Mitogenesis in glioblastoma multiforme cell lines: a role for NGF and its TrkA receptors.

Neurotrophins have definitive roles in the growth/maintenance of neuronal populations, but their function in malignant gliomas is unknown. The ability for nerve growth factor (NGF) to serve as a mitogenic agent was investigated in several human glioblastoma multiforme (GBM) cell lines, including U251, U87, and U373. In a serum-free medium, the addition of NGF (200 ng/ml) to these cell lines increased cell counts over controls, after 3 days in culture by 9%, 16%, and 33%, respectively. Dose-dependent increases in cell counts and [3H]thymidine uptake were found in the more rigorously investigated U373 cell line. Proteins for both the high affinity NGF-specific tyrosine kinase binding site (p140TrkA; TrkA) and the low affinity neurotrophin (p75NTR) receptor were present in all three GBM cell lines. TrkA mRNA was identified in U373 (only cell line studied). NGF-stimulated proliferation was inhibited in a dose-dependent fashion by K252a, a blocker of Trk-induced receptor kinases. NGF, measured by ELISA, was detectable in all GBM cell lines even after 7 days of growth in serum-free medium. These data suggest that GBM cell growth can be enhanced by NGF acting via Trk receptor phosphorylation. Future studies of antiproliferative therapies should consider agents directed against intracellular Trk signaling cascades.

Amino acid changes in the Sindbis virus E2 glycoprotein that increase neurovirulence improve entry into neuroblastoma cells.

Sindbis virus (SV) is an alphavirus that causes encephalitis in mice and results in age-dependent mortality. The outcome is dependent on the virus strain. Residues at 55 and 172 in the E2 glycoprotein determine the neurovirulence for mice of different ages and the efficiency of replication in the nervous system and neuronal cells. To determine the effects of these two residues on the initial steps in replication, we studied viruses with a histidine or glutamine at E2 position 55 and a glycine or an arginine at position 172, E2[H55G172], E2[Q55G172], E2[H55R172], and E2[Q55R172]. The production of virus was detected earlier for viruses with a histidine at E2 position 55 in BHK-21 cells (4 to 6 versus 6 to 8 h) and for E2[H55G172] in N18 cells (6 versus 8 to 10 h). As shown previously, viruses with a glycine at E2 position 172 bound more efficiently to N18 cells and a histidine at E2 position 55 further improved binding only slightly. Viruses with E2[H55] exhibited more rapid internalization and degradation of viral proteins in both BHK-21 and N18 cells. Incubation of E2[H55G172] and E2[Q55G172] at various pHs and temperatures did not reveal differences in virion stability. These data suggest that the amino acids at E2 positions 172 and 55 affect both adsorption and penetration of SV and that these early steps in the replicative pathway contribute to increased neurovirulence.

Second messenger systems in Tourette's syndrome.

Abnormalities within second messenger systems have been hypothesized as the underlying pathophysiologic mechanism in a variety of neuropsychiatric disorders. In the Gilles de la Tourette syndrome (TS) prior studies have shown that the concentration of adenosine 3',5'-monophosphate (cAMP) is reduced in cortical and putamen brain regions. In this study, postmortem cortical tissues from 4 adults (mean age 59.5 years) with the lifetime diagnosis of TS and 5 controls (mean age 63.8 years) were analyzed for functional activities within the cAMP and phosphoinositide systems. In addition, plasma cAMP was quantified in children with TS (n = 33) and controls (n = 17). In frontal (A4, A6) and occipital (A17) cortical tissues there were no significant differences for adenylyl cyclase activity whether assayed under basal conditions or after stimulation with GTP gamma S (a non-hydrolyzable GTP analog), forskolin (a selective enzyme stimulator), or (-)-isoproterenol (a beta-adrenergic agonist). D2 receptor activation (quinpirole) and assessment of the inhibitory guanine nucleotide protein also showed no significant alterations in TS samples. Activity of cAMP phosphodiesterase was increased insignificantly in A4 and A17 TS brain regions. Plasma concentrations of cAMP in plasma were similar in children with TS (135.4 +/- 8.3 pmol/ml) and controls (132.6 +/- 7.9 pmol/ml). Postmortem membrane receptor binding for markers within the phosphoinositide (PI) system showed that TS samples had increased [3H]phorbol ester binding to protein kinase C sites in area A17, but normal binding in A4. In contrast, [3H] inositol 1,4,5-triphosphate binding to IP3 receptors showed no significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)