Biochemical studies on functional proteins in the brain nervous system. Neurobiochemical studies on nerve growth factor

Abstract

Nerve growth factor (NGF) is a polypeptide that is necessary for the survival and growth of developing sympathetic and sensory neurons as well as basal forebrain cholinergic neurons in the brain. The effects of NGF are mediated by the binding of the factor to its specific receptor present on the surface of NGF-responsive cells. Since NGF-responsive basal forebrain cholinergic neurons are lost in Alzheimer's disease, treatment with NGF may be therapeutically beneficial for the patients with this disease. Our studies were focused on the purification, amino acid sequence, enzyme immunoassay (EIA), NGF-biosynthesizing cells, regulation of the biosynthesis, compounds stimulating NGF-biosynthesis/secretion, etc. The major results obtained are summarized as follows: 1) We purified NGFs from snake venoms and determined their amino acid sequences. Among them, Crotalus adamanteus-and Vipera russelli-NGFs were glycoproteins. 2) We developed highly sensitive (0.03-0.05 pg/tube or bead), simple, and reliable EIA systems for NGFs and NT-3. 3) Catecholamine, its derivatives, p-quinone derivatives, nicotine, nicotine derivatives, coenzymes, etc. enhanced the NGF-biosynthesis/secretion of fibroblasts and astrocytes by increasing their cellular content of NGF mRNA. 4) Basal forebrain-lesioned rats (an animal model of amnesia) administered 6-(4-hydroxybutyl)-2,3,5-trimethyl-1,4-benzoquinone (TMQ) orally showed improvement not only their NGF level and choline acetyltransferase (CAT) activity in the brain but also their memory and learning. 5) Interleukins (IL)-4 and -5 significantly increased the amounts of NGF secreted by mouse astrocytes; whereas IL-2, -3, and -6 had no significant effect. 6) Interferons-beta and -lambda inhibited the DNA- and NGF-synthesis in growing astrocytes cultured from neonatal mouse brain but they had no effect on the NGF-synthesis/secretion in quiescent astrocytes. 7) Alkylcatechols regulated the NGF gene expression in astrocytes via both protein kinase C- and cAMP-independent mechanisms.