Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pituitary adenomas cause clinical manifestations because of mass effects and excess hormone production. This group of tumors represents a tractable target for gene therapy because they are rarely metastatic and because reductions in tumor size and function, in addition to those achieved after surgery, may be of clinical benefit. In this report we describe a strategy for targeting the expression of toxic genes to pituitary cells using adenoviral vectors. Pituitary hormone promoters (human GH or glycoprotein hormone alpha-subunit) were used to express either a marker gene [beta-galactosidase (beta-gal)] or a toxic gene [herpes simplex virus thymidine kinase (TK)]. In GH-producing GH3 cells and in alpha-subunit-producing pituitary tumor cell lines, recombinant adenoviruses containing either the alpha-subunit promoter (Ad alpha Gal; AdaTK) or the GH promoter (AdGHGal; AdGHTK) were expressed at-high levels. Using histological studies and assays for beta-gal activity, expression was shown to persist for at least 21 days, and it was relatively selective for pituitary cell lines. Cytotoxicity studies were performed using the TK-containing vectors and treatment with ganciclovir. Both AdGHTK and AdaTK caused greater than 95% cytotoxicity of GH3 and alphaT3 cells, respectively, at a viral dose (multiplicity of infection, 5 plaque-forming units/cell) that induced minimal toxicity using control viruses. Little cellular toxicity was seen using a nonpituitary cell line (T47D breast tumor cells). The AdGHTK virus also caused marked reduction in the size of GH3 cell tumors that were propagated in nude mice. These studies suggest that adenoviral vectors carrying human pituitary gland specific promoters may be useful for developing gene therapy strategies for the treatment of pituitary adenomas.
 ...
PMID:Targeted expression of toxic genes directed by pituitary hormone promoters: a potential strategy for adenovirus-mediated gene therapy of pituitary tumors. 1002 54

The level of LH secretion is determined by both alterations in gonadotrope responsiveness and alterations in GnRH secretion. The molecular mechanisms underlying gonadotrope responsiveness are unknown, but may include G protein-coupled receptor kinases (GRKs). Typically, GRKs phosphorylate the intracellular regions of seven-transmembrane receptors permitting beta-arrestin to bind, which prevents receptor activation of its G protein. Previously, we reported that heterologous expression of GRK2, -3, and -6 in GnRH receptor-expressing COS cells by complementary DNA transfection suppressed GnRH-stimulated inositol trisphosphate production, and that coexpression of GRK2 and beta-arrestin-2 was more inhibitory than either expressed alone. Here, we have investigated the effect of GRK2 on GnRH-stimulated LH secretion using adenovirus-mediated gene transfer in normal pituitary gonadotropes. Pituitary cells were infected with adeno-GRK2 or adeno-beta-galactosidase constructs at a multiplicity of infection of 60 (number of viral particles per cell). Seventy-two hours later, GRK2 expression was measured by enzyme-linked immunosorbent assay, and GnRH-stimulated LH secretion (10(-7) M GnRH-A for 90 min) was assayed by RIA. Adeno-beta-galactosidase infected 96-99% of the cells based on X-Gal staining. Uninfected and adeno-beta-galactosidase-infected cells exhibited endogenous GRK immunoreactivity of about 0.5 (OD405), and LH secretion of 14.8-17.7 ng/ml. Adeno-GRK2-infected cells showed a GRK2 immunoreactivity of about 2.5 (OD405) and LH secretion of 2.5 ng/ml. Therefore, adeno-GRK2 infection resulted in a 5-fold increase in the GRK2 OD405 value, which was accompanied by an 80-85% decrease in GnRH-stimulated LH secretion. GnRH-stimulated inositol trisphosphate production by gonadotropes also was inhibited, suggesting a site of action for GRK2 at phospholipase Cbeta or earlier in the signal transduction pathway. The significance of these findings is 2-fold: 1) adenoviral-mediated gene transfer permits investigation of the regulatory role of gene products in the cell of interest, the gonadotrope, rather than in heterologous cell systems; and 2) additional, stronger evidence is provided that supports a role for GRKs in setting the responsiveness of GnRH receptor signaling.
 ...
PMID:High efficiency method for gene transfer in normal pituitary gonadotropes: adenoviral-mediated expression of G protein-coupled receptor kinase 2 suppresses luteinizing hormone secretion. 1034 43