cytochalasin-d and staurosporine-aglycone

Integrin adhesion receptors regulate gene expression during growth and differentiation in various cell types. Recent work, implicating integrins in functional synaptic plasticity, suggest they may have similar activities in adult brain. The present study tested if integrins binding the arginine-glycine-aspartate (RGD) matrix sequence regulate neurotrophin and neurotrophin receptor gene expression in cultured hippocampal slices. The soluble RGD-containing peptide glycine-arginine-glycine-aspartate-serine-proline (GRGDSP) increased neurotrophin mRNA levels in transcript- and subfield-specific fashions. Integrin ligand effects were greatest for brain-derived neurotrophic factor transcripts I and II and barely detectable for transcript III. In accordance with increased nerve growth factor mRNA levels, GRGDSP increased c-fos expression as well. In contrast, growth-associated protein-43, amyloid precursor protein and fibroblast growth factor-1 mRNAs were not elevated. Ligand effects on brain-derived neurotrophic factor transcript II and c-fos mRNA did not depend on the integrity of the actin cytoskeleton, neuronal activity, or various signaling pathways but were blocked by L-type voltage-sensitive calcium-channel blockers. These results indicate that in mature hippocampal neurons integrin engagement regulates expression of a subset of growth-related genes at least in part through effects on calcium influx. Accordingly, these synaptic adhesion receptors may play the same role in maintaining an adult, differentiated state in brain as they do in other tissues and changes in integrin activation and/or engagement may contribute to dynamic changes in neurotrophin expression and to neuronal calcium signaling.

Topics: Anesthetics, Local; Animals; Animals, Newborn; Brain-Derived Neurotrophic Factor; Calcium Channel Blockers; Calcium Channels; Carbazoles; Cytochalasin D; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Exons; Gene Expression Regulation; Genes, fos; Glycoproteins; Hippocampus; Immunohistochemistry; In Situ Hybridization; In Vitro Techniques; Indole Alkaloids; Integrins; Neurotrophin 3; Nifedipine; Nimodipine; Nucleic Acid Synthesis Inhibitors; Oligopeptides; Rats; Rats, Sprague-Dawley; Receptor, trkB; Receptor, trkC; RNA Precursors; RNA, Messenger; Sesterterpenes; Terpenes; Tetrodotoxin; Time Factors; Transcription, Genetic; Trifluoperazine

Increasing evidence suggests that the nervous system is involved in allergic inflammation. One of the potential regulatory molecules of the neuroimmune system is nerve growth factor (NGF). Recent studies from our group demonstrated the presence of a functional NGF receptor (NGFR) on human B lymphocytes. Moreover, we showed that gp140trk tyrosine kinase, which serves as an NGFR, was involved in transduction of early signaling events in human B lymphocytes. The mechanisms by which NGF initiates the signaling cascade and the link between the neuroimmune systems are unknown. We have focused on the role of the cytoskeleton as a possible mediator for transduction of signals induced by NGF. Polymerized actin (F-actin) content was determined by fluorescent staining and immunoblotting with antiactin antibody. Addition of NGF caused a time- and concentration-dependent increase in F-actin content, and maximum effects were noted after 1 min. These increases in F-actin content and NGF-induced thymidine incorporation could be blocked by incubating the cells with cytochalasin D and botulinum C2 toxin before the addition of NGF. Incubation of human B lymphocytes with 10 nM K252a, an inhibitor of Trk kinase, decreased NGF-induced microfilament assembly by 75%. In immunoprecipitation experiments, addition of NGF to B cells induced a rapid increase in the tyrosine phosphorylation of paxillin, one of a group of focal adhesion proteins involved in linking actin filaments to the plasma membrane. Coimmunoprecipitation studies demonstrated the association between gp140trk kinase and paxillin. Together, these observations suggest that actin assembly is involved in NGF signaling in human B cells, and that paxillin may be essential in this pathway after phosphorylation by gp140trk kinase.

Topics: Actin Cytoskeleton; Actins; B-Lymphocytes; Botulinum Toxins; Carbazoles; Cytochalasin D; Cytoskeletal Proteins; Humans; Indole Alkaloids; Nerve Growth Factors; Paxillin; Phosphoproteins; Phosphorylation; Proto-Oncogene Proteins; Receptor Protein-Tyrosine Kinases; Receptor, trkA; Receptors, Nerve Growth Factor; Signal Transduction