RESUMO
New neurons are continuously generated in the adult brain through a process called adult neurogenesis. This form of plasticity has been correlated with numerous behavioral and cognitive phenomena, but it remains unclear if and how adult-born neurons (abNs) contribute to mature neural circuits. We established a highly specific and efficient experimental system to target abNs for causal manipulations. Using this system with chemogenetics and imaging, we found that abNs effectively sharpen mitral cells (MCs) tuning and improve their power to discriminate among odors. The effects on MCs responses peaked when abNs were young and decreased as they matured. To explain the mechanism of our observations, we simulated the olfactory bulb circuit by modelling the incorporation of abNs into the circuit. We show that higher excitability and broad input connectivity, two well-characterized features of young neurons, underlie their unique ability to boost circuit computation.
Assuntos
Neurônios/fisiologia , Odorantes , Bulbo Olfatório/citologia , Fatores Etários , Animais , Cálcio/metabolismo , Potenciais Evocados/fisiologia , Feminino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Biológicos , Neurogênese/fisiologia , Bulbo Olfatório/efeitos dos fármacos , Bulbo Olfatório/fisiologia , Tamoxifeno/farmacologiaRESUMO
Vav functions as a specific GDP/GTP nucleotide exchange factor which is regulated by tyrosine phosphorylation in the hematopoietic system. Loss of the amino-terminus sequences of Vav was sufficient to control its transforming potential and its function in T cells. We report here the identification of the hematopoietic GDP dissociation inhibitor protein, Ly-GDI, as a protein that interacts with the amino-terminus of Vav. Further analysis confirmed that Vav and Ly-GDI interact both in in vitro and in in vivo assays. This association is maximal only when the amino region of Vav is intact and requires an intact carboxy-terminus of Ly-GDI. The interaction between Vav and Ly-GDI is not dependent on the tyrosine phosphorylation status of Vav. In addition, Rho-GDI, the highly homologous protein to Ly-GDI, associates with Vav as well. The contribution of the interaction between Vav and GDIs, proteins that are involved in the GDP/GTP exchange processes, to the biological function of Vav is further discussed.
Assuntos
Proteínas de Ciclo Celular , Inibidores de Dissociação do Nucleotídeo Guanina/metabolismo , Guanosina Difosfato/metabolismo , Guanosina Trifosfato/metabolismo , Proteínas/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Animais , Linhagem Celular , Inibidores de Dissociação do Nucleotídeo Guanina/química , Inibidores de Dissociação do Nucleotídeo Guanina/genética , Humanos , Camundongos , Antígenos de Histocompatibilidade Menor , Peso Molecular , Muromonab-CD3/farmacologia , Fosforilação/efeitos dos fármacos , Fosfotirosina/metabolismo , Testes de Precipitina , Ligação Proteica/efeitos dos fármacos , Proteínas/química , Proteínas/genética , Proteínas Proto-Oncogênicas/química , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas c-vav , Receptores de Antígenos de Linfócitos T/metabolismo , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Deleção de Sequência , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismo , Transfecção , Proteínas Supressoras de Tumor , Técnicas do Sistema de Duplo-Híbrido , Inibidor beta de Dissociação do Nucleotídeo Guanina rho , Inibidores da Dissociação do Nucleotídeo Guanina rho-EspecíficoRESUMO
The vav proto-oncogene encodes a protein with multiple modulae domains that enable it to function as a mediator, linking tyrosine signaling to downstream events in hematopoietic cells. Circumstantial evidence suggests that protein-protein interactions exerted by two of these domains, the Src homology 2 (SH2) and the Src homology 3 (SH3), play an important role in the regulation of Vav activity. To study the relevance of the SH3 domain for the function of vav as a transforming gene, we have created several mutations in the SH3 domain located at its carboxy region. Substitution of the non-conserved aspartic acid 797 (to asparagine, D797N) retained the transforming potential of the vav oncogene, whereas substitutions of five highly conserved amino-acids: alanine 789 (to asparagine, A789N), leucine 801 (to arginine, L801R), tryptophan 821 (to arginine, W821R), glycine 830 (to valine, G830V) and valine 837 (to glutamic acid, V837E) greatly reduced its transforming potential. The mutant proteins resemble Vav in many biochemical properties; however, while the transforming mutant protein (D797N) associates with several unidentified proteins in a manner similar to that of Vav, the non-transforming mutant Vav proteins react very poorly with these proteins. Among the known Vav-interacting proteins, hnRNP-K associates with all mutant proteins except A789N and V837E whereas binding of Zyxin to any of the mutant proteins is not affected. Taken together, our results clearly demonstrate that the SH3 domain has a positive effect on vav activity and is needed for vav transformation. The vavSH3C associating protein(s) that are crucial for its activity as a transforming gene have probably not yet been identified.
