A Newly Established Cell Line from Normal Human Bone Responds to 1alpha, 25-Dihydroxyvitamin D3, Retinoic Acid and Transforming Growth Factor-beta1

We have recently established a new osteoblastic cell line, designated SV-HFO, from normal human bone by immortalization with simian virus 40. In the present study, we examined the effects of diffusive factors on the expression of osteoblastic phenotype in SV-HFO cell line. lα, 25-dihydroxyvitamin D? in-duced the expression of alkaline phosphatase (ALP) and osteocalcin. Retinoic acid down-regulated the expression of ALP, whereas it up-regulated the expres-sion of osteocalcin. Transforming growth factor-β?, reduced the expression of both osteoblastic properties. These effects were time- and dose-dependent. These results show that the SV-HFO cell line maintains responsiveness to these diffusive factors. This cell line is suitable model for studying both metabolism and multistep carcinogenesis of human bone

Oligomerization of Hepatitis C Virus Core Protein is Crucial for Interaction with the Cytoplasmic Domain of E1 Envelope Protein

Hepatitis C virus (HCV) contains two membrane-associated envelope glycoproteins, E1 and E2, which assemble as a heterodimer in the endoplasmic reticulum (ER). In this study, predictive algorithms and genetic analyses of deletion mutants and glycosylation site variants of the E1 glycoprotein were used to suggest that the glycoprotein can adopt two topologies in the ER membrane: the conventional type I membrane topology and a polytopic topology in which the protein spans the ER membrane twice with an intervening cytoplasmic loop (amino acid residues 288 to 360). We also demonstrate that the E1 glycoprotein is able to associate with the HCV core protein, but only upon oligomerization of the core protein in the presence of tRNA to form capsid-like structures. Yeast two-hybrid and immunoprecipitation analyses reveal that oligomerization of the core protein is promoted by amino acid residues 72 to 91 in the core. Furthermore, the association between the E1 glycoprotein and the assembled core can be recapitulated using a fusion protein containing the putative cytoplasmic loop of the E1 glycoprotein. This fusion protein is also able to compete with the intact E1 glycoprotein for binding to the core. Mutagenesis of the cytoplasmic loop of E1 was used to define a region of four amino acids (residues 312 to 315) that is important for interaction with the assembled HCV core. Taken together, our studies suggest that interaction between the self-oligomerized HCV core and the E1 glycoprotein is mediated through the cytoplasmic loop present in a polytopic form of the E1 glycoprotein