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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine triphosphate (ATP) is a potent agonist of surfactant secretion from type II pneumocytes. The extracellular ATP signal is transduced by both P1- and P2-purinergic pathways, which respectively initiate cyclic adenosine monophosphate formation and phosphatidyl inositol hydrolysis to inositol phosphates (Ins P). We investigated the role of inositol triphosphate (Ins P3) isomer formation in this signal transduction pathway. Primary cultures of rat type II pneumocytes were labeled with 30 microCi [3H]myoinositol/5 x 10(6) cells for 48 h. After preincubation with 10 mM LiCl for 20 min, the cells were stimulated with ATP (10(-4) M) and then were rapidly frozen with liquid N2. The Ins P3 isomers were analyzed by high performance liquid chromatography. A 4-fold increase in Ins 1,4,5 P3 occurred within 2 s after stimulation with ATP, decreased to half maximum by 60 s, and returned close to baseline values by 2 min. In contrast, Ins 1,3,4 P3 did not increase until 15 s, peaked by 60 s with a 4-fold increase, and returned to baseline values by 2 min. Intracellular calcium [( Ca2+]i), measured as Indo-1 fluorescence, also increased 3-fold within 2 s of exposure to ATP (10(-4)M) and fell to a plateau level 25% above baseline values by 10 s. We conclude that Ins 1,4,5 P3 formation and [Ca2+]i release both occur rapidly after exposure of type II pneumocytes to extracellular ATP. We speculate that these early events in type II pneumocyte signal transduction play a role in the initiation of stimulation of surfactant secretion by extracellular ATP.
Am J Respir Cell Mol Biol 1991 Jun
PMID:Role of inositol triphosphate isomer formation in type II pneumocyte signal transduction. 164 77

In this paper we report that three different rat liver mitochondrial fractions, differing in density, exhibit differential effects when the animals are made hypo- or hyperthyroid. The investigations have been performed by correlating the protein content, the succinic dehydrogenase behaviour and the respiratory features of the three fractions in different thyroid states with morphometric-stereologic analysis the electron micrographic level. The results indicate that the thyroid hormone influences both the mass and the functionality of the heavy (H) and light (L) fraction. In hypothyroid rats the H fraction increases (+43%) while the L fraction decreases (-32%) and their respiratory activity is drastically reduced. Adenosine triphosphate (ATP) synthesis in the H fraction is also inhibited. Triiodothyronine (T3) administration to the above animals restores the values observed in control rats. At morphometric level we note in hypothyroid rats an increase in the number of mitochondria together with a concomitant increase in the average volume of a single mitochondrion. We are inclined to explain the above results through an action exerted by T3 on a hypothetical mitochondrial cycle starting with the formation of light organelles from heavy ones.
Mol Cell Endocrinol 1989 Mar
PMID:The effect of thyroid state on respiratory activities of three rat liver mitochondrial fractions. 274 21

Aminoacyl-tRNA synthetases are capable of converting 5'-ATP into 5',5'-diadenosine tetraphosphate. The reaction reflects the reversal of enzyme-bound aminoacyl-adenylate by ATP instead of PPi. In the case of a few prokaryotic as well as eukaryotic aminoacyl-tRNA synthetases, the initial rate of diadenosine tetraphosphate synthesis can be greatly enhanced upon adding small amounts of zinc. This observation enables us to establish a relationship between diadenosine tetraphosphate, a nucleotide possibly involved in controlling cell proliferation, and a metallic cofactor, which is believed to play a role in tumour growth.
Mol Cell Biochem 1983
PMID:The role of zinc in 5',5'-diadenosine tetraphosphate production by aminoacyl-transfer RNA synthetases. 634 51

Adenosine triphosphate (ATP) acting through epithelial nucleotide receptors exerts multiple physiologic actions on airway mucociliary clearance and caliber. However, the effect of ATP on arachidonate metabolism in the airway remains unknown. In this study, the ability of ATP to regulate eicosanoid production was studied in vitro in full-thickness rabbit tracheal strips and separately in rabbit epithelial explant cultures. In the freshly isolated strips, ATP increased prostaglandin E2 (PGE2) release in a dose-dependent fashion, with an activation threshold at 10 microM ATP and a 3.5-fold increase in PGE2 output at 1 mM ATP. Epithelium removal decreased 1 mM ATP-evoked PGE2 release by 68%. Reverse-phase, high-pressure liquid chromatography (HPLC) of media from 3H-arachidonic acid-incubated epithelial explants exposed to 1 mM ATP demonstrated increased output of the cyclooxygenase products PGE2 and prostaglandin F2a (PGF2a). Other identifiable eicosanoids did not increase. The concentration-response for ATP-induced PGE2 release by explants was similar to that of tracheal strips. PGE2 release by 1 mM ATP was 27% of that elicited by ionomycin (10 microM) and was markedly inhibited by indomethacin (10 microM). Purinoceptor agonist-stimulated PGE2 release by the epithelium yielded a rank order of potency of uridine triphosphate (UTP) > or = ATP > 2-methylthio-ATP (2MeSATP) >> alpha,beta-methyleneadenosine-5'-triphosphate (AMP-CPP) > or = adenosine. These results indicate that ATP, acting primarily through an epithelial P2-purinoceptor similar to the P2a subtype, stimulates eicosanoid metabolism in rabbit airway epithelium via the cyclooxygenase pathway, producing PGE2 as the predominant species.
Am J Respir Cell Mol Biol 1995 Oct
PMID:Eicosanoid production in rabbit tracheal epithelium by adenine nucleotides: mediation by P2-purinoceptors. 754 70

Adenosine triphosphate metabolism in caudal epididymis bovine spermatozoa was studied. Measurements by HPLC at appropriate time intervals of the spermatozoa content of ATP and its derivatives were carried out under different experimental conditions. In the presence of 2-D-glucose, cellular ATP was transformed almost quantitatively into ADP and AMP at a rate of 2.3 nmol/min per 10(8) cells. At the same time, ADP and AMP accumulated at a rate of 1.52 and 0.58 nmol/min per 10(8) cells, respectively. In the first 4 min, about 50% of total ATP was degraded, the AEC of the cells dropped to non-physiological values while the content of other nucleosides did not vary significantly. Inorganic P(i) content also remained unchanged. Under non-induced conditions up to 240 min, no variations of the adenylic content and of the EC value was observed. Under induced and non-induced conditions, IMP and adenosine were not detected within the spermatozoa. The lack of IMP might be ascribed either to the absence of AMP deaminase, whose activity has never been found in the spermatozoa or to the intracellular environment which down regulates the activity of the enzyme. In order to explain low levels and absence of variations of adenosine, several enzymic investigations were carried out. Adenosine kinase activity was not determined, therefore the transformation of adenosine into AMP had to be excluded. Nevertheless, enzymic activities potentially able to dephosphorylate the formed AMP are present in the spermatozoa. Our findings are indicative of the existence in the spermatozoa of acid and alkaline phosphatase and of 5'-nucleotidase membrane-derived.(ABSTRACT TRUNCATED AT 250 WORDS)
Comp Biochem Physiol B Biochem Mol Biol 1995 Mar
PMID:Adenosine triphosphate catabolism in bovine spermatozoa. 758 34

Kinetic studies on the two major isoforms of Serratia marcescens nuclease, Sm2 and Sm1, have revealed them to be functionally equivalent. Both isoforms display marked substrate inhibition by DNA and RNA. They both require magnesium for optimal activity, but retain low catalytic activity in its absence. Both are moderately inhibited by mononucleotides including 5'-ATP, 5'-AMP, 5'-TTP and 3'5'-pTp. The two strongest mononucleotide inhibitors studied, 5'-ATP and 5'-AMP, display inhibition constants, KI, on the order of 10(-5) M. In assessing the strength of mononucleotide inhibition the type of nucleotide base appears to be more important than the number of phosphate moieties.
Biochem Mol Biol Int 1994 Aug
PMID:Kinetic studies of the Serratia marcescens extracellular nuclease isoforms. 780 50

Adenosine triphosphate (ATP) regulates surfactant phospholipid secretion from alveolar type II cells by interacting with P2-purinoceptors on the alveolar type II cell surface. To further characterize regulation of surfactant secretion, we have cloned the type II cell P2u-purinoceptor and expressed a functional receptor in an unrelated cell line. The coding sequence of the P2u clone isolated from a type II cell cDNA library was 1.1 kb, encoding a putative protein of 374 amino acids. The putative protein demonstrated > 97% homology with the P2u-purinoceptor previously identified in the hybrid neuroblastoma x glioma cell line, NG 108-15, 87% homology to the recently cloned human P2u-purinoceptor, and 34% homology to the P2u-purinoceptor cloned from chicken brain. The putative type II cell P2u protein contains seven membrane-spanning domains, characteristic of G-protein-coupled receptors. The type II cell P2u-purinoceptor nucleotide sequence also demonstrated > 95% homology to the nucleotide sequence of the NG 108-15 clone. However, the type II cell cDNA also demonstrated presence of an additional 208 bp insert in the 5' untranslated region, which was not present in the NG 108-15 clone. Using reverse transcriptase polymerase chain reaction, we examined expression of the two different sizes of mRNA in various rat tissues. Only the larger type II cell mRNA was expressed in rat heart, kidney, lung, spleen, and testis, with no expression of P2u-purinoceptor mRNA noted in brain or liver. The smaller species of mRNA was only detected in mouse N18-TG2 cells, and these cells expressed a larger species as well, found in the rat tissues noted.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1995 Jan
PMID:Cloning and expression of the alveolar type II cell P2u-purinergic receptor. 781 68

We have characterized a gene encoding an Adenosine triphosphate (ATP) Binding Cassette (ABC) transmembrane protein from Trichomonas vaginalis, an early-diverging protozoan parasite. This gene, Tvpgp1, encodes a 589-amino acid protein with an amino-terminal hydrophobic region, 6 potential membrane-spanning segments and a carboxy-terminal ATP binding site. Tvpgp1 is most similar in sequence to mammalian P-glycoproteins, 170 kDa transport proteins which are frequently overexpressed in multiple drug-resistant (Mdr) tumor cell lines. However, Tvpgp1 is half the size of typical P-glycoproteins which are tandem duplications. These data suggest that the duplication/fusion events which gave rise to the bipartite structure comprised of 2 similar halves which characterize eukaryotic P-glycoproteins may have occurred after the divergence of trichomonads (Parabasalia) from the main line of eukaryotic evolutionary descent. We have examined 7 metronidazole resistant strains of T. vaginalis to determine whether the Tvpgp1 gene is overexpressed or amplified. 2 drug resistant strains show a 2-3-fold overexpression and one shows a 20-fold overexpression of Tvpgp mRNA. The gene is not amplified in any of the drug resistant strains. On the contrary, 4 of the 7 resistant strains lack one of 2 Tvpgp genes found in drug-sensitive strains.
Mol Biochem Parasitol 1994 Jul
PMID:Analysis of a single-domain P-glycoprotein-like gene in the early-diverging protist Trichomonas vaginalis. 798 75

Erythromycin (EM) therapy is known to decrease airway secretion in chronic inflammatory airway diseases such as diffuse panbronchiolitis. Airway secretion is regulated by intracellular Ca2+ concentration ([Ca2+]i). To elucidate the intracellular site of action of EM in airway epithelium, we examined the effect of EM on Ca2+ dynamics in cultured bovine tracheal epithelial cells using fura-2. EM per se did not cause any change in [Ca2+]i. Adenosine triphosphate (ATP; 10(-4) M) induced a biphasic [Ca2+]i increase, consisting of a transient response followed by a sustained response. Pretreatment of cells with EM had little effect on the ATP-induced transient Ca2+ response but substantially reduced the sustained response in a dose-dependent manner. Clarithromycin, another 14-membered ring macrolide, likewise showed the inhibitory effect, but ampicillin and cephasolin did not. Uridine triphosphate (UTP; 10(-4) M) induced a biphasic [Ca2+]i increase similar to ATP, and the UTP-induced sustained Ca2+ response was also inhibited by EM. In Ca2+-deficient medium (1 mM ethyleneglycol-bis-(beta-aminoethyl ether)-N, N'-tetraacetic acid [EGTA]) or in the presence of La3+, the sustained Ca2+ response disappeared, suggesting that EM may inhibit Ca2+ influx induced by P2u purinoceptor stimulation. In single-cell Ca2+ image analysis, low concentration of ATP (10(-6) M) induced Ca2+ oscillations, which were also inhibited by EM. The disappearance of [Ca2+]i oscillations after addition of EM was similar to that after addition of EGTA. These results suggest that EM may decrease Ca2+-dependent airway secretion by inhibiting agonist-stimulated Ca2+ influx.
Am J Respir Cell Mol Biol 1998 Nov
PMID:Erythromycin inhibits ATP-induced intracellular calcium responses in bovine tracheal epithelial cells. 980 44

Adenosine triphosphate (ATP) and catecholamine (CA) released from cultured porcine adrenal chromaffin cells were continuously measured with an ATP photometer (luciferin-luciferase method) and electrochemical detector, respectively. Application of acetylcholine (ACh, 0.1 mM) or high K+ (60 mM) caused increases of ATP and CA in perfused effluent with the same time course. The peak molar ratio of CA to ATP in the effluent was about 10 for ACh and high K+ stimulation. The high-performance liquid chromatographic (HPLC) analysis of adenine nucleotides in the collected effluent revealed that the relative amounts of ATP, ADP and AMP were almost the same throughout the period of stimulation, suggesting that ATP breakdown in the effluent was constant. Changes in the peak molar ratio of CA to ATP appearing in the effluent did not occur with repetitive high K+ or sustained Ba2+ stimulation (5 mM). The similarity between the time courses of ATP and CA appearing in the effluent suggests that releasable chromaffin granules have a constant molar ratio of CA to ATP. The on-line system developed is a simple and rapid method for examining ATP and CA secretion, simultaneously.
Comp Biochem Physiol A Mol Integr Physiol 1999 Mar
PMID:On-line measurement of adenosine triphosphate and catecholamine released from adrenal chromaffin cells. 1035 64


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