Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanisms by which blood levels of prothrombin (PT) are regulated in the vitamin K-sufficient state are unknown. We have studied PT synthesis by Reuber H-35 rat hepatoma cells exposed to vitamin K and [3H]leucine in serum-free cultures. Administration to the culture system of exogenous bovine PT and rat PT was characterized by increases in endogenous PT synthesis and secretion of 2- and 3-fold, respectively. This induction required endogenous proteolytic degradation of PT. Studies conducted with bovine PT fragment 1 (residues 1-156) demonstrated up to 5-fold increases in PT synthesis. This induction was dose dependent and saturable. Addition of bovine PT chymotryptic fragments to the cells indicated that the NH2-terminal peptide of prothrombin (residues 1-42) contained the requisite structural elements for the induction. Peptide-bound gamma-carboxyglutamate residues were required for the observed stimulation of PT synthesis. These results suggest that PT synthesis might be regulated physiologically by the products formed during its normal turnover and consumption during blood coagulation.
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PMID:Induction of prothrombin synthesis by prothrombin fragments. 694 25

Factor X in plasma is a gamma-carboxylated two-chain glycoprotein which, in activated form, plays a pivotal role in blood coagulation. We have utilized purified rat Factor X antibody, coupled to Sepharose, to isolate and characterize Factor X in rat liver, plasma, and hepatoma cells. Rat factor X is synthesized as a single chain precursor (Mr = 63,000). It is this form which undergoes vitamin K-dependent carboxylation in rat liver microsomes. Only after secretion is Factor X converted into its two-chain mature form. Single chain X synthesis and secretion in hepatoma cells is enhanced by vitamin K. The amount of single chain X secreted by these cells is one-half that of prothrombin. The NH2-terminal gamma-carboxylated fragments of prothrombin which induce prothrombin synthesis (Graves, C. B., Munns, T. W., Carlisle, T. L., Grant, G. A., and Strauss, A. W. (1981) Proc. Natl. Acad. Sci. U. S. A. 78, 4772-4776) also induce single chain X synthesis by hepatoma cells. We propose that synthesis of all vitamin K-dependent proteins may be regulated by this common control mechanism.
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PMID:Rat factor X is synthesized as a single chain precursor inducible by prothrombin fragments. 713 Jan 96

gamma-Glutamyl hydrolase is a ubiquitous enzyme that has the capacity to cleave gamma-glutamyl bonds of cellular folyl- and antifolylpoly-gamma-glutamates. This study has revealed that the enzyme is secreted by primary cultures of rat hepatocytes and by H35 hepatoma cells. It was found that more than 99% of the total enzyme from H35 cells accumulated in the medium after 48 hr incubation with the serum-free medium. The cells were shown to remain intact during the secretion period since lactate dehydrogenase, dihydrofolate reductase and lysosomal hydrolases other than gamma-glutamyl hydrolase were retained within the cell. When PteGlu5 (folylGlu4) is used as a substrate the initial product is PteGlu (folate), and there is no appearance of intermediate chain length pteroyl polyglutamates. Therefore, the secreted and cellular gamma-glutamyl hydrolase from hepatoma cells appears to be an endopeptidase. Polyclonal antibodies to the poly-gamma-glutamate substrates of the enzyme were prepared and characterized. The antibodies recognize the structural differences between alpha- and gamma-glutamyl linkages but appear equally active with PteGlu5 and its analogs such as 4-NH2-10-CH3PteGlu5 and pABAGlu5. The affinity of the antibodies is related to the gamma-glutamyl structure since L-glutamic acid, folate or p-aminobenzoic acid are inactive with the antibodies. Furthermore, poly-gamma-glutamate has lower affinity for the antibodies than the poly-gamma-glutamate derivatives of PteGlu, 4-NH2-10-CH3PteGlu or pABA.
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PMID:The properties and function of gamma-glutamyl hydrolase and poly-gamma-glutamate. 768 89

Two unusual aminopropyl acceptors found in a survey of putrescine binding sites of mammalian spermidine synthase, N-methylputrescine (I) and 4-aminomethylpiperidine (II), were examined for their aminopropyl derivatives. Studies under in vitro incubation conditions suggested that the aminopropyl derivatives of the secondary amine of I and II, N4-methylspermidine (Is) and 1-N-(3-aminopropyl)-4-aminomethylpiperidine (IIs), and of the primary amine of I and II, N8-methylspermidine (Ip) and 4-[N-(3-aminopropyl)aminomethyl]piperidine (IIp), respectively, were biosynthesized by rat spermidine synthase. Studies on the cell culture system of cultured rat hepatoma (HTC) cells treated with alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, clearly showed the presence of Is and Ip when I was administered, and IIs and IIp when II was administered, with no detection of putrescine or spermidine. These results suggested that mammalian spermidine synthase can transfer the aminopropyl moiety of decarboxylated S-adenosylmethionine to certain secondary amines in living cells.
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PMID:Enzymatic aminopropylation of certain secondary amines. 774 12

The arginine deiminase (AD) gene was cloned from Mycoplasma arginini and expressed in the cytosol of Escherichia coli as inclusion bodies with an expression level of at least 20% of the total bacterial proteins. The inclusion bodies were solubilized with 6 M guanidine hydrochloride (Gdn-HCl) under reducing conditions, in order to avoid incorrect disulfide-bond formation of the recombinant (r-) AD molecules, and renaturation was performed under various refolding conditions. The optimum renaturation conditions were found to be incubation for 90 h at pH 7.5 and 15 degrees C. The resulting completely refolded r-AD was purified to homogeneity by anion-exchange and arginine-affinity chromatography and its activity yield was 72.5%. The specific activity of the purified r-AD was comparable to and its amino acid composition was identical to those of Mycoplasma AD, and NH2-terminal sequence analysis revealed that its methionine residue corresponding to the translation initiation codon had been removed completely. Anti-tumor activity analyses showed that r-AD inhibited the growth of two mouse cell lines, hepatoma MH134 and fibrosarcoma Meth A, strongly in vitro at concentrations in excess of 10 ng ml-1. Moreover, when MH134-implanted mice were given single intravenous injections of r-AD at doses of 50 mg kg-1 and higher, their survival times were prolonged significantly. These results, taken together, indicate that the enzymatic properties and biological actions of r-AD were highly consistent with those of Mycoplasma AD.
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PMID:High-level expression of Mycoplasma arginine deiminase in Escherichia coli and its efficient renaturation as an anti-tumor enzyme. 776 34

L-type pyruvate kinase (L-PK) gene transcription is induced by glucose through its glucose response element (GlRE) composed of two degenerated E boxes able to bind in vitro ubiquitous upstream stimulator factor (USF) proteins. Here we demonstrate in vivo, by transient transfections in hepatoma cells, that (i) native USF proteins synthesized from expression vectors can act as transactivators of the L-PK promoter via the GlRE, stimulating transcription without glucose and, therefore, decreasing the glucose responsiveness of the promoter; (ii) expression of the truncated USF proteins, able to bind the GlRE but devoid of the NH2-terminal activation domain, represses the activation of the L-PK promoter by glucose; and (iii) a similar repression of the glucose effect is observed upon expression of mutant USF proteins devoid of the basic DNA binding domain, able to dimerize with endogenous USF but not to bind the GlRE. We conclude that USF proteins are components of the transcriptional glucose response complex assembled on the L-PK gene promoter.
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PMID:Upstream stimulatory factor proteins are major components of the glucose response complex of the L-type pyruvate kinase gene promoter. 785 31

Peptide 23 is a newly identified protein secreted by rat pituitary cells in primary culture. Although the secretion of this protein is stimulated by GH-releasing hormone and inhibited by somatostatin, the N-terminal amino acid sequence of peptide 23 shows no homology to rat GH. Using the polymerase chain reaction technique, we cloned and sequenced the peptide 23 complementary DNA (cDNA). By means of the mixed oligonucleotide-primed amplification of cDNA technique, primers corresponding to the NH2-amino acid sequence of peptide 23 were used to amplify, clone, and sequence a 74-basepair cDNA of peptide 23. This polymerase chain reaction product was then used as a primer to amplify the complete peptide 23 cDNA by means of the rapid amplification of cDNA ends procedure. The cDNA of peptide 23 obtained by the rapid amplification of cDNA ends procedure contained 777 nucleotides and encoded a 175-amino acid protein with a 26-amino acid putative signal peptide. The calculated mol wt of the mature protein (16,613 daltons) was in good agreement with that estimated by polyacrylamide gel electrophoresis (16 kilodaltons). Northern blot analysis revealed a major messenger RNA species of about 0.9 kilobase and a minor species of about 1.7 kilobases in cultured rat anterior pituitary cells. In rats, peptide 23 was most abundant in the pancreas and gastrointestinal tract. A GenBank sequence search revealed complete sequence identity between peptide 23 cDNA and pancreatitis-associated protein cDNA, an approximately 73% homology with human hepatocellular carcinoma cDNA from human hepatocellular carcinoma, 64% homology with bovine pancreatic thread protein cDNA, and 55% homology with rat and human reg cDNAs, which have been reported to be expressed in regenerating pancreatic islets. Therefore, peptide 23 is identical to pancreatitis-associated protein and a member of the C-type lectin supergene family.
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PMID:Molecular cloning and expression of peptide 23, a growth hormone-releasing hormone-inducible pituitary protein. 789 43

cDNA encoding the precursor of rat very-long-chain acyl-CoA dehydrogenase (VLCAD) was cloned and sequenced. The longest cDNA insert had 2117 bases. This cDNA encodes the entire protein of 655 amino acids, including a 40-amino acid leader peptide and a 615-amino acid mature polypeptide. The identity of the VLCAD clone was confirmed by matching the amino acid sequence predicted from the cDNA to the NH2 terminus and seven internal proteolytic peptide sequences from purified rat liver VLCAD. The calculated molecular masses of the precursor protein, the mature protein, and the leader peptide are 70,961, 66,508, and 4,470 daltons, respectively. At the amino acid level, the significant homology to the other acyl-CoA dehydrogenases was found at the range from the 94th to the 473rd amino acid residue of the amino-terminal side. The catalytic residue and the residue lying near the dimethylbenzene side (si-side) of the flavin ring were speculated to be Glu-462 and Trp-249, respectively. The VLCAD cDNA was expressed in four kinds of hepatoma cells using a vaccinia virus expression system and was shown to encode the catalytically active enzyme. The cDNA expression in both rat hepatoma H4IIEC3 and McA-RH7777 enhanced about 3-fold mitochondrial beta-oxidation activity of long-chain fatty acids such as palmitic acid and stearic acid; hence, VLCAD is probably a rate-limiting enzyme in the long-chain fatty acid beta-oxidation system in these cell lines.
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PMID:Rat very-long-chain acyl-CoA dehydrogenase, a novel mitochondrial acyl-CoA dehydrogenase gene product, is a rate-limiting enzyme in long-chain fatty acid beta-oxidation system. cDNA and deduced amino acid sequence and distinct specificities of the cDNA-expressed protein. 803 67

A novel member of the cadherin family of cell adhesion molecules has been characterized by cloning from rat liver, sequencing of the corresponding cDNA, and functional analysis after heterologous expression in nonadhesive S2 cells. cDNA clones were isolated using a polyclonal antibody inhibiting Ca(2+)-dependent intercellular adhesion of hepatoma cells. As inferred from the deduced amino acid sequence, the novel molecule has homologies with E-, P-, and N-cadherins, but differs from these classical cadherins in four characteristics. Its extracellular domain is composed of five homologous repeated domains instead of four characteristic for the classical cadherins. Four of the five domains are characterized by the sequence motifs DXNDN and DXD or modifications thereof representing putative Ca(2+)-binding sites of classical cadherins. In its NH2-terminal region, this cadherin lacks both the precursor segment and the endogenous protease cleavage site RXKR found in classical cadherins. In the extracellular EC1 domain, the novel cadherin contains an AAL sequence in place of the HAV sequence motif representing the common cell adhesion recognition sequence of E-, P-, and N-cadherin. In contrast to the conserved cytoplasmic domain of classical cadherins with a length of 150-160 amino acid residues, that of the novel cadherin has only 18 amino acids. Examination of transfected S2 cells showed that despite these structural differences, this cadherin mediates intercellular adhesion in a Ca(2+)-dependent manner. The novel cadherin is solely expressed in liver and intestine and was, hence, assigned the name LI-cadherin. In these tissues, LI-cadherin is localized to the basolateral domain of hepatocytes and enterocytes. These results suggest that LI-cadherin represents a new cadherin subtype and may have a role in the morphological organization of liver and intestine.
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PMID:Liver-intestine cadherin: molecular cloning and characterization of a novel Ca(2+)-dependent cell adhesion molecule expressed in liver and intestine. 820 63

gamma-Glutamyl hydrolase has been partially purified and characterized from conditioned culture medium of H35 hepatoma cells. Evidence for heterogeneity of the enzyme is derived from its elution as three distinct peaks of enzymatic activity when the enzyme is purified by TSK-butyl-Sepharose column chromatography. These three enzyme fractions appear to have identical catalytic properties but, as yet, the basis for their resolution is not understood. A rapid, sensitive and simple assay based on reverse-phase HPLC fluorescent detection with pre-column derivatization using o-phthalaldehyde (OPA) was developed to separate OPA-derivatives of poly-gamma-glutamates and glutamic acid. Using this assay and the standard HPLC assay for pteroylpolyglutamates, the enzyme appears to be an endopeptidase with respect to pteroylpenta-gamma-glutamate (PteGlu5), methotrexate penta-gamma-glutamate (4-NH2-10-CH3PteGlu5) and p-aminobenzoyl-penta-gamma-glutamate (pABAGlu5). The initial products are PteGlu1 (or 4-NH2-10-CH3PteGlu1 or pABAGlu1) and intact tetra-gamma-glutamate, which is subsequently degraded to glutamic acid. When penta-gamma-glutamate is the substrate, the cleavage of the gamma-bonds by the enzyme is less ordered, with the early appearance of mono-, di-, tri- and tetraglutamate. Poly-alpha-glutamate is not a substrate nor are pABA-gamma-Glu5 or penta-gamma-glutamate covalently linked to albumin. 4-NH2-10-CH3PteGlu2 or Glu5 bound to dihydrofolate reductase is not a substrate for the enzyme, offering further evidence that protein-associated poly-gamma-glutamates are poor substrates for gamma-glutamyl hydrolase from H35 hepatoma cells.
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PMID:The properties of the secreted gamma-glutamyl hydrolases from H35 hepatoma cells. 834 22


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