Identification and characterization of receptor for mammalian hepatopoietin that is homologous to yeast ERV1.
Hepatopoietin (HPO) is a novel polypeptide mitogen specific for hepatocytes and hepatoma cell lines, which is derived from liver and supports its regeneration. To determine whether HPO acts via a receptor-based signal transduction, recombinant human hepatopoietin was labeled by iodination and used to characterize its binding activity by specific displacement test and Scatchard analysis in primarily cultured rat hepatocytes and human hepatoma Hep-G2 cells. The binding was saturable and specific because it was replaceable by HPO but not by epidermal growth factor, transforming growth factor-alpha, or insulin. Scatchard analysis indicated the presence of a single class of high affinity receptor with dissociation constant (Kd) of 2 and 0.7 pM, and a receptor density of about 10, 000 sites/cell and 55,000 sites/cell in the rat hepatocytes and human hepatoma cells, respectively. The Kd values were consistent with the half-maximum dose of HPO activity. Affinity cross-linking of the receptor with 125I-HPO revealed a polypeptide of molecular mass approximately 90 kDa by SDS-polyacrylamide gel electrophoresis. Thus, the molecular mass of the HPO receptor was calculated to be about 75 kDa. These data demonstrated the existence of an HPO receptor in hepatocytes and hepatoma cells, which may account for biological effect.
Wang
G
G
Beijing Institute of Radiation Medicine, Chinese National Human Genome Center, 27 Taiping Road, Beijing 100850, People's Republic of China.
Yang
X
X
Zhang
Y
Y
Wang
Q
Q
Chen
H
H
Wei
H
H
Xing
G
G
Xie
L
L
Hu
Z
Z
Zhang
C
C
Fang
D
D
Wu
C
C
He
F
F
D000818:Animals; D002478:Cells, Cultured; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D024101:Mitochondrial Proteins; D050862:Oxidoreductases Acting on Sulfur Group Donors; D011485:Protein Binding; D019859:Proto-Oncogene Proteins c-met / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D029701:Saccharomyces cerevisiae Proteins; D014407:Tumor Cells, Cultured
D005656:Fungal Proteins; D007457:Iodine Radioisotopes; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; D017228:Hepatocyte Growth Factor; D050862:Oxidoreductases Acting on Sulfur Group Donors; C073790:ERV1 protein, S cerevisiae; D019859:Proto-Oncogene Proteins c-met