RESUMEN
JNK signaling is a critical regulator of inflammation and regeneration, but how it is controlled in specific tissue contexts remains unclear. Here we show that, in the Drosophila intestine, the TNF-type ligand, Eiger (Egr), is expressed exclusively by intestinal stem cells (ISCs) and enteroblasts (EBs), where it is induced by stress and during aging. Egr preferentially activates JNK signaling in a paracrine fashion in differentiated enterocytes (ECs) via its receptor, Grindelwald (Grnd). N-glycosylation genes (Alg3, Alg9) restrain this activation, and stress-induced downregulation of Alg3 and Alg9 correlates with JNK activation, suggesting a regulatory switch. JNK activity in ECs induces expression of the intermembrane protease Rhomboid (Rho), driving secretion of EGFR ligands Keren (Krn) and Spitz (Spi), which in turn activate EGFR signaling in progenitor cells (ISCs and EBs) to stimulate their growth and division, as well as to produce more Egr. This study uncovers an N-glycosylation-controlled, paracrine JNK-EGFR-JNK feedforward loop that sustains ISC proliferation during stress-induced gut regeneration.
Asunto(s)
Proteínas de Drosophila , Receptores ErbB , Intestinos , Sistema de Señalización de MAP Quinasas , Animales , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Receptores ErbB/metabolismo , Receptores ErbB/genética , Intestinos/citología , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Enterocitos/metabolismo , Enterocitos/citología , Células Madre/metabolismo , Células Madre/citología , Mucosa Intestinal/metabolismo , Mucosa Intestinal/citología , Drosophila/metabolismo , Glicosilación , Receptores de Péptidos de Invertebrados/metabolismo , Receptores de Péptidos de Invertebrados/genética , Proliferación Celular , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Transducción de Señal , Comunicación Celular , Diferenciación Celular , Factor de Crecimiento Epidérmico , Proteínas de la MembranaRESUMEN
Across diverse insect taxa, the behavior and physiology of females dramatically changes after mating-processes largely triggered by the transfer of seminal proteins from their mates. In the vinegar fly Drosophila melanogaster, the seminal protein sex peptide (SP) decreases the likelihood of female flies remating and causes additional behavioral and physiological changes that promote fertility including increasing egg production. Although SP is only found in the Drosophila genus, its receptor, sex peptide receptor (SPR), is the widely conserved myoinhibitory peptide (MIP) receptor. To test the functional role of SPR in mediating postmating responses in a non-Drosophila dipteran, we generated 2 independent Spr-knockout alleles in the yellow fever mosquito, Aedes aegypti. Although SPR is needed for postmating responses in Drosophila and the cotton bollworm Helicoverpa armigera, Spr mutant Ae. aegypti show completely normal postmating decreases in remating propensity and increases in egg laying. In addition, injection of synthetic SP or accessory gland homogenate from D. melanogaster into virgin female mosquitoes did not elicit these postmating responses. Our results demonstrate that Spr is not required for these canonical postmating responses in Ae. aegypti, indicating that other, as yet unknown, signaling pathways are likely responsible for these behavioral switches in this disease vector.
Asunto(s)
Aedes , Proteínas de Insectos , Oviposición , Receptores de Péptidos de Invertebrados , Animales , Femenino , Masculino , Aedes/genética , Aedes/fisiología , Drosophila melanogaster/fisiología , Drosophila melanogaster/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Receptores de Péptidos de Invertebrados/metabolismo , Receptores de Péptidos de Invertebrados/genética , Conducta Sexual AnimalRESUMEN
The Epidermal Growth Factor Receptor (EGFR) signaling pathway plays a critical role in regulating tissue patterning. Drosophila EGFR signaling achieves specificity through multiple ligands and feedback loops to finetune signaling outcomes spatiotemporally. The principal Drosophila EGF ligand, cleaved Spitz, and the negative feedback regulator, Argos are diffusible and can act both in a cell autonomous and non-autonomous manner. The expression dose of Spitz and Argos early in photoreceptor cell fate determination has been shown to be critical in patterning the Drosophila eye, but the exact identity of the cells expressing these genes in the larval eye disc has been elusive. Using single molecule RNA Fluorescence in situ Hybridization (smFISH), we reveal an intriguing differential expression of spitz and argos mRNA in the Drosophila third instar eye imaginal disc indicative of directional non-autonomous EGFR signaling. By genetically tuning EGFR signaling, we show that rather than absolute levels of expression, the ratio of expression of spitz-to-argos to be a critical determinant of the final adult eye phenotype. Proximate effects on EGFR signaling in terms of cell cycle and differentiation markers are affected differently in the different perturbations. Proper ommatidial patterning is robust to thresholds around a tightly maintained wildtype spitz-to-argos ratio, and breaks down beyond. This provides a powerful instance of developmental buffering against gene expression fluctuations.
Asunto(s)
Proteínas de Drosophila , Drosophila , Animales , Drosophila/genética , Receptores ErbB/genética , Receptores ErbB/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Hibridación Fluorescente in Situ , Factor de Crecimiento Epidérmico/genética , Transducción de Señal/genética , Ojo/metabolismo , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismoRESUMEN
EGFR-RAS-ERK signaling promotes growth and proliferation in many cell types, and genetic hyperactivation of RAS-ERK signaling drives many cancers. Yet, despite intensive study of upstream components in EGFR signal transduction, the identities and functions of downstream effectors in the pathway are poorly understood. In Drosophila intestinal stem cells (ISCs), the transcriptional repressor Capicua (Cic) and its targets, the ETS-type transcriptional activators Pointed (pnt) and Ets21C, are essential downstream effectors of mitogenic EGFR signaling. Here, we show that these factors promote EGFR-dependent metabolic changes that increase ISC mass, mitochondrial growth, and mitochondrial activity. Gene target analysis using RNA and DamID sequencing revealed that Pnt and Ets21C directly upregulate not only DNA replication and cell cycle genes but also genes for oxidative phosphorylation, the TCA cycle, and fatty acid beta-oxidation. Metabolite analysis substantiated these metabolic functions. The mitochondrial transcription factor B2 (mtTFB2), a direct target of Pnt, was required and partially sufficient for EGFR-driven ISC growth, mitochondrial biogenesis, and proliferation. MEK-dependent EGF signaling stimulated mitochondrial biogenesis in human RPE-1 cells, indicating the conservation of these metabolic effects. This work illustrates how EGFR signaling alters metabolism to coordinately activate cell growth and cell division.
Asunto(s)
Proteínas de Drosophila , Animales , Proliferación Celular , Proteínas de Unión al ADN/metabolismo , Drosophila/fisiología , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Receptores ErbB/genética , Receptores ErbB/metabolismo , Humanos , Proteínas del Tejido Nervioso , Biogénesis de Organelos , Proteínas Proto-Oncogénicas , Proteínas Proto-Oncogénicas c-ets/genética , Proteínas Proto-Oncogénicas c-ets/metabolismo , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Transducción de Señal/fisiología , Células Madre/metabolismo , Factores de Transcripción/metabolismoRESUMEN
How cell to cell interactions control local tissue growth to attain a species-specific organ size is a central question in developmental biology. The Drosophila Neural Cell Adhesion Molecule, Fasciclin 2, is expressed during the development of neural and epithelial organs. Fasciclin 2 is a homophilic-interaction protein that shows moderate levels of expression in the proliferating epithelia and high levels in the differentiating non-proliferative cells of imaginal discs. Genetic interactions and mosaic analyses reveal a cell autonomous requirement of Fasciclin 2 to promote cell proliferation in imaginal discs. This function is mediated by the EGFR, and indirectly involves the JNK and Hippo signaling pathways. We further show that Fasciclin 2 physically interacts with EGFR and that, in turn, EGFR activity promotes the cell autonomous expression of Fasciclin 2 during imaginal disc growth. We propose that this auto-stimulatory loop between EGFR and Fasciclin 2 is at the core of a cell to cell interaction mechanism that controls the amount of intercalary growth in imaginal discs.
Asunto(s)
Proteínas de Drosophila , Discos Imaginales , Animales , Proliferación Celular/genética , Drosophila/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Receptores ErbB/genética , Receptores de Péptidos de Invertebrados/genética , Alas de AnimalesRESUMEN
Adult stem cells are maintained in niches, specialized microenvironments that regulate their self-renewal and differentiation. In the adult Drosophila testis stem cell niche, somatic hub cells produce signals that regulate adjacent germline stem cells (GSCs) and somatic cyst stem cells (CySCs). Hub cells are normally quiescent, but after complete genetic ablation of CySCs, they can proliferate and transdifferentiate into new CySCs. Here we find that Epidermal growth factor receptor (EGFR) signaling is upregulated in hub cells after CySC ablation and that the ability of testes to recover from ablation is inhibited by reduced EGFR signaling. In addition, activation of the EGFR pathway in hub cells is sufficient to induce their proliferation and transdifferentiation into CySCs. We propose that EGFR signaling, which is normally required in adult cyst cells, is actively inhibited in adult hub cells to maintain their fate but is repurposed to drive stem cell regeneration after CySC ablation.
Asunto(s)
Quistes , Proteínas de Drosophila , Animales , Transdiferenciación Celular , Quistes/metabolismo , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Receptores ErbB/metabolismo , Masculino , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Células Madre/fisiología , Testículo/metabolismo , Microambiente TumoralRESUMEN
Adult tissue homeostasis is maintained by residential stem cells. The proliferation and differentiation of adult stem cells must be tightly balanced to avoid excessive proliferation or premature differentiation. However, how stem cell proliferation is properly controlled remains elusive. Here, we find that auxilin (Aux) restricts intestinal stem cell (ISC) proliferation mainly through EGFR signaling. aux depletion leads to excessive ISC proliferation and midgut homeostasis disruption, which is unlikely caused by defective Notch signaling. Aux is expressed in multiple types of intestinal cells. Interestingly, aux depletion causes a dramatic increase in EGFR signaling, with a strong accumulation of EGFR at the plasma membrane and an increased expression of EGFR ligands in response to tissue stress. Furthermore, Aux co-localizes and associates with EGFR. Finally, blocking EGFR signaling completely suppresses the defects caused by aux depletion. Together, these data demonstrate that Aux mainly safeguards EGFR activation to keep a proper ISC proliferation rate to maintain midgut homeostasis.
Asunto(s)
Proteínas de Drosophila , Animales , Auxilinas/metabolismo , Proliferación Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Receptores ErbB/metabolismo , Intestinos , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismoRESUMEN
In holometabolous insects, metamorphic timing and body size are controlled by a neuroendocrine axis composed of the ecdysone-producing prothoracic gland (PG) and its presynaptic neurons (PGNs) producing PTTH. Although PTTH/Torso signaling is considered the primary mediator of metamorphic timing, recent studies indicate that other unidentified PGN-derived factors also affect timing. Here, we demonstrate that the receptor tyrosine kinases anaplastic lymphoma kinase (Alk) and PDGF and VEGF receptor-related (Pvr), function in coordination with PTTH/Torso signaling to regulate pupariation timing and body size. Both Alk and Pvr trigger Ras/Erk signaling in the PG to upregulate expression of ecdysone biosynthetic enzymes, while Alk also suppresses autophagy by activating phosphatidylinositol 3-kinase (PI3K)/Akt. The Alk ligand Jelly belly (Jeb) is produced by the PGNs and serves as a second PGN-derived tropic factor, while Pvr activation mainly relies on autocrine signaling by PG-derived Pvf2 and Pvf3. These findings illustrate that a combination of juxtacrine and autocrine signaling regulates metamorphic timing, the defining event of holometabolous development.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , Glándulas Endocrinas/enzimología , Metamorfosis Biológica , Proteínas Tirosina Quinasas Receptoras/metabolismo , Animales , Animales Modificados Genéticamente , Comunicación Autocrina , Tamaño Corporal , Proteínas de Drosophila/genética , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Ecdisona/metabolismo , Glándulas Endocrinas/embriología , Receptores ErbB/genética , Receptores ErbB/metabolismo , Quinasas MAP Reguladas por Señal Extracelular/genética , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Regulación del Desarrollo de la Expresión Génica , IMP Deshidrogenasa/genética , IMP Deshidrogenasa/metabolismo , Quinasas Janus/genética , Quinasas Janus/metabolismo , Mutación , Proteínas Tirosina Quinasas Receptoras/genética , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Factores de Transcripción STAT/genética , Factores de Transcripción STAT/metabolismo , Transducción de Señal , Factores de Tiempo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Factores de Crecimiento Endotelial Vascular/genética , Factores de Crecimiento Endotelial Vascular/metabolismoRESUMEN
Activation of Ras signaling occurs in ~30% of human cancers. However, activated Ras alone is insufficient to produce malignancy. Thus, it is imperative to identify those genes cooperating with activated Ras in driving tumoral growth. In this work, we have identified a novel EGFR inhibitor, which we have named EGFRAP, for EGFR adaptor protein. Elimination of EGFRAP potentiates activated Ras-induced overgrowth in the Drosophila wing imaginal disc. We show that EGFRAP interacts physically with the phosphorylated form of EGFR via its SH2 domain. EGFRAP is expressed at high levels in regions of maximal EGFR/Ras pathway activity, such as at the presumptive wing margin. In addition, EGFRAP expression is up-regulated in conditions of oncogenic EGFR/Ras activation. Normal and oncogenic EGFR/Ras-mediated upregulation of EGRAP levels depend on the Notch pathway. We also find that elimination of EGFRAP does not affect overall organogenesis or viability. However, simultaneous downregulation of EGFRAP and its ortholog PVRAP results in defects associated with increased EGFR function. Based on these results, we propose that EGFRAP is a new negative regulator of the EGFR/Ras pathway, which, while being required redundantly for normal morphogenesis, behaves as an important modulator of EGFR/Ras-driven tissue hyperplasia. We suggest that the ability of EGFRAP to functionally inhibit the EGFR pathway in oncogenic cells results from the activation of a feedback loop leading to increase EGFRAP expression. This could act as a surveillance mechanism to prevent excessive EGFR activity and uncontrolled cell growth.
Asunto(s)
Receptores ErbB/antagonistas & inhibidores , Genes ras/genética , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Ciclo Celular , Proliferación Celular/genética , Proteínas de Drosophila/antagonistas & inhibidores , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Receptores ErbB/genética , Receptores ErbB/metabolismo , Expresión Génica/genética , Regulación Neoplásica de la Expresión Génica/genética , Genes ras/fisiología , Discos Imaginales/metabolismo , Morfogénesis , Fosforilación , Receptores de Péptidos de Invertebrados/antagonistas & inhibidores , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Transducción de Señal/genética , Proteínas ras/genéticaRESUMEN
RAS-like (RAL) GTPases function in Wnt signalling-dependent intestinal stem cell proliferation and regeneration. Whether RAL proteins work as canonical RAS effectors in the intestine and the mechanisms of how they contribute to tumourigenesis remain unclear. Here, we show that RAL GTPases are necessary and sufficient to activate EGFR/MAPK signalling in the intestine, via induction of EGFR internalisation. Knocking down Drosophila RalA from intestinal stem and progenitor cells leads to increased levels of plasma membrane-associated EGFR and decreased MAPK pathway activation. Importantly, in addition to influencing stem cell proliferation during damage-induced intestinal regeneration, this role of RAL GTPases impacts on EGFR-dependent tumourigenic growth in the intestine and in human mammary epithelium. However, the effect of oncogenic RAS in the intestine is independent from RAL function. Altogether, our results reveal previously unrecognised cellular and molecular contexts where RAL GTPases become essential mediators of adult tissue homeostasis and malignant transformation.
Asunto(s)
Proliferación Celular , Transformación Celular Neoplásica/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/enzimología , Receptores ErbB/metabolismo , Mucosa Intestinal/metabolismo , Proteínas de Unión al GTP Monoméricas/metabolismo , Receptores de Péptidos de Invertebrados/metabolismo , Células Madre/metabolismo , Proteínas de Unión al GTP ral/metabolismo , Animales , Animales Modificados Genéticamente , Neoplasias de la Mama/enzimología , Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Línea Celular Tumoral , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/patología , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Endocitosis , Receptores ErbB/genética , Femenino , Humanos , Hiperplasia , Mucosa Intestinal/patología , Neoplasias Pulmonares/enzimología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Glándulas Mamarias Humanas/enzimología , Glándulas Mamarias Humanas/patología , Ratones Endogámicos C57BL , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Proteínas de Unión al GTP Monoméricas/genética , Receptores de Péptidos de Invertebrados/genética , Transducción de Señal , Células Madre/patología , Proteínas de Unión al GTP ral/genéticaRESUMEN
A major goal in the study of adult stem cells is to understand how cell fates are specified at the proper time and place to facilitate tissue homeostasis. Here, we found that an E2 ubiquitin ligase, Bendless (Ben), has multiple roles in the Drosophila ovarian epithelial follicle stem cell (FSC) lineage. First, Ben is part of the JNK signaling pathway, and we found that it, as well as other JNK pathway genes, are essential for differentiation of FSC daughter cells. Our data suggest that JNK signaling promotes differentiation by suppressing the activation of the EGFR effector, ERK. Also, we found that loss of ben, but not the JNK kinase hemipterous, resulted in an upregulation of hedgehog signaling, increased proliferation and increased niche competition. Lastly, we demonstrate that the hypercompetition phenotype caused by loss of ben is suppressed by decreasing the rate of proliferation or knockdown of the hedgehog pathway effector, Smoothened (Smo). Taken together, our findings reveal a new layer of regulation in which a single gene influences cell signaling at multiple stages of differentiation in the early FSC lineage.
Asunto(s)
Proteínas de Drosophila/genética , Receptores ErbB/genética , Proteínas Hedgehog/genética , Folículo Ovárico/crecimiento & desarrollo , Receptores de Péptidos de Invertebrados/genética , Receptor Smoothened/genética , Enzimas Ubiquitina-Conjugadoras/genética , Animales , Diferenciación Celular/genética , Linaje de la Célula/genética , Proliferación Celular/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Células Epiteliales/citología , Femenino , Sistema de Señalización de MAP Quinasas/genética , Folículo Ovárico/metabolismo , Nicho de Células Madre/genética , Células Madre/citologíaRESUMEN
To bridge the gap between qualitative and quantitative analyses of the epidermal growth factor receptor (EGFR) in tissues, we generated an sfGFP-tagged EGF receptor (EGFR-sfGFP) in Drosophila The homozygous fly appears similar to wild type with EGFR expression and activation patterns that are consistent with previous reports in the ovary, early embryo, and imaginal discs. Using ELISA, we quantified an average of 1100, 6200 and 2500 receptors per follicle cell (FC) at stages 8/9, 10 and ≥11 of oogenesis, respectively. Interestingly, the spatial localization of the EGFR to the apical side of the FCs at early stages depended on the TGFα-like ligand Gurken. At later stages, EGFR localized to basolateral positions of the FCs. Finally, we followed the endosomal localization of EGFR in the FCs. The EGFR colocalized with the late endosome, but no significant colocalization of the receptor was found with the early endosome. The EGFR-sfGFP fly is an exciting new resource for studying cellular localization and regulation of EGFR in tissues.
Asunto(s)
Proteínas de Drosophila/metabolismo , Células Epiteliales/metabolismo , Receptores ErbB/metabolismo , Folículo Ovárico/metabolismo , Receptores de Péptidos de Invertebrados/metabolismo , Transducción de Señal , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Endosomas/genética , Endosomas/metabolismo , Células Epiteliales/citología , Epitelio/metabolismo , Receptores ErbB/genética , Femenino , Folículo Ovárico/citología , Receptores de Péptidos de Invertebrados/genética , Factor de Crecimiento Transformador alfa/genética , Factor de Crecimiento Transformador alfa/metabolismoRESUMEN
Aldosterone is produced by the mammalian adrenal cortex to modulate blood pressure and fluid balance; however, excessive, prolonged aldosterone promotes fibrosis and kidney failure. How aldosterone triggers disease may involve actions independent of its canonical mineralocorticoid receptor. Here, we present a Drosophila model of renal pathology caused by excess extracellular matrix formation, stimulated by exogenous aldosterone and by insect ecdysone. Chronic administration of aldosterone or ecdysone induces expression and accumulation of collagen-like Pericardin in adult nephrocytes - podocyte-like cells that filter circulating hemolymph. Excess Pericardin deposition disrupts nephrocyte (glomerular) filtration and causes proteinuria in Drosophila, hallmarks of mammalian kidney failure. Steroid-induced Pericardin production arises from cardiomyocytes associated with nephrocytes, potentially reflecting an analogous role of mammalian myofibroblasts in fibrotic disease. Remarkably, the canonical ecdysteroid nuclear hormone receptor, Ecdysone receptor (EcR), is not required for aldosterone or ecdysone to stimulate Pericardin production or associated renal pathology. Instead, these hormones require a cardiomyocyte-associated G-protein-coupled receptor, Dopamine-EcR (DopEcR), a membrane-associated receptor previously characterized in the fly brain to affect behavior. DopEcR in the brain is known to affect behavior through interactions with the Drosophila Epidermal growth factor receptor (Egfr), referred to as dEGFR. Here, we find that the steroids ecdysone and aldosterone require dEGFR in cardiomyocytes to induce fibrosis of the cardiac-renal system. In addition, endogenous ecdysone that becomes elevated with age is found to foster age-associated fibrosis, and to require both cardiomyocyte DopEcR and dEGFR. This Drosophila renal disease model reveals a novel signaling pathway through which steroids may modulate mammalian fibrosis through potential orthologs of DopEcR.
Asunto(s)
Drosophila melanogaster/metabolismo , Matriz Extracelular/metabolismo , Enfermedades Renales/metabolismo , Riñón/metabolismo , Miocitos Cardíacos/metabolismo , Receptores de Esteroides/metabolismo , Factores de Edad , Aldosterona , Animales , Animales Modificados Genéticamente , Colágeno Tipo IV/genética , Colágeno Tipo IV/metabolismo , Modelos Animales de Enfermedad , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Ecdisona , Receptores ErbB/genética , Receptores ErbB/metabolismo , Matriz Extracelular/genética , Matriz Extracelular/patología , Fibrosis , Riñón/patología , Enfermedades Renales/inducido químicamente , Enfermedades Renales/genética , Enfermedades Renales/patología , Miocitos Cardíacos/patología , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Receptores de Esteroides/genética , Transducción de SeñalRESUMEN
Understanding the mechanisms that determine final body size of animals is a central question in biology. In animals with determinate growth, such as mammals or insects, the size at which the immature organism transforms into the adult defines the final body size, as adult individuals do not grow [1]. In Drosophila, the growth period ends when the immature larva undergoes the metamorphic transition to develop the mature adult [2]. This metamorphic transition is triggered by a sharp increase of the steroid ecdysone, synthetized in the prothoracic gland (PG), that occurs at the end of the third instar larvae (L3) [3-6]. It is widely accepted that ecdysone biosynthesis in Drosophila is mainly induced by the activation of tyrosine kinase (RTK) Torso by the prothoracicotropic hormone (Ptth) produced into two pairs of neurosecretory cells that project their axons onto the PG [7, 8]. However, the fact that neither Ptth nor torso-null mutant animals arrest larval development but only present a delay in the larva-pupa transition [9-11] mandates for a reconsideration of the conventional model. Here, we show that Egfr signaling, rather than Ptth/torso, is the major contributor of ecdysone biosynthesis in Drosophila. We found that Egfr signaling is activated in the PG in an autocrine mode by the EGF ligands spitz and vein, which in turn are regulated by the levels of ecdysone. This regulatory positive feedback loop ensures the production of ecdysone to trigger metamorphosis by a progressive Egfr-dependent activation of MAPK/ERK pathway, thus determining the animal final body size.
Asunto(s)
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Ecdisona/biosíntesis , Receptores ErbB/genética , Receptores de Péptidos de Invertebrados/genética , Transducción de Señal/genética , Animales , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/metabolismo , Receptores ErbB/metabolismo , Larva/crecimiento & desarrollo , Larva/metabolismo , Pupa/crecimiento & desarrollo , Pupa/metabolismo , Receptores de Péptidos de Invertebrados/metabolismoRESUMEN
Although typically upregulated upon cellular stress, autophagy can also be utilized under homeostatic conditions as a quality control mechanism or in response to developmental cues. Here, we report that autophagy is required for the maintenance of somatic cyst stem cells (CySCs) in the Drosophila testis. Disruption of autophagy in CySCs and early cyst cells (CCs) by the depletion of autophagy-related (Atg) genes reduced early CC numbers and affected CC function, resembling decreased epidermal growth factor receptor (EGFR) signaling. Indeed, our data indicate that EGFR acts to stimulate autophagy to preserve early CC function, whereas target of rapamycin (TOR) negatively regulates autophagy in the differentiating CCs. Finally, we show that the EGFR-mediated stimulation of autophagy regulates lipid levels in CySCs and CCs. These results demonstrate a key role for autophagy in regulating somatic stem cell behavior and tissue homeostasis by integrating cues from both the EGFR and TOR signaling pathways to control lipid metabolism.
Asunto(s)
Autofagia/genética , Proteínas de Drosophila/metabolismo , Drosophila/metabolismo , Receptores ErbB/metabolismo , Células Germinativas/metabolismo , Metabolismo de los Lípidos/genética , Receptores de Péptidos de Invertebrados/metabolismo , Células Madre/metabolismo , Animales , Animales Modificados Genéticamente , Autofagosomas/metabolismo , Diferenciación Celular/genética , Proteínas de Drosophila/genética , Receptores ErbB/genética , Técnicas de Silenciamiento del Gen , Células Germinativas/crecimiento & desarrollo , Homeostasis , Sistema de Señalización de MAP Quinasas/genética , Masculino , Interferencia de ARN , Receptores de Péptidos de Invertebrados/genética , Serina-Treonina Quinasas TOR/metabolismo , Testículo/citología , Testículo/metabolismo , Factor de Transcripción AP-1/genética , Factor de Transcripción AP-1/metabolismoRESUMEN
In all metazoans, a small number of evolutionarily conserved signaling pathways are reiteratively used during development to orchestrate critical patterning and morphogenetic processes. Among these, Notch (N) signaling is essential for most aspects of tissue patterning where it mediates the communication between adjacent cells to control cell fate specification. In Drosophila, Notch signaling is required for several features of eye development, including the R3/R4 cell fate choice and R7 specification. Here we show that hypomorphic alleles of Notch, belonging to the Nfacet class, reveal a novel phenotype: while photoreceptor specification in the mutant ommatidia is largely normal, defects are observed in ommatidial rotation (OR), a planar cell polarity (PCP)-mediated cell motility process. We demonstrate that during OR Notch signaling is specifically required in the R4 photoreceptor to upregulate the transcription of argos (aos), an inhibitory ligand to the epidermal growth factor receptor (EGFR), to fine-tune the activity of EGFR signaling. Consistently, the loss-of-function defects of Nfacet alleles and EGFR-signaling pathway mutants are largely indistinguishable. A Notch-regulated aos enhancer confers R4 specific expression arguing that aos is directly regulated by Notch signaling in this context via Su(H)-Mam-dependent transcription.
Asunto(s)
Proteínas de Drosophila/genética , Receptores ErbB/genética , Proteínas del Ojo/genética , Proteínas del Tejido Nervioso/genética , Receptores de Péptidos de Invertebrados/genética , Receptores Notch/genética , Animales , Diferenciación Celular/genética , Linaje de la Célula/genética , Polaridad Celular/genética , Drosophila melanogaster/genética , Ojo/metabolismo , Receptores Frizzled/genética , Morfogénesis/genética , Células Fotorreceptoras de Invertebrados/metabolismoRESUMEN
In Drosophila development, the axes of the egg and future embryo are established during oogenesis. To learn about the underlying genetic and molecular pathways that lead to axis formation, I conducted a large-scale genetic screen at the beginning of my independent career. This led to the eventual understanding that both anterior-posterior and dorsal-ventral pattern information is transmitted from the oocyte to the surrounding follicle cells and in turn from the follicle cells back to the oocyte. How I came to conduct this screen and what further insights were gained by studying the mutants isolated in the screen are the topics of this autobiographical article.
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Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Genética/historia , Óvulo/fisiología , Animales , Tipificación del Cuerpo/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Embrión no Mamífero , Receptores ErbB/genética , Receptores ErbB/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica , Historia del Siglo XX , Historia del Siglo XXI , Masculino , Oocitos/fisiología , Ovario/crecimiento & desarrollo , Ovario/fisiología , Receptores de Péptidos de Invertebrados/genética , Receptores de Péptidos de Invertebrados/metabolismo , Análisis para Determinación del Sexo , Procesos de Determinación del Sexo , Estados UnidosRESUMEN
Mitochondria are essential organelles that have recently emerged as hubs for several metabolic and signaling pathways in the cell. Mitochondrial morphology is regulated by constant fusion and fission events to maintain a functional mitochondrial network and to remodel the mitochondrial network in response to external stimuli. Although the role of mitochondria in later stages of spermatogenesis has been investigated in depth, the role of mitochondrial dynamics in regulating early germ cell behavior is relatively less-well understood. We previously demonstrated that mitochondrial fusion is required for germline stem cell (GSC) maintenance in the Drosophila testis. Here, we show that mitochondrial fission is also important for regulating the maintenance of early germ cells in larval testes. Inhibition of Drp1 in early germ cells resulted in the loss of GSCs and spermatogonia due to the accumulation of reactive oxygen species (ROS) and activation of the EGFR pathway in adjacent somatic cyst cells. EGFR activation contributed to premature germ cell differentiation. Our data provide insights into how mitochondrial dynamics can impact germ cell maintenance and differentiation via distinct mechanisms throughout development.
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Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/metabolismo , Receptores ErbB/metabolismo , Dinámicas Mitocondriales/fisiología , Receptores de Péptidos de Invertebrados/metabolismo , Espermatozoides/metabolismo , Testículo/citología , Testículo/metabolismo , Células Madre Germinales Adultas/citología , Células Madre Germinales Adultas/metabolismo , Animales , Animales Modificados Genéticamente , Diferenciación Celular , Proteínas del Citoesqueleto/deficiencia , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Factor de Crecimiento Epidérmico/metabolismo , Receptores ErbB/genética , Proteínas de Unión al GTP/deficiencia , Proteínas de Unión al GTP/genética , Proteínas de Unión al GTP/metabolismo , Larva/citología , Larva/metabolismo , Masculino , Especies Reactivas de Oxígeno/metabolismo , Receptores de Péptidos de Invertebrados/genética , Transducción de Señal , Espermatogénesis/fisiología , Espermatogonias/citología , Espermatogonias/metabolismo , Espermatozoides/citologíaRESUMEN
The regenerative activity of adult stem cells carries a risk of cancer, particularly in highly renewable tissues. Members of the family of inhibitor of apoptosis proteins (IAPs) inhibit caspases and cell death, and are often deregulated in adult cancers; however, their roles in normal adult tissue homeostasis are unclear. Here, we show that regulation of the number of enterocyte-committed progenitor (enteroblast) cells in the adult Drosophila involves a caspase-mediated physiological apoptosis, which adaptively eliminates excess enteroblast cells produced by intestinal stem cells (ISCs) and, when blocked, can also lead to tumorigenesis. Importantly, we found that Diap1 is expressed by enteroblast cells and that loss and gain of Diap1 led to changes in enteroblast numbers. We also found that antagonistic interplay between Notch and EGFR signalling governs enteroblast life/death decisions via the Klumpfuss/WT1 and Lozenge/RUNX transcription regulators, which also regulate enteroblast differentiation and cell fate plasticity. These data provide new insights into how caspases drive adult tissue renewal and protect against the formation of tumours.
Asunto(s)
Apoptosis , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/fisiología , Enterocitos/patología , Receptores ErbB/metabolismo , Intestinos/patología , Receptores de Péptidos de Invertebrados/metabolismo , Receptores Notch/metabolismo , Células Madre/patología , Animales , Caspasas , Diferenciación Celular , Linaje de la Célula , Proteínas de Drosophila/genética , Enterocitos/metabolismo , Receptores ErbB/genética , Femenino , Homeostasis , Proteínas Inhibidoras de la Apoptosis/genética , Proteínas Inhibidoras de la Apoptosis/metabolismo , Masculino , Receptores de Péptidos de Invertebrados/genética , Receptores Notch/genética , Transducción de Señal , Células Madre/metabolismoRESUMEN
The Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) and epidermal growth factor receptor (EGFR) signaling pathways are conserved regulators of tissue patterning, morphogenesis, and other cell biological processes. During Drosophila oogenesis, these pathways determine the fates of epithelial follicle cells (FCs). JAK/STAT and EGFR together specify a population of cells called the posterior follicle cells (PFCs), which signal to the oocyte to establish the embryonic axes. In this study, whole genome expression analysis was performed to identify genes activated by JAK/STAT and/or EGFR. We observed that 317 genes were transcriptionally upregulated in egg chambers with ectopic JAK/STAT and EGFR activity in the FCs. The list was enriched for genes encoding extracellular matrix (ECM) components and ECM-associated proteins. We tested 69 candidates for a role in axis establishment using RNAi knockdown in the FCs. We report that the signaling protein Semaphorin 1b becomes enriched in the PFCs in response to JAK/STAT and EGFR. We also identified ADAM metallopeptidase with thrombospondin type 1 motif A (AdamTS-A) as a novel target of JAK/STAT in the FCs that regulates egg chamber shape. AdamTS-A mRNA becomes enriched at the anterior and posterior poles of the egg chamber at stages 6 to 7 and is regulated by JAK/STAT. Altering AdamTS-A expression in the poles or middle of the egg chamber produces rounder egg chambers. We propose that AdamTS-A regulates egg shape by remodeling the basement membrane.