RESUMO
Although developmental signalling pathways control tumourigenic growth, the cellular mechanisms that abnormally proliferating cells rely on are still largely unknown. Drosophila melanogaster is a genetically tractable model that is used to study how specific genetic changes confer advantageous tumourigenic traits. Despite recent efforts, the role of deubiquitylating enzymes in cancer is particularly understudied. We performed a Drosophila in vivo RNAi screen to identify deubiquitylating enzymes that modulate RasV12-induced hyperplastic growth. We identified the spliceosome core component Prp8 as a crucial regulator of Ras-, EGFR-, Notch- or RET-driven hyperplasia. Loss of prp8 function alone decreased cell proliferation, increased cell death, and affected cell differentiation and polarity. In hyperplasia, Prp8 supported tissue overgrowth independently of caspase-dependent cell death. The depletion of prp8 efficiently blocked Ras-, EGFR- and Notch-driven tumours but, in contrast, enhanced tumours that were driven by oncogenic RET, suggesting a context-specific role in hyperplasia. These data show, for the first time, that Prp8 regulates hyperplasia, and extend recent observations on the potential role of the spliceosome in cancer. Our findings suggest that targeting Prp8 could be beneficial in specific tumour types.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Oncogenes , Fatores de Processamento de RNA/metabolismo , Actinas/metabolismo , Animais , Carcinogênese , Morte Celular , Diferenciação Celular , Polaridade Celular , Proliferação de Células , Olho/crescimento & desenvolvimento , Olho/metabolismo , Trato Gastrointestinal/metabolismo , Trato Gastrointestinal/patologia , Técnicas de Silenciamento de Genes , Hiperplasia , Invasividade Neoplásica , Neoplasias/metabolismo , Neoplasias/patologia , Especificidade de Órgãos , Fenótipo , Interferência de RNA , Proteínas ras/metabolismoRESUMO
Development of an organism requires accurate coordination between the growth of a tissue and orientation of cells within the tissue. The large cadherin Fat has been shown to play a role in both of these processes. Fat is involved in the establishment of planar cell polarity and regulates growth through the Hippo pathway, a developmental cascade that controls proliferation and apoptosis. Both Fat and the Hippo pathway are known to regulate transcription of four-jointed, although the nature of this regulation is unknown. In this study, we test whether Fat affects four-jointed transcription via or independently of Hippo pathway. Our analysis of the four-jointed regulatory region reveals a 1.2â¯kb element that functions as an enhancer for graded expression of Four-jointed in the eye imaginal disc. Within this enhancer element, we identify a 20 bp fragment that is critical for regulation by Fat but not by Hippo. Our findings suggest that Fat and the Hippo pathway control four-jointed expression independently of each other and none of the transcription factors known to function downstream of the Hippo pathway are required to regulate four-jointed expression through the 1.2â¯kb element.
Assuntos
Moléculas de Adesão Celular , Proteínas de Drosophila , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Peptídeos e Proteínas de Sinalização Intracelular , Glicoproteínas de Membrana , Proteínas Serina-Treonina Quinases , Transdução de Sinais , Transcrição Gênica , Animais , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Proteínas de Drosophila/biossíntese , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Genes Reporter , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Glicoproteínas de Membrana/biossíntese , Glicoproteínas de Membrana/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismoRESUMO
The Hippo pathway is a conserved and critical regulator of tissue growth. The FERM protein Expanded is a key signaling hub that promotes activation of the Hippo pathway, thereby inhibiting the transcriptional co-activator Yorkie. Previous work identified the polarity determinant Crumbs as a primary regulator of Expanded. Here, we show that the giant cadherin Fat also regulates Expanded directly and independently of Crumbs. We show that direct binding between Expanded and a highly conserved region of the Fat cytoplasmic domain recruits Expanded to the apicolateral junctional zone and stabilizes Expanded. In vivo deletion of Expanded binding regions in Fat causes loss of apical Expanded and promotes tissue overgrowth. Unexpectedly, we find Fat can bind its ligand Dachsous via interactions of their cytoplasmic domains, in addition to the known extracellular interactions. Importantly, Expanded is stabilized by Fat independently of Dachsous binding. These data provide new mechanistic insights into how Fat regulates Expanded, and how Hippo signaling is regulated during organ growth.
Assuntos
Moléculas de Adesão Celular , Proteínas de Drosophila , Drosophila melanogaster , Via de Sinalização Hippo , Proteínas de Membrana , Animais , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Fatores de Transcrição/metabolismo , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismoRESUMO
Precisely controlled organisation at the cellular and tissue level is crucial to establish and maintain complex organisms. The atypical cadherins Fat (Ft), Fat2 and Dachsous (Ds) contribute to this organisation by regulating growth and planar cell polarity. Here we describe the recent advances in understanding how these large cadherins coordinate these processes, and discuss additional progress extending their function in regulation of microtubules, migration and disease.
Assuntos
Caderinas/metabolismo , Polaridade Celular/fisiologia , Proteínas de Drosophila/fisiologia , Animais , Caderinas/fisiologiaRESUMO
Drosophila melanogaster has been widely used in the study of developmental growth control and has been instrumental in the discovery and delineation of many signalling pathways that contribute to this growth, in particular the Hippo pathway. Quantitative analysis of adult tissue size has remained a vital tool in the study of tissue growth. This chapter will describe how to dissect, image, and quantify two tissues commonly used to measure growth, the Drosophila wing and eye.
Assuntos
Proteínas de Drosophila/genética , Drosophila/crescimento & desenvolvimento , Drosophila/genética , Estudos de Associação Genética , Animais , Proteínas de Drosophila/metabolismo , Olho/citologia , Olho/metabolismo , Feminino , Estágios do Ciclo de Vida , Microscopia , Asas de Animais/anatomia & histologia , Asas de Animais/metabolismoRESUMO
Hippo signalling integrates diverse stimuli related to epithelial architecture to regulate tissue growth and cell fate decisions. The Hippo kinase cascade represses the growth-promoting transcription co-activator Yorkie. The FERM protein Expanded is one of the main upstream Hippo signalling regulators in Drosophila as it promotes Hippo kinase signalling and directly inhibits Yorkie. To fulfil its function, Expanded is recruited to the plasma membrane by the polarity protein Crumbs. However, Crumbs-mediated recruitment also promotes Expanded turnover via a phosphodegron-mediated interaction with a Slimb/ß-TrCP SCF E3 ligase complex. Here, we show that the Casein Kinase 1 (CKI) family is required for Expanded phosphorylation. CKI expression promotes Expanded phosphorylation and interaction with Slimb/ß-TrCP. Conversely, CKI depletion in S2 cells impairs Expanded degradation downstream of Crumbs. In wing imaginal discs, CKI loss leads to elevated Expanded and Crumbs levels. Thus, phospho-dependent Expanded turnover ensures a tight coupling of Hippo pathway activity to epithelial architecture.
Assuntos
Caseína Quinase I/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de Membrana/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Drosophila , Regulação da Expressão Gênica , Fosforilação , Ligação Proteica , Mapas de Interação de Proteínas , Processamento de Proteína Pós-Traducional , Proteólise , Proteínas Contendo Repetições de beta-Transducina/metabolismoRESUMO
Cellular signalling lies at the heart of every decision involved in the development and homeostasis of multicellular organisms. The Hippo pathway was discovered nearly two decades ago through seminal work in Drosophila and rapidly emerged as a crucial signalling network implicated in developmental and oncogenic growth, tissue regeneration and stem cell biology. Here, we review recent advances in the field relating to the upstream regulation of Hippo signalling and the intracellular tug-of-war that tightly controls its main target, the transcriptional co-activator Yorkie/YAP.