Regulation of phosphatidylcholine synthesis in fetal type II cells by CTP:phosphocholine cytidylyltransferase

1993 ◽  
Vol 264 (6) ◽  
pp. L575-L580 ◽  
Author(s):  
L. J. Zimmermann ◽  
M. Hogan ◽  
K. S. Carlson ◽  
B. T. Smith ◽  
M. Post
Keyword(s):  
De Novo ◽  
Late Gestation ◽  
Molar Ratio ◽  
Type Ii Cells ◽  
Type Ii ◽  
Developmental Profile ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Fetal Rat ◽  
Saturated Form ◽  
Phosphatidylcholine Synthesis

Phosphatidylcholine synthesis increases in fetal rat type II cells during late gestation, as demonstrated by an increased incorporation of radiolabeled palmitate, glycerol, acetate, and choline into phosphatidylcholine. However, the percentage of phosphatidylcholine present in the saturated form remains essentially constant. The developmental profile of the enzymes of the CDP-choline pathway suggests that CTP:choline-phosphate cytidylyltransferase catalyses a rate regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. When cytidylyltransferase activity is assayed in different subcellular fractions, the greatest increase, as a function of development, is found in microsomes. This developmental increase is accompanied by a shift in subcellular distribution of cytidylyltransferase activity from cytosol to microsomes in fetal type II cells during late gestation. This shift is evident even when cytidylyltransferase activity is assayed in the presence of 0.5 mM phosphatidylcholine/oleic acid (1/1 molar ratio) vesicles. We speculate that either a subcellular translocation of CTP:phosphocholine cytidylyltransferase from cytosol to microsomes or an increase in cytidylyltransferase gene expression are responsible for the developmental increase of de novo phosphatidylcholine synthesis by fetal type II cells.

Increased expression of CTP:phosphocholine cytidylyltransferase in maturing type II cells

1994 ◽  
Vol 267 (1) ◽  
pp. L25-L32 ◽  
Author(s):  
M. Hogan ◽  
L. J. Zimmermann ◽  
J. Wang ◽  
M. Kuliszewski ◽  
J. Liu ◽  
...  
Keyword(s):  
Rat Liver ◽  
Type Ii Cells ◽  
Mrna Levels ◽  
Type Ii ◽  
Rat Lung ◽  
Protein Levels ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Fetal Rat ◽  
Fetal Rat Lung ◽  
Phosphatidylcholine Synthesis

We previously reported that phosphatidylcholine synthesis increased in fetal rat lung type II cells with advancing gestation. This increase was accompanied by an increase in CTP:phosphocholine cytidylyltransferase activity, which catalyses a rate regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. To determine whether this increase in cytidylyltransferase activity is due to an increase in cytidylyltransferase protein levels, the gene and protein expression of cytidylyltransferase was investigated in maturing type II cells. The cytidylyltransferase cDNA was cloned from fetal rat type II cells and showed 99% sequence homology with rat liver cDNA. The cDNA detected two mRNA transcripts (1.8 and 7.5 kb) in fetal rat lung. By reverse-transcriptase polymerase chain reaction (RT-PCR) analysis, cytidyltransferase mRNA content increased three-fold in fetal type II cells with advancing gestation, whereas cytidylyltransferase mRNA levels in fibroblasts remained constant. An antibody against rat liver cytidylyltransferase was used to assess cytidylyltransferase protein. Western blotting revealed that cytidylyltransferase protein content increased threefold in the microsomal fraction of type II cells with advancing gestation. The enzyme protein levels in the cytosolic fraction did not significantly change with development. Enzyme activity studies confirmed these latter observations. We conclude that the increase in surfactant phosphatidylcholine synthesis by type II cells at late fetal gestation is due in part to an increase in the amount of cytidylyltransferase protein.

scholarly journals Regulation of phosphatidylcholine synthesis in maturing type II cells: increased mRNA stability of CTP:phosphocholine cytidylyltransferase

1996 ◽  
Vol 314 (3) ◽  
pp. 799-803 ◽  
Author(s):  
Martina HOGAN ◽  
Maciej KULISZEWSKI ◽  
Wensu LEE ◽  
Martin POST
Keyword(s):  
De Novo ◽  
Fetal Lung ◽  
Type Ii Cells ◽  
Type Ii ◽  
Glucocorticoid Treatment ◽  
Pregnant Rats ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Gene And Protein Expression ◽  
Type Ii Cell ◽  
Phosphatidylcholine Synthesis

Pulmonary surfactant phosphatidylcholine synthesis increases in fetal lung type II cells with advancing gestation. This increase is accompanied by an increase in gene and protein expression of CTP:phosphocholine cytidylyltransferase (CT; EC 2.7.7.15), which catalyses a regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. In the present study we investigated the role of transcriptional and post-transcriptional mechanisms in the developmental induction of CT mRNA in maturing type II cells. We found that CT mRNA increased 2-fold from days 18 to 21 of fetal rat gestation (term 22 d). This increase in CT mRNA was not accompanied by a developmental increase in CT gene transcription. However, CT mRNA was more stable on day 21 (t½ 48 h) compared with that on day 18 (t½ 17 h). Glucocorticoids have been shown to enhance surfactant phosphatidylcholine synthesis in fetal type II cells. Therefore we also examined the effect of maternal glucocorticoid administration to pregnant rats at 19 d of gestation on CT mRNA expression in fetal type II cells isolated 24 h later. Glucocorticoid treatment did not increase type II cell CT mRNA. As reported previously, however, glucocorticoids increased CT activity in the microsomal membrane fraction of fetal type II cells, whereas no differences in cytosolic CT activity were observed. We conclude that the developmental increase in CT mRNA in fetal type II cells is due to a decreased breakdown of the CT transcript and that glucocorticoids regulate fetal type II cell CT activity at a post-translational level.

scholarly journals Maternal administration of dexamethasone stimulates choline-phosphate cytidylyltransferase in fetal type II cells

1987 ◽  
Vol 241 (1) ◽  
pp. 291-296 ◽  
Author(s):  
M Post
Keyword(s):  
Enzyme Activity ◽  
Specific Activity ◽  
Active Form ◽  
Type Ii Cells ◽  
Type Ii ◽  
Rat Lung ◽  
Dexamethasone Treatment ◽  
Fetal Rat ◽  
Fetal Rat Lung ◽  
Choline Phosphate

Administration of dexamethasone to pregnant rats at 19 days gestation increased phosphatidylcholine synthesis (45%) from radioactive choline in type II cells. This enhanced synthesis of phosphatidylcholine was accompanied by an increased conversion of choline phosphate into CDP-choline. Similar results were obtained by incubating organotypic cultures of 19-day-fetal rat lung with cortisol. The increased conversion of choline phosphate into CDP-choline correlated with an enhanced choline-phosphate cytidylyltransferase activity (31% after dexamethasone treatment; 47% after cortisol exposure) in the cell homogenates. A similar increase (26% after dexamethasone treatment; 39% after cortisol exposure) was found in the microsomal-associated enzyme. No differences in cytosolic enzyme activity were observed. The specific activity of the microsomal enzyme was 3-4 times that of the cytosolic enzyme. Most of the enzyme activity was located in the microsomal fraction (58-65%). The treatments had no effect on the total amount of enzyme recovered from the cell homogenates. These results, taken collectively, are interpreted to indicate that the active form of cytidylyltransferase in type II cells is the membrane-bound enzyme and that cytidylyltransferase activation in type II cells from fetal rat lung after maternal glucocorticoid administration occurs by binding of inactive cytosolic enzyme to endoplasmic reticulum.

Fatty-acid synthase activity and mRNA level in hypertrophic type II cells from silica-treated rats

1994 ◽  
Vol 267 (2) ◽  
pp. L128-L136
Author(s):  
J. Rami ◽  
W. Stenzel ◽  
S. M. Sasic ◽  
C. Puel-M'Rini ◽  
J. P. Besombes ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Fatty Acid Biosynthesis ◽  
De Novo ◽  
Mrna Level ◽  
Type Ii Cells ◽  
Mrna Levels ◽  
Type Ii ◽  
Maximum Increase

Silica instillation causes a massive increase in lung surfactant. Two populations of type II pneumocytes can be isolated from rats administered silica by intratracheal injection: type IIA cells similar to type II cells from normal rats and type IIB cells, which are larger and contain elevated levels of surfactant protein A and phospholipid. Activities of choline-phosphate cytidylyltransferase, a rate-regulatory enzyme in phosphatidylcholine biosynthesis, and fatty-acid synthase (FAS) are increased in type IIB cells isolated from rats 14 days after silica injection. In the present study, we examined the increase in FAS and cytidylyltransferase activities in type IIB cells as a function of time after silica administration. FAS activity increased rapidly, was approximately threefold elevated 1 day after silica administration and has reached close to the maximum increase by 3 days. Cytidylyltransferase activity was not increased on day 1, was significantly increased on day 3 but was not maximally increased until day 7. Inhibition of de novo fatty-acid biosynthesis, by in vivo injection of hydroxycitric acid and inclusion of agaric acid in the type II cell culture medium, abolished the increase in cytidylyltransferase activity on day 3 but not FAS and had no effect on activities of two other enzymes of phospholipid synthesis. FAS mRNA levels were not increased in type IIB cells isolated 1-14 days after silica injection. These data show that the increase in FAS activity in type IIB cells is an early response to silica, that it mediates the increase in cytidylyltransferase activity, and that it is not due to enhanced FAS gene expression.

Prostaglandin and leukotriene production by alveolar type II cells in vitro

1990 ◽  
Vol 258 (4) ◽  
pp. L179-L187 ◽  
Author(s):  
G. R. Cott ◽  
J. Y. Westcott ◽  
N. F. Voelkel
Keyword(s):  
De Novo ◽  
Primary Cultures ◽  
Calcium Ionophore ◽  
Alveolar Type ◽  
Ionophore A23187 ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Adult Rats ◽  
The Media

Alveolar type II cells were isolated from adult rats, cultured for 22 h, and individual eicosanoids in the media from unstimulated and stimulated cells were quantified by immunoassay. Stimulation with the calcium ionophore A23187 significantly increased the media levels of prostaglandins (prostaglandin and 6-keto-prostaglandin F1 alpha greater than thromboxane B2). In contrast to previous reports, increased media levels of leukotrienes were also recovered from cells incubated with A23187, but only for cells in culture for less than or equal to 24 h. The production of leukotriene C4 was confirmed by a combination of high-performance liquid chromatography and spectrophotometric analysis. The profile of eicosanoids produced by cultures of alveolar type II cells was distinctly different than that of similarly cultured alveolar macrophages. Finally, stimulation of alveolar type II cell cultures with either a phorbol ester or phospholipase C increased media prostaglandin levels but failed to increase leukotriene levels. We conclude that primary cultures of alveolar type II cells are capable of the de novo metabolism of arachidonic acid to both cyclooxygenase and lipoxygenase products and that the production of leukotrienes is dependent on both time in culture and agonist. Thus alveolar type II cells are a potential source for the production of these eicosanoids in vivo, and the particular lipid mediators produced may vary depending on the pathophysiologic stimulus.

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