The human beta1-adrenergic receptor (AR) and hamster beta2-AR transcripts can be post-transcriptionally regulated at the level of mRNA stability and undergo accelerated agonist-mediated degradation via interaction of their 3' untranslated regions (UTR) with RNA binding proteins. Using RNase protection assays, we have determined that chronic isoproterenol exposure of rat C6 glioma cells results in the accelerated reduction of beta1-AR mRNAs. To determine the role of cellular environment on the agonist-independent and agonist-mediated degradation of beta1-AR mRNAs, we transfected rat beta1-AR expression recombinants into both hamster DDT1MF2 cells and rat L6 cells. The rat beta1-AR mRNAs in the two transfectant cell pools retain longer agonist-independent half-lives than in the C6 environment and undergo accelerated degradation upon chronic agonist exposure. Using UV-cross-linking/immunoblot and immunoprecipitation analyses, we have determined that the rat beta1-AR 3' UTR recognizes a predominant M(r) 39,000 component, identified as the mammalian elav-like protein HuR, and several other minor components, including the heteronuclear protein hnRNP A1. HuR levels are more highly expressed in C6 cells than in DDT1MF2 and L6 cells and are induced after chronic isoproterenol treatment. Furthermore, C6 transfectants containing an HuR expression recombinant exhibit reduced beta1-AR mRNA half-lives that were statistically comparable with half-lives identified in isoproterenol-treated C6 cells. These results imply that HuR plays a potential role in the agonist-independent and agonist-mediated down-regulation of beta1-AR mRNAs.

Genetic transfer approaches have received recent con-The use of specific regulatable promoters may also provide sideration as potential treatment modalities for human cenpotential control of gene expression required for dose-spetral and peripheral nervous system (CNS and PNS, cific or time-specific therapeutic strategies. In this article, respectively) neurodegenerative disorders, including Parkwe review the potential use of activated promoters in ex inson's disease, Alzheimer's disease, and amyotrophic latvivo systems for the potential genetic therapy of neurodegeral sclerosis. Transplantation of genetically modified cells enerative disorders, and then describe our own studies into the brain represents a promising strategy for the delivusing the zinc-inducible metallothionein promoter for the ery and expression of specific neurotrophic factors, neuroregulated expression of nerve growth factor (NGF) in transmitter-synthesizing enzymes, and cellular regulatory rodent brain transplants. proteins for intervention in neurodegenerative diseases.Keywords: gene transfer; nerve growth factor; regulatable promoters; promoter-activated vectors; brain transplant Biological properties of nerve growth factorNerve growth factor (NGF), the prototypical member of the neurotrophin family, is an important molecule that regulates neuronal survival and differentiation.1-3 NGF and other members of the neurotrophin family, including brain-derived growth factor (BDNF) and a series of structurally related proteins NT3 and NT4/5, support the survival of specific types of neurons and neurotransmitter systems, and are synthesized and secreted by cells that are the targets of specific innervating neurons. 4 NGF responsiveness has been demonstrated for a number of nervous system regions, including the basal forebrain, substantia nigra, brain stem, cortex, and spinal cord. 1-3Other neurotrophic factors have also been shown to promote the survival of particular neuronal subpopulations; these factors include the glial cell line-derived neurotrophic factor (GDNF) for dopaminergic neurons and motor neurons, and the ciliary neurotrophic factor (CNTF) for motor and spinal cord neurons.NGF plays a role in the maintenance of the cholinergic neurotransmitter system in specific populations of neurons, including a group of cholinergic forebrain neurons.1-3 Deprivation of NGF to the cholinergic forebrain neurons can result in the decrease of somal size and choline acetyltransferase levels; subsequent delivery of NGF to these neurons can reverse these morphological and biochemical alterations. This response forms the rationale

No abstract