RESUMEN
The Salvador/Warts/Hippo (Hippo) signaling pathway defines a novel signaling cascade regulating cell contact inhibition, organ size control, cell growth, proliferation, apoptosis and cancer development in mammals. The upstream regulation of this pathway has been less well defined than the core kinase cassette. KIBRA has been shown to function as an upstream member of the Hippo pathway by influencing the phosphorylation of LATS and YAP, but functional consequences of these biochemical changes have not been previously addressed. We show that in MCF10A cells, loss of KIBRA expression displays epithelial-to-mesenchymal transition (EMT) features, which are concomitant with decreased LATS and YAP phosphorylation, but not MST1/2. In addition, ectopic KIBRA expression antagonizes YAP via the serine 127 phosphorylation site and we show that KIBRA, Willin and Merlin differentially regulate genes controlled by YAP. Finally, reduced KIBRA expression in primary breast cancer specimens correlates with the recently described claudin-low subtype, an aggressive sub-group with EMT features and a poor prognosis.
Asunto(s)
Transición Epitelial-Mesenquimal , Factor de Crecimiento de Hepatocito/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Factores de Transcripción/metabolismo , Apoptosis , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Western Blotting , Mama/citología , Mama/metabolismo , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/patología , Carcinoma Ductal de Mama/genética , Carcinoma Ductal de Mama/metabolismo , Carcinoma Ductal de Mama/patología , Adhesión Celular , Proteínas de Ciclo Celular , Movimiento Celular , Proliferación Celular , Células Cultivadas , Claudina-1/genética , Claudina-1/metabolismo , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , Femenino , Perfilación de la Expresión Génica , Factor de Crecimiento de Hepatocito/antagonistas & inhibidores , Factor de Crecimiento de Hepatocito/genética , Humanos , Técnicas para Inmunoenzimas , Péptidos y Proteínas de Señalización Intracelular/antagonistas & inhibidores , Péptidos y Proteínas de Señalización Intracelular/genética , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Neurofibromina 2/genética , Neurofibromina 2/metabolismo , Proteínas Nucleares/antagonistas & inhibidores , Proteínas Nucleares/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Fosfoproteínas/antagonistas & inhibidores , Fosfoproteínas/genética , Fosforilación , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/genética , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/genética , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Serina-Treonina Quinasa 3 , Transducción de Señal , Factores de Transcripción/antagonistas & inhibidoresRESUMEN
The Salvador/Warts/Hippo (Hippo) signaling pathway defines a novel signaling cascade regulating cell contact inhibition, organ size control, cell growth, proliferation, apoptosis and cancer development in mammals. The Drosophila melanogaster protein Expanded acts in the Hippo signaling pathway to control organ size. Previously, willin/FRMD6 has been proposed as the human orthologue of Expanded. Willin lacks C-terminal sequences that are present in Expanded and, to date, little is known about the functional role of willin in mammalian cells. When willin is expressed in D. melanogaster epithelial tissues, it has the same subcellular localization as Expanded, but cannot rescue growth defects associated with expanded deficiency. However, we show that ectopic willin expression causes an increase in phosphorylation of the core Hippo signaling pathway components MST1/2, LATS1 and YAP, an effect that can be antagonized by ezrin. In MCF10A cells, loss of willin expression displays epithelial-to-mesenchymal transition features and willin overexpression antagonizes YAP activity via the N-terminal FERM domain of willin. Therefore, in mammalian cells willin influences Hippo signaling activity by activating the core Hippo pathway kinase cassette.