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Involvement of a Na +-coupled Oligopeptide Transport System for β-amyloid Peptide (Aβ 1-42) in Brain Cells. Pharm Res 2020; 37:98. [PMID: 32419062 DOI: 10.1007/s11095-020-02835-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 04/27/2020] [Indexed: 01/01/2023]
Abstract
PURPOSE A Na+-coupled transport system in mammalian cells is responsible for the uptake of oligopeptides consisting of 5 or more amino acids. Here we investigated if this transport system is expressed in brain cells and transports the 42-amino-acid β-amyloid peptide (Aβ1-42). METHODS The human and mouse neuronal cell lines SK-N-SH and HT22, human microglial cell line HMC-3, and human blood-brain barrier endothelial cell line hCMEC/D3 were used to monitor the uptake of [3H]-deltorphin II (a heptapeptide) and fluorescence-labeled Aβ1-42. RESULTS All four cell lines exhibited Na+-coupled uptake of deltorphin II. Aβ1-42 competed with deltorphin II for the uptake. Uptake of fluorescence-labeled Aβ1-42 was detectable in these cell lines, and the uptake was Na+-dependent and inhibitable by deltorphin II. The Na+-coupled uptake disappeared at high concentrations of Aβ1-42 due to oligomerization of the peptide. Exposure of the cells to excess iron abolished the uptake. In hCMEC/D3 cells cultured on Transwell filters, the uptake was localized preferentially to the abluminal membrane. CONCLUSION A Na+-coupled transport system mediates the uptake of Aβ1-42 monomers in neuronal and microglial cells. The same system is also responsible for the uptake of Aβ1-42 from brain into blood-brain barrier endothelial cells. These findings have relevance to Alzheimer's disease.
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Zhang W, Zhang DG, Liang X, Zhang WL, Ma JX. Effects of apelin on retinal microglial cells in a rat model of oxygen-induced retinopathy of prematurity. J Cell Biochem 2017; 119:2900-2910. [PMID: 29091306 DOI: 10.1002/jcb.26473] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Accepted: 10/24/2017] [Indexed: 12/19/2022]
Abstract
This study explores the effects of apelin on retinal microglial cells in rat models of oxygen-induced retinopathy of prematurity (ROP). Totally, 274 rats were selected for establishing oxygen-induced retinopathy (OIR) models, and 92 healthy rats for control group. OIR rats were assigned into OIR, 10-5 g/L apelin, 10-4 g/L apelin, and 10-3 g/L apelin groups. Immunohistochemistry was employed to determine morphology of microglial cells and cell number. CDllb, ionized calcium-binding adapter molecule 1 (IBA-1), TNF-α, and iNOS mRNA and protein expressions were identified using RT-qPCR and Western blotting, respectively. ELISA was employed to determine the levels of VEGF and glial fibrillary acidic protein (GFAP). The amoeboid microglial cells were found in the OIR and 10-3 g/L apelin groups, while bipolar microglial cells were found in the normal control, 10-5 g/L apelin and 10-4 g/L apelin groups. In the 1, 2, 3, and 4th week after apelin treatment, there were significantly decreased bipolar microglial cells, lower mRNA and protein expressions of CDllb, IBA-1, TNF-α and iNOS, and the levels of VEGF and GFAP in the 10-4 g/L apelin group than in the OIR, 10-3 g/L apelin and 10-5 g/L apelin groups. The differences between the normal control and 10-4 g/L apelin groups are not significant. Compared with the OIR group, the 10-5 g/L apelin and 10-3 g/L apelin groups presented decreased microglial cells and mRNA and protein expressions of CDllb, IBA-1, TNF-α, and iNOS. Appropriate concentration of apelin may reduce retinal microglial cells in a rat model of oxygen-induced ROP.
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Affiliation(s)
- Wei Zhang
- Department of Ophthalmology, the Second Hospital of Hebei Medical University, Shijiazhuang, P.R. China.,Department of Ophthalmology, Shanxi Dayi Hospital, Taiyuan, P.R. China
| | - Ding-Guo Zhang
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, P.R. China
| | - Xing Liang
- Department of Ophthalmology, Shanxi Dayi Hospital, Taiyuan, P.R. China
| | - Wei-Liang Zhang
- Department of Ophthalmology, Shanxi Dayi Hospital, Taiyuan, P.R. China
| | - Jing-Xue Ma
- Department of Ophthalmology, the Second Hospital of Hebei Medical University, Shijiazhuang, P.R. China
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Fitting S, Stevens DL, Khan FA, Scoggins KL, Enga RM, Beardsley PM, Knapp PE, Dewey WL, Hauser KF. Morphine Tolerance and Physical Dependence Are Altered in Conditional HIV-1 Tat Transgenic Mice. J Pharmacol Exp Ther 2015; 356:96-105. [PMID: 26542403 DOI: 10.1124/jpet.115.226407] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 11/04/2015] [Indexed: 12/22/2022] Open
Abstract
Despite considerable evidence that chronic opiate use selectively affects the pathophysiologic consequences of human immunodeficiency virus type 1 (HIV-1) infection in the nervous system, few studies have examined whether neuro-acquired immune deficiency syndrome (neuroAIDS) might intrinsically alter the pharmacologic responses to chronic opiate exposure. This is an important matter because HIV-1 and opiate abuse are interrelated epidemics, and HIV-1 patients are often prescribed opiates as a treatment of HIV-1-related neuropathic pain. Tolerance and physical dependence are inevitable consequences of frequent and repeated administration of morphine. In the present study, mice expressing HIV-1 Tat in a doxycycline (DOX)-inducible manner [Tat(+)], their Tat(-) controls, and control C57BL/6 mice were chronically exposed to placebo or 75-mg morphine pellets to explore the effects of Tat induction on morphine tolerance and dependence. Antinociceptive tolerance and locomotor activity tolerance were assessed using tail-flick and locomotor activity assays, respectively, and physical dependence was measured with the platform-jumping assay and recording of other withdrawal signs. We found that Tat(+) mice treated with DOX [Tat(+)/DOX] developed an increased tolerance in the tail-flick assay compared with control Tat(-)/DOX and/or C57/DOX mice. Equivalent tolerance was developed in all mice when assessed by locomotor activity. Further, Tat(+)/DOX mice expressed reduced levels of physical dependence to chronic morphine exposure after a 1-mg/kg naloxone challenge compared with control Tat(-)/DOX and/or C57/DOX mice. Assuming the results seen in Tat transgenic mice can be generalized to neuroAIDS, our findings suggest that HIV-1-infected individuals may display heightened analgesic tolerance to similar doses of opiates compared with uninfected individuals and show fewer symptoms of physical dependence.
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Affiliation(s)
- Sylvia Fitting
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - David L Stevens
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Fayez A Khan
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Krista L Scoggins
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Rachel M Enga
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Patrick M Beardsley
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Pamela E Knapp
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - William L Dewey
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
| | - Kurt F Hauser
- Department of Pharmacology and Toxicology (S.F., D.L.S., F.A.K., K.L.S., R.M.E., P.M.B., P.E.K., W.L.D., K.F.H.), Department of Anatomy and Neurobiology (P.E.K., K.F.H.), Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia
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Sreekumar PG, Chothe P, Sharma KK, Baid R, Kompella U, Spee C, Kannan N, Manh C, Ryan SJ, Ganapathy V, Kannan R, Hinton DR. Antiapoptotic properties of α-crystallin-derived peptide chaperones and characterization of their uptake transporters in human RPE cells. Invest Ophthalmol Vis Sci 2013; 54:2787-98. [PMID: 23532520 DOI: 10.1167/iovs.12-11571] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The chaperone proteins, α-crystallins, also possess antiapoptotic properties. The purpose of the present study was to investigate whether 19 to 20-mer α-crystallin-derived mini-chaperone peptides (α-crystallin mini-chaperone) are antiapoptotic, and to identify their putative transporters in human fetal RPE (hfRPE) cells. METHODS Cell death and caspase-3 activation induced by oxidative stress were quantified in early passage hfRPE cells in the presence of 19 to 20-mer αA- or αB-crystallin-derived or scrambled peptides. Cellular uptake of fluorescein-labeled, α-crystallin-derived mini-peptides and recombinant full-length αB-crystallin was determined in confluent hfRPE. The entry mechanism in hfRPE cells for α-crystallin mini-peptides was investigated. The protective role of polycaprolactone (PCL) nanoparticle encapsulated αB-crystallin mini-chaperone peptides from H2O2-induced cell death was studied. RESULTS Primary hfRPE cells exposed to oxidative stress and either αA- or αB-crystallin mini-chaperones remained viable and showed marked inhibition of both cell death and activation of caspase-3. Uptake of full-length αB-crystallin was minimal while a time-dependent uptake of αB-crystallin-derived peptide was observed. The mini-peptides entered the hfRPE cells via the sodium-coupled oligopeptide transporters 1 and 2 (SOPT1, SOPT2). PCL nanoparticles containing αB-crystallin mini-chaperone were also taken up and protected hfRPE from H2O2-induced cell death at significantly lower concentrations than free αB-crystallin mini-chaperone peptide. CONCLUSIONS αA- and αB-crystallin mini-chaperones offer protection to hfRPE cells and inhibit caspase-3 activation. The oligopeptide transporters SOPT1 and SOPT2 mediate the uptake of these peptides in RPE cells. Nanodelivery of αB-crystallin-derived mini-chaperone peptide offers an alternative approach for protection of hfRPE cells from oxidant injury.
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Affiliation(s)
- Parameswaran G Sreekumar
- Arnold and Mabel Beckman Macular Research Center, Doheny Eye Institute, Los Angeles, California, USA
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Ananth S, Thakkar SV, Gnana-Prakasam JP, Martin PM, Ganapathy PS, Smith SB, Ganapathy V. Transport of the synthetic opioid peptide DADLE ([D-Ala2,D-Leu5]-enkephalin) in neuronal cells. J Pharm Sci 2011; 101:154-63. [PMID: 21905028 DOI: 10.1002/jps.22733] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 07/07/2011] [Accepted: 08/02/2011] [Indexed: 01/08/2023]
Abstract
The sodium-coupled oligopeptide transporters 1 and 2 (SOPT1 and SOPT2) transport peptides consisting of at least five amino acids and show potential for the delivery of therapeutically relevant peptides/peptidomimetics. Here, we examined the expression of these two transporters in the retinal neuronal cell line RGC-5. These cells showed robust uptake activity for the synthetic pentapeptide DADLE ([D-Ala(2),D-Leu(5)]-Enkephalin). The uptake was Na(+) dependent and saturable (K(t), 6.2 ± 0.6 μM). A variety of oligopeptides inhibited DADLE uptake. The uptake of the competing oligopeptides was directly demonstrated with fluorescein isothiocyanate-labeled Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys in RGC-5 cells and primary mouse retinal ganglion cells. The characteristics of DADLE uptake matched those of SOPT2. We then examined the expression of SOPT1 in these cells with deltorphin II (Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH(2)) as the substrate and found that RGC-5 cells also expressed SOPT1. As it is already known that SOPT1 is expressed in the neuronal cell line SK-N-SH, we investigated SOPT2 expression in these cells to determine whether the presence of both oligopeptide transporters is a common feature of neuronal cells. These studies showed that SK-N-SH cells also expressed SOPT2. This constitutes the first report on the functional characterization of SOPT1 and SOPT2 in retinal neuronal cells and on the expression of SOPT2 in nonretinal neuronal cells.
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Affiliation(s)
- Sudha Ananth
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia, USA
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Chothe P, Singh N, Ganapathy V. Evidence for two different broad-specificity oligopeptide transporters in intestinal cell line Caco-2 and colonic cell line CCD841. Am J Physiol Cell Physiol 2011; 300:C1260-9. [PMID: 21307350 DOI: 10.1152/ajpcell.00299.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Recently the existence of two different Na(+)-coupled oligopeptide transport systems has been described in mammalian cells. These transport systems are distinct from the previously known H(+)/peptide cotransporters PEPT1 and PEPT2, which transport only dipeptides and tripeptides. To date, the only peptide transport system known to exist in the intestine is PEPT1. Here we investigated the expression of the Na(+)-coupled oligopeptide transporters in intestinal cell lines, using the hydrolysis-resistant synthetic oligopeptides deltorphin II and [d-Ala(2),d-Leu(5)]enkephalin (DADLE) as model substrates. Caco-2 cells and CCD841 cells, both representing epithelial cells from human intestinal tract, were able to take up these oligopeptides. Uptake of deltorphin II was mostly Na(+) dependent, with more than 2 Na(+) involved in the uptake process. In contrast, DADLE uptake was only partially Na(+) dependent. The uptake of both peptides was also influenced by H(+) and Cl(-), although to a varying degree. The processes responsible for the uptake of deltorphin II and DADLE could be differentiated not only by their Na(+) dependence but also by their modulation by small peptides. Several dipeptides and tripeptides stimulated deltorphin II uptake but inhibited DADLE uptake. These modulating small peptides were, however, not transportable substrates for the transport systems that mediate deltorphin II or DADLE uptake. These two oligopeptide transport systems were also able to take up several nonopioid oligopeptides, consisting of 9-17 amino acids. This represents the first report on the existence of transport systems in intestinal cells that are distinct from PEPT1 and capable of transporting oligopeptides consisting of five or more amino acids.
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Affiliation(s)
- Paresh Chothe
- Dept. of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912-2100, USA
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Chothe PP, Gnana-Prakasam JP, Ananth S, Martin PM, Kannan R, Hinton DR, Smith SB, Ganapathy V. Transport of hepcidin, an iron-regulatory peptide hormone, into retinal pigment epithelial cells via oligopeptide transporters and its relevance to iron homeostasis. Biochem Biophys Res Commun 2011; 405:244-9. [PMID: 21219868 DOI: 10.1016/j.bbrc.2011.01.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 01/05/2011] [Indexed: 12/16/2022]
Abstract
Retinal pigment epithelial cells (RPE) express two transport systems (SOPT1 and SOPT2) for oligopeptides. Hepcidin is an iron-regulatory peptide hormone consisting of 25 amino acids. This hormone binds to ferroportin, an iron exporter expressed on the cell surface, and facilitates its degradation. Here we investigated if hepcidin is a substrate for SOPT1 and SOPT2 and if the hormone has any intracellular function in RPE. Hepcidin inhibited competitively the uptake of deltorphin II (a synthetic oligopeptide substrate for SOPT1) and DADLE (a synthetic oligopeptide substrate for SOPT2) with IC50 values in the range of 0.4-1.7 μM. FITC-hepcidin was taken up into RPE, and this uptake was inhibited by deltorphin II and DADLE. The entry of FITC-hepcidin into cells was confirmed by flow cytometry. Incubation of RPE with hepcidin decreased the levels of ferroportin mRNA. This effect was not a consequence of hepcidin-induced ferroportin degradation because excessive iron accumulation in RPE, which is expected to occur in these cells as a result of ferroportin degradation, did not decrease but instead increased the levels of ferroportin mRNA. This study reveals for the first time a novel intracellular function for hepcidin other than its established cell surface action on ferroportin.
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Affiliation(s)
- Paresh P Chothe
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA, USA
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Brandsch M, Knütter I, Bosse-Doenecke E. Pharmaceutical and pharmacological importance of peptide transporters. J Pharm Pharmacol 2010; 60:543-85. [DOI: 10.1211/jpp.60.5.0002] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AbstractPeptide transport is currently a prominent topic in membrane research. The transport proteins involved are under intense investigation because of their physiological importance in protein absorption and also because peptide transporters are possible vehicles for drug delivery. Moreover, in many tissues peptide carriers transduce peptidic signals across membranes that are relevant in information processing. The focus of this review is on the pharmaceutical relevance of the human peptide transporters PEPT1 and PEPT2. In addition to their physiological substrates, both carriers transport many β-lactam antibiotics, valaciclovir and other drugs and prodrugs because of their sterical resemblance to di- and tripeptides. The primary structure, tissue distribution and substrate specificity of PEPT1 and PEPT2 have been well characterized. However, there is a dearth of knowledge on the substrate binding sites and the three-dimensional structure of these proteins. Until this pivotal information becomes available by X-ray crystallography, the development of new drug substrates relies on classical transport studies combined with molecular modelling. In more than thirty years of research, data on the interaction of well over 700 di- and tripeptides, amino acid and peptide derivatives, drugs and prodrugs with peptide transporters have been gathered. The aim of this review is to put the reports on peptide transporter-mediated drug uptake into perspective. We also review the current knowledge on pharmacogenomics and clinical relevance of human peptide transporters. Finally, the reader's attention is drawn to other known or proposed human peptide-transporting proteins.
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Affiliation(s)
- Matthias Brandsch
- Membrane Transport Group, Biozentrum of the Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
| | - Ilka Knütter
- Membrane Transport Group, Biozentrum of the Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
| | - Eva Bosse-Doenecke
- Institute of Biochemistry/Biotechnology, Faculty of Science I, Martin-Luther-University Halle-Wittenberg, D-06120 Halle, Germany
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Chothe PP, Thakkar SV, Gnana-Prakasam JP, Ananth S, Hinton DR, Kannan R, Smith SB, Martin PM, Ganapathy V. Identification of a novel sodium-coupled oligopeptide transporter (SOPT2) in mouse and human retinal pigment epithelial cells. Invest Ophthalmol Vis Sci 2009; 51:413-20. [PMID: 19643969 DOI: 10.1167/iovs.09-4048] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE A sodium-coupled oligopeptide transporter (SOPT1) was described originally in ARPE-19 cells. The transporter is inducible by HIV-1 Tat. Recent studies of conjunctival epithelial cells have identified a second oligopeptide transporter (SOPT2). This study was conducted to determine whether the newly discovered SOPT2 is expressed in ARPE-19 cells, to examine whether the new transporter is also inducible by HIV-1 Tat, and to find out whether this transporter is expressed in primary RPE cells. METHODS The transport activity of SOPT2 was monitored in control and Tat-expressing ARPE-19 cells and in primary mouse and human fetal RPE cells by the uptake of the synthetic opioid peptide DADLE ((H-Tyr-D-Ala-Gly-Phe-D-Leu-OH) and by its susceptibility to inhibition by small peptides. Substrate selectivity was examined by competition studies and kinetic parameters were determined by saturation analysis. RESULTS ARPE-19 cells express DADLE uptake activity that is inhibited by small peptides, indicating expression of SOPT2 in these cells. The activity of SOPT2 is induced by HIV-1 Tat. SOPT2 accepts endogenous and synthetic opioid peptides as substrates, but nonpeptide opiate antagonists are excluded. An 11-amino-acid HIV-1 Tat peptide also serves as a high-affinity substrate for the transporter. Primary cultures of mouse and human fetal RPE cells express SOPT2. The transporter is partially Na(+)-dependent with comparable substrate selectivity and inhibitor specificity in the presence and absence of Na(+). CONCLUSIONS ARPE-19 cells as well as primary mouse and human fetal RPE cells express the newly discovered oligopeptide transporter SOPT2, and the transporter is induced by HIV-1 Tat in ARPE-19 cells.
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Affiliation(s)
- Paresh P Chothe
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA
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Thakkar SV, Miyauchi S, Prasad PD, Ganapathy V. Stimulation of Na+/Cl--coupled opioid peptide transport system in SK-N-SH cells by L-kyotorphin, an endogenous substrate for H+-coupled peptide transporter PEPT2. Drug Metab Pharmacokinet 2008; 23:254-62. [PMID: 18762712 DOI: 10.2133/dmpk.23.254] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have recently identified a Na+/Cl--coupled transport system in mammalian cells for endogenous and synthetic opioid peptides. This transport system does not transport dipeptides/tripeptides, but is stimulated by these small peptides. Here we investigated the influence of L-kyotorphin (L-Tyr-L-Arg), an endogenous dipeptide with opioid activity, on this transport system. The activity of the transport system, measured in SK-N-SH cells (a human neuronal cell line) with deltorphin II as a model substrate, was stimulated approximately 2.5-fold by L-kyotorphin, with half-maximal stimulation occurring at approximately 100 microM. The stimulation was associated primarily with an increase in the affinity for deltorphin II. The stimulation caused by L-kyotorphin was stereospecific; L-Tyr-D-Arg (D-kyotorphin) had minimal effect. The influence of L-kyotorphin was observed also in a different cell line which expressed the opioid peptide transport system. While L-kyotorphin is a stimulator of opioid peptide transport, it is a transportable substrate for the H+-coupled peptide transporter PEPT2, which is expressed widely in the brain. Since the activity of the opioid peptide transport system is modulated by extracellular L-kyotorphin and since PEPT2 is an important determinant of extracellular L-kyotorphin in the brain, the expression/activity of PEPT2 may be a critical factor in the modulation of opioidergic neurotransmission in vivo.
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Affiliation(s)
- Santoshanand V Thakkar
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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Guzevatykh LS. Identification of functionally important dipeptide in sequences of atypical opioid peptides. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2008; 34:591-609. [DOI: 10.1134/s1068162008050026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Functional identification of a novel transport system for endogenous and synthetic opioid peptides in the rabbit conjunctival epithelial cell line CJVE. Pharm Res 2008; 26:1226-35. [PMID: 18781380 DOI: 10.1007/s11095-008-9709-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 08/12/2008] [Indexed: 12/15/2022]
Abstract
PURPOSE To investigate whether conjunctival epithelial cells express transport processes for opioid peptides. METHODS We monitored the uptake of [(3)H]deltorphin II and [(3)H]DADLE, two hydrolysis-resistant synthetic opioid peptides, in the rabbit conjunctival epithelial cell line CJVE and elucidated the characteristics of the uptake process. RESULTS CJVE cells express robust uptake activity for deltorphin II and DADLE. Both opioid peptides compete with each other for transport. Several endogenous and synthetic opioid peptides, but not non-peptide opioid antagonists, are recognized by the transport process. Though various peptides inhibit the uptake of deltorphin II and DADLE in a similar manner, the uptake of deltorphin II is partly Na(+)-dependent whereas that of DADLE mostly Na(+)-independent. The transport process shows high affinity for many endogenous/synthetic opioid peptides. Functional features reveal that this transport process may be distinct from the opioid peptide transport system described in the retinal pigment epithelial cell line ARPE-19 and also from the organic anion transporting polypeptides, which are known to transport opioid peptides. CONCLUSIONS CJVE cells express a novel, hitherto unknown transport process for endogenous/synthetic opioid peptides. This new transport process may offer an effective delivery route for opioid peptide drugs to the posterior segment of the eye.
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Miyauchi S, Gopal E, Thakkar SV, Ichikawa S, Prasad PD, Ganapathy V. Differential modulation of sodium- and chloride-dependent opioid peptide transport system by small nonopioid peptides and free amino acids. J Pharmacol Exp Ther 2007; 321:257-64. [PMID: 17259448 DOI: 10.1124/jpet.106.116806] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We recently identified a novel opioid peptide transport system in the retinal pigment epithelium that transports opioid peptides by a Na+/Cl--dependent process. Here we describe a similar transport system expressed in SK-N-SH cells (a human neuronal cell line) and show for the first time that the activity of the transport system is modulated differentially by lysine and small nonopioid peptides. The transport process in SK-N-SH cells, monitored with deltorphin II as the substrate, is Na+/Cl--dependent and interacts with several opioid peptides, consisting of 5 to 13 amino acids. The activity of this transport system is markedly stimulated by specific dipeptides and tripeptides, with significant stimulation observable at low micromolar concentrations. The ion dependence, Na+/Cl--activation kinetics, and opioid peptide selectivity of the transport system, however, remain unchanged. The stimulation by the modulatory peptides is associated with an increase in maximal velocity with no change in substrate affinity of the system. Amino acids have no or little effect on the transport system, with the exception of lysine. This cationic amino acid inhibits the transport system, with significant inhibition occurring at physiologic concentrations of the amino acid. The inhibitory effect is primarily associated with a decrease in the maximal velocity of the transport system with little change in substrate affinity. Methyl and ethyl esters of lysine retain the inhibitory potency, but most other structural analogs have no effect. The differential modulation of the transport system by lysine and specific small peptides has important implications in the biology and pharmacology of opioid peptides.
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Affiliation(s)
- Seiji Miyauchi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA
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15
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Daniel H, Spanier B, Kottra G, Weitz D. From bacteria to man: archaic proton-dependent peptide transporters at work. Physiology (Bethesda) 2006; 21:93-102. [PMID: 16565475 DOI: 10.1152/physiol.00054.2005] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Uptake of nutrients into cells is essential to life and occurs in all organisms at the expense of energy. Whereas in most prokaryotic and simple eukaryotic cells electrochemical transmembrane proton gradients provide the central driving force for nutrient uptake, in higher eukaryotes it is more frequently coupled to sodium movement along the transmembrane sodium gradient, occurs via uniport mechanisms driven by the substrate gradient only, or is linked to the countertransport of a similar organic solute. With the cloning of a large number of mammalian nutrient transport proteins, it became obvious that a few "archaic'' transporters that utilize a transmembrane proton gradient for nutrient transport into cells can still be found in mammals. The present review focuses on the electrogenic peptide transporters as the best studied examples of proton-dependent nutrient transporters in mammals and summarizes the most recent findings on their physiological importance. Taking peptide transport as a general phenomenon found in nature, we also include peptide transport mechanisms in bacteria, yeast, invertebrates, and lower vertebrates, which are not that often addressed in physiology journals.
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Affiliation(s)
- Hannelore Daniel
- Department of Food and Nutrition, Molecular Nutrition Unit, Technical University of Munich, Freising-Weihenstephan, Germany.
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16
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Baldelli B, Vecchio L, Bottone MG, Muzzonigro G, Biggiogera M, Malatesta M. The effect of the enkephalin DADLE on transcription does not depend on opioid receptors. Histochem Cell Biol 2006; 126:189-97. [PMID: 16416021 DOI: 10.1007/s00418-006-0145-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2005] [Indexed: 11/25/2022]
Abstract
[D-Ala(2),D-Leu(5)] enkephalin (DADLE) is a synthetic peptide capable of inducing a hibernation-like state in mammals in vivo and in cultured cells in vitro. The effects of DADLE seem to be due to its binding to opioid receptors; however, it inhibits the growth of LNCaP cells, devoid of opioid receptors. We have investigated the effects of DADLE on this cell line using transmission electron microscopy, immunocytochemistry and cytometry, in order to elucidate the general mechanism(s) by which this enkephalin affects cell metabolism. We demonstrated that, similar to cell lines provided with opioid receptors, in LNCaP cells DADLE induces structural modifications of cytoplasmic and nuclear constituents, as well as a decrease in transcription and proliferation. However, DADLE does not provoke an increase in apoptotic or necrotic cell fraction, and, after removing the enkephalin from the culture medium, all effects disappear. We also demonstrated that DADLE molecules enter the cytoplasm and the nucleus of LNCaP cells, mostly binding to perichromatin fibrils and dense fibrillar component, where transcription and early splicing of pre-mRNAs and pre-rRNAs occur. In conclusion, our data demonstrate that the effect of DADLE on transcription and on cultured cells does not depend on opioid receptors. DADLE can, therefore, be envisaged as an extremely promising molecule to be used for inducing a reversible hypometabolic state in various cultured cells, without provoking cell damage or death.
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Affiliation(s)
- Beatrice Baldelli
- Istituto di Istologia e Analisi di Laboratorio, University of Urbino Carlo Bo, 61029 Urbino, Italy
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17
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Ganapathy V, Miyauchi S. Transport systems for opioid peptides in mammalian tissues. AAPS JOURNAL 2005; 7:E852-6. [PMID: 16594637 PMCID: PMC2750954 DOI: 10.1208/aapsj070482] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Transmembrane transport of endogenous as well as synthetic opioid peptides is a critical determinant of pharmacokinetics and biologic efficacy of these peptides. This transport process influences the distribution of opioid peptides across the blood-brain barrier and their elimination from the body. A multitude of transport systems that recognize opioid peptides as substrates have been characterized at the functional level, and these transport systems are expressed differentially at different sites in the body. Many of these transport systems have been identified at the molecular level. These include the H(+)-coupled peptide transporters PEPT1 and PEPT2, the adenosine triphosphate-dependent efflux transporters P-glycoprotein and multidrug resistance-related protein 2, and several members of the organic anion-transporting polypeptide gene family. There are however many additional transport systems that are known to transport opioid peptides but their molecular identities still remain unknown.
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Affiliation(s)
- Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA.
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18
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Dietz GPH, Bähr M. Delivery of bioactive molecules into the cell: the Trojan horse approach. Mol Cell Neurosci 2005; 27:85-131. [PMID: 15485768 DOI: 10.1016/j.mcn.2004.03.005] [Citation(s) in RCA: 358] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2003] [Revised: 02/17/2004] [Accepted: 03/16/2004] [Indexed: 01/12/2023] Open
Abstract
In recent years, vast amounts of data on the mechanisms of neural de- and regeneration have accumulated. However, only in disproportionally few cases has this led to efficient therapies for human patients. Part of the problem is to deliver cell death-averting genes or gene products across the blood-brain barrier (BBB) and cellular membranes. The discovery of Antennapedia (Antp)-mediated transduction of heterologous proteins into cells in 1992 and other "Trojan horse peptides" raised hopes that often-frustrating attempts to deliver proteins would now be history. The demonstration that proteins fused to the Tat protein transduction domain (PTD) are capable of crossing the BBB may revolutionize molecular research and neurobiological therapy. However, it was only recently that PTD-mediated delivery of proteins with therapeutic potential has been achieved in models of neural degeneration in nerve trauma and ischemia. Several groups have published the first positive results using protein transduction domains for the delivery of therapeutic proteins in relevant animal models of human neurological disorders. Here, we give an extensive review of peptide-mediated protein transduction from its early beginnings to new advances, discuss their application, with particular focus on a critical evaluation of the limitations of the method, as well as alternative approaches. Besides applications in neurobiology, a large number of reports using PTD in other systems are included as well. Because each protein requires an individual purification scheme that yields sufficient quantities of soluble, transducible material, the neurobiologist will benefit from the experiences of other researchers in the growing field of protein transduction.
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Bridges CC, Hu H, Miyauchi S, Siddaramappa UN, Ganapathy ME, Ignatowicz L, Maddox DM, Smith SB, Ganapathy V. Induction of cystine-glutamate transporter xc- by human immunodeficiency virus type 1 transactivator protein tat in retinal pigment epithelium. Invest Ophthalmol Vis Sci 2004; 45:2906-14. [PMID: 15326101 PMCID: PMC2735043 DOI: 10.1167/iovs.03-1355] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The transactivator protein Tat encoded by the human immunodeficiency virus-1 (HIV-1) genome reduces glutathione levels in mammalian cells. Because the retina contains large amounts of glutathione, a study was undertaken to determine the influence of Tat on glutathione levels, gamma-glutamyl transpeptidase activity, and the expression and activity of the cystine-glutamate transporter xc- in the human retinal pigment epithelial cell line ARPE-19 and in retina from Tat-transgenic mice. METHODS The transport function of xc- was measured as glutamate uptake in the absence of Na+. mRNA levels for xCT and 4F2hc, the two subunits of system xc-, were monitored by RT-PCR and Northern blot and protein levels by Western blot. The expression pattern of xCT and 4F2hc in the mouse retina was analyzed by immunofluorescence. RESULTS Expression of Tat in ARPE-19 cells led to a decrease in glutathione levels and an increase in gamma-glutamyl transpeptidase activity. The transport function of xc- was upregulated, and this increase was accompanied by increases in the levels of mRNAs for xCT and 4F2hc and in corresponding protein levels. The influence of Tat on the expression of xc- was independent of the cellular status of glutathione. Most of these findings were confirmed in the retina of Tat-transgenic mice. CONCLUSIONS Expression of HIV-1 Tat in the retina decreases glutathione levels and increases gamma-glutamyl transpeptidase activity. Tat also upregulates the expression of system xc-. Glutathione levels may be decreased and the expression of xc- enhanced in the retina of patients with HIV-1 infection, leading to oxidative stress and excitotoxicity.
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Affiliation(s)
- Christy C. Bridges
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia
| | - Huankai Hu
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia
| | - Seiji Miyauchi
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia
| | | | | | - Leszek Ignatowicz
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia
| | - Dennis M. Maddox
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia
| | - Sylvia B. Smith
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia
| | - Vadivel Ganapathy
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia
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