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Ravera S, Bertola N, Puddu A, Bruno S, Maggi D, Panfoli I. Crosstalk between the Rod Outer Segments and Retinal Pigmented Epithelium in the Generation of Oxidative Stress in an In Vitro Model. Cells 2023; 12:2173. [PMID: 37681906 PMCID: PMC10487269 DOI: 10.3390/cells12172173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 08/21/2023] [Accepted: 08/22/2023] [Indexed: 09/09/2023] Open
Abstract
Dysfunction of the retinal pigment epithelium (RPE) is associated with several diseases characterized by retinal degeneration, such as diabetic retinopathy (DR). However, it has recently been proposed that outer retinal neurons also participate in the damage triggering. Therefore, we have evaluated the possible crosstalk between RPE and photoreceptors in priming and maintaining oxidative damage of the RPE. For this purpose, we used ARPE-19 cells as a model of human RPE, grown in normal (NG, 5.6 mM) or high glucose (HG, 25 mM) and unoxidized (UOx) or oxidized (Ox) mammalian retinal rod outer segments (OSs). ARPE-19 cells were efficient at phagocytizing rod OSs in both NG and HG settings. However, in HG, ARPE-19 cells treated with Ox-rod OSs accumulated MDA and lipofuscins and displayed altered LC3, GRP78, and caspase 8 expression compared to untreated and UOx-rod-OS-treated cells. Data suggest that early oxidative damage may originate from the photoreceptors and subsequently extend to the RPE, providing a new perspective to the idea that retinal degeneration depends solely on a redox alteration of the RPE.
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Affiliation(s)
- Silvia Ravera
- Department of Experimental Medicine, Università di Genoa, Via De Toni 14, 16132 Genova, Italy
| | - Nadia Bertola
- Molecular Pathology Unit, IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Alessandra Puddu
- Department of Internal Medicine and Medical Specialties, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Silvia Bruno
- Department of Experimental Medicine, Università di Genoa, Via De Toni 14, 16132 Genova, Italy
| | - Davide Maggi
- Department of Internal Medicine and Medical Specialties, University of Genova, Viale Benedetto XV 6, 16132 Genova, Italy
| | - Isabella Panfoli
- Department of Pharmacy-(DIFAR), Università di Genova, Viale Benedetto XV 3, 16132 Genova, Italy
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The Flavone Cirsiliol from Salvia x jamensis Binds the F 1 Moiety of ATP Synthase, Modulating Free Radical Production. Cells 2022; 11:cells11193169. [PMID: 36231131 PMCID: PMC9562182 DOI: 10.3390/cells11193169] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/25/2022] [Accepted: 10/04/2022] [Indexed: 11/16/2022] Open
Abstract
Several studies have shown that mammalian retinal rod outer segments (OS) are peculiar structures devoid of mitochondria, characterized by ectopic expression of the molecular machinery for oxidative phosphorylation. Such ectopic aerobic metabolism would provide the chemical energy for the phototransduction taking place in the OS. Natural polyphenols include a large variety of molecules having pleiotropic effects, ranging from anti-inflammatory to antioxidant and others. Our goal in the present study was to investigate the potential of the flavonoid cirsiliol, a trihydroxy-6,7-dimethoxyflavone extracted from Salvia x jamensis, in modulating reactive oxygen species production by the ectopic oxidative phosphorylation taking place in the OS. Our molecular docking analysis identified cirsiliol binding sites inside the F1 moiety of the nanomotor F1Fo-ATP synthase. The experimental approach was based on luminometry, spectrophotometry and cytofluorimetry to evaluate ATP synthesis, respiratory chain complex activity and H2O2 production, respectively. The results showed significant dose-dependent inhibition of ATP production by cirsiliol. Moreover, cirsiliol was effective in reducing the free radical production by the OS exposed to ambient light. We report a considerable protective effect of cirsiliol on the structural stability of rod OS, suggesting it may be considered a promising compound against oxidative stress.
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Ravera S, Bartolucci M, Calzia D, Morelli AM, Panfoli I. Efficient extra-mitochondrial aerobic ATP synthesis in neuronal membrane systems. J Neurosci Res 2021; 99:2250-2260. [PMID: 34085315 DOI: 10.1002/jnr.24865] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 04/29/2021] [Accepted: 05/10/2021] [Indexed: 11/09/2022]
Abstract
The nervous system displays high energy consumption, apparently not fulfilled by mitochondria, which are underrepresented therein. The oxidative phosphorylation (OxPhos) activity, a mitochondrial process that aerobically provides ATP, has also been reported also in the myelin sheath and the rod outer segment (OS) disks. Thus, commonalities and differences between the extra-mitochondrial and mitochondrial aerobic metabolism were evaluated in bovine isolated myelin (IM), rod OS, and mitochondria-enriched fractions (MIT). The subcellular fraction quality and the absence of contamination fractions have been estimated by western blot analysis. Oxygen consumption and ATP synthesis were stimulated by conventional (pyruvate + malate or succinate) and unconventional (NADH) substrates, observing that oxygen consumption and ATP synthesis by IM and rod OS are more efficient than by MIT, in the presence of both kinds of respiratory substrates. Mitochondria did not utilize NADH as a respiring substrate. When ATP synthesis by either sample was assayed in the presence of 10-100 µM ATP in the assay medium, only in IM and OS it was not inhibited, suggesting that the ATP exportation by the mitochondria is limited by extravesicular ATP concentration. Interestingly, IM and OS but not mitochondria appear able to synthesize ATP at a later time with respect to exposure to respiratory substrates, supporting the hypothesis that the proton gradient produced by the electron transport chain is buffered by membrane phospholipids. The putative transfer mode of the OxPhos molecular machinery from mitochondria to the extra-mitochondrial structures is also discussed, opening new perspectives in the field of neurophysiology.
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Affiliation(s)
- Silvia Ravera
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
| | - Martina Bartolucci
- Laboratory of Mass Spectrometry - Core Facilities, Istituto Giannina Gaslini, Genoa, Italy.,Department of Pharmacy, Biochemistry Lab., University of Genoa, Genoa, Italy
| | - Daniela Calzia
- Department of Pharmacy, Biochemistry Lab., University of Genoa, Genoa, Italy
| | | | - Isabella Panfoli
- Department of Pharmacy, Biochemistry Lab., University of Genoa, Genoa, Italy
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First 3D-Structural Data of Full-Length Guanylyl Cyclase 1 in Rod-Outer-Segment Preparations of Bovine Retina by Cross-Linking/Mass Spectrometry. J Mol Biol 2021; 433:166947. [PMID: 33744315 DOI: 10.1016/j.jmb.2021.166947] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/10/2021] [Accepted: 03/11/2021] [Indexed: 11/24/2022]
Abstract
The rod-outer-segment guanylyl cyclase 1 (ROS-GC1) is a key transmembrane protein for retinal phototransduction. Mutations of ROS-GC1 correlate with different retinal diseases that often lead to blindness. No structural data are available for ROS-GC1 so far. We performed a 3D-structural analysis of native ROS-GC1 from bovine retina by cross-linking/mass spectrometry (XL-MS) and computational modeling. Absolute quantification and activity measurements of native ROS-GC1 were performed by MS-based assays directly in bovine retina samples. Our data present the first 3D-structural analysis of active, full-length ROS-GC1 derived from bovine retina. We propose a novel domain organization for the intracellular domain ROS-GC1. Our XL-MS data of native ROS-GC1 from rod-outer-segment preparations of bovine retina agree with a dimeric architecture. Our integrated approach can serve as a blueprint for conducting 3D-structural studies of membrane proteins in their native environment.
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Ravera S, Esposito A, Degan P, Caicci F, Manni L, Liguori A, Bisio A, Iobbi V, Schito A, Traverso CE, Panfoli I. The diterpene Manool extracted from Salvia tingitana lowers free radical production in retinal rod outer segments by inhibiting the extramitochondrial F 1 F o ATP synthase. Cell Biochem Funct 2021; 39:528-535. [PMID: 33472276 DOI: 10.1002/cbf.3618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/17/2020] [Accepted: 12/28/2020] [Indexed: 11/05/2022]
Abstract
Uncontrolled oxidative stress production, especially in the outer retina is one of the causes of retinal degenerations. Mitochondria are considered the principal source of oxidative stress. However, a Reactive Oxygen Intermediates (ROI) production in the retinal photoreceptor layer seems to depend also on the expression of an extramitochondrial oxidative phosphorylation (OxPhos) machinery in the rod outer segments (OS). In fact, OS conduct aerobic metabolism, producing ATP through oxygen consumption, although it is devoid of mitochondria. As diterpenes display an antioxidant effect, we have evaluated the effect Manool, extracted from Salvia tingitana, on the extramitochondrial OxPhos and the ROI production in the retinal rod OS. Results confirm that the OxPhos machinery is ectopically expressed in the OS and that F1 Fo -ATP synthase is a target of Manool, which inhibited the OS ATP synthesis, binding the F1 moiety with high affinity, as analysed by molecular docking. Moreover, the overall slowdown of OxPhos metabolism reduced the ROI production elicited in the OS by light exposure, in vitro. In conclusion, data are consistent with the antioxidant properties of Salvia spp., suggesting its ability to lower oxidative stress production, a primary risk factor for degenerative retinal diseases. SIGNIFICANCE OF THE STUDY: Here we show that Manool, a diterpene extracted from Salvia tingitana has the potential to lower the free radical production by light-exposed rod outer segments in vitro, by specifically targeting the rod OS F1 Fo -ATP synthase belonging to the extramitochondrial OxPhos expressed on the disk membrane. The chosen experimental model allowed to show that the rod OS is a primary producer of oxidative stress linked to the pathogenesis of degenerative retinal diseases. Data are also consistent with the antioxidant and anti-inflammatory action of Salvia spp., suggesting a beneficial effect also in vivo.
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Affiliation(s)
- Silvia Ravera
- Dipartimento di Medicina Sperimentale, Università di Genova, Genova, Italy
| | - Alfonso Esposito
- Centro di Biologia Integrata (CIBIO), Università di Trento, Trento, Italy
| | - Paolo Degan
- UOC Mutagenesi, IRCCS Policlinico San Martino -IST (Istituto Nazionale per la Ricerca sul Cancro), Genova, Italy
| | - Federico Caicci
- Dipartimento di Biologia, Università di Padova, Padova, Italy
| | - Lucia Manni
- Dipartimento di Biologia, Università di Padova, Padova, Italy
| | - Anna Liguori
- Dipartimento di Farmacia (DIFAR), Università di Genova, Genova, Italy
| | - Angela Bisio
- Dipartimento di Farmacia (DIFAR), Università di Genova, Genova, Italy
| | - Valeria Iobbi
- Dipartimento di Farmacia (DIFAR), Università di Genova, Genova, Italy
| | - Anna Schito
- Dipartimento di Scienze Chirurgiche e Diagnostiche Integrate (DISC), Sezione di Microbiologia, Università di Genova, Genova, Italy
| | | | - Isabella Panfoli
- Dipartimento di Farmacia (DIFAR), Università di Genova, Genova, Italy
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Ravera S, Esposito A, Degan P, Caicci F, Calzia D, Perrotta E, Manni L, Bisio A, Iobbi V, Schito A, Traverso CE, Panfoli I. Sclareol modulates free radical production in the retinal rod outer segment by inhibiting the ectopic f 1f o-atp synthase. Free Radic Biol Med 2020; 160:368-375. [PMID: 32853720 DOI: 10.1016/j.freeradbiomed.2020.08.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 08/15/2020] [Accepted: 08/18/2020] [Indexed: 01/06/2023]
Abstract
We have previously shown that the retinal rod outer segments (OS) produce reactive oxygen species in the function of illumination in vitro, establishing a relationship among the extra-mitochondrial oxidative phosphorylation and phototransduction. This source of oxidative stress in the OS can be modulated by polyphenols, acting as inhibitors of F1Fo-ATP synthase. The present study aimed at exploring whether sclareol, a diterpene, interacts with F1Fo-ATP synthase mitigating the light-induced free radical production in the rod OS. Characterization of bovine retinal sections was conducted by immunogold analysis. Reactive oxygen intermediates production, oxygen consumption, the activity of the four respiratory complexes and ATP synthesis were evaluated in purified bovine rod OS. Molecular docking analyses were also conducted. Sclareol reduced free radical production by light-exposed rod OS. Such antioxidant effect was associated with an inhibition of the respiratory complexes and oxygen consumption (OCR), in coupled conditions. Sclareol also inhibited the rod OS ATP synthetic ability. Since the inhibitor effect on respiratory complexes and OCR is not observed in uncoupled conditions, it is supposed that the modulating effect of sclareol on the ectopic oxidative phosphorylation in the rod OS targets specifically the F1Fo-ATP synthase. This hypothesis is confirmed by the in silico molecular docking analyses, which shows that sclareol binds the F1 moiety of ATP synthase with high affinity. In conclusion, a beneficial effect of sclareol can be envisaged as a modulator of oxidative stress in the photoreceptor, a risk factor for the degenerative retinal diseases, suggestive of its potential beneficial action also in vivo.
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Affiliation(s)
- Silvia Ravera
- Dipartimento di Medicina Sperimentale, Università di Genoa, Via De Toni 14, 16132, Genova, Italy
| | - Alfonso Esposito
- Centro di Biologia Integrata (CIBIO), Università di Trento, Via Sommarive, 9, Povo, 38123, Trento, Italy
| | - Paolo Degan
- UOC Mutagenesi, IRCCS Policlinico San Martino -IST, Istituto Nazionale per La Ricerca Sul Cancro), Largo Rosanna Benzi 10, 16132, Genova, Italy
| | - Federico Caicci
- Dipartimento di Biologia, Università di Padova, Via U. Bassi 58/B, 35121, Padova, Italy
| | - Daniela Calzia
- Dipartimento di Farmacia (DIFAR), Università di Genova, V.le Benedetto XV 3, 16132, Genova, Italy
| | - Eleonora Perrotta
- Dipartimento di Medicina Sperimentale, Università di Genoa, Via De Toni 14, 16132, Genova, Italy
| | - Lucia Manni
- Dipartimento di Biologia, Università di Padova, Via U. Bassi 58/B, 35121, Padova, Italy
| | - Angela Bisio
- Dipartimento di Farmacia (DIFAR), Università di Genova, V.le Benedetto XV 3, 16132, Genova, Italy
| | - Valeria Iobbi
- Dipartimento di Farmacia (DIFAR), Università di Genova, V.le Benedetto XV 3, 16132, Genova, Italy
| | - Anna Schito
- Dipartimento di Scienze Chirurgiche e Diagnostiche Integrate (DISC), Sezione di Microbiologia, Università di Genova, Largo Rosanna Benzi 8, 16145, Genova, Italy
| | - Carlo Enrico Traverso
- Clinica Oculistica, (DINOGMI) Università di Genova, V.le Benedetto XV 6, 16132, Genova, Italy
| | - Isabella Panfoli
- Dipartimento di Farmacia (DIFAR), Università di Genova, V.le Benedetto XV 3, 16132, Genova, Italy.
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7
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Ravera S, Caicci F, Degan P, Maggi D, Manni L, Puddu A, Nicolò M, Traverso CE, Panfoli I. Inhibitory Action of Antidiabetic Drugs on the Free Radical Production by the Rod Outer Segment Ectopic Aerobic Metabolism. Antioxidants (Basel) 2020; 9:E1133. [PMID: 33203090 PMCID: PMC7696108 DOI: 10.3390/antiox9111133] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/04/2020] [Accepted: 11/12/2020] [Indexed: 12/17/2022] Open
Abstract
Rod outer segments (OS) express the FoF1-ATP synthase and the respiratory chain, conducting an ectopic aerobic metabolism that produces free radicals in vitro. Diabetic retinopathy, a leading cause of vision loss, is associated with oxidative stress in the outer retina. Since metformin and glibenclamide, two anti-type 2 diabetes drugs, target the respiratory complexes, we studied the effect of these two drugs, individually or in association, on the free radical production in purified bovine rod OS. ATP synthesis, oxygen consumption, and oxidative stress production were assayed by luminometry, oximetry and flow cytometry, respectively. The expression of FoF1-ATP synthase was studied by immunogold electron microscopy. Metformin had a hormetic effect on the OS complex I and ATP synthetic activities, being stimulatory at concentrations below 1 mM, and inhibitory above. Glibenclamide inhibited complexes I and III, as well as ATP production in a concentration-dependent manner. Maximal concentrations of both drugs inhibited the ROI production by the light-exposed OS. Data, consistent with the delaying effect of these drugs on the onset of diabetic retinopathy, suggest that a combination of the two drugs at the beginning of the treatment might reduce the oxidative stress production helping the endogenous antioxidant defences in avoiding retinal damage.
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Affiliation(s)
- Silvia Ravera
- Dipartimento di Medicina Sperimentale, Università di Genoa, Via De Toni 14, 16132 Genova, Italy;
| | - Federico Caicci
- Dipartimento di Biologia, Università di Padova, via U. Bassi 58/B, 35121 Padova, Italy; (F.C.); (L.M.)
| | - Paolo Degan
- U.O. Mutagenesis and Preventive Oncology, IRCCS Ospedale Policlinico San Martino, L.go R. Benzi, 10, 16132 Genova, Italy;
| | - Davide Maggi
- Department of Internal Medicine and Medical Specialties, University of Genova, 16132 Genova, Italy; (D.M.); (A.P.)
| | - Lucia Manni
- Dipartimento di Biologia, Università di Padova, via U. Bassi 58/B, 35121 Padova, Italy; (F.C.); (L.M.)
| | - Alessandra Puddu
- Department of Internal Medicine and Medical Specialties, University of Genova, 16132 Genova, Italy; (D.M.); (A.P.)
| | - Massimo Nicolò
- Clinica Oculistica (DINOGMI), Università di Genova, V.le Benedetto XV 6, 16132 Genova, Italy; (M.N.); (C.E.T.)
- Fondazione per la Macula onlus, Università di Genova, V.le Benedetto XV 6, 16132 Genova, Italy
| | - Carlo E. Traverso
- Clinica Oculistica (DINOGMI), Università di Genova, V.le Benedetto XV 6, 16132 Genova, Italy; (M.N.); (C.E.T.)
| | - Isabella Panfoli
- Dipartimento di Farmacia (DIFAR), Università di Genova, V.le Benedetto XV 3, 16132 Genova, Italy
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Bruschi M, Bartolucci M, Petretto A, Calzia D, Caicci F, Manni L, Traverso CE, Candiano G, Panfoli I. Differential expression of the five redox complexes in the retinal mitochondria or rod outer segment disks is consistent with their different functionality. FASEB Bioadv 2020; 2:315-324. [PMID: 32395704 PMCID: PMC7211042 DOI: 10.1096/fba.2019-00093] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 11/27/2019] [Accepted: 03/05/2020] [Indexed: 12/28/2022] Open
Abstract
PURPOSE The retinal rod outer segment (OS) disk membranes, devoid of mitochondria, conducts oxidative phosphorylation (OxPhos). This study aimed at identifying which proteins expressed in the retinal rod OS disks determined the considerable adenosine-5'-triphosphate production and oxygen consumption observed in comparison with retinal mitochondria. PROCEDURES Characterization was conducted by immunogold transmission electron microscopy on retinal sections. OxPhos was studied by oximetry and luminometry. The proteomes of OS disks and mitochondria purified from bovine retinas were studied by mass spectrometry. Statistical and bioinformatic analyses were conducted by univariate, multivariate, and machine learning methods. RESULTS Weighted gene coexpression network analysis identified two protein expression profile modules functionally associated with either retinal mitochondria or disk samples, in function of a strikingly different ability of each sample to utilized diverse substrate for F1Fo-ATP synthase. The OS disk proteins correlated better than mitochondria with the tricarboxylic acids cycle and OxPhos proteins. CONCLUSIONS The differential enrichment of the expression profile of the OxPhos proteins in the disks versus mitochondria suggests that these proteins may represent a true proteome component of the former, with different functionality. These findings may shed new light on the pathogenesis of rod-driven retinal degenerative diseases.
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Affiliation(s)
- Maurizio Bruschi
- Laboratory of Molecular NephrologyIstituto Giannina GasliniGenoaItaly
| | - Martina Bartolucci
- Laboratory of Mass Spectrometry‐Core FacilitiesIstituto Giannina GasliniGenovaItaly
| | - Andrea Petretto
- Laboratory of Mass Spectrometry‐Core FacilitiesIstituto Giannina GasliniGenovaItaly
| | - Daniela Calzia
- Dipartimento di Farmacia‐DIFARUniversità di GenovaGenoaItaly
| | | | - Lucia Manni
- Department of BiologyUniversità di PadovaPadovaItaly
| | - Carlo Enrico Traverso
- Clinica Oculistica, (Di.N.O.G.M.I.) Università Department of Intensive Care di GenovaIRCCS Azienda Ospedaliera Universitaria San Martino‐ISTGenoaItaly
| | - Giovanni Candiano
- Laboratory of Molecular NephrologyIstituto Giannina GasliniGenoaItaly
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Bisio A, Schito AM, Pedrelli F, Danton O, Reinhardt JK, Poli G, Tuccinardi T, Bürgi T, De Riccardis F, Giacomini M, Calzia D, Panfoli I, Schito GC, Hamburger M, De Tommasi N. Antibacterial and ATP Synthesis Modulating Compounds from Salvia tingitana. JOURNAL OF NATURAL PRODUCTS 2020; 83:1027-1042. [PMID: 32182064 PMCID: PMC7997632 DOI: 10.1021/acs.jnatprod.9b01024] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Indexed: 05/05/2023]
Abstract
A surface extract of the aerial parts of Salvia tingitana afforded a nor-sesterterpenoid (1) and eight new sesterterpenoids (2-̵9), along with five known sesterterpenoids, five labdane and one abietane diterpenoid, one sesquiterpenoid, and four flavonoids. The structures of the new compounds were established by 1D and 2D NMR spectroscopy, HRESIMS, and VCD data and Mosher's esters analysis. The antimicrobial activity of compounds was evaluated against 30 human pathogens including 27 clinical strains and three isolates of marine origin for their possible implications on human health. The methyl ester of salvileucolide (10), salvileucolide-6,23-lactone (11), sclareol (15), and manool (17) were the most active against Gram-positive bacteria. The compounds were also tested for the inhibition of ATP production in purified mammalian rod outer segments. Terpenoids 10, 11, 15, and 17 inhibited ATP production, while only 17 inhibited also ATP hydrolysis. Molecular modeling studies confirmed the capacity of 17 to interact with mammalian ATP synthase. A significant reduction of ATP production in the presence of 17 was observed in Enterococcus faecalis and E. faecium isolates.
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Affiliation(s)
- Angela Bisio
- Department
of Pharmacy, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Anna M. Schito
- Department
of Integrated Surgical and Diagnostical Sciences, University of Genova, Largo Rosanna Benzi 8, 16145 Genova, Italy
| | - Francesca Pedrelli
- Department
of Pharmacy, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Ombeline Danton
- Department
of Pharmaceutical Sciences, University of
Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Jakob K. Reinhardt
- Department
of Pharmaceutical Sciences, University of
Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Giulio Poli
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Tiziano Tuccinardi
- Department
of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Thomas Bürgi
- Department
of Chemical Physics, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Francesco De Riccardis
- Department
of Chemistry and Biology, University of
Salerno, Via Giovanni Paolo II 132, 84084 Salerno, Italy
| | - Mauro Giacomini
- Department
of Informatics Bioengineering Robotics and System Engineering, University of Genova, Via all’Opera Pia, 13, 16145 Genova, Italy
| | - Daniela Calzia
- Department
of Pharmacy, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Isabella Panfoli
- Department
of Pharmacy, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Gian Carlo Schito
- Department
of Pharmacy, University of Genova, Viale Cembrano 4, 16148 Genova, Italy
| | - Matthias Hamburger
- Department
of Pharmaceutical Sciences, University of
Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Nunziatina De Tommasi
- Department
of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084 Salerno, Italy
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10
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Calzia D, Degan P, Caicci F, Bruschi M, Manni L, Ramenghi LA, Candiano G, Traverso CE, Panfoli I. Modulation of the rod outer segment aerobic metabolism diminishes the production of radicals due to light absorption. Free Radic Biol Med 2018; 117:110-118. [PMID: 29378336 DOI: 10.1016/j.freeradbiomed.2018.01.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 01/17/2018] [Accepted: 01/23/2018] [Indexed: 12/19/2022]
Abstract
Oxidative stress is a primary risk factor for both inflammatory and degenerative retinopathies. Our previous data on blue light-irradiated retinas demonstrated an oxidative stress higher in the rod outer segment (OS) than in the inner limb, leading to impairment of the rod OS extra-mitochondrial aerobic metabolism. Here the oxidative metabolism and Reactive Oxygen Intermediates (ROI) production was evaluated in purified bovine rod OS in function of exposure to different illumination conditions. A dose response was observed to varying light intensities and duration in terms of both ROI production and ATP synthesis. Pretreatment with resveratrol, inhibitor of F1Fo-ATP synthase, or metformin, inhibitor of the respiratory complex I, significantly diminished the ROI production. Metformin also diminished the rod OS Complex I activity and reduced the maximal OS response to light in ATP production. Data show for the first time the relationship existing in the rod OS between its -aerobic- metabolism, light absorption, and ROI production. A beneficial effect was exerted by metformin and resveratrol, in modulating the ROI production in the illuminated rod OS, suggestive of their beneficial action also in vivo. Data shed new light on preventative interventions for cone loss secondary to rod damage due to oxidative stress.
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Affiliation(s)
- Daniela Calzia
- Dipartimento di Farmacia-DIFAR,-Biochemistry Lab., University of Genoa, V.le Benedetto XV 3, 16132 Genova, Italy.
| | - Paolo Degan
- UOC Mutagenesi, IRCCS AOU San Martino - IST (Istituto Nazionale per la Ricerca sul Cancro), Genova, Italy
| | - Federico Caicci
- Department of Biology, Università di Padova, via U. Bassi 58/B, 35121 Padova, Italy
| | - Maurizio Bruschi
- Laboratory of Pathophysiology of Uremia, Istituto Giannina Gaslini, Genova, Italy
| | - Lucia Manni
- Department of Biology, Università di Padova, via U. Bassi 58/B, 35121 Padova, Italy
| | - Luca A Ramenghi
- Neonatal Intensive Care Unit, U.O.S. Malattie Metaboliche, V.le Benedetto XV 6, Genova, Italy
| | - Giovanni Candiano
- Neonatal Intensive Care Unit, U.O.S. Malattie Metaboliche, V.le Benedetto XV 6, Genova, Italy
| | - Carlo Enrico Traverso
- Clinica Oculistica, (DINOGMI) University of Genoa, V.le Benedetto XV 6, Genova, Italy
| | - Isabella Panfoli
- Dipartimento di Farmacia-DIFAR,-Biochemistry Lab., University of Genoa, V.le Benedetto XV 3, 16132 Genova, Italy
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Bruschi M, Petretto A, Caicci F, Bartolucci M, Calzia D, Santucci L, Manni L, Ramenghi LA, Ghiggeri G, Traverso CE, Candiano G, Panfoli I. Proteome of Bovine Mitochondria and Rod Outer Segment Disks: Commonalities and Differences. J Proteome Res 2018; 17:918-925. [PMID: 29299929 DOI: 10.1021/acs.jproteome.7b00741] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The retinal rod outer segment (OS) is a stack of disks surrounded by the plasma membrane, housing proteins related to phototransduction, as well as mitochondrial proteins involved in oxidative phosphorylation (OxPhos). This prompted us to compare the proteome of bovine OS disks and mitochondria to assess the significant top gene signatures of each sample. The two proteomes, obtained by LTQ-Orbitrap Velos mass spectrometry, were compared by statistical analyses. In total, 4139 proteins were identified, 2045 of which overlapping in the two sets. Nonhierarchical Spearman's correlogram revealed that the groups were clearly discriminated. Partial least square discriminant plus support vector machine analysis identified the major discriminative proteins, implied in phototransduction and lipid metabolism, respectively. Gene Ontology analysis identified top gene signatures of the disk proteome, enriched in vesiculation, glycolysis, and OxPhos proteins. The tricarboxylic acid cycle and the electron transport proteins were similarly enriched in the two samples, but the latter was up regulated in disks. Data suggest that the mitochondrial OxPhos proteins may represent a true OS proteome component, outside the mitochondrion. This knowledge may help the scientific community in the further studies of retinal physiology and pathology.
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Affiliation(s)
| | | | - Federico Caicci
- Department of Biology, Università di Padova , 35121 Padova, Italy
| | | | - Daniela Calzia
- Dipartimento di Farmacia-DIFAR, Università di Genova , 16132 Genoa, Italy
| | | | - Lucia Manni
- Department of Biology, Università di Padova , 35121 Padova, Italy
| | | | | | - Carlo E Traverso
- Clinica Oculistica, (Di.N.O.G.M.I.) Università Department of Intensive Care di Genova, IRCCS Azienda Ospedaliera Universitaria San Martino-IST , 16132 Genoa, Italy
| | | | - Isabella Panfoli
- Dipartimento di Farmacia-DIFAR, Università di Genova , 16132 Genoa, Italy
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Calzia D, Oneto M, Caicci F, Bianchini P, Ravera S, Bartolucci M, Diaspro A, Degan P, Manni L, Traverso CE, Panfoli I. Effect of polyphenolic phytochemicals on ectopic oxidative phosphorylation in rod outer segments of bovine retina. Br J Pharmacol 2015; 172:3890-903. [PMID: 25917043 DOI: 10.1111/bph.13173] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 03/24/2015] [Accepted: 04/20/2015] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND PURPOSE The rod outer segments (OS) of the retina are specialized organelles where phototransduction takes place. The mitochondrial electron transport complexes I-IV, cytochrome c and Fo F1 -ATP synthase are functionally expressed in the OS disks. Here, we have studied the effect of some polyphenolic compounds acting as inhibitors of mitochondrial ATPase/synthase activity on the OS ectopic Fo F1 - ATP synthase. The mechanism of apoptosis in the OS was also investigated studying the expression of cytochrome c, caspase 9 and 3 and Apaf-1. EXPERIMENTAL APPROACH We prepared OS from fresh bovine retinae. Semi-quantitative Western blotting, confocal and electron microscopy, and cytofluorimetry were used along with biochemical analyses such as oximetry, ATP synthesis and hydrolysis. KEY RESULTS Resveratrol and curcumin plus piperine inhibited ATP synthesis and oxygen consumption in the OS. Epigallocatechin gallate and quercetin inhibited ATP hydrolysis and oxygen consumption in the OS. Malondialdehyde and hydrogen peroxide were produced in respiring OS in the presence of substrates. Cytochrome c was located inside the disk membranes. Procaspase 9 and 3, as well as Apaf-1 were expressed in the OS. CONCLUSIONS AND IMPLICATIONS These polyphenolic phytochemicals modulated the Fo F1 -ATP synthase activity of the the OS reducing production of reactive oxygen intermediates by the OS ectopic electron transport chain. Polyphenols decrease membrane peroxidation and cytochrome c release from disks, preventing the induction of caspase-dependent apoptosis in the OS Such effects are relevant in the design of protection against functional impairment of the OS following oxidative stress from exposure to intense illumination.
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Affiliation(s)
- Daniela Calzia
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Laboratory, University of Genoa, Genova, Italy
| | - Michele Oneto
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Laboratory, University of Genoa, Genova, Italy
| | | | - Paolo Bianchini
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
| | - Silvia Ravera
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Laboratory, University of Genoa, Genova, Italy
| | - Martina Bartolucci
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Laboratory, University of Genoa, Genova, Italy
| | - Alberto Diaspro
- Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
| | - Paolo Degan
- UOC Mutagenesi, IRCCS Azienda Ospedaliera Universitaria San Martino - Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy
| | - Lucia Manni
- Department of Biology, Università di Padova, Padova, Italy
| | - Carlo Enrico Traverso
- Clinica Oculistica, Di.N.O.G.M.I., University of Genoa, IRCCS Azienda Ospedaliera Universitaria San Martino - Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy
| | - Isabella Panfoli
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Laboratory, University of Genoa, Genova, Italy
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13
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Calzia D, Barabino S, Bianchini P, Garbarino G, Oneto M, Caicci F, Diaspro A, Tacchetti C, Manni L, Candiani S, Ravera S, Morelli A, Enrico Traverso C, Panfoli I. New findings in ATP supply in rod outer segments: insights for retinopathies. Biol Cell 2013; 105:345-58. [PMID: 23659850 DOI: 10.1111/boc.201300003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 05/03/2013] [Indexed: 01/10/2023]
Abstract
BACKGROUND INFORMATION The rod outer segment (OS) is the specialised organelle where phototransduction takes place. Our previous proteomic and biochemical analyses on purified rod disks showed the functional expression of the respiratory chain complexes I-IV and F1 Fo -ATP synthase in OS disks, as well as active soluble tricarboxylic acid cycle enzymes. Here, we focussed our study on the whole OS that contains the cytosol and plasma membrane and disks as native flattened saccules, unlike spherical osmotically intact disks. RESULTS OS were purified from bovine retinas and characterised for purity. Oximetry, ATP synthesis and cytochrome c oxidase (COX) assays were performed. The presence of COX and F₁F₀-ATP synthase (ATP synthase) was assessed by semi-quantitative Western blotting, immunofluorescence or confocal laser scanning microscopy on whole bovine retinas and bovine retinal sections and by immunogold transmission electron microscopy (TEM) of purified OS or bovine retinal sections. Both ATP synthase and COX are catalytically active in OS. These are able to consume oxygen (O₂) in the presence of pyruvate and malate. CLSM analyses showed that rhodopsin autofluorescence and MitoTracker Deep Red 633 fluorescence co-localise on rod OS. Data are confirmed by co-localisation studies of ATP synthase with Rh in rod OS by immunofluorescence and TEM in bovine retinal sections. CONCLUSIONS Our data confirm the expression and activity of COX and ATP synthase in OS, suggestive of the presence of an extra-mitochondrial oxidative phosphorylation in rod OS, meant to supply ATP for the visual transduction. In this respect, the membrane rich OS environment would be meant to absorb both light and O₂. The ability of OS to manipulate O₂ may shed light on the pathogenesis of many retinal degenerative diseases ascribed to oxidative stress, as well as on the efficacy of the treatment with dietary supplements, presently utilised as supporting therapies.
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Affiliation(s)
- Daniela Calzia
- Department of Pharmacy-DIFAR, Biochemistry and Physiology Lab, University of Genoa, Genova, Italy
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14
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Are rod outer segment ATP-ase and ATP-synthase activity expression of the same protein? Cell Mol Neurobiol 2013; 33:637-49. [PMID: 23568658 DOI: 10.1007/s10571-013-9926-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 03/12/2013] [Indexed: 12/15/2022]
Abstract
Vertebrate retinal rod outer segments (OS) consist of a stack of disks surrounded by the plasma membrane, where phototransduction takes place. Energetic metabolism in rod OS remains obscure. Literature described a so-called Mg(2+)-dependent ATPase activity, while our previous results demonstrated the presence of oxidative phosphorylation (OXPHOS) in OS, sustained by an ATP synthetic activity. Here we propose that the OS ATPase and ATP synthase are the expression of the same protein, i.e., of F1Fo-ATP synthase. Imaging on bovine retinal sections showed that some OXPHOS proteins are expressed in the OS. Biochemical data on bovine purified rod OS, characterized for purity, show an ATP synthase activity, inhibited by classical F1Fo-ATP synthase inhibitors. Moreover, OS possess a pH-dependent ATP hydrolysis, inhibited by pH values below 7, suggestive of the functioning of the inhibitor of F1 (IF1) protein. WB confirmed the presence of IF1 in OS, substantiating the expression of F1Fo ATP synthase in OS. Data suggest that the OS F1Fo ATP synthase is able to hydrolyze or synthesize ATP, depending on in vitro or in vivo conditions and that the role of IF1 would be pivotal in the prevention of the reversal of ATP synthase in OS, for example during hypoxia, granting photoreceptor survival.
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15
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Panfoli I, Calzia D, Bruschi M, Oneto M, Bianchini P, Ravera S, Petretto A, Diaspro A, Candiano G. Functional expression of oxidative phosphorylation proteins in the rod outer segment disc. Cell Biochem Funct 2013; 31:532-8. [PMID: 23322616 DOI: 10.1002/cbf.2943] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/06/2012] [Accepted: 11/28/2012] [Indexed: 11/09/2022]
Abstract
The rod Outer Segment (OS) disc, an organelle devoid of mitochondria, is specialized in phototransduction, a process requiring a continual chemical energy supply. We have shown that OS discs express functional mitochondrial electron transport chains, Fo F1 -ATP synthase and the tricarboxylic acid cycle enzymes, all mitochondrial features. Here, we focus on oxygen consumption and adenosine triphosphate (ATP) synthesis by OS discs analysing electron transport chain I-III-IV and II-II-IV pathways, supported by reduced nicotinamide adenine dinucleotide and succinate, respectively. Interestingly, respiratory capacity of discs was measurable also in the presence of 3-hydroxy-butyrrate, a typical metabolic substrate for the brain. Data were supported by a two-dimensional electrophoresis analyses conducted as our previous one, but focused to those mitochondrial proteins that are involved in oxidative phosphorylation. Carbonic anhydrase was also found active in OS discs. Moreover, colocalization of Rhodopsin with respiratory complex I and ATP synthase seems a further step in the characterization of some proteins typical of the mitochondrial inner membranes that are expressed in the rod discs. The existence of oxygen utilization in the outer retina, likely supplying ATP for phototransduction, may shed light on some retinal pathologies related to oxidative stress of the outer retina.
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Affiliation(s)
- Isabella Panfoli
- DIFAR-Biochemistry Lab., University of Genoa, 16132 Genova, Italy.
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16
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Panfoli I, Calzia D, Ravera S, Bruschi M, Tacchetti C, Candiani S, Morelli A, Candiano G. Extramitochondrial tricarboxylic acid cycle in retinal rod outer segments. Biochimie 2011; 93:1565-75. [PMID: 21683117 DOI: 10.1016/j.biochi.2011.05.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 05/23/2011] [Indexed: 01/23/2023]
Abstract
Vertebrate retinal rod Outer Segments (OS) are the site of visual transduction, an energy demanding process for which mechanisms of ATP supply are still poorly known. Glycolysis or diffusion of either ATP or phosphocreatine from the Inner Segment (IS) does not seem to display adequate timing to supply ATP for phototransduction. We have previously reported data suggesting an aerobic metabolism in OS, which would largely account for the light-stimulated ATP need of the photoreceptor. Here, by oxymetry and biochemical analyses we show that: (i) disks isolated by Ficoll flotation consume O(2) in the presence of physiological respiring substrates either in coupled or uncoupled conditions; (ii) OS homogenates contain the whole biochemical machinery for the degradation of glucose, i.e. glycolysis and the tricarboxylic acid cycle (TCA cycle), consistently with the results of our previous proteomic study. Activities of the 8 TCA cycle enzymes in OS were comparable to those in retinal mitochondria-enriched fractions. Disk and OS preparations were subjected to TEM analysis, and while they can be considered free of inner segment contaminants, immunogold with specific antibodies demonstrate the expression therein of both the visual pigment rhodopsin and F(o)F(1)-ATP synthase. Finally, double immunofluorescence on mouse retina sections demonstrated a colocalization of some respiratory complex mitochondrial proteins with rhodopsin in rod OS. Data, suggestive of the exportability of the mitochondrial machinery for aerobic metabolism, may shed light on those retinal pathologies related to energy supply impairment in OS and to mutations in TCA enzymes.
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Affiliation(s)
- Isabella Panfoli
- Department of Biology, University of Genoa, Viale Benedetto XV, 5, 16132 Genova, Italy.
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17
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Abstract
Cyclic ADP-ribose (cADPR) is a second messenger modulating intracellular calcium levels. We have previously described a cADPR-dependent calcium signaling pathway in bovine rod outer segments (ROS), where calcium ions play a pivotal role. ROS ADP-ribosyl cyclase (ADPR-cyclase) was localized in the membrane fraction. In the present work, we examined the properties of the disk ADPR-cyclase through the production of cyclic GDP-ribose from the NAD(+) analogue NGD(+). The enzyme displayed an estimated K(m) for NGD(+) of 12.5 ± 0.3 μM, a V(max) of 26.50 ± 0.70 pmol cyclic GDP-ribose synthesized/min/mg, and optimal pH of 6.5. The effect of divalent cations (Zn(2+), Cu(2+), and Ca(2+)) was also tested. Micromolar Zn(2+) and Cu(2+) inhibited the disk ADPR-cyclase activity (half maximal inhibitory concentration, IC50=1.1 and 3.6 μM, respectively). By contrast, Ca(2+) ions had no effect. Interestingly, the properties of the intracellular membrane-associated ROS disk ADPR-cyclase are more similar to those of the ADPR-cyclase found in CD38-deficient mouse brain, than to those of CD38 or CD157. The novel intracellular mammalian ADPR-cyclase would elicit Ca(2+) release from the disks at various rates in response to change in free Ca(2+) concentrations, caused by light versus dark adaptation, in fact there was no difference in disk ADPR-cyclase activity in light or dark conditions. Data suggest that disk ADPR-cyclase may be a potential target of retinal toxicity of Zn(2+) and may shed light to the role of Cu(2+) and Zn(2+) deficiency in retina.
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18
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Komolov KE, Koch KW. Application of surface plasmon resonance spectroscopy to study G-protein coupled receptor signalling. Methods Mol Biol 2010; 627:249-60. [PMID: 20217627 DOI: 10.1007/978-1-60761-670-2_17] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The G-protein coupled receptor rhodopsin is a classical example of a seven transmembrane helix receptor; it is photoexcited and transmits this light signal to a G-protein mediated cascade. Many components of this receptor-triggered cascade can be purified in their native forms from natural sources making this system most suitable for biophysical studies. A central aspect of cellular signal transduction routes is to understand protein-protein interactions in a quantitative way. Surface plasmon resonance (SPR) spectroscopy is a biosensor-based technique that allows investigating molecular interactions by determining kinetic parameters. We here show how dark-adapted rhodopsin can be immobilized on the sensor chip surface. A laser device implemented in the SPR system allowed us to trigger light-induced conformational changes in rhodopsin and to monitor light-dependent binding of the photoreceptor cell G-protein transducin to rhodopsin. The sensor chip surface can be regenerated and used for several rounds of interaction analysis. Furthermore, illuminated rhodopsin can be regenerated by applying 9-cis-retinal on the sensor chip surface.
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19
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Panfoli I, Calzia D, Ravera S, Bianchini P, Diaspro A. Immunochemical or fluorescent labeling of vesicular subcellular fractions for microscopy imaging. Microsc Res Tech 2010; 73:1086-90. [DOI: 10.1002/jemt.20852] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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20
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Mitchell KAP, Szabo G, Otero ADS. Methods for the isolation of sensory and primary cilia--an overview. Methods Cell Biol 2009; 94:87-101. [PMID: 20362086 DOI: 10.1016/s0091-679x(08)94004-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Detailed proteomic analyses of mammalian olfactory and rod photoreceptor sensory cilia are now available, providing an inventory of resident ciliary proteins and laying the foundation for future studies of developmental and spatiotemporal changes in the composition of sensory cilia. Cilia purification methods that were elaborated and perfected over several decades were essential for these advances. In contrast, the proteome of primary cilia is yet to be established, because purification procedures for this organelle have been developed only recently. In this chapter, we review current techniques for the purification of olfactory and photoreceptor cilia, and evaluate methods designed for the selective isolation of primary cilia.
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Affiliation(s)
- Kimberly A P Mitchell
- Department of Biology and Chemistry, Liberty University, Lynchburg, Virginia 24502, USA
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21
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Evidence for aerobic metabolism in retinal rod outer segment disks. Int J Biochem Cell Biol 2009; 41:2555-65. [PMID: 19715769 DOI: 10.1016/j.biocel.2009.08.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 08/11/2009] [Accepted: 08/20/2009] [Indexed: 12/15/2022]
Abstract
The disks of the vertebrate retinal rod Outer Segment (OS), devoid of mitochondria, are the site of visual transduction, a very energy demanding process. In a previous proteomic study we reported the expression of the respiratory chain complexes I-IV and the oxidative phosphorylation Complex V (F(1)F(0)-ATP synthase) in disks. In the present study, the functional localization of these proteins in disks was investigated by biochemical analyses, oxymetry, membrane potential measurements, and confocal laser scanning microscopy. Disk preparations, isolated by Ficoll flotation, were characterized for purity. An oxygen consumption, stimulated by NADH and Succinate and reverted by rotenone, antimycin A and KCN was measured in disks, either in coupled or uncoupled conditions. Rhodamine-123 fluorescence quenching kinetics showed the existence of a proton potential difference across the disk membranes. Citrate synthase activity was assayed and found enriched in disks with respect to ROS. ATP synthesis by disks (0.7 micromol ATP/min/mg), sensitive to the common mitochondrial ATP synthase inhibitors, would largely account for the rod ATP need in the light. Overall, data indicate that an oxidative phosphorylation occurs in rod OS, which do not contain mitochondria, thank to the presence of ectopically located mitochondrial proteins. These findings may provide important new insight into energy production in outer segments via aerobic metabolism and additional information about protein components in OS disk membranes.
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22
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Panfoli I, Musante L, Bachi A, Ravera S, Calzia D, Cattaneo A, Bruschi M, Bianchini P, Diaspro A, Morelli A, Pepe IM, Tacchetti C, Candiano G. Proteomic analysis of the retinal rod outer segment disks. J Proteome Res 2008; 7:2654-69. [PMID: 18489131 DOI: 10.1021/pr7006939] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The initial events of vision at low light take place in vertebrate retinal rods. The rod outer segment consists of a stack of flattened disks surrounded by the plasma membrane. A list of the proteins that reside in disks has not been achieved yet. We present the first comprehensive proteomic analysis of purified rod disks, obtained by combining the results of two-dimensional gel electrophoresis separation of disk proteins to MALDI-TOF or nLC-ESI-MS/MS mass spectrometry techniques. Intact disks were isolated from bovine retinal rod outer segments by a method that minimizes contamination from inner segment. Out of a total of 187 excised spots, 148 proteins were unambiguously identified. An additional set of 61 proteins (partially overlapping with the previous ones) was generated by one-dimensional (1D) gel nLC-ESI-MS/MS method. Proteins involved in vision as well as in aerobic metabolism were found, among which are the five complexes of oxidative phosphorylation. Results from biochemical, Western blot, and confocal laser scanning microscopy immunochemistry experiments suggest that F 1F o-ATP synthase is located and catalytically active in ROS disk membranes. This study represents a step toward a global physiological characterization of the disk proteome and provides information necessary for future studies on energy supply for phototransduction.
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Affiliation(s)
- Isabella Panfoli
- Department of Biology, University of Genoa, V.le Benedetto XV 3, 16132 Genova, Italy. ,
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23
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Ravera S, Calzia D, Bianchini P, Diaspro A, Panfoli I. Confocal laser scanning microscopy of retinal rod outer segment intact disks: new labeling technique. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:050501. [PMID: 17994858 DOI: 10.1117/1.2790919] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Vertebrate retinal rod outer segment disks house the proteins involved in the phototransduction cascade that converts light into neuronal signal. We develop a technique for the immunofluorescent labeling of osmotically intact isolated rod outer segment disks for confocal laser scanning microscopy imaging. Osmotically intact Ficoll-flotation isolated bovine disks are directly labeled with antibodies in solution. For the first time, osmotically intact single disks can be visualized. Thus, imaging of purified disks, based on advanced optical techniques, may serve as a powerful complement to other methods in studies on phototransduction. In fact, even though much is known about the rod outer segment photoresponse, some unanswered questions remain, particularly about ATP supply, light adaptation, and morphogenesis.
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24
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Ravera S, Musante L, Calzia D, Panfoli I, Bruschi M, Candiano G, Pepe IM, Morelli A. Expression of adenylate kinase 1 in bovine retinal cytosol. Curr Eye Res 2007; 32:249-57. [PMID: 17453945 DOI: 10.1080/02713680601161212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Adenylate kinases (AKs) are ubiquitous phosphotransferases that contribute to homeostasis of adenine nucleotide composition in cells. Six AK isoforms were found in vertebrates. We report that soluble AK isoform 1 is expressed in the cytosol of bovine retina consistently devoid of rod outer segments. Immunoblotting analysis with a polyclonal antibody raised against soluble adenylate kinase and subsequent sequencing of eluted peptide by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry allowed enzyme isolation by joining purification methods to two-dimensional electrophoresis. In this study, we found that cytosolic adenylate kinase isoform 1 is expressed in bovine retina. Cytoplasmic AK1 would physiologically contribute to retinal energy metabolism.
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Affiliation(s)
- Silvia Ravera
- Biology Department, University of Genoa, Genova, Italy
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25
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Ravera S, Calzia D, Panfoli I, Pepe IM, Morelli A. Simultaneous detection of molecular weight and activity of adenylate kinases after electrophoretic separation. Electrophoresis 2007; 28:291-300. [PMID: 17203507 DOI: 10.1002/elps.200600353] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Adenylate kinases (AKs) are ubiquitous monomeric phosphotransferases catalyzing the reversible reaction, AMP + MgATP = ADP + MgADP, which plays a pivotal role in the energetic metabolism. In vertebrates, six AK isoforms are known. In this work, we report the detection of many AK isoforms directly on gel or NC after separation by denaturing electrophoresis and electroblotting, by an optimized protocol for the enzyme detection. The method allows to clarify the apparent MW of most of those AK isozymes that follow the cited reaction, especially onto NC where bands are sharper due to the absence of protein diffusion. In contrast, GTP:AMP phosphotransferases are not detectable. AK activity from many sources can be detected in both its reaction courses; ATP production appears as dark-blue bands, while ADP formation appears as nonfluorescent bands over a fluorescent background, under long-wavelength UV light. We show that nondenaturing gel electrophoresis is not the first choice for AK activity detection. Our method is different from the preceding reports on AK activity detection in bacteria after native polyacrylamide gel separations, in the absence of SDS or methanol. The procedure is also quantitative, allowing to determine the amount of enzyme present in samples.
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Affiliation(s)
- Silvia Ravera
- Department of Biology, University of Genoa, Genova, Italy.
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26
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Batra-Safferling R, Abarca-Heidemann K, Körschen HG, Tziatzios C, Stoldt M, Budyak I, Willbold D, Schwalbe H, Klein-Seetharaman J, Kaupp UB. Glutamic acid-rich proteins of rod photoreceptors are natively unfolded. J Biol Chem 2005; 281:1449-60. [PMID: 16280326 DOI: 10.1074/jbc.m505012200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The outer segment of vertebrate photoreceptors is a specialized compartment that hosts all the signaling components required for visual transduction. Specific to rod photoreceptors is an unusual set of three glutamic acid-rich proteins (GARPs) as follows: two soluble forms, GARP1 and GARP2, and the N-terminal cytoplasmic domain (GARP' part) of the B1 subunit of the cyclic GMP-gated channel. GARPs have been shown to interact with proteins at the rim of the disc membrane. Here we characterized native GARP1 and GARP2 purified from bovine rod photoreceptors. Amino acid sequence analysis of GARPs revealed structural features typical of "natively unfolded" proteins. By using biophysical techniques, including size-exclusion chromatography, dynamic light scattering, NMR spectroscopy, and circular dichroism, we showed that GARPs indeed exhibit a large degree of intrinsic disorder. Analytical ultracentrifugation and chemical cross-linking showed that GARPs exist in a monomer/multimer equilibrium. The results suggested that the function of GARP proteins is linked to their structural disorder. They may provide flexible spacers or linkers tethering the cyclic GMP-gated channel in the plasma membrane to peripherin at the disc rim to produce a stack of rings of these protein complexes along the long axis of the outer segment. GARP proteins could then provide the environment needed for protein interactions in the rim region of discs.
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Affiliation(s)
- Renu Batra-Safferling
- Institut für Biologische Informationsverarbeitung 1, Forschungszentrum Jülich, Germany
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27
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Morelli A, Ravera S, Panfoli I, Pepe IM. Effects of extremely low frequency electromagnetic fields on membrane-associated enzymes. Arch Biochem Biophys 2005; 441:191-8. [PMID: 16126157 DOI: 10.1016/j.abb.2005.07.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Accepted: 07/23/2005] [Indexed: 10/25/2022]
Abstract
The effects of extremely low frequency electromagnetic fields of 75 Hz were studied on different membrane-associated enzymes. Only the activities of three enzymes out of seven exposed to the field decreased approximately of about 54-61% with field amplitudes above a threshold of 73-151 microT depending on the enzyme. The same field had no effect on the activities of either integral membrane enzymes such as Ca,ATPase, Na/K,ATPase, and succinic dehydrogenase or peripheral membrane enzymes such as photoreceptor PDE. The decrease in enzymatic activity of the field-sensitive enzymes was independent of the time of permanence in the field and was completely reversible. When these enzymes were solubilized with Triton, no effect of the field was obtained on the enzymatic activity, suggesting the crucial role of the membrane in determining the conditions for enzyme inactivation. The role of the particular linkage of the field-sensitive enzymes to the membranes is also discussed.
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Affiliation(s)
- A Morelli
- Department of DIBISAA, University of Genoa, viale Benedetto XV, 3 Genova 16131, Italy
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Ravera S, Repaci E, Morelli A, Pepe IM, Botter R, Beruto D. Effects of extremely low frequency electromagnetic fields on the adenylate kinase activity of rod outer segment of bovine retina. Bioelectromagnetics 2005; 25:545-51. [PMID: 15376242 DOI: 10.1002/bem.20031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Extremely low frequency electromagnetic fields (ELF-EMFs) of 75 Hz with amplitudes above a threshold of about 125 microT have a dramatic effect on the adenylate kinase (AK) activity of the rod outer segment (ROS) membranes. In fact, the ATP production by ROS membranes or by purified disk membranes placed in the field decreased by approximately 54%. The decrease in enzymatic activity was independent of the time of exposure to the field and was completely reversible. When disk membranes were solubilized with Triton or a soluble isoform of AK was used, negligible effects of the field were obtained on the enzymatic activity, suggesting that the membrane has an important role in determining the conditions for the enzyme inactivation.
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Affiliation(s)
- S Ravera
- Department of DIBISAA, University of Genoa, Genoa, Italy
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29
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Norton AW, Hosier S, Terew JM, Li N, Dhingra A, Vardi N, Baehr W, Cote RH. Evaluation of the 17-kDa prenyl-binding protein as a regulatory protein for phototransduction in retinal photoreceptors. J Biol Chem 2005; 280:1248-56. [PMID: 15504722 PMCID: PMC3392308 DOI: 10.1074/jbc.m410475200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mammalian rod photoreceptor phosphodiesterase (PDE6) holoenzyme is isolated in both a membrane-associated and a soluble form. Membrane binding is a consequence of prenylation of PDE6 catalytic subunits, whereas soluble PDE6 is purified with a 17-kDa prenyl-binding protein (PDEdelta) tightly bound. This protein, here termed PrBP/delta, has been hypothesized to reduce activation of PDE6 by transducin, thereby desensitizing the photoresponse. To test the potential role of PrBP/delta in regulating phototransduction, we examined the abundance, localization, and potential binding partners of PrBP/delta in retina and in purified rod outer segment (ROS) suspensions whose physiological and biochemical properties are well characterized. The amphibian homologue of PrBP/delta was cloned and sequenced and found to have 82% amino acid sequence identity with mammalian PrBP/delta. In contrast to bovine ROS, all of the PDE6 in purified frog ROS is membrane-associated. However, addition of recombinant frog PrBP/delta can solubilize PDE6 and prevent its activation by transducin. PrBP/delta also binds other prenylated photoreceptor proteins in vitro, including opsin kinase (GRK1/GRK7) and rab8. Quantitative immunoblot analysis of the PrBP/delta content of purified ROS reveals insufficient amounts of PrBP/delta (<0.1 PrBP/delta per PDE6) to serve as a subunit of PDE6 in either mammalian or amphibian photoreceptors. The immunolocalization of PrBP/delta in frog and bovine retina shows greatest PrBP/delta immunolabeling outside the photoreceptor cell layer. Within photoreceptors, only the inner segments of frog double cones are strongly labeled, whereas bovine photoreceptors reveal more PrBP/delta labeling near the junction of the inner and outer segments (connecting cilium) of photoreceptors. Together, these results rule out PrBP/delta as a PDE6 subunit and implicate PrBP/delta in the transport and membrane targeting of prenylated proteins (including PDE6) from their site of synthesis in the inner segment to their final destination in the outer segment of rods and cones.
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Affiliation(s)
- Angela W. Norton
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Suzanne Hosier
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Jennifer M. Terew
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
| | - Ning Li
- Moran Eye Center, University of Utah Health Center, Salt Lake City, Utah 84132
| | - Anuradha Dhingra
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Noga Vardi
- Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Wolfgang Baehr
- Moran Eye Center, University of Utah Health Center, Salt Lake City, Utah 84132
| | - Rick H. Cote
- Department of Biochemistry and Molecular Biology, University of New Hampshire, Durham, New Hampshire 03824-2617
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30
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Ravera S, Repaci E, Morelli A, Pepe IM, Botter R, Beruto D. Electromagnetic field of extremely low frequency decreased adenylate kinase activity in retinal rod outer segment membranes. Bioelectrochemistry 2004; 63:317-20. [PMID: 15110295 DOI: 10.1016/j.bioelechem.2003.10.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Revised: 09/19/2003] [Accepted: 10/06/2003] [Indexed: 10/26/2022]
Abstract
Adenylate kinase activity in rod outer segment membranes of bovine retina decreased of about 55% when exposed to an extremely low frequency electromagnetic field of 75 Hz and 250 microT. The effect was independent of the time of permanence in the field. Negligible effects of the field were found on the enzymatic activity of a soluble isoform of adenylate kinase or of rod outer segment membranes solubilized with Triton, suggesting the importance of the membrane in determining the conditions of the enzyme inactivation.
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Affiliation(s)
- S Ravera
- Department of DIBISAA, University of Genoa, Genoa, Italy
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31
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Weitz D, Ficek N, Kremmer E, Bauer PJ, Kaupp UB. Subunit stoichiometry of the CNG channel of rod photoreceptors. Neuron 2002; 36:881-9. [PMID: 12467591 DOI: 10.1016/s0896-6273(02)01098-x] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Cyclic nucleotide-gated (CNG) channels play a central role in the conversion of sensory stimuli into electrical signals. CNG channels form heterooligomeric complexes built of A and B subunits. Here, we study the subunit stoichiometry of the native rod CNG channel by chemical crosslinking. The apparent molecular weight (M(w)) of each crosslink product was determined by SDS-PAGE, and its composition was analyzed by Western blotting using antibodies specific for the A1 or B1 subunit. The number of crosslink products and their M(w) as well as the immunological identification of A1 and B1 subunits in the crosslink products led us to conclude that the native rod CNG channel is a tetramer composed of three A1 and one B1 subunit. This is an example of violation of symmetry in tetrameric channels.
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Affiliation(s)
- Dietmar Weitz
- Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, Germany
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32
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Higgins MK, Weitz D, Warne T, Schertler GF, Kaupp U. Molecular architecture of a retinal cGMP-gated channel: the arrangement of the cytoplasmic domains. EMBO J 2002; 21:2087-94. [PMID: 11980705 PMCID: PMC125374 DOI: 10.1093/emboj/21.9.2087] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2002] [Revised: 03/08/2002] [Accepted: 03/08/2002] [Indexed: 02/04/2023] Open
Abstract
Cyclic nucleotide-gated (CNG) channels play a central role in the conversion of sensory information, such as light and scent, into primary electrical signals. We have purified the CNG channel from bovine retina and have studied it using electron microscopy and image processing. We present the structure of the channel to 35 A resolution. This three-dimensional reconstruction provides insight into the architecture of the protein, suggesting that the cyclic nucleotide-binding domains, which initiate the response to ligand, 'hang' below the pore-forming part of the channel, attached by narrow linkers. The structure also suggests that the four cyclic nucleotide-binding domains present in each channel form two distinct domains, lending structural weight to the suggestion that the four subunits of the CNG channels are arranged as a pair of dimers.
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Affiliation(s)
| | - Dietmar Weitz
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and
Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany Corresponding authors e-mail: or M.K.Higgins and D.Weitz contributed equally to this work
| | | | - Gebhard F.X. Schertler
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and
Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany Corresponding authors e-mail: or M.K.Higgins and D.Weitz contributed equally to this work
| | - U.Benjamin Kaupp
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK and
Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, D-52425 Jülich, Germany Corresponding authors e-mail: or M.K.Higgins and D.Weitz contributed equally to this work
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33
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Sitaramayya A, Margulis A. Effects of lithium on basal and modulated activities of the particulate and soluble guanylate cyclases in retinal rod outer segments. Biochemistry 2002; 31:10652-6. [PMID: 1358198 DOI: 10.1021/bi00159a002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A large amount of information regarding the kinetics of biochemical reactions involved in visual transduction was derived from electrophysiological studies on dark-adapted rod outer segments. Hodgkin et al. [(1985) J. Physiol. 358, 447-468] observed that when Na was replaced with Li in the perfusion solution bathing the rod outer segment, the dark current slowly declined to zero. This decline was thought to result from a rise in intracellular calcium which was hypothesized to inhibit guanylate cyclase activity and reduce the cyclic GMP concentration. Rod outer segments contain membrane and soluble guanylate cyclase activities, and we show here that Li directly inhibits both types of activities very strongly. Both the basal (at high calcium) and the stimulated (at low calcium) activities of the membrane enzyme were inhibited by Li. Half-maximal inhibition of the stimulated enzyme was at 30 mM Li while for the basal activity it was at 100 mM. Over 80% of the activated enzyme was inhibited at 110 mM Li. The soluble guanylate cyclase activity was stimulated by nitroprusside. One hundred millimolar Li inhibited the basal activity by 20-30%, but the inhibition of the nitroprusside-stimulated (soluble) enzyme was much stronger, resembling that of the activated membrane enzyme. Half-maximal inhibition occurred at 30 mM, and about 80% inhibition was found at 100 mM Li. Stimulation of the soluble enzyme by nitroprusside was independent of calcium in the physiological range. The inhibition of the stimulated enzyme by Li was similarly independent of calcium, except at unphysiologically high concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Sitaramayya
- Pennsylvania College of Optometry, Philadelphia 19141
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34
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Pepe IM, Notari L, Cugnoli C, Panfoli I, Morelli A. ATP synthesis in the disk membranes of rod outer segments of bovine retina. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2002; 66:148-52. [PMID: 11897515 DOI: 10.1016/s1011-1344(02)00238-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
ATP is synthesized on the disk membrane isolated from rod outer segments of the bovine retina. Together with a slow component which accounted for a constant rate of about 22 nmol ATP/min/mg of protein and which was due to the adenylate kinase activity, a fast component with a maximal activity of about 58 nmol ATP/min/mg of protein was measured at physiological calcium concentrations. This fast activity disappeared in the presence of the Ca(2+) ionophore A23187, was inhibited by vanadate or thapsigargin but not by oligomycin, suggesting that this ATP synthesis is due to the reversal functioning of the Ca(2+)-ATPase previously found on the disk membranes.
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Affiliation(s)
- I M Pepe
- Istituto di Biofisica, Facoltá di Medicina, Universitá di Genova, Corso Europa, I-16132 Genoa, Italy.
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35
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Notari L, Pepe IM, Cugnoli C, Morelli A. Adenylate kinase activity in rod outer segments of bovine retina. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1504:438-43. [PMID: 11245807 DOI: 10.1016/s0005-2728(01)00160-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The rod outer segments of bovine retina contain two different adenylate kinases: a soluble activity, which is not sensitive to calcium ion, and an activity bound to disk membranes, which is dependent on the calcium levels. In fact, the maximal activity associated to the disks is reached at Ca(2+) concentrations between 10(-6) and 10(-7) M, which is the range of calcium level actually present in the rod cell. The Michaelis-Menten kinetics of the enzyme activity on disk membranes was determined and the actual concentrations of ATP, AMP and ADP were measured in the photoreceptor outer segment. Therefore, the physiological relevance of the adenylate kinase activity was discussed considering the above results. The formation of ATP catalyzed by the enzyme seems appropriate to supply at least some of the reactions necessary for phototransduction, indicating that ATP could be regenerated from ADP directly on the disk membranes where the photoreception events take place.
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Affiliation(s)
- L Notari
- Institute of Biochemistry, University of Genoa, Italy
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36
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Cooper CB, Szerencsei RT, Schnetkamp PP. Spectrofluorometric detection of Na+/Ca(2+)-K+ exchange. Methods Enzymol 2000; 315:847-64. [PMID: 10736745 DOI: 10.1016/s0076-6879(00)15886-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- C B Cooper
- Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Alberta, Canada
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37
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Pepe IM, Panfoli I, Notari L, Morelli A. ATP synthesis in rod outer segments of bovine retina by the reversal of the disk Ca(2+) pump. Biochem Biophys Res Commun 2000; 268:625-7. [PMID: 10679254 DOI: 10.1006/bbrc.2000.2160] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Purified disk membranes from rod outer segments of the bovine retina were able to synthesize ATP with a maximal activity (about 52 nmoles ATP/min/mg of protein) at physiological calcium concentrations. This activity was inhibited by vanadate or thapsigargin but not by oligomycin, suggesting the reversal functioning of the disk Ca(2+)-ATPase, which would act as a ATP synthesizer at the expense of the calcium gradient between the disks and the cytoplasm of the rod outer segment. The results are discussed in terms of the need of an immediate source of ATP on the disk membranes where the energy is required to supply the rapid reactions of the photoreception processes.
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Affiliation(s)
- I M Pepe
- Istituto di Biofisica, Istituto di Chimica Biologica, Universita' di Genova, Corso Europa 30, Genoa, 16132, Italy
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38
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Abstract
Recent studies on rhodopsin structure and function are reviewed and the properties of vertebrate as well as invertebrate rhodopsin described. Open issues such as the 'red shift' of the absorbance spectra are emphasized in the light of the present model of the retinal-binding pocket. The processes that restore the rhodopsin content in photoreceptors are also presented with a comparison between vertebrate and invertebrate visual systems. The central role of rhodopsin in the phototransduction cascade becomes evident by examining the main reports on light-activated conformational changes of rhodopsin and its interaction with transducin. Shut-off mechanisms are considered by reporting the studies on the sites of rhodopsin phosphorylation and arrestin binding. Furthermore, recent findings on the energetics of phototransduction point out that the ATP needed for photoreception in vertebrates is synthesized in the outer segments where phototransduction events take place.
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Affiliation(s)
- I M Pepe
- Institute of Biophysics, Faculty of Medicine, University of Genoa, Italy.
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39
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Palczewski K, Subbaraya I, Gorczyca WA, Helekar BS, Ruiz CC, Ohguro H, Huang J, Zhao X, Crabb JW, Johnson RS. Molecular cloning and characterization of retinal photoreceptor guanylyl cyclase-activating protein. Neuron 1994; 13:395-404. [PMID: 7520254 DOI: 10.1016/0896-6273(94)90355-7] [Citation(s) in RCA: 314] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Guanylyl cyclase-activating protein (GCAP) is thought to mediate Ca(2+)-sensitive regulation of guanylyl cyclase (GC), a key event in recovery of the dark state of rod photoreceptors following light exposure. Here, we characterize GCAP from several vertebrate species by molecular cloning and provide evidence that GCAP contains a heterogeneously acylated N-terminal region that interacts with GC. Vertebrate GCAPs consist of 201-205 amino acids, and sequence analysis indicates the presence fo three EF hand Ca(2+)-binding motifs. These results establish that GCAP is a novel photoreceptor-specific member of a large family of Ca(2+)-binding proteins and suggest that it participates in the Ca(2+)-binding proteins and suggest that it participates in the Ca(2+)-sensitive activation of GC.
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Affiliation(s)
- K Palczewski
- Department of Ophthalmology, University of Washington, Seattle 98195
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40
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Panfoli I, Morelli A, Pepe IM. Calcium pump in the disk membranes isolated from bovine retinal rod outer segments. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1994; 24:187-94. [PMID: 7965415 DOI: 10.1016/1011-1344(94)07019-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The existence of a Ca2+ pump in rod outer segment disks of bovine retina is strongly suggested by the isolation on sodium dodecyl sulfate polyacrylamide gel electrophoresis of a hydroxylamine-sensitive phosphorylated intermediate (E-P) of molecular mass of about 100 kDa as well as by measurements of active calcium transport and adenosine 5'-triphosphate (ATP) hydrolysis. Active Ca2+ uptake by disks was dependent on the presence of Mg(2+)-ATP, was inhibited by vanadate or lanthanum and appeared poorly sensitive to calmodulin. ATP hydrolysis by disk membranes was a function of free Ca2+ concentration in the absence of exogenous Mg2+. The presence of a Ca2+ pump on disk membranes is discussed in terms of its possible role in Ca2+ ion buffering during photoreceptor cell functioning.
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Affiliation(s)
- I Panfoli
- Istituto Policattedra di Chimica Biologica, Università, Genoa, Italy
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41
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Palczewski K, Buczylko J, Ohguro H, Annan RS, Carr SA, Crabb JW, Kaplan MW, Johnson RS, Walsh KA. Characterization of a truncated form of arrestin isolated from bovine rod outer segments. Protein Sci 1994; 3:314-24. [PMID: 8003967 PMCID: PMC2142797 DOI: 10.1002/pro.5560030215] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The inactivation of photolyzed rhodopsin requires phosphorylation of the receptor and binding of a 48-kDa regulatory protein, arrestin. By binding to phosphorylated photolyzed rhodopsin, arrestin inhibits G protein (Gt) activation and blocks premature dephosphorylation, thereby preventing the reentry of photolyzed rhodopsin into the phototransduction pathway. In this study, we isolated a 44-kDa form of arrestin, called p44, from fresh bovine rod outer segments and characterized its structure and function. A partial primary structure of p44 was established by a combination of mass spectrometry and automated Edman degradation of proteolytic peptides. The amino acid sequence was found to be identical with arrestin, except that the C-terminal 35 residues (positions 370-404) are replaced by a single alanine. p44 appeared to be generated by alternative mRNA splicing, because intron 15 interrupts within the nucleotide codon for 369Ser in the arrestin gene. Functionally, p44 binds avidly to photolyzed or phosphorylated and photolyzed rhodopsin. As a consequence of its relatively high affinity for bleached rhodopsin, p44 blocks Gt activation. The binding characteristics of p44 set it apart from tryptic forms of arrestin (truncated at the N- and C-termini), which require phosphorylation of rhodopsin for tight binding. We propose that p44 is a novel splice variant of arrestin that could be involved in the regulation of Gt activation.
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Affiliation(s)
- K Palczewski
- Department of Ophthalmology, University of Washington, Seattle 98195
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42
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Azarian SM, Schlamp CL, Williams DS. Characterization of calpain II in the retina and photoreceptor outer segments. J Cell Sci 1993; 105 ( Pt 3):787-98. [PMID: 8408304 DOI: 10.1242/jcs.105.3.787] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Calpain II was purified to apparent homogeneity from bovine neural retinas. It was found to be biochemically similar to brain calpain II, purified by the same procedure, with respect to: subunit mobility in SDS-polyacrylamide gel electrophoresis; Ca2+ sensitivity; inhibition by calpeptin and other cysteine protease inhibitors; and optimal pH. Semithin cryosections were immuno-labeled with antibodies specific for the catalytic subunit of calpain II. Calpain II was detected in most layers of the retina, with the most pronounced label present in the plexiform layers (synaptic regions) and the photoreceptor outer segments. In dark-adapted retinas, the label was distributed throughout the outer segments. In light-adapted retinas, outer segment labeling was concentrated in the connecting cilium, and the inner segments were labeled. A partially pure preparation of calpain II from isolated rod outer segments was found to have the same biochemical characteristics as calpain II prepared in the same way from the whole retina. The enzyme was distributed fairly evenly between the cytosolic and cytoskeletal fractions of isolated rod outer segments. Immunoblots of the rod outer segment cytoskeleton were used to determine the susceptibility of known components of the actin-based cytoskeleton to proteolysis by calpain II in vitro. Actin was not proteolyzed at all, alpha-actinin was only slowly degraded, but myosin II heavy chain was rapidly proteolyzed. Actin filaments have been shown previously to be associated with myosin II and alpha-actinin in a small domain within the connecting cilium, where they play an essential role in the morphogenesis of new disk membranes. The localization of calpain II in the connecting cilium after light exposure, combined with the in vitro proteolysis of myosin II, suggests that calpain II could be involved in light-dependent regulation of disk membrane morphogenesis by proteolysis of myosin II.
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Affiliation(s)
- S M Azarian
- Laboratory of Cell Biology, School of Optometry, Indiana University, Bloomington 47405
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43
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Pongs O, Lindemeier J, Zhu XR, Theil T, Engelkamp D, Krah-Jentgens I, Lambrecht HG, Koch KW, Schwemer J, Rivosecchi R. Frequenin--a novel calcium-binding protein that modulates synaptic efficacy in the Drosophila nervous system. Neuron 1993; 11:15-28. [PMID: 8101711 DOI: 10.1016/0896-6273(93)90267-u] [Citation(s) in RCA: 296] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The T(X;Y)V7 rearrangement in Drosophila has originally been recognized as a Shaker-like mutant because of its behavioral and electrophysiological phenotype. The gene whose expression is altered by the V7 rearrangement has been characterized. It encodes a novel Ca(2+)-binding protein named frequenin, which is related to recoverin and visinin. In vitro, the frequenin protein functions like recoverin as a Ca(2+)-sensitive guanylyl cyclase activator. Anti-frequenin antibodies stain the central and peripheral nervous system in Drosophila embryos and in larval and adult tissue sections. Frequenin appears to be particularly enriched in synapses, such as the motor nerve endings at neuromuscular junctions. Neuromuscular junctions of transgenic flies, which overexpress frequenin upon heat shock, exhibit an extraordinarily enhanced, frequency-dependent facilitation of neurotransmitter release, with properties identical to those observed in V7 junctions. We propose that frequenin represents a new element for the Ca(2+)-dependent modulation of synaptic efficacy.
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Affiliation(s)
- O Pongs
- Zentrum für Molekulare Neurobiologie Institut für Neurale Signalverarbeitung, Hamburg, Federal Republic of Germany
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44
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Lambrecht HG, Koch KW. Phosphorylation of recoverin, the calcium-sensitive activator of photoreceptor guanylyl cyclase. FEBS Lett 1991; 294:207-9. [PMID: 1684552 DOI: 10.1016/0014-5793(91)80670-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Recoverin, a new calcium binding protein from bovine rod photoreceptor cells, activates guanylyl cyclase below a free calcium concentration of 200 nM. We show here that recoverin is phosphorylated by an endogenous kinase and Mg-ATP at the same decreased calcium concentration. The calcium-dependent activation of guanylyl cyclase is enhanced in the presence of ATP. We suggest that phosphorylation of recoverin reinforces the stimulation of guanylyl cyclase at decreased calcium concentrations.
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Affiliation(s)
- H G Lambrecht
- Institut für Biologische Informationsverarbeitung, Forschungszentrum Jülich, Germany
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45
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46
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Panfoli I, Morelli A, Pepe I. Calcium ion-regulated phospholipase C activity in bovine rod outer segments. Biochem Biophys Res Commun 1990; 173:283-8. [PMID: 2175180 DOI: 10.1016/s0006-291x(05)81054-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Bovine retinal rod outer segment membranes are enriched in a phosphoinositide-specific phosphodiesterase (phospholipase C) activity strictly modulated by free calcium ion concentration. The enzyme(s) was highly active on phosphatidylinositol 4,5-bisphosphate: maximal hydrolysis rate was attained at 10(-5)M Ca2+ and accounted for 91 +/- 4 nmoles hydrolyzed/min/mg of protein. The results support the notion that in vivo the enzyme(s) is regulated so as to conform to the phototransduction events.
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Affiliation(s)
- I Panfoli
- Istituto Policattedra di Chimica Biologica, Università degli Studi di Genova, Italy
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47
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Morelli A, Panfoli I, Pepe I. Detection of novel guanine nucleotide binding proteins in bovine retinal rod outer segments. Biochem Biophys Res Commun 1990; 170:719-25. [PMID: 2116796 DOI: 10.1016/0006-291x(90)92150-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In the rod outer segment membranes of the bovine retina at least two members of the small molecular weight guanine nucleotide binding proteins were identified by means of the technique of binding radiolabeled GTP to nitrocellulose Western blots of proteins separated by sodium dodecyl sulphate gel electrophoresis. Such proteins, of 23 and 25 kDa, are able to specifically bind guanine nucleotides after denaturing treatments, and are not labeled by pertussis or cholera toxin-catalyzed ADP-ribosylation. The binding site is specific for GTP.
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Affiliation(s)
- A Morelli
- Istituto Policattedra di Chimica Biologica, Università degli Studi di Genova, Italy
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48
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Pepe IM, Cugnoli C, Schwemer J. Rhodopsin reconstitution in bleached rod outer segment membranes in the presence of a retinal-binding protein from the honeybee. FEBS Lett 1990; 268:177-9. [PMID: 2143484 DOI: 10.1016/0014-5793(90)81002-6] [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: 12/30/2022]
Abstract
The physiological role of a retinal-binding protein from honeybee is investigated. This protein, upon previous loading with all-trans retinal and subsequent irradiation with monochromatic light of wavelength 490 nm, is able to promote the reconstitution of rhodopsin when added to a suspension of opsin membranes from bleached bovine rod outer segments. In this respect this retinal-binding protein could have a role very similar to that postulated for the well-known cephalopod retinochrome, that serves to catalyze the formation in the presence of light of 11-cis retinal in photo-receptor cells and to provide it for the reconstitution of rhodopsin during the visual cycle.
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Affiliation(s)
- I M Pepe
- Istituto di Cibernetica e Biofisica del CNR, Genova, Italy
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Williams DS, Shuster TA, Moldrawski MR, Blest AD, Farber DB. Isolation of rod outer segments on Percoll gradients: effect of specific protease inhibition. Exp Eye Res 1989; 49:439-44. [PMID: 2551708 DOI: 10.1016/0014-4835(89)90052-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rat rod outer segments (ROSs) were isolated by vortexing retinas and separating the detached components on performed Percoll gradients. A lighter band of 20 x 10(6) unsealed ROSs per ten retinas, and a heavier band of 60 x 10(6) sealed ROSs per ten retinas were obtained from each 12 ml gradient. The yield of sealed ROSs (but not unsealed ROSs) was increased up to twofold in the presence of the specific cysteine protease inhibitor, Ep-475. Aprotinin, pepstatin, PMSF, TPCK and EGTA plus EDTA had no effect. These results indicate that during isolation, ROSs are vulnerable to damage by cysteine protease activity either from damaged retinal cells or from within.
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Affiliation(s)
- D S Williams
- School of Optometry, Indiana University, Bloomington 47405
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Palczewski K, McDowell JH, Jakes S, Ingebritsen TS, Hargrave PA. Regulation of Rhodopsin Dephosphorylation by Arrestin. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)71543-3] [Citation(s) in RCA: 102] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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