Identification of a family of insulin-like growth factor II secreted by cultured rat epithelial-like cell line 18,54-SF: application of a monoclonal antibody.

Somatomedin/insulin-like growth factor (IGF)-like polypeptides (designated SMP) were purified from the serum-free conditioned medium of cultured rat epithelial-like cells, 18,54-SF. A monoclonal antibody (MAb) was produced against partially purified SMP. The antibody was immunoglobulin G1 relatively specific for multiplication-stimulating activity III-2 (rat IGF-II), with a Kd value of 5.6 X 10(-9) M. The antibody showed 100% cross-reactivity with human IGF-II and 10% cross-reactivity with human IGF-I, but did not cross-react with insulin. For purification of SMP, therefore, immunoaffinity chromatography on Sepharose coupled with the MAb was used besides a procedure including ion exchange chromatography, gel filtration, and reverse phase HPLC. The purified SMP (at least five polypeptides) each gave a single peak on reverse phase HPLC and appeared as a single band with an apparent mol wt of 5000-8000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The major components of SMP (designated HP1-SMP and HP3-SMP), which were purified about 100-fold from conditioned medium, stimulated DNA synthesis in human fibroblasts in culture and sulfation in chick embryonic cartilage in culture. These polypeptides showed almost the same cross-reactivity as multiplication-stimulating activity III-2 on RIA with the MAb. The partial amino acid sequences of HP1- and HP3-SMP were determined, and these polypeptides were identified with rat IGF-II.

Identification of trypsin inhibitor in bovine pituitary extracts as a survival factor for adult rat hepatocytes in primary culture.

Adult rat hepatocytes in primary culture cannot survive more than 2 days in the absence of calf serum. An extract of bovine pituitary gland had a similar effect to calf serum on the survival of hepatocytes, but its specific activity was 70 times that of calf serum. The survival factor was purified from bovine pituitary gland, and obtained in a homogeneous state judging by sodium dodecylsulfate-polyacrylamide gel electrophoresis and high performance liquid chromatography. Its purification was achieved by acid extraction of the pituitary gland, gel filtrations on Sephadex G-75 and Ultrogel AcA 202, ion-exchanger chromatography on CM-cellulose, and then reverse phase high performance liquid chromatography. The purified factor was effective at 10 ng/ml and maximally effective at 100 ng/ml. The overall recovery of its activity was 30%, and the specific activity of the purified factor was 3,100 times that in the acid extract. The molecular weight (Mr 8,000), estimated by Sephadex G-200 filtration, and the strong basic character (pI 10.5) of the purified survival factor suggested that it may be the trypsin inhibitor found in various tissues. Indeed, the amino acid composition of the pure material was identical with that of bovine pancreatic trypsin inhibitor (bPTI). The purified survival factor had the same inhibitory activity on trypsin as commercial bPTI and, conversely, commercial bPTI greatly enhanced survival of rat hepatocytes. Thus, the survival factor in bovine pituitary gland was identified as bPTI.

Purification and characterization of hepatocyte growth factor from injured liver of carbon tetrachloride-treated rats.

A hepatocyte growth factor (HGF)-like substance that strongly stimulated DNA synthesis of adult rat hepatocytes in primary culture was found to increase markedly in liver of rats treated with carbon tetrachloride (CCl4). This increase of HGF-like activity was time- and dose-dependent, and 36 h after a dose of CCl4 of 0.2 ml per 100 g body weight the activity was about 20-times the normal level. The extent of induction of HGF-like factor correlated well with the extent of liver damage. The HGF-like factor was purified to homogeneity from the liver of CCl4-treated rats by a four-step procedure. The purified HGF-like factor had a molecular weight of 82-85 kDa, as estimated by SDS-PAGE, and was a heterodimer composed of a large subunit of about 69 kDa and a small subunit of 34 kDa linked by disulfide bridges. This factor had similar biological and chemical properties to HGF purified from rat platelets. Moreover, the N-terminal amino acid sequence of its 34-kDa subunit was identical to that of the small subunit of rat HGF. These findings indicate that the HGF-like factor in damaged liver of CCl4-treated rats is HGF and that liver itself can produce HGF when injured.

Isolation of a protease-deficient mutant of Bacillus brevis and efficient secretion of a fungal protein disulfide isomerase by the mutant.

The efficient production of a thermostable protein disulfide isomerase (PDI) was successfully achieved using the newly isolated protease-deficient mutant, Bacillus brevis 31-OK. Extracellular protease (exoprotease) activity was about a quarter of that in the parent, and the mutant was deficient in at least one of the major exoproteases. The cDNA encoding the fungal PDI was inserted downstream of the signal peptide-encoding region in an expression-secretion vector for B. brevis. Efficient production of PDI was feasible using B. brevis 31-OK as a host and modified signal sequences composed of three leucine residues inserted in the hydrophobic region of the MWP (middle wall protein) signal sequence. The maximal secretion of PDI into the culture medium was 1.1 g/l, which is about twice that by the parent strain and fifty times greater than the amount of rat and murine PDIs produced by Escherichia coli. The enzymatic properties such as the specific activity and thermal stability of the recombinant PDI are similar to those of natural PDI derived from Humicola insolens mycelia. B. brevis 31-OK was able to maintain its exoprotease activity at a low level throughout the cultivation and is considered to be useful host for production of a protease-sensitive protein and for increase of protein productivity due to stable accumulation.

Disulfide bond formation in refolding of thermophilic fungal protein disulfide isomerase.

Disulfide bond formation in the refolding of thermophilic fungal protein disulfide isomerase (PDI) was investigated. It was revealed that (i) a disulfide bond buried inside the molecule is preferentially formed and contributes to the thermal stability and the isomerizing power of PDI, and (ii) formation of disulfide bonds in active sites located on the molecular surface causes deformation of the optimum conformation resulting in a decrease in the thermal stability.

[Clinical characteristics of the lung diseases due to Mycobacterium avium and Mycobacterium intracellulare classified by DNA probe test].

Clinical characteristics of the lung diseases due to M. avium and M. intracellulare classified by DNA probe test were investigated. Between M. avium and M. intracellulare, there was no significant differences in the samples' backgrounds and the clinical characteristics except for their prognoses. The prognosis of the lung diseases due to M. intracellulare was better than those due to M. avium, and M. avium was revealed to be highly susceptible to Cyclocerine than M. intracellulare. No remarkable difference was found in the susceptibility to other antituberculous drugs.

Increased survival of rat hepatocytes in serum-free medium by inhibition of a trypsin-like protease associated with their plasma membranes.

Bovine pancreatic trypsin-inhibitor (bPTI) is required for survival of adult rat hepatocytes for more than 2 days in primary cultures in serum-free medium. Of the various protease inhibitors tested, all trypsin inhibitors increased the survival of rat hepatocytes in serum-free medium, their potencies being in the order bPTI greater than alpha 2-plasmin inhibitor greater than leupeptin greater than soybean trypsin inhibitor greater than alpha 1-antitrypsin = alpha 2-macroglobulin. Elastatinal, a specific inhibitor of elastase, was also effective. bPTI did not inhibit the degradation of proteins with short or long lives, suggesting that it did not increase the survival of hepatocytes by inhibiting cellular protein degradation. alpha 2-Plasmin inhibitor immobilized on Sepharose 4B caused dose-dependent increase in survival. Plasma membranes purified from adult rat liver had significant protease activity, about 80% of which was sensitive to bPTI, alpha 2-plasmin inhibitor and leupeptin. From its specificity for substrates and sensitivity to inhibitors, the membrane-bound protease was characterized as a trypsin-like protease. The effects of various inhibitors on the membrane-bound protease correlated well with their abilities to increase survival of rat hepatocytes. Therefore, it seems that bPTI acts on the cell surface and increases hepatocyte survival in serum-free cultures by inhibiting a trypsin-like protease associated with the plasma membranes.

Extracellular production of an intact and biologically active human growth hormone by the Bacillus brevis system.

The characteristic features of the Bacillus brevis system are very high productivity of heterologous proteins and very low extracellular protease activity. However, degradation of some heterologous proteins, especially mammalian proteins, can be observed and resulted in a lowering of protein productivity. By using a mutant expressing low levels of proteases and the addition of EDTA to the medium, intact human growth hormone (hGH) was successfully produced with the B. brevis system. Signal peptide modification with higher basicity in the amino terminal region and higher hydrophobicity in the middle region brought about a twelve-fold increase in hGH production. The hGH yield was further elevated to 240 mg L-1 by optimization of culture conditions. Thus, biologically active and mature hGH can be efficiently produced directly in the medium with the B. brevis system.

Molecular cloning of a fungal cDNA encoding protein disulfide isomerase.

Based on the partial amino acid sequences of a protein disulfide isomerase (PDI) from Humicola insolens, two primers were synthesized for reverse transcriptase mediated polymerase chain reaction (RT-PCR) of a fungal RNA. A 0.2-kbp fragment around the consensus sequence of PDIs was obtained and used as a probe for screening a fungal cDNA library. A cDNA clone of PDI from H. insolens was isolated and encoded a polypeptide consisting of 505 amino acids, which was characterized by a N-terminal signal sequence composed of 20 amino acids, a consensus sequence (WCGHCK) at two positions, and a C-terminal endoplasmic reticulum retention signal (HDEL). Bacillus brevis harboring an expression plasmid bearing the fungal PDI cDNA was prepared and its culture supernatant showed a significant PDI activity. This indicates that glycosylation of a fungal PDI is not essential for the enzymatic activity related to an interchange of disulfide bonds.

Isolation and expression of cDNA for different forms of hepatocyte growth factor from human leukocyte.

Human leukocyte cDNA library was screened to isolate cDNA clones coding for hepatocyte growth factor using cDNA from human liver as a probe. Nucleotide and deduced amino acid sequences were analyzed for two of four clones obtained. One of them contained an open reading frame coding for a polypeptide chain of 728 amino acid residues like that of cDNA clone derived from human liver. In another clone a spontaneous deletion of 15 base pairs was found within the coding sequence. When expressed transiently using COS-1 cells both clones produced protein with similar biological activity against rat hepatocyte in vitro.