Yoshiko Yoshiyama

Identification of the N-terminal residue of the heavy chain of both native and recombinant human hepatocyte growth factor.

The N-terminal amino acid of the heavy chain of native (purified from human plasma) and recombinant human hepatocyte growth factor (hHGF) was determined by analyses of amino acid composition and sequence of peptide fragments derived by enzymatic cleavage, peptide mapping, and fast atom bombardment mass spectrometry. Our results indicate that the N-terminal amino acid of the heavy chain of hHGF, both native and recombinant, is pyroglutamate, derived from glutamine at the 32nd residue from the initiation methionine.

Internalization and degradation of hepatocyte growth factor in hepatocytes with down-regulation of the receptor/c-Met

Hepatocyte growth factor (HGF) promotes proliferation of cultured hepatocytes by its interaction with cell surface receptors. In this paper, we examined the metabolic fate of HGF using hepatocytes. Kinetic analysis using [125I]HGF showed that 40% of surface‐bound HGF was rapidly internalized in hepatocytes within 30 min at 37°C. Under these conditions, the amount of HGF‐bound c‐Met, the high‐affinity receptor, decreased from the cell surface. Furthermore, the internalized HGF was degraded and released from the cells. These results indicate that cell surface‐bound HGF is internalized and degraded by the receptors, including c‐Met, on hepatocytes.

Isolation and purification of a non-A, non-B hepatitis-associated microtubular aggregates protein

Blood-borne type non-A, non-B (NANB) hepatitis-associated microtubular aggregates protein was isolated and partially sequenced. The microtubular aggregates were isolated from the hepatocytes of NANB-infected chimpanzees and were found to have a buoyant density in sucrose solution of 1.21 to 1.23 g/ml. A single protein, recognized by our anti-microtubular aggregates monoclonal antibodies, was found to have an Mr of 44,000 (p44). This p44 protein was not found in uninfected chimpanzees. We determined a partial amino acid sequence for p44, and showed that it has no homology to any known proteins.

cloning, sequencing and expression in Escherichia coli of cDNA for a non-A, non-B hepatitis-associated microtubular aggregates protein

A 1.7 kb cDNA encoding a novel antigen (p44; apparent Mr 44K) associated with non-A, non-B (NANB) hepatitis, was isolated from the hepatic cDNA library of a chimpanzee infected with NANB hepatitis. The library was screened with a monoclonal antibody against this antigen. The cDNA cloned contained an open reading frame encoding a 444 amino acid protein with an Mr calculated to be 50,468. The cDNA hybridized to a 1.9 kb mRNA obtained from chimpanzee hepatocytes infected with either the NANB or hepatitis delta viruses. It hybridized weakly to mRNA from hepatitis B virus-infected hepatocytes, and not at all to mRNA from normal chimpanzee hepatocytes. Southern blot analysis revealed that p44 is a host protein in chimpanzees, and that an identical gene exists in the human genome.