[Protein tyrosine kinase inhibitor genistein suppresses in vitro invasion of HT1080 human fibrosarcoma cells]

OBJECTIVE

To investigate the effects of genistein on cancer invasion and associated cellular characteristics and explore the possibility of developing protein tyrosine kinase inhibitors as anti-metastasis drugs.

METHODS

HT1080 human fibrosarcoma cells were exposed to 20 mumol/L or 40 mumol/L genistein for 3 days. The abilities of the genistein-treated cells to invade through reconstituted matrigel or migrate through polycarbonate filters in transwell chambers were then investigated. Northern blot and laser densitometry were used to estimate the relative mRNA amounts of MMP-2, MMP-9 and TIMP-1 in the cells.

RESULTS

The ability of the genistein-treated HT1080 cells to invade the reconstituted basement membrane was decreased significantly (P < 0.01). In consistent with the lowered invasive potential, migration rates of the drug-treated cells decreased dramatically. genistein did not, however, significantly affect attachment of HT1080 cells on fibronectin, laminin or Matrigel. Though exposure to genistein led to a small increase in MMP-2 and MMP-9 gene expression, a much greater increase in the amount of TIMP-1 mRNA was observed. Imbalanced enhancement of gene expression between matrix metalloproteinases and their inhibitors in favor of the latter may imply that matrix degradation is impaired in the genistein-treated cells.

CONCLUSION

Genistein suppresses invasion of HT1080 cells at relatively low concentrations. genistein and other protein tyrosine kinase inhibitors might be valuable candidate drugs for the treatment of invasion and metastasis of cancer.

Amplification, analysis and chromosome mapping of novel homeobox-containing and homeobox-flanking sequences in rice

Homeobox genes, widely distributed among animal and plant kingdoms, play an important role in developmental process. Several homeobox conserved fragments were amplified by PCR and the flanking regions were also obtained by an LM-PCR procedure. Sequencing and Southern analysis showed that they belong to a homeobox gene family of rice. Six homeobox-containing fragments were mapped on the molecular linkage map of rice. They were located on chromosomes 3, 4 and 7 respectively. It is noteworthy that there are 4 homeobox fragments located on rice chromosome 3 and the result is also consistent with the comparative genomics between rice and maize.

The modulation of excitatory synaptic transmission by adenosine in area CA1 of the rat hippocampus is temperature dependent

We tested the possibility that extracellular adenosine concentration varies with tissue temperature by measuring the tonic adenosinergic inhibition of excitatory synaptic transmission at different temperatures in the in vitro rat hippocampus. Application of the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) enhanced population excitatory postsynaptic potentials (EPSPs) by antagonizing tonic adenosinergic inhibition; this effect was greatest at 25 degrees C, and was progressively reduced at 35 and 37.5 degrees C. These results demonstrate that tonic adenosinergic inhibition is inversely related to temperature. In a second experiment, an exogenous A1 agonist, N6-cyclohexyladenosine (CHA), was applied to slices to inhibit evoked EPSPs. CHA inhibition of EPSPs was greater at 35 than at 25 degrees C, demonstrating that the reduced adenosinergic inhibition at higher temperatures is not a result of reduced A1 receptor function.

Inhibition of hSP-B promoter in respiratory epithelial cells by a dominant negative retinoic acid receptor

Retinoic acid (RA) receptors (RARs) belong to the nuclear hormone receptor superfamily and play important roles in lung differentiation, growth, and gene regulation. Surfactant protein (SP) B is a small hydrophobic protein synthesized and secreted by respiratory epithelial cells in the lung. Expression of the SP-B gene is modulated at the transcriptional and posttranscriptional levels. In the present work, immunohistochemical staining revealed that RAR-alpha is present on day 14.5 of gestation in the fetal mouse lung. To assess whether RAR is required for SP-B gene transcription, a dominant negative mutant human (h) RAR-alpha403 was generated. The hRAR-alpha403 mutant was transcribed and translated into the truncated protein product by reticulocyte lysate in vitro. The mutant retained DNA binding activity in the presence of retinoid X receptor-gamma to an RA response element in the hSP-B promoter. When transiently transfected into pulmonary adenocarcinoma epithelial cells (H441 cells), the mutant hRAR-alpha403 was readily detected in the cell nucleus. Cotransfection of the mutant hRAR-alpha403 repressed activity of the hSP-B promoter and inhibited RA-induced surfactant proprotein B production in H441 cells, supporting the concept that RAR is required for hSP-B gene transcription in vitro.

Hyperthermia-induced apoptosis and the inhibition of DNA laddering by zinc supplementation and withdrawal of calcium and magnesium in suspension culture of tobacco cells

In the present paper we report examination of stereotypic hallmarks of apoptosis in heat-treated tobacco cells. Hyperthermia (44 °C, 4 h) caused apoptosis in 53.6% of cells when assayed 24 h after heat treatment. The induction of apoptosis by heat treatment was confirmed by flow cytometric assay. Cytological observations revealed condensation of the cytoplasm and nucleus, as well as nuclear collapse. DNA ladders were observed in DNA extracted from heat-treated cells, whereas DNA from control cells remained undegraded. The terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay revealed that 51.8% of the heat-treated cells (44 °C, 4 h) show positive reaction after a 24-h recovery. When cells were cultured in a medium supplemented with 0.4-5.0 mM ZnSO4, internucleosomal DNA fragmentation induced by heat shock was completely negated. Strikingly, when cells were cultured in Ca(2+) and/or Mg(2+) free medium for 44 h followed by heat treatment, DNA laddering was not observed. The results suggest hyperthermia-induced apoptosis and a correlation between the regulation of endonucleases and heat shock signal in apoptotic tobacco cells.

An epizootic of lymphoplasmacytic gastritis attributed to Helicobacter pylori infection in cynomolgus monkeys (Macaca fascicularis)

An epizootic of subclinical lymphoplasmacytic gastritis occurred in cynomolgus monkeys maintained at our research facility. Gastric pathology data and histologic sections of 63 adolescent monkeys (2.5-3.5 years old) sacrificed during the epizootic were reviewed. Localized to multifocal reddening of the gastric mucosa was noted grossly in 7 of 44 (16%) monkeys harboring Helicobacter pylori, but not in any of 19 monkeys in which these bacteria were not seen. Gastritis, characterized by accentuation of lymphoplasmacytic infiltrates in antral and to a lesser degree cardiac mucosa, occurred in 42 of 63 (67%) monkeys evaluated and in 42 of 44 (93%) monkeys in which H. pylori was observed microscopically. Two monkeys with H. pylori infection had infiltrate scores that overlapped with the upper limit of scores of H. pylori-negative animals. Coincident with accentuated infiltrates were gastric gland epithelial hyperplasia, reduction in mucin content of surface and gland epithelia, and comparatively minor infiltrates of neutrophils in superficial lamina propria and gastric glands. Antral mucosa thickness often exceeded 1.5 to 2 times normal. Antral mucosal erosions occurred in 7 of 44 (16%) monkeys with H. pylori. Argyrophilic bacteria morphologically consistent with H. pylori were present in antral and less commonly cardiac mucosal glands. Intensity of bacterial colonization correlated with lymphoplasmacytic infiltrates (r = 0.754) and hyperplasia (r = 0.700), although responses were quite variable. These bacteria were not detected in fundic mucosa except in instances where parietal cells were substantially depleted in glands coincident with localized increases in lamina propria inflammatory cell infiltrates. Helicobacter heilmannii-like organisms (HHLOs) were present in fundic glands of all 63 monkeys; colonization was often pronounced. Scores for fundic mucosal inflammation did not correlate with presence or intensity of colonization with HHLOs (r = 0.005). Rather, fundic inflammation scores positively correlated with the antral inflammation scores (r = 0.548). Bacteria morphologically, biochemically, and genetically consistent with H. pylori were cultured from gastric mucosal specimens confirming bacterial identification. These findings demonstrate that adolescent cynomolgus monkeys are susceptible to natural infection with H. pylori and develop many morphologic hallmarks of H. pylori-related gastritis in humans.

NMR studies of the structure and dynamics of peptide E, an endogenous opioid peptide that binds with high affinity to multiple opioid receptor subtypes

Structural and dynamic properties of opioid peptide E have been examined in an sodium dodecyl sulfate (SDS) micelle. Structural and dynamic studies both indicate that this peptide exhibits greater segmental mobility than typical structured proteins. An nmr structural analysis of adrenal peptide E in SDS micelles indicated the presence of two well-defined beta-turns, one at the N-terminus encompassing residues 3 to 6, and the second in the region between residues 15 and 18. Certain side chain dihedral angles were also remarkably well defined, such as the chi 1 angle of F4, which exhibited a trans configuration. These calculated structures were based on a set of 9.5 restraints per residue. The backbone dynamics of peptide E in SDS micelles were examined through an analysis of 15N-relaxation parameters. An extended model-free analysis was used to interpret the relaxation data. The overall rotational correlation time is 19.7 ns. the average order parameter S2 is 0.66 +/- 0.15. The N-terminal loop region residues including G3 to R6 have an average order parameter of 0.70 +/- 0.23. The average order parameter lies somewhere between that observed for a random coil (e.g., S2 = 0.3) and that of a well-defined tertiary fold (e.g., S2 = 0.86). This suggests that peptide E in SDS micelles adopts a restricted range of conformations rather than a random coil. Based on the helical structure recently obtained for the highly homologous kappa-agonist dynorphin-A(1-17) and the beta-turn in the same region of peptide E, it is reasonable to assume that these two elements of secondary structure reflect different receptor subtype binding geometries. The intermediate order parameters observed for peptide E in an SDS micelle suggest a degree of dynamic mobility that may enable facile interconversion between helical and beta-turn geometries in the N-terminal agonist domain.

Fluid shear stress stimulates big mitogen-activated protein kinase 1 (BMK1) activity in endothelial cells. Dependence on tyrosine kinases and intracellular calcium

Mitogen-activated protein (MAP) kinases including ERK1/2 and JNK play an important role in shear stress-mediated gene expression in endothelial cells (EC). A new MAP kinase termed big MAP kinase 1 (BMK1/ERK5) has been shown to phosphorylate and activate the transcription factor MEF2C, which is highly expressed in EC. To determine the effects of shear stress on BMK1, bovine aortic EC were exposed to steady laminar flow (shear stress = 12 dynes/cm2). Flow activated BMK1 within 10 min with peak activation at 60 min (7.1 +/- 0.6-fold) in a force-dependent manner. Flow was the most powerful activator of BMK1, significantly greater than H2O2 or sorbitol. An important role for non-Src tyrosine kinases in flow-mediated BMK1 activation was demonstrated by inhibition with herbimycin A, but not with the Src inhibitor PP1 or overexpression of kinase-inactive c-Src. BMK1 activation was calcium-dependent as shown by inhibition with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxymethyl ester or thapsigargin. As shown by specific inhibitors or activators, flow-mediated BMK1 activation was not regulated by the following: intracellular redox state; intracellular NO; protein kinase A, C, or G; calcium/calmodulin-dependent kinase; phosphatidylinositol 3-kinase; or arachidonic acid metabolism. In summary, flow potently stimulates BMK1 in EC by a mechanism dependent on a tyrosine kinase(s) and calcium mobilization, but not on c-Src, redox state, or NO production.

Crm1p mediates regulated nuclear export of a yeast AP-1-like transcription factor

The yeast AP-1-like transcription factor, Yap1p, activates genes required for the response to oxidative stress. Yap1p is normally cytoplasmic and inactive, but will activate by nuclear translocation if cells are placed in an oxidative environment. Here we show that Yap1p is a target of the beta-karyopherin-like nuclear exporter, Crm1p. Yap1p is constitutively nuclear in a crm1 mutant, and Crm1p binds to a nuclear export sequence (NES)-like sequence in Yap1p in the presence of RanGTP. Recognition of Yap1p by Crm1p is inhibited by oxidation, and this inhibition requires at least one of the three cysteine residues flanking the NES. These results suggest that Yap1p localization is largely regulated at the level of nuclear export, and that the oxidation state affects the accessibility of the Yap1p NES to Crm1p directly. We also show that a mutation in RanGAP (rna1-1) is synthetically lethal with crm1 mutants. Yap1p export is inhibited in both rna1-1 and prp20 (RanGNRF) mutant strains, but Yap1p rapidly accumulates at the nuclear periphery after shifting rna1-1, but not other mutant cells to the non-permissive temperature. Thus, disassembly of export complexes in response to RanGTP hydrolysis may be required for release of substrate from a terminal binding site at the nuclear pore complex (NPC).

[Effects of butylphthalide on extracellular 6-keto-PGF1 alpha, TXB2 and 6-keto-PGF1 alpha/TXB2 ratio in cultured rat cortical neurons]

The effects of 3-n-butylphthalide(NBP) on the levels of 6-keto-PGF1 alpha, TXB2 and 6-keto-PGF1 alpha/TXB2 ratio were studied with methods of RIA. d-NBP and l-NBP(0.1-100 mumol.L-1) concentration-dependently increased 6-keto-PGF1 alpha release, decreased TXB2 release from neuronal cells, and significantly enhanced extracellular 6-keto-PGF1 alpha/TXB2 ratio in primary cultured rat cortical neurons exposed to hypoxic-hypoglycemic media for 5 h or hypoxic-hypoglycemic media for 5 h following normal media for 3 h. Aspirin(0.1-100 mumol.L-1) was also shown to inhibit TXB2 release from cortical neurons in a dose-dependent manner. However aspirin only increased 6-keto-PGF1 alpha/TXB2 ratio at low dose because aspirin inhibited both 6-keto-PGF1 alpha and TXB2 release simultaneously at large dose(10-100 mumol.L-1). This suggests that the action of l-NBP, d-NBP and dl-NBP on the increase of 6-keto-PGF1 alpha/TXB2 ratio might be one of the mechanisms in which NBP enhanced focal cerebral blood flow and improved ischemic brain damage.

[Expression of cell adhesion molecule CD44 variant isoform correlated with the clinical behavior of renal cell carcinoma]

OBJECTIVE

To determinate whether the expression of CD44v in renal cell carcinoma (RCC) is associated with tumor malignant behavior.

METHOD

Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect CD44v in 31 human renal cell carcinoma (RCC) in addition to 18 normal renal tissues from patients with non-malignant disease.

RESULT

Eighteen RCCs showed positive expression while none of normal renal tissue expressed CD44v (P < 0.001). CD44v was expressed in metastatic or high pathological stage RCC, but the expression of CD44v was not correlated with cellular differentiation.

CONCLUSION

Our data indicate that a role for CD44v in human RCC progression and metastases, and CD44v may prove to be a marker for high metastasis potential of RCC.

Retinoic acid-receptor activation of SP-B gene transcription in respiratory epithelial cells

Retinoids are known to play important roles in organ development of the lung. Retinoids exert their activity by modulating the expression of numerous genes, generally influencing gene transcription, in target cells. In the present work, the mechanism by which retinoic acid (RA) regulates surfactant protein (SP) B expression was assessed in vitro. RA (9-cis-RA) enhanced SP-B mRNA in pulmonary adenocarcinoma cells (H441 cells) and increased transcriptional activity of the SP-B promoter in both H441 and mouse lung epithelial cells (MLE-15). Cotransfection of H441 cells with retinoid nuclear receptor (RAR)-alpha, -beta, and -gamma and retinoid X receptor (RXR)-gamma further increased the response of the SP-B promoter to RA. Treatment of H441 cells with RA increased immunostaining for the SP-B proprotein and increased the number of cells in which the SP-B proprotein was detected. An RA responsive element mediating RA stimulation of the human SP-B promoter was identified. RAR-alpha and -gamma and RXR-alpha but not RAR-beta or RXR-beta and -gamma were detected by immunohistochemical analysis of H441 cells. RA, by activating RAR activity, stimulated the transcription and synthesis of SP-B in pulmonary adenocarcinoma cells.

Genotoxicity and chronic health effects of automobile exhaust: a study on the traffic policemen in the city of Lanzhou

A study on the health and genotoxic effects of occupational exposure to automobile exhaust was carried out among traffic policemen in Lanzhou (China) in 1996. A total of 78 traffic policemen working in the field was the exposed group, and 57 household register policemen working in the office was the control group. The health effects were evaluated by health questionnaires. Significant differences were observed between the exposed and control groups with respect to the morbidity of rhinitis, pharyngitis, trachoma, syndrome of neurasthenia and joint pain, apart from disorders in the digestive system. The percentage of rhinitis and pharyngitis obtained in the two groups was significantly higher among the smokers than among the nonsmokers. The frequencies of micronuclei (MN) and sister-chromatid exchanges (SCEs) were measured in peripheral blood lymphocytes from the two groups of volunteers. Compared with the control group, statistically significant increases of MN and SCE were found for the exposed group. The increase in the induction of MN and SCE among the traffic policemen and household register policemen is enhanced further by smoking.

Genistein suppresses adhesion-induced protein tyrosine phosphorylation and invasion of B16-BL6 melanoma cells

Protein tyrosine phosphorylation occurs as one of the earlier events in cancer cell-extracellular matrix (ECM) interaction. With immunoblot analysis and immunofluorescence microscopy, genistein was found to suppress the tyrosine phosphorylation of proteins located at the cell periphery, including a 125 kDa protein, when B16-BL6 melanoma cells attached to and interacted with ECM. When accompanied by the suppression of adhesion-induced protein tyrosine phosphorylation, the invasive potential of B16-BL6 cells through reconstituted basement membrane was decreased significantly. However, neither adhesive capability nor cell growth was significantly affected by genistein. Therefore, the interruption of cancer cell-ECM interaction by suppression of protein tyrosine phosphorylation may contribute to invasion prevention of genistein.

[Protective effects of d-, l-, and dl-3-n-butylphthalide on neuronal damage induced by hypoxia/hypoglycemia in cultured rat cortical neurons]

The effects of l-3-n-butylphthalide(l-NBP) and d-3-n-butylphthalide(d-NBP) on hypoxia/hypoglycemia-induced cytotoxicity in primary cultured rat cortical neurons were studied. l-NBP and d-NBP(1-100 mumol.L-1) were shown to inhibit hypoxia/hypoglycemia-induced LDH release, decrease the percent of cell death and improve the damaged cellular morphology at 10 mumol.L-1 concentration. In addition, l-NBP, d-NBP and dl-NBP were also found to significantly reduce the liberation of polyribosomes from the neuronal rough endoplasmic reticulum and disaggregation of polyribosomes induced by hypoxia/hypoglycemia. These data suggest that l-NBP, d-NBP and dl-NBP can remarkably protect cultured neurons against hypoxia/hypoglycemia induced damage.

The origin of differences in the physical properties of the equilibrium forms of cytochrome b5 revealed through high-resolution NMR structures and backbone dynamic analyses

On the basis of a comparison of high-resolution solution structures calculated for both equilibrium forms of rat ferrocytochrome b5, differences in reduction potential and thermodyanmic stability have been characterized in terms of significant structural and dynamic differences between the two forms. The dominant difference between A and B conformations has long been known to be due to a 180 degrees rotation of the heme in the binding pocket about an axis defined by the alpha- and gamma-meso carbons, however, the B form has not been structurally characterized until now. The most significant differences observed between the two forms were the presence of a hydrogen bond between the 7-propionate and the S64 amide in the A form but not the B form and surprisingly a displacement of the heme out of the binding pocket by 0.9 A in the B form relative to the A form. The magnitude of other factors which could contribute to the known difference in reduction potentials in the bovine protein [Walker, F. A., Emrick, D., Rivera, J. E., Hanquet, B. J., and Buttlaire, D. H. (1988) J. Am. Chem. Soc. 110, 6234-6240], such as differences in the orientation of the axial imidazoles and differences in hydrogen bond strength to the imidazoles, have been evaluated. The dominant effector of the reduction potential would appear to be the lack of the hydrogen bond to the S64 amide in the B form which frees up the propionate to charge stabilize the iron in the oxidized state and thus lower the reduction potential of the B form. The structure we report for the A form, based on heteronuclear NMR restraints, involving a total of 1288 restraints strongly resembles both the X-ray crystal structure of the bovine protein and a recently reported structure for the A form of the rat protein based on homonuclear data alone [Banci, L., Bertini, I., Ferroni, F., and Rosato, A. (1997) Eur. J. Biochem. 249, 270-279]. The rmsd for the backbone atoms of the A form is 0.54 A (0.92 A for all non-hydrogens). The rmsd for the backbone of the B form is 0.51 A (0. 90 A for all non-hydrogen atoms). An analysis of backbone dynamics based on a model-free analysis of 15N relaxation data, which incorporated axially symmetric diffusion tensor modeling of the cytochrome, indicates that the protein is more rigid in the reduced state relative to the oxidized state, based on a comparison with order parameters reported for the bovine protein in the oxidized state [Kelly, G. P., Muskett, F. W., and Whitford, D. (1997) Eur. J. Biochem. 245, 349-354].

[Effects of d-3-n-butylphthalide and l-3-n-butylphthalide on extracellular no level and intracellular cGMP level in primary cultured rat cortical neurons]

The effects of l-3-n-butylphthalide(l-NBP) and d-3-n-butylphthalide(d-NBP) on extracellular nitric oxide (NO) levels and intracellular cyclic GMP (cGMP) levels were studied in primary cultured rat cortical neuronal cells. Nitric oxide and cGMP levels were measured by using spectrometry and radioimmunological analysis(RIA), respectively. The results showed that d-NBP (0.1-100 mumol: L-1) markedly increased extracellular NO levels and intracellular cGMP levels in primary cultured neurons that were exposed for 10 h to hypoxic/hypoglycemic, N-methyl-D-aspartate (NMDA), or KCl media. On the contrary, l-NBP(0.1-100 mumol.L-1) significantly decreased extracellular NO levels and intracellular cGMP levels. It is suggested that there is a contrary effect of d-NBP and l-NBP on NO release and cGMP production induced by hypoxia/hypoglycemia, NMDA, or KCl.

[Study on changes of plasma substance P in essential hypertension with left ventricular hypertrophy patients and the effect of promoting blood circulation and eliminating phlegm]

OBJECTIVE

Exploring the relationship between the plasma substance P(SP) and essential hypertension with left ventricular hypertrophy (EH-LVH) and the effect of promoting blood circulation and eliminating phlegm.

METHODS

Before and after treatment, the changes of SP in patients wiith EH-LVH were measured by radioimmunoassay. Meanwhile, the changes of plasma renin activity (PRA), angiotension II (Ang II), left ventricular mass index (LVMI) and mean arterial pressure (MAP) were measured.

RESULTS

The level of plasma SP in patients with EH-LVH was markedly lower than that of patients without EH-NLVH and healthy subjects (P < 0.001); the levels of PRA and Ang II were higher than those in control group (P < 0.01 or < 0.05). After treatment, the level of SP was significantly increased, while LVMI, MAP, PRA and Ang II were significantly decrease (P < 0.01 or < 0.05). The levels between SP and LVMI, MAP, PRA, Ang II were markedly negative correlated (P < 0.01) while levels between LVMI and PRA, Ang II were markedly positive correlated.

CONCLUSIONS

The SP may be involved in the pathogenesis of EH-LVH; the mechanism of promoting blood circulation and eliminating phlegm reversing LVH might be related to its increasing the plasma SP.

Nuclear localization domain of thyroid transcription factor-1 in respiratory epithelial cells

Thyroid transcription factor-1 (TITF-1) is a homeodomain containing transcription factor that binds to and selectively activates the expression of genes in thyroid and pulmonary epithelial cells. TITF-1 plays a critical role in gene expression and in organogenesis of lung and thyroid. In the present work, epitope-tagged TITF-1 proteins were used to identify the regions of the TITF-1 polypeptide that mediate nuclear localization and transcriptional activity in human lung adenocarcinoma cells. A series of TITF-1-flag deletion mutants was generated and transfected into H441 cells to determine amino acid sequences involved in translocation to the nucleus. Transfection of the TITF-1-flag mutants demonstrated that a nuclear localization signal (NLS) sequence, located at the N-terminus of the homeodomain, is critical for nuclear targeting. The NLS was essential but not sufficient for translocation of TITF-1 to the nucleus, since deletion of the homeodomain itself also blocked nuclear translocation in the presence of NLS. Deletion of the N-terminal transactivation domain of TITF-1 completely abolished its transcriptional activation on the human surfactant protein-B promoter, and deletion of the C-terminal domain partially reduced its stimulatory activity. Nuclear translocation of TITF-1 depends on both an NLS and the homeodomain of the polypeptide. Both C- and N-terminal regions of TITF-1 are involved in transactivation of surfactant protein B gene expression in pulmonary cells.

Hepatocyte nuclear factor-3beta limits cellular diversity in the developing respiratory epithelium and alters lung morphogenesis in vivo

Hepatocyte nuclear factor-3beta (HNF-3beta), a nuclear protein of the winged helix family of transcription factors, is known to play a critical role in the formation of the embryonic node, notochord, and foregut endoderm. HNF-3beta influences the expression of a number of target genes in the respiratory epithelium, activating transcription of thyroid transcription factor-1, surfactant protein-B and clara cell secretory protein. In order to discern the role of HNF-3beta in differentiation and gene expression in the lung, HNF-3beta was expressed in developing respiratory epithelial cells of transgenic mice, under the control of the human surfactant protein C gene promoter. Pulmonary abnormalities were observed in the lungs of fetal mice bearing the HNF-3beta transgene. Differentiation of distal respiratory epithelial cells was arrested in the early pseudoglandular stage. Branching morphogenesis and vasculogenesis were markedly disrupted in association with decreased E-cadherin and vascular endothelial growth factor expression. HNF-3beta limits cellular diversity of developing respiratory epithelium and alters lung morphogenesis in vivo, suggesting that precise temporal-spatial regulation of HNF-3beta expression is critical for respiratory epithelial cell differentiation and lung morphogenesis.

Protein kinase A activation of the surfactant protein B gene is mediated by phosphorylation of thyroid transcription factor 1

Thyroid transcription factor 1 (TTF-1) is a homeodomain-containing nuclear transcription factor expressed in epithelial cells of the lung and thyroid. TTF-1 binds to and activates the transcription of genes expressed selectively in the respiratory epithelium including pulmonary surfactant A, B, C and Clara cell secretory protein. Transfection with a plasmid encoding the cyclic AMP-dependent protein kinase (protein kinase A; PKA) catalytic subunit, Cat-beta, stimulated the phosphorylation of a TTF-1-flag fusion protein 6-7-fold in H441 pulmonary adenocarcinoma cells. Recombinant TTF-1 was phosphorylated by purified PKA catalytic subunit in the presence of [gamma-32P]ATP. PKA catalytic subunit family members, Cat-alpha and Cat-beta, markedly enhanced the transcriptional activation of surfactant B gene promoters by TTF-1 in vitro. Peptide mapping was used to identify a PKA phosphorylation site at the NH2 terminus of TTF-1. A 17-amino acid synthetic peptide comprising this site completely inhibited the PKA-dependent phosphorylation of TTF-1 in vitro. A substitution mutation of TTF-1 (Thr9 two head right arrow Ala) abolished phosphorylation by PKA and reduced transactivation of the surfactant B gene promoter. Transfection with a plasmid encoding the cAMP regulatory element binding factor inhibited transcriptional activity of the surfactant protein B gene promoter. Phosphorylation of TTF-1 mediates PKA-dependent activation of surfactant protein B gene transcription.