Biomedical subjects

N Ghosh-Choudhury

Publications and source records attributed to N Ghosh-Choudhury.

23 records · Page 2Linked to original sources

PubMed1994

Effects of transforming growth factor beta on bone nodule formation and expression of bone morphogenetic protein 2, osteocalcin, osteopontin, alkaline phosphatase, and type I collagen mRNA in long-term cultures of fetal rat calvarial osteoblasts.

Transforming growth factor beta (TGF-beta) is one of the most abundant of the known growth regulatory factors stored within the bone matrix. When bone is resorbed, TGF-beta is released in an active form and is a powerful bone growth stimulant. When injected into the subcutaneous tissue over the calvarial surface of rodents, it rapidly causes proliferation of the periosteal layer and accumulation of new woven bone. In this report, we describe the effects of TGF-beta 1 on first subcultures of fetal rat osteoblasts obtained from calvarial bones and cultured from confluence with ascorbic acid and beta-glycerophosphate. Under these conditions, nodules with characteristics of normal bone appear by day 8. Similar to experiments described by Antosz et al., TGF-beta added to confluent cultures inhibited the formation of bone nodules. Both the number and total area of the nodules were quantitated and shown to be completely inhibited by 2 ng/ml of TGF-beta 1. TGF-beta also impaired the expression of genes associated with bone formation, including type I collagen, alkaline phosphatase, osteopontin, and osteocalcin. TGF-beta also inhibited the expression of mRNA for the bone morphogenetic protein 2 (BMP-2). These results, showing suppression of markers representative of osteoblast differentiation, suggest that the effects of TGF-beta to stimulate bone formation in vivo are not likely a result of effects on differentiated mineralizing osteoblasts but, as suggested by previous studies, more likely are caused by effects on osteoblast precursors. These results also suggest that endogenous BMP-2 expression in fetal rat calvaria cells is important for bone cell differentiation.

Alkaline Phosphatase↗

PubMed1994

Expression of the BMP 2 gene during bone cell differentiation.

Bone morphogenetic protein 2 (BMP 2) and transforming growth factor beta (TGF beta) are actively involved in bone formation and remodeling. TGF beta, a powerful stimulant in the early stage of bone cell growth and matrix formation, inhibits differentiation and in vitro mineralized nodule formation in primary fetal rat calvarial osteoblast system. TGF beta also negatively regulates BMP 2 expression at the transcriptional level. BMP 2 gene expression is controlled by a battery of transcriptional factors, some known and some yet to be identified. Immortalized osteoblast cell lines generated from a transgenic mouse carrying BMP 2 promoter-driven SV40 large T antigen transgene are described as powerful tools for studying regulation of BMP 2 gene expression and bone cell differentiation at the molecular level.

Animals↗

PubMed1990

Expression from cloned DNA of biologically active glycoprotein C of herpes simplex virus type 1 in mammalian cells.

A DNA fragment of the herpes simplex virus type 1 genome encoding glycoprotein C (gC-1) has been cloned into different eukaryotic expression vectors for transient and stable expression of the glycoprotein in a number of cell lines. All of these expression vectors use a non-HSV promoter, such as the adenovirus major late promoter or murine leukemia virus long terminal repeat promoter to express gC-1 in COS and CHO cells or 3T3 cells. The gC-1 protein synthesized was fully glycosylated with both N- and O-linked oligosaccharides. Synthesis of the mature 120K gC-1 glycoprotein involved partially glycosylated 100K and 105K proteins and the non-glycosylated 70K protein as intermediate molecules. Immunofluorescence studies showed that the expressed gC-1 was localized intracellularly in the nuclear envelope as well as on the cell surface. The expressed gC-1 was biologically active and could act as a receptor for the complement component C3b in the absence of other HSV proteins.

Animals↗

PubMed1987

Herpes simplex virus type 2 glycoprotein biogenesis: effect of monensin on glycoprotein maturation, intracellular transport and virus infectivity.

The ionophore monensin inhibited the formation of herpes simplex virus type 2 (HSV-2) particles by about 30% but the yields of infectious particles were reduced to 5% and 1% for cell-associated and extracellular virus, respectively. The presence of monensin did not affect the processing of the two viral glycoproteins gB-2 and gG-2. However, two other glycoproteins, gC-2 and gD-2, were not processed to their fully mature forms in the monensin-treated cells and only the faster moving pgC-2 and pgD-2 were detected. The cell-associated virus particles contained the glycoproteins gB-2, gC-2, gD-2 and gG-2, whereas the extracellular virus particles contained only gG-2 glycoprotein. These results suggest that HSV-2 particles containing all the viral glycoproteins are transported via the Golgi apparatus to the cell surface but that virus particles containing only gG-2 may follow a different pathway for transport and release.

Animals↗

PubMedDate not supplied

Effect of tunicamycin and monensin on the transport to the cell surface and secretion of a viral membrane glycoprotein containing both N- and O-linked sugars.

Most membrane glycoproteins contain either N-linked or O-linked oligosaccharides, which play important roles in correct folding, stability, and intracellular transport. Some glycoproteins, however, contain both the N- and O-linked sugars. To study the roles of the two types of glycosylation in intracellular transport we have used as a model the glycoprotein gC-1 of herpes simplex virus type 1 (HSV-1), which contains both N- and O-linked oligosaccharides. Cloned gene of gC-1 was expressed constitutively in mammalian cells to produce the gC-1 glycoprotein containing both types of glycosylation. Only a fraction of the gC-1 glycoprotein was secreted into the medium. Addition of tunicamycin blocked N-glycosylation and the gC-1 protein of reduced size containing only O-linked sugars was formed. This O-glycosylated gC-1 protein was transported to the cell surface and secreted into the medium, indicating that glycoprotein transport to and across the cell surface occurs in the absence of N-glycans. The data suggest either that O-glycans may contribute to this process or that transport can occur in the absence of both N- and O-glycans.

Animals↗