Localization of the cyclic ADP-ribose-dependent calcium signaling pathway in bovine rod outer segments. 2007

Isabella Panfoli, and Silvia Ravera, and Andrea Fabiano, and Raffaella Magrassi, and Alberto Diaspro, and Alessandro Morelli, and Isidoro M Pepe
Department of Biology, University of Genoa, Genova, Italy. isabella.panfoli@unige.it

OBJECTIVE Calcium ions play a pivotal role in phototransduction. In this study, the presence and functional role of the adenosine diphosphoribosyl (ADPR)-cyclase-cyclic ADP-ribose (cADPR) system in bovine retinal rod outer segments (ROS) was investigated. METHODS A Ca(2+) release from osmotically intact ROS discs elicited by cADPR was studied in the presence of the Ca(2+) tracer fluo-3. Endogenous cyclic guanosine diphosphate ribose (cGDPR) formation in discs was investigated by spectrophotometric detection of its synthesis from nicotinamide guanine dinucleotide (NGD(+)). ADPR-cyclase was also investigated at a structural level on mildly denaturing SDS-PAGE by production of cyclic inosine diphosphate ribose from nicotinamide hypoxantine dinucleotide (NHD(+)). Western immunoblot analysis with a specific antibody was conducted to verify the presence of ryanodine-sensitive Ca(2+) channels (RyRs) in ROS discs. RESULTS cADPR-dependent Ca(2+) release was a linear function of extravesicular free Ca(2+) concentration, between 200 and 900 nM Ca(2+). When free Ca(2+) was 203 +/- 10 nM the mean Ca(2+) release was 23 +/- 3 pmol/mL per milligram protein. The average rate of cGDPR production was 13 +/- 2 nmol cGDPR/min per milligram protein, by a putative enzyme with an apparent molecular mass of 53 +/- 1 kDa. ROS ADPR-cyclase was localized in the membranous fraction. No nicotinamide adenine dinucleotide glycohydrolase (NADase) activity was detected. The presence of RyR channels in pure disc preparations was confirmed by confocal laser scanning microscopy. CONCLUSIONS A cADPR metabolism may be present in retinal ROS discs, which may be Ca(2+) stores operated by cADPR. A model is proposed for the physiological role of cADPR-mediated Ca(2+) release in bovine ROS.

UI MeSH Term Description Entries
D007292 Inosine Nucleotides Inosine Phosphates,Nucleotides, Inosine,Phosphates, Inosine
D009244 NAD+ Nucleosidase An enzyme that catalyzes the hydrolysis of nicotinamide adenine dinucleotide (NAD) to NICOTINAMIDE and ADENOSINE DIPHOSPHATE RIBOSE. Some are extracellular (ectoenzymes).The enzyme from some sources also catalyses the hydrolysis of nicotinamide adenine dinucleotide phosphate (NADP). DPNase,Diphosphopyridine Nucleotidase,NAD+ Glycohydrolase,NADase,Diphosphopyridine Nucleotidases,Ecto-NAD+ Glycohydrolase,NAD(P) Nucleosidase,NAD+ Nucleosidases,NAD-Glycohydrolase,NAD-Glycohydrolases,NADP Nucleosidase,NADP-Glycohydrolase,NADases,Ecto NAD+ Glycohydrolase,Glycohydrolase, Ecto-NAD+,Glycohydrolase, NAD+,NAD Glycohydrolase,NAD Glycohydrolases,NADP Glycohydrolase,Nucleosidase, NAD+,Nucleosidase, NADP,Nucleosidases, NAD+,Nucleotidase, Diphosphopyridine,Nucleotidases, Diphosphopyridine
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D004591 Electrophoresis, Polyacrylamide Gel Electrophoresis in which a polyacrylamide gel is used as the diffusion medium. Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D006156 Guanosine Diphosphate Sugars Esters formed between the aldehydic carbon of sugars and the terminal phosphate of guanosine diphosphate. GDP Sugars,Diphosphate Sugars, Guanosine,Sugars, GDP,Sugars, Guanosine Diphosphate
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012243 Rhodopsin A purplish-red, light-sensitive pigment found in RETINAL ROD CELLS of most vertebrates. It is a complex consisting of a molecule of ROD OPSIN and a molecule of 11-cis retinal (RETINALDEHYDE). Rhodopsin exhibits peak absorption wavelength at about 500 nm. Visual Purple
D012374 Rod Cell Outer Segment The portion of a retinal rod cell situated between the ROD INNER SEGMENT and the RETINAL PIGMENT EPITHELIUM. It contains a stack of photosensitive disk membranes laden with RHODOPSIN. Rod Outer Segment,Rod Outer Segments,Outer Segment, Rod,Outer Segments, Rod
D013054 Spectrophotometry, Atomic Spectrophotometric techniques by which the absorption or emmision spectra of radiation from atoms are produced and analyzed. Spectrophotometry, Atomic Absorption,AA Spectrophotometry,AE Spectrophotometry,Atomic Absorption Spectrophotometry,Atomic Emission Spectrophotometry,Atomic Spectrophotometry,Inductively Coupled Plasma Atomic Emission Spectrophotometry,Inductively Coupled Plasma Atomic Emission Spectroscopy,Spectrophotometry, Atomic Emission,AA Spectrophotometries,AE Spectrophotometries,Absorption Spectrophotometry, Atomic,Emission Spectrophotometry, Atomic,Spectrophotometries, AA,Spectrophotometries, AE,Spectrophotometry, AA,Spectrophotometry, AE

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