RESUMO
The enormous variability in electrical properties of neurons is largely affected by a multitude of potassium channel subunits. Kv2.1 is a widely expressed voltage-dependent potassium channel and an important regulator of neuronal excitability. The Kv2.1 auxiliary subunit AMIGO constitutes an integral part of the Kv2.1 channel complex in brain and regulates the activity of the channel. AMIGO and Kv2.1 localize to the distinct somatodendritic clusters at the neuronal plasma membrane. Here we have created and characterized a mouse line lacking the AMIGO gene. Absence of AMIGO clearly reduced the amount of the Kv2.1 channel protein in mouse brain and altered the electrophysiological properties of neurons. These changes were accompanied by behavioral and pharmacological abnormalities reminiscent of those identified in schizophrenia. Concomitantly, we have detected an association of a rare, population-specific polymorphism of KV2.1 (KCNB1) with human schizophrenia in a genetic isolate enriched with schizophrenia. Our study demonstrates the involvement of AMIGO-Kv2.1 channel complex in schizophrenia-related behavioral domains in mice and identifies KV2.1 (KCNB1) as a strong susceptibility gene for schizophrenia spectrum disorders in humans.
Assuntos
Comportamento Animal , Encéfalo/metabolismo , Glicoproteínas de Membrana/genética , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Esquizofrenia/genética , Canais de Potássio Shab/genética , Adulto , Animais , Antipsicóticos/farmacologia , Comportamento Animal/efeitos dos fármacos , Western Blotting , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Membrana Celular/metabolismo , Clozapina/farmacologia , Maleato de Dizocilpina/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Predisposição Genética para Doença , Haloperidol/farmacologia , Proteínas de Choque Térmico , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/fisiopatologia , Humanos , Imuno-Histoquímica , Proteínas de Membrana , Camundongos , Camundongos Knockout , Pessoa de Meia-Idade , Neurônios/fisiologia , Técnicas de Patch-Clamp , Fragmentos de Peptídeos , Fenótipo , Serotonina/metabolismo , Adulto JovemRESUMO
The Amigo protein family consists of three transmembrane proteins characterized by six leucine-rich repeat domains and one immunoglobulin-like domain in their extracellular moieties. Previous in vitro studies have suggested a role as homophilic adhesion molecules in brain neurons, but the in vivo functions remain unknown. Here we have cloned all three zebrafish amigos and show that amigo1 is the predominant family member expressed during nervous system development in zebrafish. Knockdown of amigo1 expression using morpholino oligonucleotides impairs the formation of fasciculated tracts in early fiber scaffolds of brain. A similar defect in fiber tract development is caused by mRNA-mediated expression of the Amigo1 ectodomain that inhibits adhesion mediated by the full-length protein. Analysis of differentiated neural circuits reveals defects in the catecholaminergic system. At the behavioral level, the disturbed formation of neural circuitry is reflected in enhanced locomotor activity and in the inability of the larvae to perform normal escape responses. We suggest that Amigo1 is essential for the development of neural circuits of zebrafish, where its mechanism involves homophilic interactions within the developing fiber tracts and regulation of the Kv2.1 potassium channel to form functional neural circuitry that controls locomotion.
Assuntos
Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Moléculas de Adesão Celular Neuronais/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Moléculas de Adesão de Célula Nervosa/metabolismo , Proteínas de Peixe-Zebra/metabolismo , Peixe-Zebra/crescimento & desenvolvimento , Peixe-Zebra/metabolismo , Animais , Moléculas de Adesão Celular Neuronais/antagonistas & inibidores , Moléculas de Adesão Celular Neuronais/genética , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Silenciamento de Genes , Larva/crescimento & desenvolvimento , Larva/metabolismo , Masculino , Rede Nervosa/crescimento & desenvolvimento , Rede Nervosa/metabolismo , Proteínas do Tecido Nervoso/antagonistas & inibidores , Proteínas do Tecido Nervoso/genética , Moléculas de Adesão de Célula Nervosa/antagonistas & inibidores , Moléculas de Adesão de Célula Nervosa/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Canais de Potássio Shab/genética , Canais de Potássio Shab/metabolismo , Peixe-Zebra/genética , Proteínas de Peixe-Zebra/antagonistas & inibidores , Proteínas de Peixe-Zebra/genéticaRESUMO
Kv2.1 is a potassium channel α-subunit abundantly expressed throughout the brain. It is a main component of delayed rectifier current (I(K)) in several neuronal types and a regulator of excitability during high-frequency firing. Here we identify AMIGO (amphoterin-induced gene and ORF), a neuronal adhesion protein with leucine-rich repeat and immunoglobin domains, as an integral part of the Kv2.1 channel complex. AMIGO shows extensive spatial and temporal colocalization and association with Kv2.1 in the mouse brain. The colocalization of AMIGO and Kv2.1 is retained even during stimulus-induced changes in Kv2.1 localization. AMIGO increases Kv2.1 conductance in a voltage-dependent manner in HEK cells. Accordingly, inhibition of endogenous AMIGO suppresses neuronal I(K) at negative membrane voltages. In conclusion, our data indicate AMIGO as a function-modulating auxiliary subunit for Kv2.1 and thus provide new insights into regulation of neuronal excitability.
