Reduced expression of kan-1 (encoding putative bile acid-CoA-amino acid N-acyltransferase) mRNA in livers of rats after partial hepatectomy and during sepsis

Impact of SLC6A Transporters in Physiological Taurine Transport at the Blood-Retinal Barrier and in the Liver

Cumulative studies showed that taurine (2-aminoethanesulfonic acid) contributes to a variety of physiological events. Transport study suggested the cellular taurine transport in an Na⁺- and Cl^--dependent manner, and the several members of SLC6A family have been shown as taurine transporter. At the inner blood-retinal barrier (BRB), taurine transporter (TauT/SLC6A) is involved in the transport of taurine to the retina from the circulating blood. The involvement of TauT is also suggested in γ-aminobutyric acid (GABA) transport at the inner BRB, and its role is assumed in the elimination of GABA from the retinal interstitial fluid. In the retina, taurine is thought to be a major organic osmolyte, and its influx and efflux through TauT and volume-sensitive organic osmolyte and anion channel (VSOAC) in Müller cells regulate the osmolarity in the retinal microenvironment to maintain a healthy retina. In the liver, hepatocytes take up taurine via GABA transporter 2 (GAT2/SLC6A13, the orthologue of mouse GAT3) expressed at the sinusoidal membrane of periportal hepatocytes, contributing to the metabolism of bile acid. Site-directed mutagenesis study suggests amino acid residues that are crucial in the recognition of substrates by GATs and TauT. The evidence suggests the physiological impact of taurine transporters in tissues.

[COMPOSITION OF GASTRIC JUICE AND BILE IN RATS AT THE EXPERIMENTAL CHRONIC PANCREATITIS]

Chronic pancreatitis is an inflammatory disease of the pancreas, which is characterized by destruction of pancreatic secretory parenchyma and progressing exocrine and endocrine insufficiency. Usually these patients have complications as cardiovascular, renal, respiratory and liver failure, and various gastric dysfunctions. The data of clinical observations do not reveal fully the functional state of the stomach and liver in chronic pancreatitis also remains an open question about the quality of the gastric juices and bile by this pathology. Therefore our aim was to investigate the secretory functions of the stomach and liver features in rats at the experimental chronic pancreatitis. This pathology modeled using L-arginine. Basal gastric secretion was investigated in chronic experiment by aspiration method for 10th and 63rd days, and pancreas and liver--in acute experiments at 13th and 68th days after the last administration of L-arginine. It was established that the character of the secretory response of the digestive tract depends on the duration of the pathology course. On the 10th day the functional state of the gastric secretory glands in rats with chronic pancreatitis characterized by twice increase of gastric acid production but decrease the level of hexosamines on 23.8% (P < 0.001) that indicate a increase of gastric content aggressiveness and mucus producing cells secretory insufficiency. In these animals the rate of total protein decreased on 61.7% (P < 0.05). On the 13th day observed the increase of pancreatic juice on 332% (P < 0.01), hepatic secret volume on 74.9% (P < 0.001) and redistribution in the cholates spectrum: glycocholates level increased but tauro-, free and total dehydroxylated bile acids decreased. These changes suggest deterioration of bile detergent properties, inhibition of acidic pathway of bile acids biosynthesis and conjugation of cholates with taurine. In two months total deficit of amino acids in gastric juice correlated with exocrine pancreatic insufficiency. Herein the acidity of gastric content partially restored, while the level of protein and mucus secretion proceed to decline. Consequently gastric mucosa is more vulnerable. In these rats the rates of free bile acids greatly increased while tauro- and glycocholates significantly decreased. Thus the processes of hydroxylation and conjugation of bile acids with amino acids inhibited suggesting interruption of synthetic and detoxification functions of the liver. The present work is important for comprehension the pathophysiological aspects of chronic pancreatitis particularly the digestive system functioning features at this pathology. These data could be considered in the appointment of treatment to avoid complications.

Involvement of γ-aminobutyric acid transporter 2 in the hepatic uptake of taurine in rats

Taurine is essential for the hepatic synthesis of bile salts and, although taurine is synthesized mainly in pericentral hepatocytes, taurine and taurine-conjugated bile acids are abundant in periportal hepatocytes. One possible explanation for this discrepancy is that the active supply of taurine to hepatocytes from the blood stream is a key regulatory factor. The purpose of the present study is to investigate and identify the transporter responsible for taurine uptake by periportal hepatocytes. An in vivo bolus injection of [(3)H]taurine into the rat portal vein demonstrated that 25% of the injected [(3)H]taurine was taken up by the liver on a single pass. The in vivo uptake was significantly inhibited by GABA, taurine, β-alanine, and nipecotic acid, a GABA transporter (GAT) inhibitor, each at a concentration of 10 mM. The characteristics of Na(+)- and Cl(-)-dependent [(3)H]taurine uptake by freshly isolated rat hepatocytes were consistent with those of GAT2 (solute carrier SLC6A13). Indeed, the K(m) value of the saturable uptake (594 μM) was close to that of mouse SLC6A13-mediated taurine transport. Although GABA, taurine, and β-alanine inhibited the [(3)H]taurine uptake by > 50%, each at a concentration of 10 mM, GABA caused a marked inhibition with an IC(50) value of 95 μM. The [(3)H]taurine uptake exhibited a significant reduction when the GAT2 gene was silenced. Immunohistochemical analysis showed that GAT2 was localized on the sinusoidal membrane of the hepatocytes predominantly in the periportal region. These results suggest that GAT2 is responsible for taurine transport from the circulating blood to hepatocytes predominantly in the periportal region.

Retinoid X receptor alpha participation in dexamethasone-induced rat bile acid coenzyme A-amino acid N-acyltransferase expression in septic liver

To test the hypothesis that dexamethasone (Dex) treatment would restore rat hepatic bile acid coenzyme A-amino acid N-acyltransferase (rBAT) expression in septic rats after cecal ligation and puncture by increasing expression of retinoic acid X receptor alpha (RXRalpha), we assessed survival rate and bile and bile salt concentration in the Dex-treated septic group and compared these results with those for a nontreated septic group, a Dex-treated nonseptic group, and a sham group. Dexamethasone treatment (0.01 mg/kg) significantly improved the survival rate and increased the bile and bile salt concentration in the bile ducts of septic rats (P = <0.05). In our assessment of bile salt-related genes, during sepsis, there were decreases in protein and mRNA expression of rBAT and cholesterol 7 alpha-hydroxylase (CYP7A1). Treatment with Dex restored expression of rBAT and RXR[alpha] but not CYP7A1, bile salt export pump, or multidrug resistance associated protein 2 (MRP2). Na+-taurocholate cotransport protein and organic anion transporting polypeptide 1 were unchanged. In addition, treatment with Dex also restored the DNA-binding activity of RXR/farnesoid-X receptor to rBAT promoter containing inverted repeat 1 sequence. In an experiment to confirm our findings, RXR[alpha] siRNA was found to significantly block Dex-induced increases in expression of rBAT in hepatocytes taken from septic rats (P < 0.01).

CONCLUSION

Dex restored the expression of rBAT in septic rats by enhancing RXR[alpha], a process that might explain the mechanism underlying Dex's anticholestatic effect.

Release of melanotroph- and corticotroph-type proopiomelanocortin derivatives into blood after administration of corticotropin-releasing hormone in patients with septic shock without adrenocortical insufficiency

The aim of the study was to assess the adequacy of pituitary function by determining the plasma concentrations of corticotroph-type (corticotropin, beta-endorphin immunoreactive material [beta-END IRM], authentic beta-END, and beta-lipotropin IRM) as well as melanotroph-type (alpha-melanocyte-stimulating hormone [alpha-MSH] and N-acetyl-beta-END [Nac-beta-END] IRM) proopiomelanocortin (POMC) derivatives in patients under septic shock upon administration of corticotropin-releasing hormone (CRH). The objectives were to assess whether an insufficient release of corticotroph- or melanotroph-type POMC derivatives from the pituitary into the cardiovascular compartment correlates with the 28-day mortality rate. Seventeen patients with septic shock but without adrenocortical insufficiency and 16 healthy volunteers were enrolled in the study, and CRH stimulation tests were performed with an i.v. bolus injection of 100 microg human CRH. After treatment with CRH, plasma concentrations of corticotroph-type POMC derivatives increased in survivors and nonsurvivors, melanotroph-type POMC derivatives such as alpha-MSH or Nac-beta-END IRM increased only in survivors in contrast to nonsurvivors. The release of alpha-MSH and Nac-beta-END IRM was suppressed by dexamethasone in survivors but not in nonsurvivors. In patients with septic shock, the response of the pituitary to CRH stimulation in terms of alpha-MSH or Nac-beta-END IRM release was impaired in nonsurvivors compared with survivors or controls. Reduced responses of alpha-MSH or Nac-beta-END IRM to CRH and the invalid suppression by dexamethasone reflect a state of dysfunction of the melanotroph-type POMC system in nonsurvivors. Considering anticytokine and anti-inflammatory effects of alpha-MSH, this dysfunction may increase the risk of death in patients with septic shock.

Role of retinoid-X receptor-alpha in the suppression of rat bile acid coenzyme A-amino acid N-acyltransferase in liver during sepsis

Sepsis causes intrahepatic cholestasis and leads to hepatic failure. However, the pathophysiology of hepatic events is unclear. Expression of rat hepatic bile acid coenzyme A-amino acid N-acyltransferase (rBAT), a major enzyme for the conjugation of bile acids, is significantly decreased during sepsis. rBAT transcriptional regulation is mainly by a heterodimer of farnesoid-X receptor (FXR) and retinoid-X receptor-alpha (RXR-alpha) via the inverted repeat 1 sequence. During sepsis, nuclear receptors and translocation of RXR-alpha from cytosol to nucleus decrease. The purpose of this study was to further clarify the mechanisms of RXR-alpha-mediated rBAT regulation during polymicrobial sepsis and with dexamethasone treatment. Polymicrobial sepsis was induced in rats by cecal ligation and puncture (CLP). Liver tissues obtained 3, 6, 9, and 18 h after CLP were studied, and hepatocytes were isolated from rats with sepsis. Post-CLP decreases were observed in mRNA levels of rBAT (6 h), protein levels of rBAT (6 h), RXR-alpha (6 h), and FXR (9 h). DNA binding activity of FXR/RXR significantly decreased at 6 h after CLP. Dexamethasone reversed sepsis-inhibited RXR-alpha expression and the binding activity of FXR/RXR to rBAT DNA as well as rBAT protein expression. The results suggest that suppression of rBAT occurs at the transcriptional level, and the decrease in RXR-alpha by septic insult may play a critical role in rBAT suppression at the early stage of polymicrobial sepsis.

Isolation of bona fide differentially expressed genes in the 18-hour sepsis liver by suppression subtractive hybridization

In late sepsis, it has been established that the liver plays a major role in the initiation of multiorgan failure, which is the most lethal complication in hospitals. The molecular mechanism underlying liver failure that results from sepsis remains elusive. This study was undertaken to identify the bona fide differentially expressed genes in the 18-h septic liver by suppression subtractive hybridization, and the data were corroborated by Northern blot analysis. The differential gene expression profile renders a clue as to the genes involved in septic liver failure. The cecal ligation and puncture (CLP) model of a polymicrobial septic rat was used, with the late sepsis referring to animals sacrificed at 18 h after CLP. We have identified three upregulated genes (TII-kininogen, serine protease inhibitor 2.2 [Spi2.2], and alpha 2 macroglobulin [alpha M]) and six down-regulated genes (hydroxysteroid dehydrogenase [3 alpha HSD], EST189895/mouse RNase4, bile acid-CoA-amino acid N-acyltransferase [kan-1/rBAT], IF1, albumin, and alpha 2u-globulins [alpha 2u-G PGCL1]). Among these genes, the 3 alpha HSD and kan-1/rBAT are involved in bile acid metabolism. The IF1 plays a crucial role in any disease that involves ATP hydrolysis by F1F0-ATPase. The alpha 2M, TII-kininogen, and Spi2.2 are protease inhibitors. The functions of the alpha 2u-G PGCL1 and EST189895/mouse RNase4 genes are unknown. The present results suggest that the roles of disturbance of bile acid metabolism/synthesis and the abolishment of ATP production may contribute to liver failure during late sepsis.

Molecular Cloning and Characterization of Two Mouse Peroxisome Proliferator-activated Receptor α (PPARα)-regulated Peroxisomal Acyl-CoA Thioesterases

Peroxisomes are organelles that function in the beta-oxidation of long- and very long-chain acyl-CoAs, bile acid-CoA intermediates, prostaglandins, leukotrienes, thromboxanes, dicarboxylic fatty acids, pristanic acid, and xenobiotic carboxylic acids. The very long- and long-chain acyl-CoAs are mainly chain-shortened and then transported to mitochondria for further metabolism. We have now identified and characterized two peroxisomal acyl-CoA thioesterases, named PTE-Ia and PTE-Ic, that hydrolyze acyl-CoAs to the free fatty acid and coenzyme A. PTE-Ia and PTE-Ic show 82% sequence identity at the amino acid level, and a putative peroxisomal type 1 targeting signal of -AKL was identified at the carboxyl-terminal end of both proteins. Localization experiments using green fluorescent fusion protein showed PTE-Ia and PTE-Ic to be localized in peroxisomes. Despite their high level of sequence identity, we show that PTE-Ia is mainly active on long-chain acyl-CoAs, whereas PTE-Ic is mainly active on medium-chain acyl-CoAs. Lack of regulation of enzyme activity by free CoASH suggests that PTE-Ia and PTE-Ic regulate intraperoxisomal levels of acyl-CoA, and they may have a function in termination of beta-oxidation of fatty acids of different chain lengths. Tissue expression studies revealed that PTE-Ia is highly expressed in kidney, whereas PTE-Ic is most highly expressed in spleen, brain, testis, and proximal and distal intestine. Both PTE-Ia and PTE-Ic were highly up-regulated in mouse liver by treatment with the peroxisome proliferator WY-14,643 and by fasting in a peroxisome proliferator-activated receptor alpha-dependent manner. These data show that PTE-Ia and PTE-Ic have different functions based on different substrate specificities and tissue expression.

Rat liver bile acid CoA:amino acid N-acyltransferase: expression, characterization, and peroxisomal localization

Bile acid CoA:amino acid N-acyltransferase (BAT) is responsible for the amidation of bile acids with the amino acids taurine and glycine. Rat liver BAT (rBAT) cDNA was isolated from a rat liver lambdaZAP cDNA library and expressed in Sf9 insect cells using a baculoviral vector. rBAT displayed 65% amino acid sequence homology with human BAT (hBAT) and 85% homology with mouse BAT (mBAT). Similar to hBAT, expressed rBAT was capable of forming both taurine and glycine conjugates with cholyl-CoA. mBAT, which is highly homologous to rBAT, forms only taurine conjugated bile acids (Falany, C. N., H. Fortinberry, E. H. Leiter, and S. Barnes. 1997. Cloning and expression of mouse liver bile acid CoA: Amino acid N-acyltransferase. J. Lipid Res. 38: 86-95). Immunoblot analysis of rat tissues detected rBAT only in rat liver cytosol following homogenization and ultracentrifugation. Subcellular localization of rBAT detected activity and immunoreactive protein in both cytosol and isolated peroxisomes. Rat bile acid CoA ligase (rBAL), the enzyme responsible for the formation of bile acid CoA esters, was detected only in rat liver microsomes. Treatment of rats with clofibrate, a known peroxisomal proliferator, significantly induced rBAT activity, message, and immunoreactive protein in rat liver. Peroxisomal membrane protein-70, a marker for peroxisomes, was also induced by clofibrate, whereas rBAL activity and protein amount were not affected. In summary, rBAT is capable of forming both taurine and glycine bile acid conjugates and the enzyme is localized primarily in peroxisomes in rat liver.

Hepatocyte nuclear factor 4alpha is a central regulator of bile acid conjugation

Hepatocyte nuclear factor 4alpha (HNF4alpha) has an important role in regulating the expression of liver-specific genes. Because bile acids are produced from cholesterol in liver and many enzymes involved in their biosynthesis are preferentially expressed in liver, the role of HNF4alpha in the regulation of bile acid production was examined. In mice, unconjugated bile acids are conjugated with taurine by the liver-specific enzymes, bile acid-CoA ligase and bile acid-CoA:amino acid N-acyltransferase (BAT). Mice lacking hepatic HNF4alpha expression exhibited markedly decreased expression of the very long chain acyl-CoA synthase-related gene (VLACSR), a mouse candidate for bile acid-CoA ligase, and BAT. This was associated with markedly elevated levels of unconjugated and glycine-conjugated bile acids in gallbladder. HNF4alpha was found to bind directly to the mouse VLACSR and BAT gene promoters, and the promoter activities were dependent on HNF4alpha-binding sites and HNF4alpha expression. In conclusion, HNF4alpha plays a central role in bile acid conjugation by direct regulation of VLACSR and BAT in vivo.

The human bile acid-CoA:amino acid N-acyltransferase functions in the conjugation of fatty acids to glycine

Bile acid-CoA:amino acid N-acyltransferase (BACAT) catalyzes the conjugation of bile acids to glycine and taurine for excretion into bile. By use of site-directed mutagenesis and sequence comparisons, we have identified Cys-235, Asp-328, and His-362 as constituting a catalytic triad in human BACAT (hBACAT) and identifying BACAT as a member of the type I acyl-CoA thioesterase gene family. We therefore hypothesized that hBACAT may also hydrolyze fatty acyl-CoAs and/or conjugate fatty acids to glycine. We show here that recombinant hBACAT also can hydrolyze long- and very long-chain saturated acyl-CoAs (mainly C16:0-C26:0) and by mass spectrometry verified that hBACAT also conjugates fatty acids to glycine. Tissue expression studies showed strong expression of BACAT in liver, gallbladder, and the proximal and distal intestine. However, BACAT is also expressed in a variety of tissues unrelated to bile acid formation and transport, suggesting important functions also in the regulation of intracellular levels of very long-chain fatty acids. Green fluorescent protein localization experiments in human skin fibroblasts showed that the hBACAT enzyme is mainly cytosolic. Therefore, the cytosolic BACAT enzyme may play important roles in protection against toxicity by accumulation of unconjugated bile acids and non-esterified very long-chain fatty acids.

Gene expression profile in the regenerating rat liver after partial hepatectomy

BACKGROUND/AIMS

When a loss of hepatic mass occurs, the expression of a large number of genes is either induced or altered, accompanying hepatocyte proliferation. In the present study, we made an in-house cDNA microarray containing 4608 elements (Liver chip), and analyzed extensively gene expression profiles of the regenerating liver after 70% partial hepatectomy (PHx) in rats.

METHODS

RNAs were prepared from three rat livers at each time point (taken at 0, 6, 12, 18, 24, 48, 72 h, and 1 week after PHx). Using the liver chip, we performed large-scale analysis of gene expression during liver regeneration. Elements either up- or down-regulated more than twofold at one or more time points were selected.

RESULTS

Among the 4608, 382 were identified. Using cluster analysis, we found great similarity between gene-expression profiles at 12 and 18 h after PHx as well as between 48 and 72 h after PHx. We also found that there are at least six distinct temporal patterns of gene expression in the regenerating rat liver after PHx.

CONCLUSIONS

These results indicated that microarray analysis is a powerful approach for monitoring molecular events in the regenerating liver.

Conserved residues in the putative catalytic triad of human bile acid Coenzyme A:amino acid N-acyltransferase

Human bile acid-CoA:amino acid N-acyltransferase (hBAT), an enzyme catalyzing the conjugation of bile acids with the amino acids glycine or taurine has significant sequence homology with dienelactone hydrolases and other alpha/beta hydrolases. These enzymes have a conserved catalytic triad that maps onto the mammalian BATs at residues Cys-235, Asp-328, and His-362 of the human sequence, albeit that the hydrolases contain a serine instead of a cysteine. In the present study, the function of the putative catalytic triad of hBAT was examined by chemical modification with the cysteine alkylating reagent N-ethylmaleimide (NEM) and by site-directed mutagenesis of the triad residues followed by enzymology studies of mutant and wild-type hBATs. Treatment with NEM caused inactivation of wild-type hBAT. However, preincubation of wild-type hBAT with the substrate cholyl-CoA before NEM treatment prevented loss of N-acyltransferase activity. Substitution of His-362 or Asp-328 with alanine results in inactivation of hBAT. Although substitution of Cys-235 with serine generated an hBAT mutant with lower N-acyltransferase activity, it substantially increased the bile acid-CoA thioesterase activity compared with wild type. In summary, data from this study support the existence of an essential catalytic triad within hBAT consisting of Cys-235, His-362, and Asp-328 with Cys-235 serving as the probable nucleophile and thus the site of covalent attachment of the bile acid molecule.

Identification of PTE2, a human peroxisomal long-chain acyl-CoA thioesterase

Computer-based approaches identified PTE2 as a candidate human peroxisomal acyl-CoA thioesterase gene. The PTE2 gene product is highly similar to the rat cytosolic and mitochondrial thioesterases, CTE1 and MTE1, respectively, and terminates in a tripeptide sequence, serine-lysine-valine(COOH), that resembles the consensus sequence for type-1 peroxisomal targeting signals. PTE2 was targeted to peroxisomes and recombinant PTE2 showed intrinsic acyl-CoA thioesterase activity with a pH optimum of 8.5. A comparison of PTE2 and PTE1 thioesterase activities across multiple acyl-CoA substrates indicated that while PTE1 was most active on medium-chain acyl-CoAs, with little activity on long-chain acyl-CoAs, PTE2 displayed high activity on medium- and long-chain acyl-CoAs. The identification of PTE2 therefore offers an explanation for the observed long-chain acyl-CoA thioesterase activity of mammalian peroxisomes.

cDNA cloning and genomic organization of peroxisome proliferator-inducible long-chain acyl-CoA hydrolase from rat liver cytosol

The cDNA for a peroxisome proliferator-inducible long-chain acyl-CoA hydrolase from rat liver cytosol, referred to as rLACH2, was isolated and its genomic structure was determined. The cDNA encoded a 419-amino-acid polypeptide with a calculated molecular weight of 46,011. Sequence analysis identified an active-site serine motif (Gly-x-Ser-x-Gly) common to carboxylesterases and lipases. When expressed in Escherichia coli, the cDNA directed expression of a protein immunoreactive to an anti-rLACH2 antibody with a molecular mass of 47 kDa, identical to that of purified rLACH2. Northern blot analysis showed marked induction of rLACH2 mRNA in the liver after feeding rats with di(2-ethylhexyl)phthalate, a peroxisome proliferator. The rLACH2 gene spanned about 19 kb and comprised 3 exons, the intron/exon boundaries of which were consistent with the donor/acceptor splice rule. A putative peroxisome proliferator response element (AGGTCATGGTTCA) was identified in the 5'-flanking region, suggesting the involvement of peroxisome proliferator-activated receptors in the regulation of rLACH2 gene expression.

Molecular cloning and characterization of a mitochondrial peroxisome proliferator-induced acyl-CoA thioesterase from rat liver

We have previously reported the purification and characterization of the peroxisome proliferator-induced very-long-chain acyl-CoA thioesterase (MTE-I) from rat liver mitochondria [L.T. Svensson, S.E. H. Alexson and J.K. Hiltunen (1995) J. Biol. Chem. 270, 12177-12183]. Here we describe the cloning of the corresponding cDNA. One full-length clone was isolated that contained an open reading frame of 1359 bp encoding a polypeptide with a calculated molecular mass of 49707 Da. The deduced amino acid sequence contains a putative mitochondrial leader peptide of 42 residues. Expression of the cDNA in Chinese hamster ovary cells, followed by immunofluorescence, immunoelectron microscopy and Western blot analyses, showed that the product was targeted to mitochondria and processed to a mature protein of 45 kDa, which is similar to the molecular mass of the protein isolated from rat liver mitochondria. The recombinant enzyme showed the same acyl-CoA chain-length specificity as the isolated rat liver enzyme. Sequence analysis showed no similarity to known esterases, but a high degree (approx. 40%) of identity with bile acid-CoA:amino acid N-acyltransferase cloned from human and rat liver. A putative active-site serine motif (Gly-Xaa-Ser-Xaa-Gly) of several carboxylesterases and lipases was identified. Western and Northern blot analyses showed that MTE-I is constitutively expressed in heart and is strongly induced in liver by feeding rats with di(2-ethylhexyl)phthalate, a peroxisome proliferator, suggesting a role for the enzyme in lipid metabolism.

Identification of a neutrophil gelatinase-associated lipocalin mRNA in human pancreatic cancers using a modified signal sequence trap method

To identify the intercellular signal-transducing proteins and receptors produced by cancer cells, we attempted to clone cDNAs encoding secreted and type I membrane proteins using a signal sequence trap (SST) method with some modifications. By screening an SST library derived from pancreatic cancer cells, we identified two secretory proteins (neutrophil gelatinase-associated lipocalin (NGAL) and lung surfactant protein D) and three membrane proteins (carcinoembryonic antigen, BiP/GRP78 and Hsa4 mitochondrion cytochrome oxidase subunit II). NGAL mRNA was expressed in eight of the pancreatic cancer cell lines and eight pancreatic cancer tissues. The expression of NGAL mRNA was also observed in colorectal and hepatic tumors.

A glycine-rich RNA-binding protein mediating cold-inducible suppression of mammalian cell growth

In response to low ambient temperature, mammalian cells as well as microorganisms change various physiological functions, but the molecular mechanisms underlying these adaptations are just beginning to be understood. We report here the isolation of a mouse cold-inducible RNA-binding protein (cirp) cDNA and investigation of its role in cold-stress response of mammalian cells. The cirp cDNA encoded an 18-kD protein consisting of an amino-terminal RNAbinding domain and a carboxyl-terminal glycine-rich domain and exhibited structural similarity to a class of stress-induced RNA-binding proteins found in plants. Immunofluorescence microscopy showed that CIRP was localized in the nucleoplasm of BALB/3T3 mouse fibroblasts. When the culture temperature was lowered from 37 to 32 degrees C, expression of CIRP was induced and growth of BALB/3T3 cells was impaired as compared with that at 37 degrees C. By suppressing the induction of CIRP with antisense oligodeoxynucleotides, this impairment was alleviated, while overexpression of CIRP resulted in impaired growth at 37 degrees C with prolongation of G1 phase of the cell cycle. These results indicate that CIRP plays an essential role in cold-induced growth suppression of mouse fibroblasts. Identification of CIRP may provide a clue to the regulatory mechanisms of cold responses in mammalian cells.

Decreased expression and rare somatic mutation of the CIP1/WAF1 gene in human hepatocellular carcinoma

CIP1/WAF1, a critical downstream effector of tumor suppressor p53, encodes a cyclin-dependent kinase inhibitor. By Northern blot analysis, the CIP1/WAF1 mRNA level in the tumor was significantly lower than that in the corresponding normal liver from 19 Japanese patients with hepatocellular carcinoma (P < 0.05). In the tumor from only one out of 19 patients (5%), somatic mutations of the CIP1/WAF1 as well as that of p53 gene were identified by RT-PCR/SSCP analysis. These results suggest that the decreased CIP1/WAF1 expression is involved in the carcinogenesis or the progression of hepatocellular carcinoma.