RESUMEN
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.
Asunto(s)
Transducción de Señal , Proteína de Unión al GTP cdc42/metabolismo , Animales , Activación Enzimática , Factores de Intercambio de Guanina Nucleótido/química , Factores de Intercambio de Guanina Nucleótido/metabolismo , Humanos , Modelos BiológicosRESUMEN
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.
Asunto(s)
Subunidades gamma de la Proteína de Unión al GTP/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas de Pez Cebra/metabolismo , Pez Cebra/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Subunidades gamma de la Proteína de Unión al GTP/genética , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Hibridación in Situ , Datos de Secuencia Molecular , Oligonucleótidos Antisentido/farmacología , Factores de Transcripción Otx/genética , Factores de Transcripción Otx/metabolismo , Células Fotorreceptoras/metabolismo , Glándula Pineal/citología , Glándula Pineal/metabolismo , Sondas ARN , Retina/citología , Retina/metabolismo , Rodopsina/metabolismo , Homología de Secuencia de Aminoácido , Transactivadores/genética , Transactivadores/metabolismo , Pez Cebra/crecimiento & desarrollo , Pez Cebra/metabolismo , Proteínas de Pez Cebra/genéticaRESUMEN
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.
Asunto(s)
Subunidades gamma de la Proteína de Unión al GTP/farmacología , Proteínas de Unión al GTP/farmacología , Neovascularización Fisiológica/efectos de los fármacos , Subunidades de Proteína/farmacología , Transducción de Señal/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/efectos de los fármacos , Proteínas de Pez Cebra/farmacología , Animales , Subunidades gamma de la Proteína de Unión al GTP/genética , Subunidades gamma de la Proteína de Unión al GTP/fisiología , Proteínas de Unión al GTP/genética , Proteínas de Unión al GTP/fisiología , Perfilación de la Expresión Génica , Modelos Animales , Neovascularización Fisiológica/fisiología , Fenotipo , Fosfolipasa C gamma/metabolismo , Subunidades de Proteína/genética , Subunidades de Proteína/fisiología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/fisiología , Factor A de Crecimiento Endotelial Vascular/fisiología , Pez Cebra , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/fisiologíaRESUMEN
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.
