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Valverde-Pozo J, Paredes JM, Widmann TJ, Griñan-Lison C, Ceccarelli G, Gioiello A, Garcia-Rubiño ME, Marchal JA, Alvarez-Pez JM, Talavera EM. Ratiometric Two-Photon Near-Infrared Probe to Detect DPP IV in Human Plasma, Living Cells, Human Tissues, and Whole Organisms Using Zebrafish. ACS Sens 2023; 8:1064-1075. [PMID: 36847549 PMCID: PMC10043939 DOI: 10.1021/acssensors.2c02025] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
DPP IV, otherwise known as CD26 lymphocyte T surface antigen, is a transmembrane glycoprotein also found in circulation in the blood. It plays an important role in several processes like glucose metabolism and T-cell stimulation. Moreover, it is overexpressed in renal, colon, prostate, and thyroid human carcinoma tissues. It can also serve as a diagnostic in patients with lysosomal storage diseases. The biological and clinical importance of having readouts for the activity of this enzyme, in physiological and disease conditions, has led us to design a near-infrared (NIR) fluorimetric probe that also has the characteristics of being ratiometric and excitable by two simultaneous NIR photons. The probe consists of assembling an enzyme recognition group (Gly-Pro) (Mentlein, 1999; Klemann et al., 2016) on the two-photon (TP) fluorophore (derivative of dicyanomethylene-4H-pyran, DCM-NH2) disturbing its NIR characteristic internal charge transfer (ICT) emission spectrum. When the dipeptide group is released by the DPP IV-specific enzymatic action, the donor-acceptor DCM-NH2 is restored, forming a system that shows high ratiometric fluorescence output. With this new probe, we have been able to detect, quickly and efficiently, the enzymatic activity of DPP IV in living cells, human tissues, and whole organisms, using zebrafish. In addition, due to the possibility of being excited by two photons, we can avoid the autofluorescence and subsequent photobleaching that the raw plasma has when it is excited by visible light, achieving detection of the activity of DPP IV in that medium without interference.
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Affiliation(s)
- Javier Valverde-Pozo
- Nanoscopy-UGR Laboratory, Department of Physical Chemistry, Faculty of Pharmacy, Unidad de Excelencia en Quimica Aplicada a Biomedicina y Medioambiente (UEQ), University of Granada, C. U. Cartuja, 18071 Granada, Spain
| | - Jose M Paredes
- Nanoscopy-UGR Laboratory, Department of Physical Chemistry, Faculty of Pharmacy, Unidad de Excelencia en Quimica Aplicada a Biomedicina y Medioambiente (UEQ), University of Granada, C. U. Cartuja, 18071 Granada, Spain
| | - Thomas J Widmann
- GENYO, Centre for Genomics and Oncological Research, Pfizer/University of Granada/Andalusian Regional Government, 18016 Granada, Spain
| | - Carmen Griñan-Lison
- GENYO, Centre for Genomics and Oncological Research, Pfizer/University of Granada/Andalusian Regional Government, 18016 Granada, Spain
- Instituto de Investigación Biosanitaria (ibs.GRANADA), 18012 Granada, Spain
- UGC de Oncología Médica, Complejo Hospitalario de Jaen, 23007 Jaen, Spain
| | - Giada Ceccarelli
- Laboratory of Medicinal and Advanced Synthetic Chemistry (Lab MASC), Department of Pharmaceutical Sciences, University of Perugia, 06123 Perugia, Italy
| | - Antimo Gioiello
- Laboratory of Medicinal and Advanced Synthetic Chemistry (Lab MASC), Department of Pharmaceutical Sciences, University of Perugia, 06123 Perugia, Italy
| | - M Eugenia Garcia-Rubiño
- Nanoscopy-UGR Laboratory, Department of Physical Chemistry, Faculty of Pharmacy, Unidad de Excelencia en Quimica Aplicada a Biomedicina y Medioambiente (UEQ), University of Granada, C. U. Cartuja, 18071 Granada, Spain
| | - Juan A Marchal
- Instituto de Investigación Biosanitaria (ibs.GRANADA), 18012 Granada, Spain
- Centre for Biomedical Research (CIBM), Biopathology and Regenerative Medicine Institute (IBIMER), University of Granada, 18100 Granada, Spain
- Department of Human Anatomy and Embryology, Faculty of Medicine, University of Granada, 18016 Granada, Spain
| | - Jose M Alvarez-Pez
- Nanoscopy-UGR Laboratory, Department of Physical Chemistry, Faculty of Pharmacy, Unidad de Excelencia en Quimica Aplicada a Biomedicina y Medioambiente (UEQ), University of Granada, C. U. Cartuja, 18071 Granada, Spain
| | - Eva M Talavera
- Nanoscopy-UGR Laboratory, Department of Physical Chemistry, Faculty of Pharmacy, Unidad de Excelencia en Quimica Aplicada a Biomedicina y Medioambiente (UEQ), University of Granada, C. U. Cartuja, 18071 Granada, Spain
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Circulating FGF21 proteolytic processing mediated by fibroblast activation protein. Biochem J 2015; 473:605-14. [PMID: 26635356 PMCID: PMC4764976 DOI: 10.1042/bj20151085] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 12/03/2015] [Indexed: 01/08/2023]
Abstract
Fibroblast growth factor 21 (FGF21), a hormone implicated in the regulation of glucose homoeostasis, insulin sensitivity, lipid metabolism and body weight, is considered to be a promising therapeutic target for the treatment of metabolic disorders. Despite observations that FGF21 is rapidly proteolysed in circulation rending it potentially inactive, little is known regarding mechanisms by which FGF21 protein levels are regulated. We systematically investigated human FGF21 protein processing using mass spectrometry. In agreement with previous reports, circulating human FGF21 was found to be cleaved primarily after three proline residues at positions 2, 4 and 171. The extent of FGF21 processing was quantified in a small cohort of healthy human volunteers. Relative abundance of FGF21 proteins cleaved after Pro-2, Pro-4 and Pro-171 ranged from 16 to 30%, 10 to 25% and 10 to 34%, respectively. Dipeptidyl peptidase IV (DPP-IV) was found to be the primary protease responsible for N-terminal cleavages after residues Pro-2 and Pro-4. Importantly, fibroblast activation protein (FAP) was implicated as the protease responsible for C-terminal cleavage after Pro-171, rendering the protein inactive. The requirement of FAP for FGF21 proteolysis at the C-terminus was independently demonstrated by in vitro digestion, immunodepletion of FAP in human plasma, administration of an FAP-specific inhibitor and by human FGF21 protein processing patterns in FAP knockout mouse plasma. The discovery that FAP is responsible for FGF21 inactivation extends the FGF21 signalling pathway and may enable novel approaches to augment FGF21 actions for therapeutic applications.
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Chung KM, Huang CH, Cheng JH, Tsai CH, Suen CS, Hwang MJ, Chen X. Proline in transmembrane domain of type II protein DPP-IV governs its translocation behavior through endoplasmic reticulum. Biochemistry 2011; 50:7909-18. [PMID: 21834515 DOI: 10.1021/bi200605h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A transmembrane domain (TMD) at the N-terminus of a membrane protein is a signal sequence that targets the protein to the endoplasmic reticulum (ER) membrane. Proline is found more frequently in TM helices compared to water-soluble helices. To investigate the effects of proline on protein translocation and integration in mammalian cells, we made proline substitutions throughout the TMD of dipeptidyl peptidase IV, a type II membrane protease with a single TMD at its N-terminus. The proteins were expressed and their capacities for targeting and integrating into the membrane were measured in both mammalian cells and in vitro translation systems. Three proline substitutions in the central region of the TMD resulted in various defects in membrane targeting and/or integration. The replacement of proline with other amino acids of similar hydrophobicity rescued both the translocation and anchoring defects of all three proline mutants, indicating that conformational change caused by proline is a determining factor. Increasing hydrophobicity of the TMD by replacing other residues with more hydrophobic residues also effectively reversed the translocation and integration defects. Intriguingly, increasing hydrophobicity at the C-terminal end of the TMD rescued much more effectively than it did at the N-terminal end. Thus, the effect of proline on translocation and integration of the TMD is not determined solely by its conformation and hydrophobicity, but also by the location of proline in the TMD, the location of highly hydrophobic residues, and the relative position of the proline to other proline residues in the TMD.
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Affiliation(s)
- Kuei-Min Chung
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Miaoli County 350, Taiwan, ROC
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Lu C, Tilan JU, Everhart L, Czarnecka M, Soldin SJ, Mendu DR, Jeha D, Hanafy J, Lee CK, Sun J, Izycka-Swieszewska E, Toretsky JA, Kitlinska J. Dipeptidyl peptidases as survival factors in Ewing sarcoma family of tumors: implications for tumor biology and therapy. J Biol Chem 2011; 286:27494-505. [PMID: 21680731 DOI: 10.1074/jbc.m111.224089] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ewing sarcoma family of tumors (ESFT) is a group of aggressive pediatric malignancies driven by the EWS-FLI1 fusion protein, an aberrant transcription factor up-regulating specific target genes, such as neuropeptide Y (NPY) and its Y1 and Y5 receptors (Y5Rs). Previously, we have shown that both exogenous NPY and endogenous NPY stimulate ESFT cell death via its Y1 and Y5Rs. Here, we demonstrate that this effect is prevented by dipeptidyl peptidases (DPPs), which cleave NPY to its shorter form, NPY(3-36), not active at Y1Rs. We have shown that NPY-induced cell death can be abolished by overexpression of DPPs and enhanced by their down-regulation. Both NPY treatment and DPP blockade activated the same cell death pathway mediated by poly(ADP-ribose) polymerase (PARP-1) and apoptosis-inducing factor (AIF). Moreover, the decrease in cell survival induced by DPP inhibition was blocked by Y1 and Y5R antagonists, confirming its dependence on endogenous NPY. Interestingly, similar levels of NPY-driven cell death were achieved by blocking membrane DPPIV and cytosolic DPP8 and DPP9. Thus, this is the first evidence of these intracellular DPPs cleaving releasable peptides, such as NPY, in live cells. In contrast, another membrane DPP, fibroblast activation protein (FAP), did not affect NPY actions. In conclusion, DPPs act as survival factors for ESFT cells and protect them from cell death induced by endogenous NPY. This is the first demonstration that intracellular DPPs are involved in regulation of ESFT growth and may become potential therapeutic targets for these tumors.
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Affiliation(s)
- Congyi Lu
- Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, DC 20057, USA
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Chung KM, Cheng JH, Suen CS, Huang CH, Tsai CH, Huang LH, Chen YR, Wang AHJ, Jiaang WT, Hwang MJ, Chen X. The dimeric transmembrane domain of prolyl dipeptidase DPP-IV contributes to its quaternary structure and enzymatic activities. Protein Sci 2011; 19:1627-38. [PMID: 20572019 DOI: 10.1002/pro.443] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Dipeptidyl peptidase IV (DPP-IV) is a drug target in the treatment of human type II diabetes. It is a type II membrane protein with a single transmembrane domain (TMD) anchoring the extracellular catalytic domain to the membrane. DPP-IV is active as a dimer, with two dimer interacting surfaces located extracellularly. In this study, we demonstrate that the TM of DPP-IV promotes DPP-IV dimerization and rescues monomeric DPP-IV mutants into partial dimers, which is specific and irreplaceable by TMs of other type II membrane proteins. By bioluminescence resonance energy transfer (BRET) and peptide electrophoresis, we found that the TM domain of DPP-IV is dimerized in mammalian cells and in vitro. The TM dimer interaction is very stable, based on our results with TM site-directed mutagenesis. None of the mutations, including the introduction of two prolines, resulted in their complete disruption to monomers. However, these TM proline mutations result in a significant reduction of DPP-IV enzymatic activity, comparable to what is found with mutations near the active site. A systematic analysis of TM structures deposited in the Protein Data Bank showed that prolines in the TM generally produce much bigger kinking angles than occur in nonproline-containing TMs. Thus, the proline-dependent reduction in enzyme activity may result from propagated conformational changes from the TM to the extracellular active site. Our results demonstrate that TM dimerization and conformation contribute significantly to the structure and activity of DPP-IV. Optimal enzymatic activity of DPP-IV requires an optimal interaction of all three dimer interfaces, including its TM.
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Affiliation(s)
- Kuei-Min Chung
- Division of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhu Nan town, Miaoli County, Taiwan, Republic of China
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6
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Vlasak R, Vilas U, Strobl B, Kreil G. cDNA cloning and expression of secreted Xenopus laevis dipeptidyl aminopeptidase IV. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:107-13. [PMID: 9249015 DOI: 10.1111/j.1432-1033.1997.t01-1-00107.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
From a Xenopus laevis skin library a cDNA coding for dipeptidyl aminopeptidase IV (DPP IV) was isolated. The ORF codes for a protein with sequence similarity to DPP-IV-like proteins, including mammalian DPP IV and X. laevis fibroblast activation factor. In contrast to the membrane-bound mammalian enzymes, mature X. laevis DPP IV is a soluble secreted polypeptide. The frog enzyme possesses a cleavable signal sequence; the mature protein starts at Thr30 of the polypeptide predicted from the cDNA sequence. Expression of the cloned cDNA by recombinant vaccinia virus resulted in the formation of a protein with the expected molecular mass and substrate specificity. Recombinant DPP IV was present in high concentration in the supernatant of infected cells and exhibited enzymatic activity towards the synthetic substrate alanyl-prolyl-p-nitroanilide.
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Affiliation(s)
- R Vlasak
- Austrian Academy of Sciences, Institute of Molecular Biology, Salzburg
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7
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Loch N, Tauber R, Becker A, Hartel-Schenk S, Reutter W. Biosynthesis and metabolism of dipeptidylpeptidase IV in primary cultured rat hepatocytes and Morris hepatoma 7777 cells. ACTA ACUST UNITED AC 1992; 210:161-8. [PMID: 1359965 DOI: 10.1111/j.1432-1033.1992.tb17404.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Glycosylation, biosynthesis and degradation of dipeptidylpeptidase IV (EC 3.4.14.5) (DPP IV) were comparatively studied in primary cultured rat hepatocytes and Morris hepatoma 7777 cells (MH 7777 cells). DPP IV had a molecular mass of 105 kDa in rat hepatocytes and of 103 kDa in MH 7777 cells as assessed by SDS/PAGE under reducing conditions. This difference in molecular mass was caused by differences in covalently attached N-glycans. DPP IV from hepatoma cells contained a higher proportion of N-glycans of the oligomannosidic or hybrid type and therefore migrated at a slightly lower molecular mass. In both cell types DPP IV was initially synthesized as a 97-kDa precursor which was completely susceptible to digestion with endo-beta-N-acetylglucosaminidase H converting the molecular mass to 84 kDa. The precursor was processed to the mature forms of DPP IV, glycosylated with N-glycans mainly of the complex type with a half-life of 20-25 min. The transit of newly synthesized DPP IV to the cell surface displayed identical or very similar kinetics in both cell types with the major portion of DPP IV appearing at the cell surface after 60 min. DPP IV molecules were very slowly degraded in hepatocytes as well as in hepatoma cells with half-lives of approximately 45 h. Inhibition of oligosaccharide processing with 1-deoxymannojirimycin led to the formation of DPP IV molecules containing N-glycans of the oligomannosidic type. This glycosylation variant was degraded with the same half-life as complex-type glycosylated DPP IV. By contrast, inhibition of N-glycosylation with tunicamycin resulted into rapid degradation of non-N-glycosylated DPP IV molecules in both cell types. Non-N-glycosylated DPP IV could not be detected at the cell surface indicating an intracellular proteolytic process soon after biosynthesis.
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Affiliation(s)
- N Loch
- Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Federal Republic of Germany
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8
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Kornezos A, Chia W. Apical secretion and association of the Drosophila yellow gene product with developing larval cuticle structures during embryogenesis. MOLECULAR & GENERAL GENETICS : MGG 1992; 235:397-405. [PMID: 1465112 DOI: 10.1007/bf00279386] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The yellow (y) gene of Drosophila melanogaster is required for the pigmentation of larval and adult cuticle structures. The deduced y protein sequence includes two putative N-linked glycosylation sites and a putative signal peptide, suggesting that it might be a secreted molecule. Consistent with the characteristics of a secreted protein, our in vitro translation studies using RNA synthesised from the y cDNA demonstrate that the nascent y polypeptide is a preprotein that cotranslationally translocates into the endoplasmic reticulum (ER) membrane and becomes glycosylated. The N-terminal peptide is cleaved from the preprotein between the two alanine residues at positions 21 and 22, to release the final product into the lumen of the ER. Antibodies raised against the y polypeptide detect the protein starting at 13 h post-fertilization in epidermal cells and in the cuticle structures secreted by them that later become pigmented; in addition, yellow protein is detected in the cuticle structures associated with Keilin's organs. The embryonic beta-galactosidase staining pattern of a transgene, bearing a construct in which expression of the lacZ gene is driven by the y promoter, is also described and is similar to that of the y protein. Our results indicate that the y gene product is an apically secreted protein which becomes an immobilised structural component of the pigmented cuticle.
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Affiliation(s)
- A Kornezos
- Drosophila Neurobiology Laboratory, National University of Singapore, Kent Ridge Crescent
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9
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cDNA cloning for mouse thymocyte-activating molecule. A multifunctional ecto-dipeptidyl peptidase IV (CD26) included in a subgroup of serine proteases. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)45862-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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10
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Involvement of both vectorial and transcytotic pathways in the preferential apical cell surface localization of rat dipeptidyl peptidase IV in transfected LLC-PK1 cells. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55050-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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11
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Apical cell surface expression of rat dipeptidyl peptidase IV in transfected Madin-Darby canine kidney cells. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98852-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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12
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McCaughan GW, Wickson JE, Creswick PF, Gorrell MD. Identification of the bile canalicular cell surface molecule GP110 as the ectopeptidase dipeptidyl peptidase IV: an analysis by tissue distribution, purification and N-terminal amino acid sequence. Hepatology 1990; 11:534-44. [PMID: 1970322 DOI: 10.1002/hep.1840110403] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This paper describes the tissue distribution, purification and N-terminal amino acid sequence of the bile canalicular cell surface molecule dipeptidyl peptidase IV. Immunoperoxidase staining of cryostat sections of rat liver with a monoclonal antibody, Medical Research Council OX-61, indicated specific binding to hepatocyte bile canalicular domains and brush borders of bile ducts. Additional staining was seen in other epithelial brush borders (small intestine, kidney, colon, pancreatic duct); acinar structures in salivary glands; endothelial structures and T cell areas in thymus, spleen and lymph node. The tissue distribution suggested that monoclonal antibody OX-61 binds to the ectoenzyme dipeptidyl peptidase IV. This was confirmed by depletion of dipeptidyl peptidase IV activity from tissue homogenates by monoclonal antibody OX-61 coupled to Sepharose. The molecule recognized by OX-61 was then purified from liver and kidney by monoclonal antibody affinity chromatography. The molecule had a molecular weight of 110 kD under reducing conditions. The purified molecule was subsequently analyzed for amino acid composition and N-terminal amino acid sequence. Thirty-one N-terminal amino acids were sequenced and indicated identity with part of the predicted N-terminus of the previously cloned bile canalicular molecule GP110. On review, other similarities between dipeptidyl peptidase IV and GP110 were detected: molecular weight, deglycosylated form and metabolic half-life. Finally, the recent cloning of dipeptidyl peptidase IV permitted a comparison between the molecule recognized by monoclonal antibody OX-61, GP110 and dipeptidyl peptidase IV. It is concluded that these three molecules are almost certainly identical.
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Affiliation(s)
- G W McCaughan
- A.W. Morrow Gastroenterology and Liver Centre, Royal Prince Alfred Hospital, Camperdown NSW, Australia
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13
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Hong WJ, Piazza GA, Hixson DC, Doyle D. Expression of enzymatically active rat dipeptidyl peptidase IV in Chinese hamster ovary cells after transfection. Biochemistry 1989; 28:8474-9. [PMID: 2605197 DOI: 10.1021/bi00447a030] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Dipeptidyl peptidase IV (DPPIV) is a cell surface membrane glycoprotein expressed in many tissues. We have subcloned the coding region of a full-length cDNA for DPPIV into the inducible eukaryotic expression vector pMSG. The resulting construct was used to transfect Chinese hamster ovary (CHO) cells. Stable transformants were found to express DPPIV, and the expression is enhanced by dexamethasone. Metabolic labeling of the transfected cells with [35S]Met followed by immunoprecipitation revealed the presence of two specific products of apparent Mr 100,000 (100-kDa form) and 110,000 (110-kDa form), respectively. Pulse-chase experiments demonstrated that the 100-kDa form can be chased into the 110-kDa form, suggesting the 100-kDa form is the precursor of the 110-kDa form. Further studies with endo H treatment demonstrated that the carbohydrate structures are of the high-mannose type, and of the complex type for the 100- and 110-kDa forms, respectively. The 110-kDa form is present at the cell surface as shown by its accessibility to cell surface iodination. The DPPIV expressed on the cell surface is resistant to digestion by relatively high concentrations of trypsin. Studies also demonstrated that the surface DPPIV is fairly stable with a half-life for turnover of about 40 h. Furthermore, the DPPIV produced in the transfected cells displays specific dipeptidyl peptidase activity. The stably transfected cells that express enzymatically active DPPIV in an inducible manner will provide an excellent system for further biochemical, functional, and cell biological characterizations of DPPIV.
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Affiliation(s)
- W J Hong
- Department of Biological Sciences, State University of New York, Buffalo 14260
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