Phosphatidylinositol-3 kinase in fission yeast: a possible role in stress responses

A DNA fragment coding for a part of a putative phosphatidylinositol 3 kinase was cloned from Schizosaccharomyces pombe by cross-hybridization with Saccharomyces cerevisiae VPS34 gene, a yeast homologue of mammalian PI-3 kinase. The clone contained an open reading frame of 797 amino acids but lacked the initiation codon, ATG. The predicted amino acid sequence was homologous to those of S. cerevisiae VPS34 and mammalian PI-3 kinase genes. Disruption of the gene resulted in extremely low levels of PI-3-P and higher levels of PI-4-P, supporting the idea that the gene codes for the PI-3 kinase of S. pombe. The disruptants harbored large vacuoles and were sensitive to stresses such as high temperature or high concentration of monovalent and divalent cations.

Neuropathy target esterase of hen brain: active site reactions with 2-[octyl-3H]octyl-4H-1,3,2-benzodioxaphosphorin 2-oxide and 2-octyl-4H-1,3,2-[aryl-3H]benzodioxaphosphorin 2-oxide

2-Octyl-4H-1,3,2-benzodioxaphosphorin 2-oxide (octyl-BDPO) is one of the most potent inhibitors known for neuropathy target esterase (NTE) of hen brain with 50% inhibition at 0.2 nM. Two NTE-like proteins, i.e., resistant to paraoxon and sensitive to mipafox, of approximately 155 and approximately 119 kDa (designated NTE-155 and NTE-119, respectively) are labeled by [octyl-3H]octyl-BDPO and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Labeling with [aryl-3H]octyl-BDPO is only approximately 15% of that with [octyl-3H]octyl-BDPO, indicating that the majority of the phosphorylated NTE undergoes aging with only a small proportion of nonaged target or intramolecular group transfer ("alkylation"). NTE-155 and NTE-119 have the same kinetic constants and maximal number of phosphorylation sites, equivalent for each of them to 26 fmol/mg of protein and totaling at least 0.44-1.2 micrograms of NTE protein/g of brain. Structure-activity investigations involving 17 combinations of organophosphorus (OP) compounds of varied chemical type, stereochemistry, and concentration establish an excellent correlation (r = 0.95) between inhibition of NTE activity and protein labeling and thereby the toxicological relevance of these assays, which equally implicate NTE-155 and NTE-119 (probably an autolysis product of NTE-155) as target in OP-induced delayed neuropathy. [octyl-3H]-Octyl-BDPO is an improved probe for NTE in terms of its potency, reactivity, selectivity, and the formation of 3H-labeled NTE with a stable phosphorus-carbon bond.

Long-term effects of dietary fiber supplementation on serum glucose and lipoprotein levels in diabetic rats fed a high cholesterol diet

We have shown that cholesterol-fed diabetic rats developed atheromatous lesions in the aorta and coronary arteries, which were not observed in cholesterol-fed diabetic rats receiving concomitant supplementation with 15% glucomannan, a soluble dietary fiber concentrate. The present study was designed to examine the effects of the dietary fiber supplementation on serum levels of glucose and lipoproteins in cholesterol-fed diabetic rats. Feeding a diet containing 1.5% cholesterol (wt/wt) and 0.37% cholic acid for 18 weeks to rats made diabetic by streptozotocin (35 mg/kg body weight, iv) produced moderate hyperglycemia and moderate hypercholesterolemia, the latter being characterized by high concentrations not only of low density lipoproteins but also intermediate density lipoproteins and very low density lipoproteins. These changes in serum lipoproteins and hyperglycemia were substantially reduced by 18 weeks of supplementation with glucomannan but high density lipoprotein cholesterol and triglyceride levels did not change after feeding a cholesterol-rich diet in the presence or absence of glucomannan supplementation. These results suggest that amelioration in hyperlipoproteinemia and hyperglycemia induced by the dietary fiber supplementation may help retard or prevent the atheromatous formation found in cholesterol-fed diabetic rats.

[Autoimmune hemolytic anemia reactivated by alpha-interferon therapy in a case of chronic active C-type hepatitis]

A case with autoimmune hemolytic anemia (AIHA) induced by interferon-alpha (IFN-alpha) is presented. A 40-year-old male who had a previous history of autoimmune hemolytic anemia, agranulocytosis and thrombocytopenia was admitted to our hospital because of chronic C type hepatitis. Liver biopsy was performed, which diagnosed chronic active hepatitis and IFN-alpha was administrated at a dose of 3 Meg unit per day. 11 days after the initiation of the therapy he developed hemolytic anemia, but Coombs tests were negative. Although IFN was withdrawn 15 days later, anemia became progressively more serious. 20 days later, both direct and indirect Coombs tests became positive. He was diagnosed as AIHA and treated with methylprednisolone pulse therapy, then he recovered soon afterward. Further analysis of Coombs tests revealed that he had both cold type and warm type (IgG) autoantibodies which was the same type of antibodies for AIHA he suffered 10 years ago. In conclusion, latent AIHA may be reactivated by the treatment with IFN-alpha.

Serum amino acid disturbance in multiple myeloma with hyperammonemia

From October 1987 to November 1993 we evaluated the serum levels of ammonia and amino acids in 85 patients with multiple myeloma. Six of the 85 cases of multiple myeloma demonstrated hyperammonemia and none of the known causes of hyperammonemia, such as liver failure, could be identified in these patients. All six patients also showed serum amino acid disturbances and conscious disorders in various degrees. In this study we compared these abnormalities in multiple myeloma with those in chronic liver failure (n = 14), the basic diseases of which were liver cirrhosis in six cases and liver cirrhosis complicated hepatocellular carcinoma in eight cases. There was a marked difference in the levels of individual serum amino acids between these two groups. The level of glycine was significantly higher in the multiple myeloma group (P < 0.001); on the other hand, that of tyrosine was significantly higher in the liver failure group (P < 0.005). The histidine (P < 0.005) and arginine (P < 0.005) levels were lower in the myeloma group. The ratio of glycine to tyrosine (Gly/Tyr) was 16.7 +/- 4.85 in the myeloma group and 1.7 +/- 0.12 in the liver failure group. The ratio of glycine to tyrosine was an important criterion for differential diagnosis.

Detection of Y-bearing porcine spermatozoa by in situ hybridization using digoxigenin-labeled, porcine male-specific DNA probe produced by polymerase chain reaction

This study was carried out to determine whether Y-bearing porcine spermatozoa could be detected by in situ hybridization using a digoxigenin (Dig)-labelled DNA probe specific to the Y chromosome produced by polymerase chain reaction (PCR). A conventional PCR (with Dig-dUTP) was performed using a set of oligonucleotide primers (5'-AAGTGGTCAGCGTGTCCATA-3' and 5'-TTTCTCCTGTATCCTCCTGC-3') for 236 bp fragment of porcine male-specific DNA sequence and 1.25 x 10(4) template white blood cells obtained from a boar. When fluorescence in situ hybridization with the Dig-labelled DNA probe was applied to the metaphase chromosome spreads prepared from both boar and gilts, the fluorescein signal was only detected on the long arm of the Y chromosome. In addition, immunocytochemical detection with the Dig-labelled DNA probe and alkaline phosphatase-labeled anti-Dig was applied to both sperm nuclei pretreated with dithiothreitol and white blood cells; 51% of sperm nuclei and 96% of white blood cells obtained from boar were labelled, whereas none of white blood cells obtained from gilts were labelled with the Dig-labelled DNA probe. The results indicated that in situ hybridization with porcine male-specific DNA probe produced by PCR made possible the direct visualization of Y-bearing porcine spermatozoa by in situ hybridization.

Human T-cell leukemia virus type-1 (HTLV-1) Tax is expressed at the same level in infected cells of HTLV-1-associated myelopathy or tropical spastic paraparesis patients as in asymptomatic carriers but at a lower level in adult T-cell leukemia cells

Patients with human T-cell leukemia virus type-1 (HTLV-1)-associated myelopathy (HAM/TSP) generally harbor a much greater population of HTLV-1-infected T cells in peripheral blood mononuclear cells (PBMCs) than asymptomatic carriers. These cells are not malignant but frequently proliferate clonally. To investigate the possibility that higher expression of the viral activator Tax induces preferential proliferation of infected nonmalignant T cells in HAM/TSP patients, the expression of Tax mRNA in fresh PBMCs was analyzed by reverse transcriptase-mediated polymerase chain reaction. Total amount of Tax mRNA was higher in HAM/TSP patients than in carriers, but the expression level was almost the same as that in asymptomatic carriers when compared per infected cell. The expression levels in adult T-cell leukemia patients were significantly lower than those in HAM/TSP patients and asymptomatic carriers. These results indicate that tax gene is not expressed at a continuously high level in HAM/TSP patients who carry a high population of infected T cells, even in those with clonally proliferated infected T cells.

Tax protein of HTLV-1 destabilizes the complexes of NF-kappa B and I kappa B-alpha and induces nuclear translocation of NF-kappa B for transcriptional activation

Tax protein of HTLV-1 stimulates transcription of specific cellular genes through the NF-kappa B binding site. We previously showed that Tax binds to the ankyrin motifs of I kappa B-gamma, and dissociates the I kappa B-gamma/NF-kappa B complexes, resulting in nuclear translocation of NF-kappa B proteins. We herein report the effects of Tax on I kappa B-alpha, another member of I kappa B family proteins expressed in human T cells. Tax binds to I kappa B-alpha and partially dissociates the NF-kappa B/I kappa B-alpha complex in vitro. In Tax-expressing cells, Tax/I kappa B-alpha complex was detected only at low level, but NF-kappa B/I kappa B-alpha complex was mostly dissociated and NF-kappa B was translocated into the nucleus. Furthermore, Tax induced reduction of I kappa B-alpha protein. I kappa B-alpha protein was stabilized by NF-kappa B protein through forming NF-kappa B/I kappa B-alpha complex, but Tax expression cancelled this stabilization effect on I kappa B-alpha. These findings suggest that Tax induces dissociation of and/or inhibits the formation of NF-kappa B/I kappa B-alpha complexes, resulting in release of NF-kappa B and destabilization of I kappa B-alpha. Consistently, transcription of NF-kappa B directed gene was activated. These Tax effects counteract the negative feedback control of NF-kappa B by I kappa B-alpha and contribute to constitutive activation of NF-kappa B in Tax-transfected and HTLV-1-infected cells.

Radicicol, a protein tyrosine kinase inhibitor, suppresses the expression of mitogen-inducible cyclooxygenase in macrophages stimulated with lipopolysaccharide and in experimental glomerulonephritis

Two isoforms of cyclooxygenase (COX) have been identified in eukaryotic cells: a constitutively expressed COX-1 and mitogen-inducible COX-2, which is selectively expressed in response to various inflammatory stimuli. Thus, COX-2 instead of COX-1 is implicated to produce prostanoids mediating inflammatory responses. Major efforts have been focused on identifying nonsteroidal anti-inflammatory drugs (NSAIDS) which can selectively inhibit the enzyme activity of COX-2. Such NSAIDS would be more desirable anti-inflammatory agents in comparison to NSAIDS which inhibit both COX-1 and COX-2. Other than glucocorticoids, pharmacological agents which can selectively suppress the expression of COX-2 without affecting that of COX-1 have not been identified. We report here that radicicol, a fungal antibiotic, is a potent protein tyrosine kinase inhibitor, and that it inhibits the expression of COX-2 without affecting COX-1 expression in lipopolysaccharide (LPS)-stimulated macrophages with the IC50 value of 27 nM. Radicicol inhibited tyrosine phosphorylation of p53/56lyn, a Src family tyrosine kinase and one of the major tyrosine-phosphorylated proteins in LPS-stimulated macrophages. Radicicol also inhibited COX-2 expression in vivo in glomeruli of rats with experimental glomerulonephritis induced by the anti-glomerular basement membrane antibodies, in which COX-2 expression is known to be enhanced. The enzyme activity of COX-1 or COX-2 was not affected by radicicol in macrophages. Radiciciol also suppressed the COX-2 expression induced by IL-1 beta in rat smooth muscle cells. Other protein tyrosine kinase inhibitors suppressed the LPS-induced COX-2 expression in macrophages but at much higher concentrations than needed for radicicol. Radicicol did not inhibit the COX-2 expression induced by phorbol 12-myristate 13-acetate in macrophages. These results suggest that the activation of tyrosine-specific protein kinases is the proximal obligatory step in the LPS-induced signal transduction pathway leading to the induction of COX-2 expression in macrophages. The magnitude of the inhibition of COX-2 protein synthesis by radicicol was much greater than that of the steady state levels of COX-2 mRNA. These results suggest that radicicol inhibits COX-2 expression mainly at post-transcriptional steps.

Carcinoma of the reconstructed stomach tube following esophageal resection for a benign stricture: report of a case and review of the literature

We report herein the case of a 60-year-old woman who presented with dysphagia and anorexia and was subsequently diagnosed as having gastric cancer of the reconstructed stomach tube 36 years after undergoing surgery for a benign esophageal stricture. Reports on carcinoma of the reconstructed stomach tube are rarely found and interestingly, all of the previous cases, which were documented only in the Japanese literature, corresponded to metachronous double cancers after esophageal malignancies. To our knowledge, this is the first case of carcinoma of the reconstructed stomach tube following esophageal resection for a benign stricture, and it is thought that the carcinoma probably developed at the site of the anastomosis a long time after the first operation. We reviewed 30 cases of carcinoma of the reconstructed stomach tube for which the clinicopathological data was complete, and we believe that this new type of cancer needs more than 10 years to develop and should be defined as "carcinoma of the gastric remnant".

Alterations in multiple tyrosine hydroxylase mRNAs in the substantia nigra, locus coeruleus and adrenal gland of MPTP-treated parkinsonian monkeys

Monkeys are known to be highly susceptible to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which produces parkinsonism, as in humans. We have previously reported that only monkeys and humans have multiple isoforms of tyrosine hydroxylase (TH), the first enzyme for dopamine biosynthesis, with only two TH mRNA isoforms, type 1 and type 2, being present in Macaca fascicularis. In the present study we have measured TH mRNA type 1 and 2 content in the substantia nigra, locus coeruleus, and adrenal gland of normal control monkeys and in MPTP-produced parkinsonian monkeys (Macaca fascicularis) using a newly developed, sensitive and quantitative assay based on the reverse transcription-polymerase chain reaction. Marked decreases in TH mRNA type 1 and 2 content were observed, specifically in the substantia nigra of the monkeys with MPTP-parkinsonism compared to control monkeys. These results are similar to our recent data showing marked decreases in TH mRNA type 1, 2, 3 and 4 content in the substantia nigra of patients with Parkinson's disease, and suggest that MPTP-treated monkeys closely replicate changes in TH isoforms in human Parkinson's disease.

Structures of cDNAs encoding the muscle-type and non-muscle-type isozymes of lamprey fructose bisphosphate aldolases and the evolution of aldolase genes

Nearly full-length cDNA clones for muscle-type and non-muscle-type aldolase mRNAs were cloned from lambda gt10 cDNA libraries constructed from skeletal muscle and liver mRNAs of lamprey (Entosphenus japonicus). The cDNA-M8 has 2,240 bp carrying an open reading frame of 1,089 bp which encodes 362 amino acids without the amino terminal methionine, while the cDNA-L3 is 1,761 bp in length and has an open reading frame of 1,092 bp, which encodes 363 amino acids without the methionine. We designated the cDNA clones M8 and L3 as the muscle-type and non-muscle-type aldolase cDNAs, respectively. The entire amino acid sequences deduced from cDNA-M8 and -L3 show a high degree of identity to one another (76%) and also to vertebrate aldolases A (74-76%), B (68-70%), and C (71-76%) and Drosophila melanogaster aldolases alpha, beta, and gamma (66-67%). Northern blot analyses using the 3'-noncoding sequences of cDNA-M8 and -L3 as hybridization probes indicated that the muscle-type mRNA is expressed mainly in the skeletal muscle, heart muscle, brain, and some other tissues, but probably not in liver, while the non-muscle-type mRNA is expressed mainly in the liver and also in brain and other tissues, except for the heart muscle. Phylogenetic analyses showed that both muscle-type and non-muscle-type aldolases of lamprey resemble one another and might share a common ancestor with vertebrate aldolases A and C, but they are not direct ancestors of vertebrate aldolases.

[Clinical effects of carmofur (Mifurol) on advanced and recurrent breast cancer in a cooperative study. Research association for re-evaluation of direct effects of Mifurol on breast cancer]

The direct effect and safety of carmofur (Mifurol) in cases of advanced and recurrent breast cancer were evaluated as a cooperative study at twenty-two facilities nationwide. Carmofur 12 mg/kg/day within the maximum daily dose of 600 mg was administered orally for eight weeks or longer. Of 42 patients registered for the study, 38 met the eligibility criterial (qualified patients), of whom 31 completed all tests for evaluation (completely qualified patients). The response rates were 18.4% with the qualified patients (PR, 7; Long NC, 3; NC, 11; PD, 12; NE, 5; ie, 7/38), and 22.6% with the completely qualified patients (PR, 7; Long NC, 2; NC, 10; PD, 12; ie, 7/31). The interval before the onset of PR after administration of carmofur was started was a minimum 29 days, a maximum 190 days and a median 82 days. Side effects were observed in eighteen patients (42.9%). Frequent micturition, loss of appetite, dizziness or feverish feeling were major symptoms, but none were serious.

Interleukin-1 gene expression in transient retinal ischemia in the rat

PURPOSE

To determine in rats whether there are time-dependent changes in interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) gene expression in transient retinal ischemia and to localize their mRNAs in the retina.

METHODS

Retinal ischemia was induced in Sprague-Dawley rats by ligating the optic nerve. Two hours later, the ligature was released and reperfusion occurred. The levels of IL-1 alpha and IL-1 beta gene expression in the sensory retina were then compared at various times after reperfusion by a semiquantitative polymerase chain reaction method. Localization of their expressed mRNAs was examined by in situ hybridization histochemistry.

RESULTS

Little expression of IL-1 alpha and IL-1 beta genes was observed in normal retina. IL-1 alpha gene expression rapidly increased (about 30-fold greater than that of the control) as early as 1 hour after cessation of ischemia, reached a peak (about 50-fold) at 3 to 12 hours, and then gradually decreased to near baseline levels. IL-1 beta gene expression began to increase 2 hours later than did that of IL-1 alpha and had two peaks. IL-1 beta gene was found by in situ hybridization histochemistry to be expressed by retinal glial cells, endothelial cells, and neutrophils infiltrating the retina and vitreous. No gene expression was found in the control retinas.

CONCLUSIONS

Expression of IL-1 alpha and IL-1 beta genes was dramatically upregulated during reperfusion after induced retinal ischemia. IL-1 beta gene was expressed by retinal glial cells, endothelial cells, and neutrophils recruited into the retina. From these results, it appeared that IL-1 may have an important role in retinal ischemia-reperfusion injury.

The frequency of patients with 50-kd dystrophin-associated glycoprotein (50DAG or adhalin) deficiency in a muscular dystrophy patient population in Japan: immunocytochemical analysis of 50DAG, 43DAG, dystrophin, and utrophin

The 50-kd dystrophin-associated glycoprotein (50DAG or adhalin) in the skeletal muscle has been shown to be deficient in patients with severe childhood autosomal recessive muscular dystrophy prevalent in North Africa. To elucidate the frequency of patients having the 50DAG deficiency in a muscular dystrophy population in Japan, we immunocytochemically examined 50DAG, 43DAG, dystrophin, and utrophin. A total of 243 patients with muscular dystrophy, among 1,035 diagnostic muscle biopsies during the past 2.5 years, were analyzed. We identified five unrelated patients (three females and two males who have no family history) with 50DAG deficiency in the sarcolemma. Thus, 2.1% (5/243) of our muscular dystrophy patient population had 50DAG deficiency.

Modulation of the buccal muscle contraction by identified serotonergic and peptidergic neurons in the snail Achatina fulica

Serotonergic and peptidergic modulation of buccal muscle contraction at an identified neuromuscular synapse in the African giant snail Achatina fulica was examined. A pair of excitatory motoneurons of the radula protractor was identified in the buccal ganglia and these were named B10 neurons. Pharmacological experiments revealed the B10s to be cholinergic. The serotonergic cerebral neuron v-CDN enhanced B10-evoked contraction of the radula protractor, and it is suggested that this effect is mediated postsynaptically by serotonin released from the v-CDN terminals. Immunohistochemical analyses revealed that the B10 motoneurons contained an Achatina cardioexcitatory peptide-1 (ACEP-1)-like substance in their cell body, axon and terminals in the radula protractor. From electron microscopic observation, the ACEP-1-like immunoreactive substance was found to be localized in dense-cored vesicles but not in clear vesicles in the nerve terminals. ACEP-1 applied to the radula protractor markedly enhanced B10-evoked contraction of the muscle by increasing the amplitude of excitatory junction potentials (EJPs). The increase of EJP amplitude in the presence of the peptide was probably due to the increased release of acetylcholine from the terminals of B10. It is suggested that the cholinergic motoneuron B10 uses ACEP-1 as an excitatory cotransmitter.

Existence of a transcription factor for the human HMG2 gene positively related to the level of HMG2 mRNA in the cells

A functional gene encoding high mobility group 2 (HMG2) protein, which is an abundant eukaryotic DNA-binding protein, has been isolated. The expression of the HMG2 gene is enhanced in exponentially growing cells and in cells transformed with various viral genes and oncogenes. We attempted to identify and characterize the HMG2 gene structure and transcription factor(s) participating in the expression of the gene. Chloramphenicol acetyltransferase assays to characterize the 5'-flanking region of the human HMG2 gene revealed that the nucleotide sequences in two regions are necessary for expression of the HMG2 gene: one (-85 to +44 region) as a core promoter, and the other (-621 to -493 region) as a cis regulatory element(s). Electrophoresis mobility shift assay with a DNA fragment containing the cis regulatory element and a crude nuclear extract from HeLa cells gave several complexes. Chemical footprint and competition assays indicated that the component giving one of the major complexes recognizes a nucleotide sequence of -499 to -486 in the cis regulatory element. Chloramphenicol acetyltransferase assay indicated that the component giving the major complex is required for the effective transcription of the HMG2 gene. The binding component named HMG2TF (HMG2 transcription factor) contained a protein in apparent molecular size of 85,000, as determined by a UV cross-linking experiment. The amount of HMG2TF in the growing cells and transformed cells increased in positive relationship to the level of expression of HMG2 mRNA in the cells. These results suggest that HMG2 gene expression may be regulated by the relative amount of this transcription factor.

Neurotrophic effects of conditioned media of astrocytes isolated from different brain regions on hippocampal and cortical neurons

The present study was designed to reveal whether astroglial cells from different brain regions produce diffusible factors that differentially support the survival of neurons and the establishment of neuronal morphology. For this purpose, astrocyte conditioned media (ACM) were prepared by conditioning chemically-defined medium with type I astrocyte culture dissociated from cerebral cortex, hippocampus and hypothalamus. Hippocampal and cortical neurons were cultured in ACM or in non-conditioned medium. ACM derived from three brain regions all supported the survival of hippocampal and cortical neurons better than non-conditioned control medium. Of these, hypothalamic ACM was the most effective in supporting the survival of cortical neurons. The ACM also potentiated the elongation of the longest neurite of hippocampal and cortical neurons. However, there were no significant differences in the promoting effects on neurite elongation among ACM from three brain regions.

Chaperonin releases the substrate protein in a form with tendency to aggregate and ability to rebind to chaperonin

To know whether the protein released from chaperonin GroEL/ES is in a form committed to the native state or still an aggregatable non-native one, two experiments were carried out. Dilution of the [GroEL-substrate protein] binary complex prior to ATP addition significantly improved the yield of folding, suggesting that the released protein has a tendency to aggregate. When N-ethylmaleimide treated GroEL, which can form the binary complex but not release the bound protein, was added to the binary complex prior to ATP addition, productive folding was severely inhibited, indicating that the protein released from GroEL/ES can bind to N-ethylmaleimide treated chaperonin. These data favor the 'reservoir' or 'reversion' model, in which GroEL/ES acts as a buffer of folding intermediate or mediates reversion of a misfolded protein to a less folded primitive form, rather than the 'marsupium' model in which folding of the substrate protein proceeds in chaperonin.

A common topology of proteins catalyzing ATP-triggered reactions

A protein fold, six parallel beta strands surrounding the central alpha helix, is likely to be a common structure in protein families known to have a typical set of nucleotide binding consensus sequence motifs A and B and to catalyze ATP-triggered reactions. According to this ATP-triggered protein fold, the conserved Glu (or Asp), which acts as a general base to activate a water molecule for an in-line attack of the gamma-phosphate, is at the exit of the second beta strand. The fifth beta strand may be involved in propagation of conformational change triggered by ATP hydrolysis.

Insulin modulation of bronchial epithelial cell fibronectin in vitro

Fibronectin (Fn) is involved in the migration of epithelial cells in re-epithelialization of wounds. Epithelial cell-derived Fn is particularly potent as a chemotactic factor for bronchial epithelial cells (BECs) in vitro. Thus modulation of airway epithelial cell Fn may be a key aspect of airway repair. Insulin is both an important growth factor and known chemotactic factor for cultured BECs. We postulated that insulin may modulate Fn production of cultured BECs. We examined this hypothesis utilizing bovine BECs in culture with serum-free media with and without insulin. BECs grown in media without insulin released more Fn into culture supernatants and contained more Fn in cell layers than cells grown with insulin. Labeling of cells with [35S]methionine demonstrated an increase in new protein production and Fn mRNA expression was increased. Increased Fn in BEC cultures without insulin was associated with an increase in active transforming growth factor-beta (TGF-beta) release as measured by a standard bioassay. Increased BEC Fn in cultures without insulin was partially inhibited by exposure of cultures to TGF-beta antibody. Thus insulin appears to modulate BEC Fn production in vitro in part through a TGF-beta-dependent mechanism. Insulin may be involved in airway repair mechanisms through modulation of epithelial cell Fn production.