Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied lung explants in submersion organ culture to examine the role of the developing fetal alveolar epithelium in the production of lung fluid. Fourteen-day-gestation fetal rat lungs were grown in a collagen gel matrix supplemented with F-12 media and 10% fetal calf serum. In this model, the lung continues to grow, secrete fluid, and become progressively cystic in morphology. There is gradual thinning of the distal epithelial layer, which is lined by alveolar type II cells and their precursors. After 6 to 8 days in culture, we impaled the cyst walls with a microelectrode and continuously recorded the transepithelial potential (psi t). Stable, baseline transepithelial potentials of -1.1 to -6.2 mV (mean +/- SEM = -3.3 +/- 0.11 mV, lumen negative, n = 34) were measured in bicarbonate-buffered Ringer's solution, suggesting active electrolyte transport. When bumetanide, an inhibitor of chloride secretion in other systems, was added to the bathing solution, psi t decreased from a baseline of -3.5 +/- 0.07 mV (mean +/- SEM) to a value of -2.2 +/- 0.07 mV, suggesting chloride transport contributes to the voltage (n = 18, P less than 0.0005). Isoproterenol hyperpolarized psi t from a baseline of -4.3 +/- 1.0 mV to -6.5 +/- 1.0 mV (n = 7, P less than 0.005). 8-(4-Chlorophenylthio) adenosine 3':5'cyclic monophosphate (CPT-cAMP) plus isobutylmethylxanthine (IBMX) similarly hyperpolarized psi t from a baseline of -4.6 +/- 0.4 mV to -7.3 +/- 0.7 mV (n = 11, P less than 0.005). Addition of bumetanide after stimulation with isoproterenol or CPT-cAMP/IBMX depolarized psi t.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Respir Cell Mol Biol 1992 Jun
PMID:Secretion of lung fluid by the developing fetal rat alveolar epithelium in organ culture. 131 92

Transcription of the rat serine dehydratase (SDH) gene is induced by glucagon, mediated by the action of cAMP. To identify the nucleotide sequences in the SDH gene responsible for this regulation, we constructed chimeric genes containing different portions of the 5' flanking region of the rat SDH gene fused to the structural sequence encoding the bacterial reporter enzyme, chloramphenicol acetyltransferase (CAT). The transcriptional activities of the fusion genes introduced into the rat hepatoma cell line 7AD-7 were assayed by measuring CAT activity in the cell lysates. Chlorophenylthio-cyclic AMP (CPT-cAMP), a potent protein kinase A activating agent, stimulated the expression of SDH-CAT fusion genes, and these inductions could be enhanced further by the addition of dexamethasone, although the glucocorticoid alone had no effect on CAT activity. Deletion analysis demonstrated that an 80 bp region located approximately 3.5 kb upstream from the transcription initiation site of the rat SDH gene was responsible for stimulation of transcription by CPT-cAMP, whereas the 120 bp region immediately upstream of the cAMP responsive element (CRE)-containing sequences is essential for the enhancement of CPT-cAMP induction by the glucocorticoid.
Mol Cell Endocrinol 1992 Dec
PMID:Identification of regions in the rat serine dehydratase gene responsible for regulation by cyclic AMP alone and in the presence of glucocorticoids. 133 28

The formation of palmitoylcarnitine is catalyzed by carnitine palmitoyl-transferase (CPT-I) and this catalysis is the first committed step in beta-oxidation. The malonyl-CoA-inhibited isoform appears to be distinct from latent (CPT-II) activity, which is localized to the matrix side of the mitochondrial inner membrane. Sarcoplasmic reticulum from canine cardiac muscle was fractionated on a discontinuous sucrose density gradient into three major bands, all of which contained Ca(2+)-ATPase activity. Only the fraction that banded at a concentration of 38% surcrose was slightly contaminated by mitochondria. Peroxisomal uricase was low or absent in fractionated SR. All sarcoplasmic reticulum fractions contained malonyl-CoA-sensitive medium- (COT) and long-chain (CPT) carnitine acyltransferase activities. CPT activity decreased in sarcoplasmic reticulum when Triton X-100 was present. Carnitine acyltransferase activities were inactivated by preincubating the sarcoplasmic reticulum with the sulfhydryl reagent, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). In contrast, mitochondrial CPT-II activity was stable in the presence of DTNB and activated by Triton X-100. Western blots of mitochondria and sarcoplasmic reticulum fractions showed that the mitochondrial fractions reacted with antibody to mitochondrial CPT-II but not with SR protein when both were added at comparable specific activities. The data suggest that cardiac SR contains a unique malonyl-CoA-sensitive isoform of CPT, and that synthesis of acylcarnitine may occur in the microenvironment of Ca2+ transport, where the extent of production of acylcarnitine is controlled by cardiac acetyl-CoA carboxylase activity.
J Mol Cell Cardiol 1992 Mar
PMID:Evidence for malonyl-CoA-sensitive carnitine acyl-CoA transferase activity in sarcoplasmic reticulum of canine heart. 162 48

We have reported earlier that cholinephosphotransferase (EC 2.7.8.2) is present in both mitochondria and microsomes of fetal guinea pig lung. This study was designed to compare the properties of mitochondrial and microsomal cholinephosphotransferase in fetal guinea pig lung. Various parameters, such as substrate specificity, Km values, sensitivity to N-ethylmaleimide, dithiothreitol and trypsin were measured. Both showed significant preference for unsaturated diacylglycerols over saturated diacylglycerols. Data on Km and Vmax indicate that the affinity of this enzyme for different diacylglycerols varies between the two forms. The ID50 values for N-ethylmaleimide were 20 mM and 12.5 mM for the mitochondrial and microsomal form of the enzyme, respectively. Dithiothreitol showed an inhibitory effect on both; however, the mitochondrial form was inhibited less than the microsomal form. The effects of N-ethylmaleimide and dithiothreitol on both forms of enzyme indicated that the microsomal cholinephosphotransferase requires a higher concentration of -SH for its activity than the mitochondrial enzyme does. The enzyme was inhibited by trypsin in both mitochondria and microsome under isotonic condition suggesting that this enzyme is on the outside of the membrane in both endoplasmic reticulum and mitochondria.
Mol Cell Biochem 1991 Mar 13
PMID:Study of properties of cholinephosphotransferase from fetal guinea pig lung mitochondria and microsomes. 165 Apr 26

The effects of permeant cAMP analogs were studied on the function of the gamma-aminobutyric acidA (GABAA) receptor and on the activation of protein kinase A in brain synaptoneurosomes. Incubation of cerebral cortical synaptoneurosomes with permeant cAMP analogs decreased muscimol-induced 36Cl- uptake in a concentration-dependent manner. The order of potency was chlorophenylthio-cAMP (CPT-cAMP) greater than dibutyryl-cAMP greater than 8-bromo-cAMP. This order of potency was reflected by the ability of the analogs to gain access to the intravesicular compartment. cAMP, which failed to penetrate the membrane, had no effect. The half-maximal and maximal effects of the cAMP analogs were similar in the cerebral cortex, hippocampus, striatum, and cerebellum. To determine whether the cAMP analogs were acting through the activation of protein kinase A, protein kinase A activity was measured in lysed synaptoneurosomes, using kemptide as the substrate. In the lysed preparation, where the cAMP analogs have direct access to intracellular enzymes, the order of potencies of the cAMP analogs to activate protein kinase A (8-bromo-cAMP greater than CPT-cAMP greater than dibutyryl-cAMP) differed from the order of potencies to inhibit muscimol-induced 36Cl- uptake. In regional studies, the greatest effect of CPT-cAMP was observed in the cortex, whereas the smallest effect was observed in the hippocampus and cerebellum. To determine whether cAMP inhibition of GABA-gated ion flux was due to activation of protein kinase A, the time course for each response was measured. Inhibition of muscimol-induced 36Cl- uptake by cAMP analogs was nearly complete by 5 sec. Significant activation of protein kinase A by CPT-cAMP was also observed as early as 5 sec, but protein kinase A activation continued up to 10 min. The protein kinase inhibitor peptide inhibited protein kinase A activity in lysed synaptoneurosomes but had no effect on ion flux in intact synaptoneurosomes, as expected. However, a permeant kinase inhibitor, H-8, also failed to inhibit the effect of cAMP analogs on the muscimol response, yet it inhibited protein kinase A activity. The failure of H-8 to inhibit cAMP analog effects on GABAA receptor function was most likely due to the presence of ATP inside the synaptoneurosomes, because H-8 inhibition of protein kinase A was reduced in the presence of ATP. These results indicate that cAMP and cAMP analogs must penetrate the intravesicular compartment to inhibit GABAA receptor function. Although cAMP analogs decrease GABA-gated ion flux under conditions in which they activate protein kinase A, a causal relationship remains to be established.
Mol Pharmacol 1991 Mar
PMID:cAMP analogs inhibit gamma-aminobutyric acid-gated chloride flux and activate protein kinase A in brain synaptoneurosomes. 184 58

Saponin-permeabilization (30 micrograms/ml) of the platelet plasma membrane, which enables access of added compounds to mitochondrial overt carnitine palmitoyltransferase (CPT I), was applied to allow the rapid determination of CPT I activity in situ. The effects of diabetes and short-term incubation with insulin in vitro on the kinetic parameters and malonyl-CoA sensitivity of CPT I were also studied in rat platelets. CPT I exhibited ordinary Michaelis-Menten kinetics when platelets were incubated with palmitoyl-CoA. Malonyl-CoA showed an I50 (concentration giving 50% inhibition of CPT activity) of 0.92 +/- 0.11 microM in permeabilized platelets. Platelets obtained from diabetic rats (induced by streptozotocin injection) exhibited an increased Vmax and I50 for malonyl-CoA, and an unaltered Km for palmitoyl-CoA. In contrast, preincubation of platelets prepared from both fed control rats and diabetic rats with insulin (100 and 150 microU/ml) led to a decrease in enzyme activity when assayed with 75 microM palmitoyl-CoA and 0.5 mM L-carnitine as substrates. These in vivo and in vitro results suggested that insulin directly modulated rat platelet CPT I activity, as it does in the liver.
Mol Cell Biochem 1991 Apr 24
PMID:Characterization of overt carnitine palmitoyltransferase in rat platelets; involvement of insulin on its regulation. 185 44

A camptothecin-resistant subline of P388 leukemia (P388/CPT) was developed by repeated transplantation of P388 cells in mice treated with therapeutic doses of camptothecin. In mice bearing the resistant tumor, a maximally tolerated dose of camptothecin produced no net reduction in tumor cell burden, in contrast to a 5-log cell kill in the parental P388 (P388/S). The IC50 of camptothecin, as determined by colony formation assays of cultured cells, was 8 times greater for the cloned P388/CPT cell line than for P388/S. P388/CPT cells were not cross-resistant to other antineoplastic agents, including topoisomerase II inhibitors. The type I topoisomerases purified from P388/CPT and P388/S cells were identical with respect to molecular weight, specific activity, in vitro camptothecin sensitivity, and DNA cleavage specificity. Camptothecin induced fewer protein-associated DNA single-strand breaks in the resistant cells than in the wild-type P388 cells. Topoisomerase I mRNA, immunoreactivity, and extractable enzymatic activity were 2-4 times lower for P388/CPT cells than for P388/S cells. As resistance to camptothecin developed, topoisomerase I extractable activity decreased, concomitant with an increase in topoisomerase II extractable activity. Furthermore, the appearance of camptothecin resistance was associated with specific rearrangements of the topoisomerase I gene. These results suggest that development of resistance to inhibitors of topoisomerase I can occur by down-regulation of the target enzyme, thus reducing the production of lethal enzyme-mediated DNA damage. The enhanced topoisomerase II activity in these cells suggests that resistance to camptothecin may be overcome by co-treatment with topoisomerase II inhibitors.
Mol Pharmacol 1990 Oct
PMID:Development of a stable camptothecin-resistant subline of P388 leukemia with reduced topoisomerase I content. 217 65

Primary cultures of rat hepatocytes produce tissue-type plasminogen activator (tPA) and plasminogen activator-inhibitor type 1 (PAI-1). Incubation of hepatocytes with 50 microM 8-(4-chlorophenylthio)cAMP (CPT-cAMP) results in a 4-fold increase in tPA activity, whereas the synthetic glucocorticoid dexamethasone (1 microM) causes a more than 90% decrease. In combination, dexamethasone completely overcomes the CPT-cAMP effect and markedly decreases PA activity. PAI-1 is induced by both CPT-cAMP and dexamethasone, and the effects of these agents are additive. Accumulation of tPA mRNA is increased more than 4-fold by CPT-cAMP and is greatly decreased by incubation with dexamethasone. Dexamethasone in combination with CPT-cAMP totally blocks this cAMP effect. The protein synthesis inhibitor cycloheximide does not prevent either the dexamethasone-induced decrease or the CPT-cAMP-induced increase in tPA message and, in fact, augments the cAMP-induced increase in tPA mRNA. Hepatocyte PAI-1 mRNA levels are increased 2-fold by incubation with either CPT-cAMP or dexamethasone; in combination, these effectors cause a 4-fold increase in PAI-1 mRNA. Cycloheximide alone causes a marked increase in PAI-1 mRNA, but does not block the induction by either CPT-cAMP or dexamethasone. We conclude that incubation of hepatocytes with CPT-cAMP induces tPA activity by increasing tPA mRNA accumulation and that dexamethasone causes a decrease in tPA activity by both decreasing tPA mRNA and increasing PAI-1 mRNA and activity. Concomitant protein synthesis is not required for the regulation of tPA or PAI-1 mRNA by either CPT-cAMP or dexamethasone, indicating a primary effect of these agents on gene transcription or mRNA stability.
Mol Endocrinol 1989 Jan
PMID:Glucocorticoid and cyclic nucleotide regulation of plasminogen activator and plasminogen activator-inhibitor gene expression in primary cultures of rat hepatocytes. 253 89

The precise molecular events involved in growth factor-mediated cell proliferation in eukaryotes have not been entirely elucidated. Identification and characterization of the itnracellular molecular signaling systems linking growth factor function with nuclear events would provide insight into the regulatory mechanisms governing eukaryotic cell growth. In this report, we demonstrate that serum-deprived rat H4IIE hepatoma cells enter a quiescent state and remain viable in the absence of serum for up to 7 days. These cells can be stimulated to transverse the cell cycle and proliferate in response to epidermal growth factor (EGF) after a 24-h lag phase. We were able to completely mimic the mitogenic effects of EGF with 8-p-chlorophenylthio-cAMP (8-CPT-cAMP) but only partially with N6-(Bu)2-cAMP. EGF and 8-CPT-cAMP together induce a synergistic increase in H4IIE hepatoma cell proliferation. The calcium ionophore A23187 and the phorbol ester, 4 beta-phorbol 12-myristate 13-acetate had little effect on H4IIE cell proliferation. EGF treatment led to a rapid and transient increase of intracellular cAMP concentration. Both 8-CPT-cAMP and EGF were also equally effective in causing a rapid and transient induction of c-fos and c-myc protooncogene mRNA levels when added to growth-arrested H4IIE cells while A23187, N-(Bu)2-cAMP, and 4 beta-phorbol 12-myristate 13-acetate were significantly less effective. Both EGF and 8-CPT-cAMP affect protooncogene expression in growth-arrested rat H4IIE hepatoma cells primarily at the transcriptional level. Localization and semi-quantification of nuclear pp55c-fos and 63 (kilodalton)-myc protooncoproteins by immunocolloidal gold electron microscopy revealed that EGF and/or 8-CPT-cAMP treatment of quiescent H4IIE hepatoma cells led to a marked and rapid nuclear accumulation of these proteins in discrete nuclear substructures. Cummulatively, these results suggest that cAMP participates in the intracellular signaling system mediating the mitogenic and protooncogene inducing effects of EGF on growth-arrested rat H4IIE hepatoma cells.
Mol Endocrinol 1989 Mar
PMID:Epidermal growth factor induction of cellular proliferation and protooncogene expression in growth-arrested rat H4IIE hepatoma cells: role of cyclic adenosine monophosphate. 254 62

The biosynthesis of phosphatidylcholine was studied in a population of activated Type II cells isolated from the lungs of rats treated with silica. Type II cells were separated by centrifugal elutriation into two populations, designated Type IIA and Type IIB. The Type IIB or activated population consisted of Type II cells that were larger than normal cells; Type IIA cells were morphologically similar to normal Type II cells. Type IIB cells incorporated more [Me-14C]choline into both total phosphatidylcholine and disaturated phosphatidylcholine than did Type IIA or control Type II cells. Measurement of the pool sizes of the choline-containing precursors to phosphatidylcholine indicated that the biosynthesis of phosphatidylcholine was increased 4- to 5-fold in Type IIB cells. Increased conversion of cholinephosphate to CDP-choline was associated with increased phosphatidylcholine biosynthesis in Type IIB cells. Cholinephosphate cytidylyltransferase activity was increased approximately threefold in Type IIB cells. Subcellular fractionation indicated that essentially all of the increase in cytidylyltransferase activity was associated with the particulate fraction (100,000 x g pellet). In Type IIB cells, the particulate fraction contained 83% of the total cellular cytidylyltransferase activity; in control cells, this fraction contained 67% of the total activity. The specific activity of the cytidylyltransferase associated with the particulate fraction was increased twofold in Type IIB cells. The specific activity of the cytosolic enzyme was similar to that in control cells. Cholinephosphotransferase specific activity was increased approximately twofold in the activated Type II cells. The specific activity of choline kinase was the same as that in control Type II cells. These results demonstrate that the increased biosynthesis of phosphatidylcholine in Type IIB cells is a result of stimulation of the CDP-choline pathway. This study indicates that both cholinephosphate cytidylyltransferase and cholinephosphotransferase may be involved in regulating the de novo biosynthesis of phosphatidylcholine in alveolar Type II cells.
Am J Respir Cell Mol Biol 1989 Aug
PMID:Regulation of phosphatidylcholine biosynthesis in activated alveolar type II cells. 255 61


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