RESUMO
The Rho family GTPase Cdc42 regulates cytoskeletal organization and membrane trafficking in physiological processes such as cell proliferation, motility and polarity. Aberrant activation of Cdc42 results in pathogenesis, such as tumorigenesis and tumor progression, cardiovascular diseases, diabetes, and neuronal degenerative diseases. The activation of Cdc42 in response to upstream signals is mediated by guanine nucleotide exchange factors (GEFs), which converse GDP-bound inactive form to the GTP-bound active form of Cdc42. The activated Cdc42 transduces signals to downstream effectors and generates cellular effects. This review will discuss the molecular mechanism of activation of Cdc42 and postulate that signaling specificity of Cdc42 is conferred by the GEF/GTPase/Effector (GGE) complexes in response to external stimuli.
Assuntos
Transdução de Sinais , Proteína cdc42 de Ligação ao GTP/metabolismo , Animais , Ativação Enzimática , Fatores de Troca do Nucleotídeo Guanina/química , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Modelos BiológicosRESUMO
Here, we report the identification and expression analysis of the zebrafish G protein gammaT1 subunit gene (gngT1) during development. Similar to its human and mouse homologs, we confirm zebrafish gngT1 is expressed in the developing retina, where its transcription overlaps with the photoreceptor cell-specific marker, rhodopsin (rho). Surprisingly, we also show zebrafish gngT1 is expressed in the dorsal diencephalon, where its transcription overlaps with the pineal specific markers, arylalkylamine N-acetyltransferase-2 (annat-2) and extra-ocular rhodopsin (exorh). Analysis of the proximal promoter sequence of the zebrafish gngT1 gene identifies several conserved binding sites for the cone-rod homeobox/orthodenticle (Crx/Otx) homeodomain family of transcription factors. Using a morpholino anti-sense approach in zebrafish, we show that targeted knockdown of otx5 potently suppresses gngT1 expression in the pineal gland, whereas knockdown of crx markedly reduces gngT1 expression in the retina. Taken together, these data indicate that pineal- and retinal-specific expression of the gngT1 gene are controlled by different transcription factors and exogenous signals.
Assuntos
Subunidades gama da Proteína de Ligação ao GTP/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Peixe-Zebra/metabolismo , Peixe-Zebra/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , Subunidades gama da Proteína de Ligação ao GTP/genética , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Hibridização In Situ , Dados de Sequência Molecular , Oligonucleotídeos Antissenso/farmacologia , Fatores de Transcrição Otx/genética , Fatores de Transcrição Otx/metabolismo , Células Fotorreceptoras/metabolismo , Glândula Pineal/citologia , Glândula Pineal/metabolismo , Sondas RNA , Retina/citologia , Retina/metabolismo , Rodopsina/metabolismo , Homologia de Sequência de Aminoácidos , Transativadores/genética , Transativadores/metabolismo , Peixe-Zebra/crescimento & desenvolvimento , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genéticaRESUMO
Vascular endothelial growth factor (VEGF) is a major mediator of pathologic angiogenesis, a process necessary for the formation of new blood vessels to support tumor growth. Historically, VEGF has been thought to signal via receptor tyrosine kinases, which are not typically considered to be G protein dependent. Here, we show that targeted knockdown of the G protein gng2 gene (Ggamma2) blocks the normal angiogenic process in developing zebrafish embryos. Moreover, loss of gng2 function inhibits the ability of VEGF to promote the angiogenic sprouting of blood vessels by attenuating VEGF induced phosphorylation of phospholipase C-gamma1 (PLCgamma1) and serine/threonine kinase (AKT). Collectively, these results demonstrate a novel interaction between Ggamma2- and VEGF-dependent pathways to regulate the angiogenic process in a whole-animal model. Blocking VEGF function using a humanized anti-VEGF antibody has emerged as a promising treatment for colorectal, non-small lung cell, and breast cancers. However, this treatment may cause considerable side effects. Our findings provide a new opportunity for cotargeting G protein- and VEGF-dependent pathways to synergistically block pathologic angiogenesis, which may lead to a safer and more efficacious therapeutic regimen to fight cancer.
Assuntos
Subunidades gama da Proteína de Ligação ao GTP/farmacologia , Proteínas de Ligação ao GTP/farmacologia , Neovascularização Fisiológica/efeitos dos fármacos , Subunidades Proteicas/farmacologia , Transdução de Sinais/efeitos dos fármacos , Fator A de Crescimento do Endotélio Vascular/efeitos dos fármacos , Proteínas de Peixe-Zebra/farmacologia , Animais , Subunidades gama da Proteína de Ligação ao GTP/genética , Subunidades gama da Proteína de Ligação ao GTP/fisiologia , Proteínas de Ligação ao GTP/genética , Proteínas de Ligação ao GTP/fisiologia , Perfilação da Expressão Gênica , Modelos Animais , Neovascularização Fisiológica/fisiologia , Fenótipo , Fosfolipase C gama/metabolismo , Subunidades Proteicas/genética , Subunidades Proteicas/fisiologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/fisiologia , Fator A de Crescimento do Endotélio Vascular/fisiologia , Peixe-Zebra , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/fisiologiaRESUMO
Lighter variations of pigmentation in humans are associated with diminished number, size, and density of melanosomes, the pigmented organelles of melanocytes. Here we show that zebrafish golden mutants share these melanosomal changes and that golden encodes a putative cation exchanger slc24a5 (nckx5) that localizes to an intracellular membrane, likely the melanosome or its precursor. The human ortholog is highly similar in sequence and functional in zebrafish. The evolutionarily conserved ancestral allele of a human coding polymorphism predominates in African and East Asian populations. In contrast, the variant allele is nearly fixed in European populations, is associated with a substantial reduction in regional heterozygosity, and correlates with lighter skin pigmentation in admixed populations, suggesting a key role for the SLC24A5 gene in human pigmentation.