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Koch KW, Dell'Orco D. Protein and Signaling Networks in Vertebrate Photoreceptor Cells. Front Mol Neurosci 2015; 8:67. [PMID: 26635520 PMCID: PMC4646965 DOI: 10.3389/fnmol.2015.00067] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/26/2015] [Indexed: 01/10/2023] Open
Abstract
Vertebrate photoreceptor cells are exquisite light detectors operating under very dim and bright illumination. The photoexcitation and adaptation machinery in photoreceptor cells consists of protein complexes that can form highly ordered supramolecular structures and control the homeostasis and mutual dependence of the secondary messengers cyclic guanosine monophosphate (cGMP) and Ca2+. The visual pigment in rod photoreceptors, the G protein-coupled receptor rhodopsin is organized in tracks of dimers thereby providing a signaling platform for the dynamic scaffolding of the G protein transducin. Illuminated rhodopsin is turned off by phosphorylation catalyzed by rhodopsin kinase (GRK1) under control of Ca2+-recoverin. The GRK1 protein complex partly assembles in lipid raft structures, where shutting off rhodopsin seems to be more effective. Re-synthesis of cGMP is another crucial step in the recovery of the photoresponse after illumination. It is catalyzed by membrane bound sensory guanylate cyclases (GCs) and is regulated by specific neuronal Ca2+-sensor proteins called guanylate cyclase-activating proteins (GCAPs). At least one GC (ROS-GC1) was shown to be part of a multiprotein complex having strong interactions with the cytoskeleton and being controlled in a multimodal Ca2+-dependent fashion. The final target of the cGMP signaling cascade is a cyclic nucleotide-gated (CNG) channel that is a hetero-oligomeric protein located in the plasma membrane and interacting with accessory proteins in highly organized microdomains. We summarize results and interpretations of findings related to the inhomogeneous organization of signaling units in photoreceptor outer segments.
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Affiliation(s)
- Karl-Wilhelm Koch
- Department of Neurosciences, Biochemistry Group, University of Oldenburg Oldenburg, Germany
| | - Daniele Dell'Orco
- Department of Neurological, Biomedical and Movement Sciences, Section of Biological Chemistry and Center for BioMedical Computing (CBMC), University of Verona Verona, Italy
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Rajanikanth V, Sharma AK, Rajyalakshmi M, Chandra K, Chary KVR, Sharma Y. Liaison between Myristoylation and Cryptic EF-Hand Motif Confers Ca2+ Sensitivity to Neuronal Calcium Sensor-1. Biochemistry 2015; 54:1111-22. [DOI: 10.1021/bi501134g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Anand Kumar Sharma
- CSIR-Centre for
Cellular and Molecular Biology (CCMB), Hyderabad 500007, India
| | - Meduri Rajyalakshmi
- CSIR-Centre for
Cellular and Molecular Biology (CCMB), Hyderabad 500007, India
| | - Kousik Chandra
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Kandala V. R. Chary
- Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
- Center
for Interdisciplinary Sciences, Tata Institute of Fundamental Research, Hyderabad 500075, India
| | - Yogendra Sharma
- CSIR-Centre for
Cellular and Molecular Biology (CCMB), Hyderabad 500007, India
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Biophysical investigation of retinal calcium sensor function. Biochim Biophys Acta Gen Subj 2011; 1820:1228-33. [PMID: 22020050 DOI: 10.1016/j.bbagen.2011.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/05/2011] [Accepted: 10/06/2011] [Indexed: 11/22/2022]
Abstract
BACKGROUND Neuronal calcium sensor proteins represent a subgroup of the family of EF-hand calcium binding proteins. Members of this subgroup are the guanylate cyclase-activating proteins and recoverin, which operate as important calcium sensors in retinal photoreceptor cells. Physiological and biochemical data indicate that these proteins participate in shaping the photoreceptor light response. SCOPE OF REVIEW Biophysical methods have been widely applied to investigate the molecular properties of retinal calcium binding proteins like the guanylate cyclase-activating proteins and recoverin. Properties include the determination of calcium affinities by isotope techniques and spectroscopical approaches. Conformational changes are investigated for example by tryptophan fluorescence emission. A special focus of this review is laid on a new experimental approach to study conformational changes in calcium binding proteins by surface plasmon resonance spectroscopy. In addition this technique has been employed for measuring the calcium-dependent binding of calcium sensors to membranes. MAJOR CONCLUSIONS Biophysical approaches provide valuable information about key properties of calcium sensor proteins involved in intracellular signalling. Parameters of their molecular properties like calcium binding and conformational changes help to define their physiological role derived from cellular, genetic or physiological studies. GENERAL SIGNIFICANCE Calcium is an important second messenger in intracellular signaling. Calcium signals are propagated via calcium binding proteins that are able to discriminate between incremental differences in intracellular calcium and that regulate their targets with high precision and specificity. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling.
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Gensch T, Komolov KE, Senin II, Philippov PP, Koch KW. Ca2+-dependent conformational changes in the neuronal Ca2+-sensor recoverin probed by the fluorescent dye Alexa647. Proteins 2007; 66:492-9. [PMID: 17078090 DOI: 10.1002/prot.21231] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Recoverin belongs to the superfamily of EF-hand Ca2+-binding proteins and operates as a Ca2+-sensor in vertebrate photoreceptor cells, where it regulates the activity of rhodopsin kinase GRK1 in a Ca2+-dependent manner. Ca2+-dependent conformational changes in recoverin are allosterically controlled by the covalently attached myristoyl group. The amino acid sequence of recoverin harbors a unique cysteine at position 38. The cysteine can be modified by the fluorescent dye Alexa647 using a maleimide-thiol coupling step. Introduction of Alexa647 into recoverin did not disturb the biological function of recoverin, as it can regulate rhodopsin kinase activity like unlabeled recoverin. Performance of the Ca2+-myristoyl switch of labeled recoverin was monitored by Ca2+-dependent association with immobilized lipids using surface plasmon resonance spectroscopy. When the Ca2+-concentration was varied, labeled myristoylated recoverin showed a 37%-change in fluorescence emission and a 34%-change in excitation intensity, emission and excitation maxima shifted by 6 and 18 nm, respectively. In contrast, labeled nonmyristoylated recoverin exhibited only minimal changes. Time-resolved fluorescence measurements showed biexponentiell fluorescence decay, in which the slower time constant of 2 ns was specifically influenced by Ca2+-induced conformational changes. A similar influence on the slower time constant was observed with the recoverin mutant RecE85Q that has a disabled EF-hand 2, but no such influence was detected with the mutant RecE121Q (EF-hand 3 is nonfunctional) that contains the myristoyl group in a clamped position. We conclude from our results that Alexa647 bound to cysteine 38 can monitor the conformational transition in recoverin that is under control of the myristoyl group.
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Affiliation(s)
- Thomas Gensch
- IBI-1, Forschungszentrum Jülich, Jülich D-52425, Germany
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Weiergräber OH, Senin II, Zernii EY, Churumova VA, Kovaleva NA, Nazipova AA, Permyakov SE, Permyakov EA, Philippov PP, Granzin J, Koch KW. Tuning of a neuronal calcium sensor. J Biol Chem 2006; 281:37594-602. [PMID: 17015448 DOI: 10.1074/jbc.m603700200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Recoverin is a Ca(2+)-regulated signal transduction modulator expressed in the vertebrate retina that has been implicated in visual adaptation. An intriguing feature of recoverin is a cluster of charged residues at its C terminus, the functional significance of which is largely unclear. To elucidate the impact of this segment on recoverin structure and function, we have investigated a mutant lacking the C-terminal 12 amino acids. Whereas in myristoylated recoverin the truncation causes an overall decrease in Ca(2+) sensitivity, results for the non-myristoylated mutant indicate that the truncation primarily affects the high affinity EF-hand 3. The three-dimensional structure of the mutant has been determined by x-ray crystallography. In addition to significant changes in average coordinates compared with wild-type recoverin, the structure provides strong indication of increased conformational flexibility, particularly in the C-terminal domain. Based on these observations, we propose a novel role of the C-terminal segment of recoverin as an internal modulator of Ca(2+) sensitivity.
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Affiliation(s)
- Oliver H Weiergräber
- Institut für Biologische Informationsverarbeitung (IBI-2, Biologische Strukturforschung), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
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Senin II, Bosch L, Ramon E, Zernii EY, Manyosa J, Philippov PP, Garriga P. Ca2+/recoverin dependent regulation of phosphorylation of the rhodopsin mutant R135L associated with retinitis pigmentosa. Biochem Biophys Res Commun 2006; 349:345-52. [PMID: 16934219 DOI: 10.1016/j.bbrc.2006.08.048] [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] [Received: 08/04/2006] [Accepted: 08/11/2006] [Indexed: 11/19/2022]
Abstract
No single molecular mechanism accounts for the effect of mutations in rhodopsin associated with retinitis pigmentosa. Here we report on the specific effect of a Ca2+/recoverin upon phosphorylation of the autosomal dominant retinitis pigmentosa R135L rhodopsin mutant. This mutant shows specific features like impaired G-protein signaling but enhanced phosphorylation in the shut-off process. We now report that R135L hyperphosphorylation by rhodopsin kinase is less efficiently inhibited by Ca2+/recoverin than wild-type rhodopsin. This suggests an involvement of Ca2+/recoverin into the molecular pathogenic effect of the mutation in retinitis pigmentosa which is the cause of rod photoreceptor cell degeneration. This new proposed role of Ca2+/recoverin may be one of the specific features of the proposed new Type III class or rhodopsin mutations associated with retinitis pigmentosa.
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Affiliation(s)
- Ivan I Senin
- Department of Cell Signalling, A. N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Russia
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Abstract
In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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Senin II, Höppner-Heitmann D, Polkovnikova OO, Churumova VA, Tikhomirova NK, Philippov PP, Koch KW. Recoverin and rhodopsin kinase activity in detergent-resistant membrane rafts from rod outer segments. J Biol Chem 2004; 279:48647-53. [PMID: 15355976 DOI: 10.1074/jbc.m402516200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cholesterol-rich membranes or detergent-resistant membranes (DRMs) have recently been isolated from bovine rod outer segments and were shown to contain several signaling proteins such as, for example, transducin and its effector, cGMP-phosphodiesterase PDE6. Here we report the presence of rhodopsin kinase and recoverin in DRMs that were isolated in either light or dark conditions at high and low Ca2+ concentrations. Inhibition of rhodopsin kinase activity by recoverin was more effective in DRMs than in the initial rod outer segment membranes. Furthermore, the Ca2+ sensitivity of rhodopsin kinase inhibition in DRMs was shifted to lower free Ca2+ concentration in comparison with the initial rod outer segment membranes (IC50=0.76 microm in DRMs and 1.91 microm in rod outer segments). We relate this effect to the high cholesterol content of DRMs because manipulating the cholesterol content of rod outer segment membranes by methyl-beta-cyclodextrin yielded a similar shift of the Ca2+-dependent dose-response curve of rhodopsin kinase inhibition. Furthermore, a high cholesterol content in the membranes also increased the ratio of the membrane-bound form of recoverin to its cytoplasmic free form. These data suggest that the Ca2+-dependent feedback loop that involves recoverin is spatially heterogeneous in the rod cell.
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Affiliation(s)
- Ivan I Senin
- A. N. Belozersky Institute of Physico-Chemical Biology, M. V. Lomonosov Moscow State University, 119992 Moscow, Russia
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Krishnan A, Venkataraman V, Fik-Rymarkiewicz E, Duda T, Sharma RK. Structural, biochemical, and functional characterization of the calcium sensor neurocalcin delta in the inner retinal neurons and its linkage with the rod outer segment membrane guanylate cyclase transduction system. Biochemistry 2004; 43:2708-23. [PMID: 15005606 DOI: 10.1021/bi035631v] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study documents the detailed biochemical, structural, and functional identity of a novel Ca(2+)-modulated membrane guanylate cyclase transduction system in the inner retinal neurons. The guanylate cyclase is the previously characterized ROS-GC1 from the photoreceptor outer segments (PROS), and its new modulator is neurocalcin delta. At the membrane, the myristoylated form of neurocalcin delta senses submicromolar increments in free Ca(2+), binds to its specific ROS-GC1 domain, and stimulates the cyclase. Neurocalcin delta is not present in PROS, indicating the absence of the pathway in the outer segments and the dissociation of its linkage with phototransduction. Thus, the pathway is linked specifically with the visual transduction machinery in the secondary neurons of the retina. With the inclusion of this pathway, the findings broaden the understanding of the existing mechanisms showing how ROS-GC1 is able to receive and transduce diverse Ca(2+) signals into the cell-specific generation of second-messenger cyclic GMP in the retinal neurons.
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Affiliation(s)
- Anuradha Krishnan
- The Unit of Regulatory and Molecular Biology, Department of Cell Biology, SOM and NJMS, University of Medicine and Dentistry of New Jersey, Stratford, New Jersey 08084, USA
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Chehab EW, Patharkar OR, Hegeman AD, Taybi T, Cushman JC. Autophosphorylation and subcellular localization dynamics of a salt- and water deficit-induced calcium-dependent protein kinase from ice plant. PLANT PHYSIOLOGY 2004; 135:1430-46. [PMID: 15247393 PMCID: PMC519060 DOI: 10.1104/pp.103.035238] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2003] [Revised: 04/19/2004] [Accepted: 04/26/2004] [Indexed: 05/18/2023]
Abstract
A salinity and dehydration stress-responsive calcium-dependent protein kinase (CDPK) was isolated from the common ice plant (Mesembryanthemum crystallinum; McCPK1). McCPK1 undergoes myristoylation, but not palmitoylation in vitro. Removal of the N-terminal myristate acceptor site partially reduced McCPK1 plasma membrane (PM) localization as determined by transient expression of green fluorescent protein fusions in microprojectile-bombarded cells. Removal of the N-terminal domain (amino acids 1-70) completely abolished PM localization, suggesting that myristoylation and possibly the N-terminal domain contribute to membrane association of the kinase. The recombinant, Escherichia coli-expressed, full-length McCPK1 protein was catalytically active in a calcium-dependent manner (K0.5 = 0.15 microm). Autophosphorylation of recombinant McCPK1 was observed in vitro on at least two different Ser residues, with the location of two sites being mapped to Ser-62 and Ser-420. An Ala substitution at the Ser-62 or Ser-420 autophosphorylation site resulted in a slight increase in kinase activity relative to wild-type McCPK1 against a histone H1 substrate. In contrast, Ala substitutions at both sites resulted in a dramatic decrease in kinase activity relative to wild-type McCPK1 using histone H1 as substrate. McCPK1 undergoes a reversible change in subcellular localization from the PM to the nucleus, endoplasmic reticulum, and actin microfilaments of the cytoskeleton in response to reductions in humidity, as determined by transient expression of McCPK1-green fluorescent protein fusions in microprojectile-bombarded cells and confirmed by subcellular fractionation and western-blot analysis of 6x His-tagged McCPK1.
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Affiliation(s)
- E Wassim Chehab
- Department of Biochemistry/MS200, University of Nevada, Reno, Nevada 89557-0014, USA
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Ramachandran backbone potential energy surfaces of aspartic acid and aspartate residues: implications on allosteric sites in receptor–ligand complexations. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/j.theochem.2003.08.055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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