RESUMO
Glycine is an amino acid with unique properties because its side chain is composed of a single hydrogen atom. It confers conformational flexibility to proteins and conserved glycines are often indicative of protein domains involving tight turns or bends. All six beta-type connexins expressed in human epidermis (Cx26, Cx30, Cx30.3, Cx31, Cx31.1 and Cx32) contain a glycine at position 12 (G12). G12 is located about halfway through the cytoplasmic amino terminus and substitutions alter connexin function in a variety of ways, in some cases altering protein interactions and leading to cell death. There is also evidence that alteration of G12 changes the structure of the amino terminus in connexin- and amino acid- specific ways. This review integrates structural, functional and physiological information about the role of G12 in connexins, focusing on beta-connexins expressed in human epidermis. The importance of G12 substitutions in these beta-connexins is revealed in two hereditary skin disorders, keratitis ichthyosis and erythrokeratodermia variabilis, both of which result from missense mutations affecting G12.
Assuntos
Conexinas/metabolismo , Epiderme/metabolismo , Eritroceratodermia Variável/metabolismo , Junções Comunicantes/metabolismo , Ictiose/metabolismo , Mutação de Sentido Incorreto , Substituição de Aminoácidos , Conexinas/genética , Epiderme/patologia , Eritroceratodermia Variável/genética , Eritroceratodermia Variável/patologia , Junções Comunicantes/genética , Junções Comunicantes/patologia , Glicina/genética , Glicina/metabolismo , Humanos , Ictiose/genética , Ictiose/patologiaAssuntos
Conexina 43/genética , Eritroceratodermia Variável/genética , Junções Comunicantes/metabolismo , Mutação de Sentido Incorreto , Pele/metabolismo , Criança , Conexina 43/química , Conexina 43/metabolismo , Análise Mutacional de DNA , Eritroceratodermia Variável/diagnóstico , Eritroceratodermia Variável/metabolismo , Feminino , Junções Comunicantes/patologia , Predisposição Genética para Doença , Humanos , Fenótipo , Conformação Proteica , Pele/patologia , Relação Estrutura-AtividadeRESUMO
Mutations in connexin-31 (Cx31) are associated with multiple human diseases, including familial erythrokeratodermia variabilis (EKV). The pathogenic mechanism of EKV-associated Cx31 mutants remains largely elusive. Here, we show that EKV-pathogenic Cx31 mutants are un/misfolded and temperature sensitive. In Drosophila, expression of pathogenic Cx31, but not wild-type Cx31, causes depigmentation and degeneration of ommatidia that are rescued by expression of either dBip or dHsp70. Ectopic expression of Cx31 in mouse skin results in skin abnormalities resembling human EKV. The affected tissues show remarkable disrupted gap junction formation and significant upregulation of chaperones Bip and Hsp70 as well as AP-1 proteins c-Fos and JunB, in addition to molecular signatures of skin diseases. Consistently, c-Fos, JunB, Bip and Hsp70 are strikingly higher in keratinocytes of EKV patients than their matched control individuals. Furthermore, a druggable AP-1 inhibitory small molecule suppresses skin phenotype and pathological abnormalities of transgenic Cx31 mice. The study suggests that Cx31 mutant proteins are un/misfolded to cause EKV likely via an AP-1-mediated mechanism and identifies a small molecule with therapeutic potential of the disease.
Assuntos
Conexinas/metabolismo , Eritroceratodermia Variável/metabolismo , Dobramento de Proteína , Animais , Animais Geneticamente Modificados , Benzofenonas/farmacologia , Olho Composto de Artrópodes/patologia , Conexinas/antagonistas & inibidores , Conexinas/genética , Drosophila , Proteínas de Drosophila/genética , Eritroceratodermia Variável/tratamento farmacológico , Eritroceratodermia Variável/genética , Eritroceratodermia Variável/patologia , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico HSP70/metabolismo , Células HeLa , Humanos , Isoxazóis/farmacologia , Camundongos , Mutação , Pigmentação/genética , Desdobramento de Proteína , Deficiências na Proteostase/genética , Deficiências na Proteostase/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Proteínas Recombinantes de Fusão , Pele/patologia , Estresse Fisiológico , Temperatura , Fator de Transcrição TFIID/genética , Fatores de Transcrição/metabolismo , Regulação para CimaRESUMO
Endoplasmic reticulum (ER) stress triggers tissue-specific responses that culminate in either cellular adaptation or apoptosis, but the genetic networks distinguishing these responses are not well understood. Here we demonstrate that ER stress induced in the developing zebrafish causes rapid apoptosis in the brain, spinal cord, tail epidermis, lens, and epiphysis. Focusing on the tail epidermis, we uncover an apoptotic response that depends on Puma, but not on p53 or Chop. puma is transcriptionally activated during this ER stress response in a p53-independent manner, and is an essential mediator of epidermal apoptosis. We demonstrate that the p63 transcription factor is upregulated to initiate this apoptotic pathway and directly activates puma transcription in response to ER stress. We also show that a mutation of human Connexin 31, which causes erythrokeratoderma variabilis, induces ER stress and p63-dependent epidermal apoptosis in the zebrafish embryo, thus implicating this pathway in the pathogenesis of inherited disease.
