAb) MOv 18 and cytofluorimetric analysis, we investigated FBP expression in frozen neoplastic tissues from 136 patients diagnosed with epithelial ovarian cancer. FBP values were compared with clinico-pathological characteristics (age, stage, histologic grade, histologic type, DNA ploidy, percentage of S-phase cells, and previous chemotherapeutic treatment). Some amount of FBP overexpression was observed in 122 of the 136 tumours examined. The overall mean value of FBP fluorescence index (FBP FI) was 5.6 (median 2.7; min 0.8--max, 78.9). By univariate analysis, FBP FI was overexpressed to a higher degree in ovarian neoplasms with high histologic grade, advanced stage, serous histology, aneuploid status, and high percentage of cells in S-phase. Of the total number (136) of cases, 106 had all the parameters assessed and were thus selected for stepwise selection procedure. The only significant independent variable was the percentage of S-phase cells, which accounted for about 31% of variance of FBP FI. Our results indicate that FBP is associated with parameters of biological aggressiveness in ovarian cancers.
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Affiliation(s)
- G Toffoli
- Division of Experimental Oncology, Centro di Riferimento Oncologico, Aviano, Italy
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18
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Abstract
Deficiency of folic acid, an essential vitamin involved in critical metabolic pathways, occurs in several conditions, including alcoholism. In humans and animal models, chronic ethanol consumption leads to decreased plasma levels and increased urinary levels of folate. An isolated perfused rat kidney model has shown that ethanol produces increased urinary excretion of folate, suggesting a direct effect of ethanol on the kidney. Because the folate binding protein, located in the brush border membrane (BBM) of proximal tubule cells, is thought to be involved in renal folate reabsorption, the effects of ethanol on BBM binding of folate were assessed. Binding studies were conducted using isolated rat kidney cortex BBM preparations, incubated with 3H-labeled 5-methyltetrahydrofolate (5-CH3H4PteGlu) at varying concentrations (0.1-100 nM). Ethanol at 500 mg/dl did not significantly affect [3H]5-CH3H4PteGlu binding in BBM. The structural analogue, folic acid, decreased [3H]5-CH3H4PteGlu binding under similar conditions. Because of the lack of effect of ethanol on binding to isolated BBM, the effects of ethanol probably occur at other steps in the renal uptake and metabolism of folate.
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Affiliation(s)
- D M Ross
- Department of Pharmacology and Therapeutics, Louisiana State University Medical Center, Shreveport 71130, USA
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19
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Murray RC, Williams FM, Flintoff WF. Structural organization of the reduced folate carrier gene in Chinese hamster ovary cells. J Biol Chem 1996; 271:19174-9. [PMID: 8702595 DOI: 10.1074/jbc.271.32.19174] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The reduced folate carrier gene (rfc) encodes a putative protein that is involved in the intracellular accumulation of folates. In this report, we describe the organization of the rfc gene from Chinese hamster ovary cells. The hamster rfc gene contains 7 exons and 6 introns, which span 15.3 kilobases. It codes for two alternatively spliced messenger RNAs, one that contains all 7 exons and one that lacks exon 2 but contains the remaining 6 exons. The transcriptional start of the gene has been mapped to six sites approximately 200 base pairs upstream of the putative ATG initiation codon. The promoter region has no TATA box-like sequence but contains a consensus Sp1 binding site. This is the first report of the genomic structure of the reduced folate carrier gene from any species.
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Affiliation(s)
- R C Murray
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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Lee RJ, Wang S, Low PS. Measurement of endosome pH following folate receptor-mediated endocytosis. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1312:237-42. [PMID: 8703993 DOI: 10.1016/0167-4889(96)00041-9] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Free folic acid is believed to enter some cells by folate receptor-mediated endocytosis at membrane invaginations termed caveolae. Folate conjugated macromolecules also enter cells by folate receptor-mediated endocytosis, but their site of entry has never been conclusively identified. In this paper, we show that internalization of folate-macromolecule conjugates by receptor-bearing KB cells can be blocked by agents that specifically inhibit caveolae assembly or internalization such as nystatin and phorbol-12-myristate acetate (PMA). To characterize the intracellular conditions to which the macromolecule-folate conjugates are subsequently exposed, we have measured the pH of the major compartments of the folate endocytosis pathway. pH values of individual endosomal compartments in KB cells were determined by dual-excitation laser-scanning confocal microscopy, where the fluorescence ratio of folate-DM-NERF-dextran (pH-sensitive) and Texas Red-dextran (pH-insensitive) was used to calculate pH. These studies revealed that the pH of folate conjugate-containing endosomes commonly varies between 4.7 and 5.8, with the pH in some endosomes as low as 4.3. The most frequent pH value in these compartments was approximately 5.0.
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Affiliation(s)
- R J Lee
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
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In vitro characterization of renal reabsorption and secretion of folate using primary cultures of human kidney cells. J Nutr Biochem 1996. [DOI: 10.1016/0955-2863(96)00028-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Lee RJ, Huang L. Folate-targeted, anionic liposome-entrapped polylysine-condensed DNA for tumor cell-specific gene transfer. J Biol Chem 1996; 271:8481-7. [PMID: 8626549 DOI: 10.1074/jbc.271.14.8481] [Citation(s) in RCA: 324] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We have developed a lipidic gene transfer vector, LPDII, where DNA was first complexed to polylysine at a ratio of 1:0.75 (w/w) and then entrapped into folate-targeted pH-sensitive anionic liposomes composed of dioleoyl phosphatidylethanolamine (DOPE)/cholesteryl hemisuccinate/folate-polyethlene glycol-DOPE (6:4:0.01 mol/mol) via charge interaction. LPDII transfection of KB cells, a cell line overexpressing the tumor marker folate receptor, was affected by both the lipid to DNA ratio and the lipid composition. At low lipid to DNA ratios (e.g. 4 and 6), LPDII particles were positively charged; transfection and cellular uptake levels were independent of the folate receptor and did not require a pH-sensitive lipid composition. Meanwhile, transfection and uptake of negatively charged LPDII particles, i.e. those with high lipid to DNA ratios (e.g. 10 and 12), were folate receptor-dependent and required a pH-sensitive lipid composition. The transfection activity of LPDII was lost when the inverted cone-shaped DOPE was replaced by dioleoyl phosphatidylcholine. LPDII particles with lipid to DNA ratios of 4, 6, 10, and 12 were approximately 20-30 times more active than DNA.3-beta-[N-(N',N'-dimethylethane)carbamoyl]cholesterol cationic liposome complexes in KB cells and were much less cytotoxic. On the sucrose gradient, LPDII particles had a migration rate in between those of the free DNA and the DNA.polylysine complex. An electron micrograph of LPDII showed a structure of spherical particles with a positively stained core enclosed in a lipidic envelope with a mean diameter of 74 +/- 14 nm. This novel gene transfer vector may potentially be useful in gene therapy for tumor-specific delivery.
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Affiliation(s)
- R J Lee
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Williams FM, Flintoff WF. Isolation of a human cDNA that complements a mutant hamster cell defective in methotrexate uptake. J Biol Chem 1995; 270:2987-92. [PMID: 7852378 DOI: 10.1074/jbc.270.7.2987] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A clone has been isolated from a human lymphoblastic cDNA expression library that complements a mutant Chinese hamster cell defective in the uptake of the folate analogue methotrexate. When transfected with this clone the mutant cells regain the ability to transport the drug and, as a consequence, become sensitive to its cytotoxic action. The clone is 2863 base pairs long and has an open reading frame of 1770 base pairs that codes for a putative protein of 64 kDa. The putative protein has 51 and 50% identity at the amino acid level with the mouse and hamster functions, respectively, involved in the transport of reduced folates. Together these three proteins share 47% identity and have similar predicted structural features. The data are consistent with this human clone encoding either the reduced folate transporter or an auxiliary function that interacts with this transporter.
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Affiliation(s)
- F M Williams
- Department of Microbiology and Immunology, University of Western Ontario, London, Canada
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24
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Lee RJ, Low PS. Folate-mediated tumor cell targeting of liposome-entrapped doxorubicin in vitro. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1233:134-44. [PMID: 7865538 DOI: 10.1016/0005-2736(94)00235-h] [Citation(s) in RCA: 463] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Receptors for the vitamin folic acid are frequently overexpressed on epithelial cancer cells. To examine whether this overexpression might be exploited to specifically deliver liposome-encapsulated drug molecules in vitro, folate-targeted liposomes were prepared by incorporating 0.1 mol% of a folate-polyethyleneglycol-distearoylphatidylethanolamine (folate-PEG-DSPE) construct into the lipid bilayer, and were loaded with doxorubicin (DOX), an anti-cancer drug. Uptake of folate-PEG-liposomal DOX by KB cells was 45-fold higher than that of non-targeted liposomal DOX, and 1.6-times higher than that of free DOX, while the cytotoxicity was 86 and 2.7-times higher, respectively. Folate-targeting is fully compatible with PEG-coating of the liposomes, since incorporation of 4 mol% PEG2000-DSPE does not reduce the uptake or cytotoxicity of folate-PEG-liposomal DOX. Uptake of folate-PEG-liposomes was inhibited by 1 mM free folic acid but was unaffected by physiological concentrations of folate. In HeLa/WI38 co-cultures, folate-PEG-liposomes encapsulating calcein, a fluorescent dye, were found to be almost exclusively internalized by the HeLa cells which overexpress the folate receptors. We suggest that folate targeting constitutes a possible mechanism for improving the specificity of PEG-coated liposomes for cancer cells.
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Affiliation(s)
- R J Lee
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
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25
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Ross JF, Chaudhuri PK, Ratnam M. Differential regulation of folate receptor isoforms in normal and malignant tissues in vivo and in established cell lines. Physiologic and clinical implications. Cancer 1994; 73:2432-43. [PMID: 7513252 DOI: 10.1002/1097-0142(19940501)73:9<2432::aid-cncr2820730929>3.0.co;2-s] [Citation(s) in RCA: 649] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Despite significant differences in ligand binding between the two known isoforms of the human membrane folate receptor (FR), designated herein as FR-beta (placenta) and FR-alpha (placenta, KB cells), little is known about their tissue specificities, and there is no report on the relative expression of FR-beta in any tissue other than in placenta. METHODS The mRNA for each FR isoform in a wide variety of normal fetal and adult tissue explants, primary normal cell cultures, malignant tumor explants, and established tumor cell lines was estimated by a polymerase chain reaction assay. Total receptor levels were estimated by a [3H] folic acid binding assay. RESULTS Both the FR isoforms were expressed in fetal as well as adult tissues. Normal tissues generally expressed low to moderate amounts of FR-beta. FR-alpha alone was expressed in normal epithelial cells and was frequently strikingly elevated in a variety of carcinomas, with the exception of squamous cell carcinomas of the head and neck. In contrast, a variety of malignant tissues of nonepithelial origin generally expressed elevated levels of FR-beta alone. Established tumor cell lines expressed FR-alpha virtually alone and did not reflect FR expression patterns in vivo. KB cells and JEG-3 cells grown at low folate concentrations further up-regulated FR-alpha but not FR-beta. CONCLUSIONS Although FR-beta is the more common isoform, FR-alpha and FR-beta are differentially regulated in normal tissues, carcinomas, nonepithelial malignancies, and immortalized cells or in response to changes in extracellular folate concentrations. The tissue specificity of FR isoforms and their elevation in malignant tissues may be a significant factor in FR-mediated folate uptake, in tissue responsiveness to promising novel antifolates, and in FR-related immunodiagnosis/immunotherapy.
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Affiliation(s)
- J F Ross
- Department of Biochemistry and Molecular Biology, Medical College of Ohio, Toledo 43699-0008
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Mantovani LT, Miotti S, Ménard S, Canevari S, Raspagliesi F, Bottini C, Bottero F, Colnaghi MI. Folate binding protein distribution in normal tissues and biological fluids from ovarian carcinoma patients as detected by the monoclonal antibodies MOv18 and MOv19. Eur J Cancer 1994; 30A:363-9. [PMID: 8204360 DOI: 10.1016/0959-8049(94)90257-7] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Folate-binding proteins (FBP), which are molecules relevant in folate metabolism, are overexpressed in ovarian carcinomas, as detected by the monoclonal antibodies (MAb) MOv18 and MOv19, which recognise two different epitopes of the gp38/FBP. In this paper, features of the FBP such as the distribution on normal tissues and the release in biological fluids of normal and tumour origin have been investigated. Immunohistochemical analyses on frozen sections of normal tissues showed the presence of the gp38/FBP on some epithelia. The reactivity of both the MAb on Fallopian tubes was intense and comparable to that observed on ovary carcinoma sections. The kidney, bronchial glands, alveolar epithelium of the lung, oesophagus, stomach, pancreas, breast and thyroid showed different levels of staining. By MOv18/MOv19 double-determinant immunoradiometric assay (DDIRMA), the gp38/FBP was found in soluble form in ascitic fluid, serum and urine of nude mice in which the human ovary carcinoma cell line IGROV1 grew as ascitic carcinomatosis. In human biological fluids, the gp38/FBP was detected in ascites of 60% of ovarian carcinoma patients, and in 29% of those with other carcinomas, but not in patients with non-epithelial tumours or with other non-tumoral pathologies. The mean serum arbitrary units (a.u.)/ml values of ovary carcinoma patients were significantly different to those of healthy donors or patients with endometriosis (P < 0.005 and P < 0.01, respectively), but not when compared to the sera of lung carcinoma patients. In addition, the sensitivity of DDIRMA was poor, since only 24% of the ovary carcinoma patients were positive with this assay. When a restricted number of cases selected for the presence of tumour cells in the ascites was examined, the percentage of DDIRMA-positive sera and ascites rose to 41 and 94%, respectively. In the urine, a strong reactivity was observed in the samples of both normal and tumour origin.
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Affiliation(s)
- L T Mantovani
- Department of Experimental Oncology E, Istituto Nazionale Tumori, Milan, Italy
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28
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Decreased expression of the human folate receptor mediates transport-defective methotrexate resistance in KB cells. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53532-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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29
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Tomassetti A, Coney LR, Canevari S, Miotti S, Facheris P, Zurawski VR, Colnaghi MI. Isolation and biochemical characterization of the soluble and membrane forms of folate binding protein expressed in the ovarian carcinoma cell line IGROV1. FEBS Lett 1993; 317:143-6. [PMID: 8428622 DOI: 10.1016/0014-5793(93)81510-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The human ovarian carcinoma cell line, IGROV1, produces two forms of folate binding protein (FBP), the membrane form that is anchored to the cell surface by a glycosylphosphatidylinositol tail and the soluble form that is shed into the tissue culture medium. Both forms are recognized by the monoclonal antibodies MOv18 and MOv19. Here we describe their purification and biochemical characterization. The purified soluble protein appeared as a single band with an apparent Mr of 36 kDa after SDS-PAGE, whereas the membrane form appeared as a single band with an apparent Mr of 38 kDa. The size difference between the two forms of FBP was confirmed by gel filtration of both the native and the N-glycanase-treated proteins. Both purified proteins had equal capacity to bind folic acid. The immunological cross-reactivity and the folic acid binding capability of the FBPs extracted from IGROV1 gave more evidence of the possible existence of a precursor-product relationship between them.
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Affiliation(s)
- A Tomassetti
- Oncologia Sperimentale E, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy
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30
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Verma R, Gullapalli S, Antony A. Evidence that the hydrophobicity of isolated, in situ, and de novo-synthesized native human placental folate receptors is a function of glycosyl-phosphatidylinositol anchoring to membranes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50637-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Verma R, Antony A. Kinetic analysis, isolation, and characterization of hydrophilic folate-binding proteins released from chorionic villi cultured under serum-free conditions. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98930-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Elwood PC, Deutsch JC, Kolhouse JF. The conversion of the human membrane-associated folate binding protein (folate receptor) to the soluble folate binding protein by a membrane-associated metalloprotease. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52250-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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33
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Viswanadhan VN, Weinstein JN, Elwood PC. Secondary structure of the human membrane-associated folate binding protein using a joint prediction approach. J Biomol Struct Dyn 1990; 7:985-1001. [PMID: 2310527 DOI: 10.1080/07391102.1990.10508537] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The secondary structures of the human membrane-associated folate binding protein (FBP) and bovine soluble FBP are assessed by a joint prediction approach that combines neural network models, information theory, homology modeling and the Chou-Fasman methods. Two new profile maps are used to characterize the non-regular secondary structure and to assist in assigning buried and exposed parts of secondary structure: (i) the loop potential profile and (ii) the long range contact profile. Approximately half of human FBP is predicted to form regular secondary structure (alpha-helices-35% or beta-sheets - 12%, excluding the transmembrane helices) and the rest is predicted to form coil, turns or loops. The bovine milk soluble FBP is predicted to have a similar secondary structure as expected because of the high degree of homology between the FBP's. Discriminant analysis predicts two transmembrane segments for the human FBP sequence, one at the amino terminus (a leader sequence) and the other at the carboxy terminus. These predicted transmembrane domains are absent in the bovine milk soluble FBP, further supporting these predictions. The present set of secondary structural predictions for human FBP is obtained by 'consensus' to aid in modeling the super-secondary structure of the protein.
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Affiliation(s)
- V N Viswanadhan
- Theoretical Immunology Section, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
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34
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Luhrs CA, Slomiany BL. A human membrane-associated folate binding protein is anchored by a glycosyl-phosphatidylinositol tail. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(20)88200-3] [Citation(s) in RCA: 103] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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35
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Elwood PC. Molecular Cloning and Characterization of the Human Folate-binding Protein cDNA from Placenta and Malignant Tissue Culture (KB) Cells. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)63786-x] [Citation(s) in RCA: 100] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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36
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Antony AC, Verma RS. Hydrophobic erythrocyte folate binding proteins are converted to hydrophilic forms by trypsin in vitro. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 979:62-8. [PMID: 2917167 DOI: 10.1016/0005-2736(89)90523-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Human erythrocyte membranes contain high-affinity folate-binding proteins (FBPs) which on solubilization with detergents resolve into apparent 160,000 Mr moieties on Sephacryl S-200 gel filtration in Triton X-100. These FBPs share antigenic and ligand binding characteristics with particulate FBPs from other human tissues. During studies to define the vectorial orientation of these FBPs on the erythrocytes, we trypsinized intact cells with 250 micrograms trypsin per ml packed cells and quantitatively analysed the remaining cell-associated FBPs as well as the products of proteolysed FBPs in the supernatant. Incubation of intact cells with trypsin resulted in a dose-dependent decrease in their capacity to bind 125I-labelled pteroylglutamate (histamine derivative); at 250 micrograms/ml trypsin, folate binding was decreased by 77% compared to nontrypsin-treated control cells. While trypsinized cells contained proportionately lower quantities of apparent 160,000 Mr FBPs than untreated control cells, the supernatant of trypsinized cells (soluble phase) contained a single species of Mr = 40,000 which retained folate binding capacity. The sum of FBPs in trypsin supernatant and trypsin-treated cells was 87% of that found in untreated cells. Analysis of solubilized particulate erythrocyte FBPs and soluble (trypsin product) FBPs by sucrose density gradient ultracentrifugation in H2O and 2H2O above the critical micellar concentration of Triton X-100 revealed that apparent 160,000 Mr FBPs were detergent-binding (hydrophobic) species (which sedimented at Mr = 40,000 in H2O) while soluble FBPs (also sedimenting at Mr = 40,000) were hydrophilic and did not bind Triton X-100. These are the first data which show that hydrophobic FBPs can be directly converted to hydrophilic FBPs by a trypsin-mediated proteolytic event. The trypsin-sensitive site is likely to be at the junction between the detergent-binding site and the major body of the protein (Mr = 40,000) containing the folate binding site.
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Affiliation(s)
- A C Antony
- Department of Medicine, Indiana University School of Medicine, Indianapolis 46223
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Antony AC, Verma RS, Unune AR, LaRosa JA. Identification of a Mg2+-dependent protease in human placenta which cleaves hydrophobic folate-binding proteins to hydrophilic forms. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)94117-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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38
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Shane B. Folylpolyglutamate synthesis and role in the regulation of one-carbon metabolism. VITAMINS AND HORMONES 1989; 45:263-335. [PMID: 2688305 DOI: 10.1016/s0083-6729(08)60397-0] [Citation(s) in RCA: 232] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The physiological importance of folylpolyglutamates is now well established. These derivatives are the intracellular substrates and regulators of one-carbon metabolism, and their synthesis is required for normal folate retention by tissues. Over the last few years, a considerable amount of information has been obtained on the mechanism by which these compounds are synthesized, on how this synthesis is regulated, and on the effects of the polyglutamate chain on the interaction of folate substrates and inhibitors with folate-dependent enzymes. Many regulatory implications have been suggested by these studies, but the physiological relevance of some of these observations remains to be explored. Folates in mammalian tissues are metabolized to polyglutamates of chain lengths considerably longer than that required for folate retention, but the metabolic advantages of this are not entirely clear. Several in vivo model systems have been developed to explore the functioning of specific folylpolyglutamate chain lengths in metabolic cycles of one-carbon metabolism, and these are likely to shed further light on this point. The role of folate-binding proteins in folate transport, the metabolic role of glutamylhydrolases, and the role of folylpolyglutamates in putative multifunctional protein complexes are also areas that are being actively pursued at present and are likely to produce new insights in the future. Recent studies on the retention of antifolates by cells and on their substrate efficacy for folylpolyglutamate synthetases have also suggested mechanisms for the differential cytotoxicity of these agents for different tissues.
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Kamen BA, Wang MT, Streckfuss AJ, Peryea X, Anderson RG. Delivery of folates to the cytoplasm of MA104 cells is mediated by a surface membrane receptor that recycles. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68284-5] [Citation(s) in RCA: 201] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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