RESUMEN
During tumor growth-when nutrient and anabolic demands are high-autophagy supports tumor metabolism and growth through lysosomal organelle turnover and nutrient recycling. Ras-driven tumors additionally invoke non-autonomous autophagy in the microenvironment to support tumor growth, in part through transfer of amino acids. Here we uncover a third critical role of autophagy in mediating systemic organ wasting and nutrient mobilization for tumor growth using a well-characterized malignant tumor model in Drosophila melanogaster. Micro-computed X-ray tomography and metabolic profiling reveal that RasV12 ; scrib-/- tumors grow 10-fold in volume, while systemic organ wasting unfolds with progressive muscle atrophy, loss of body mass, -motility, -feeding, and eventually death. Tissue wasting is found to be mediated by autophagy and results in host mobilization of amino acids and sugars into circulation. Natural abundance Carbon 13 tracing demonstrates that tumor biomass is increasingly derived from host tissues as a nutrient source as wasting progresses. We conclude that host autophagy mediates organ wasting and nutrient mobilization that is utilized for tumor growth.
Asunto(s)
Autofagia , Metabolismo Energético , Neoplasias/etiología , Neoplasias/metabolismo , Nutrientes/metabolismo , Animales , Autofagia/genética , Caquexia/diagnóstico por imagen , Caquexia/etiología , Caquexia/patología , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Drosophila melanogaster , Humanos , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiología , Neoplasias/complicacionesRESUMEN
The molecular mechanisms underlying the interdependence between intracellular trafficking and epithelial cell polarity are poorly understood. Here we show that inactivation of class III phosphatidylinositol-3-OH kinase (CIII-PI3K), which produces phosphatidylinositol-3-phosphate (PtdIns3P) on endosomes, disrupts epithelial organization. This is caused by dysregulation of endosomally localized Liver Kinase B1 (LKB1, also known as STK11), which shows delocalized and increased activity accompanied by dysplasia-like growth and invasive behaviour of cells provoked by JNK pathway activation. CIII-PI3K inactivation cooperates with RasV12 to promote tumour growth in vivo in an LKB1-dependent manner. Strikingly, co-depletion of LKB1 reverts these phenotypes and restores epithelial integrity. The endosomal, but not autophagic, function of CIII-PI3K controls polarity. We identify the CIII-PI3K effector, WD repeat and FYVE domain-containing 2 (WDFY2), as an LKB1 regulator in Drosophila tissues and human organoids. Thus, we define a CIII-PI3K-regulated endosomal signalling platform from which LKB1 directs epithelial polarity, the dysregulation of which endows LKB1 with tumour-promoting properties.
Asunto(s)
Fosfatidilinositol 3-Quinasas Clase III/metabolismo , Proteínas de Drosophila/metabolismo , Endosomas/metabolismo , Proteínas Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Quinasas de la Proteína-Quinasa Activada por el AMP , Animales , Animales Modificados Genéticamente , Células CACO-2 , Movimiento Celular , Polaridad Celular , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Endocitosis , Epitelio/metabolismo , Técnicas de Silenciamiento del Gen , Genes de Insecto , Humanos , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Organoides/metabolismo , Transducción de SeñalRESUMEN
As malignant tumours develop, they interact intimately with their microenvironment and can activate autophagy, a catabolic process which provides nutrients during starvation. How tumours regulate autophagy in vivo and whether autophagy affects tumour growth is controversial. Here we demonstrate, using a well characterized Drosophila melanogaster malignant tumour model, that non-cell-autonomous autophagy is induced both in the tumour microenvironment and systemically in distant tissues. Tumour growth can be pharmacologically restrained using autophagy inhibitors, and early-stage tumour growth and invasion are genetically dependent on autophagy within the local tumour microenvironment. Induction of autophagy is mediated by Drosophila tumour necrosis factor and interleukin-6-like signalling from metabolically stressed tumour cells, whereas tumour growth depends on active amino acid transport. We show that dormant growth-impaired tumours from autophagy-deficient animals reactivate tumorous growth when transplanted into autophagy-proficient hosts. We conclude that transformed cells engage surrounding normal cells as active and essential microenvironmental contributors to early tumour growth through nutrient-generating autophagy.
Asunto(s)
Autofagia , Drosophila melanogaster/citología , Modelos Biológicos , Neoplasias/patología , Microambiente Tumoral , Aminoácidos/metabolismo , Animales , Autofagia/efectos de los fármacos , Autofagia/genética , Transporte Biológico , Proliferación Celular , Modelos Animales de Enfermedad , Proteínas de Drosophila/deficiencia , Proteínas de Drosophila/genética , Drosophila melanogaster/efectos de los fármacos , Drosophila melanogaster/metabolismo , Femenino , Interleucina-6/metabolismo , Proteínas de la Membrana , Invasividad Neoplásica , Neoplasias/genética , Neoplasias/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal , Factor de Necrosis Tumoral alfa/metabolismo , Proteínas Supresoras de Tumor/deficiencia , Proteínas Supresoras de Tumor/genéticaRESUMEN
Body size in Drosophila larvae, like in other animals, is controlled by nutrition. Nutrient restriction leads to catabolic responses in the majority of tissues, but the Drosophila mitotic imaginal discs continue growing. The nature of these differential control mechanisms that spare distinct tissues from starvation are poorly understood. Here, we reveal that the Ret-like receptor tyrosine kinase (RTK), Stitcher (Stit), is required for cell growth and proliferation through the PI3K-I/TORC1 pathway in the Drosophila wing disc. Both Stit and insulin receptor (InR) signaling activate PI3K-I and drive cellular proliferation and tissue growth. However, whereas optimal growth requires signaling from both InR and Stit, catabolic changes manifested by autophagy only occur when both signaling pathways are compromised. The combined activities of Stit and InR in ectodermal epithelial tissues provide an RTK-mediated, two-tiered reaction threshold to varying nutritional conditions that promote epithelial organ growth even at low levels of InR signaling.
Asunto(s)
Proteínas de Drosophila/metabolismo , Receptor de Insulina/metabolismo , Animales , Autofagia/genética , Autofagia/fisiología , Drosophila , Proteínas de Drosophila/genética , Ectodermo/citología , Receptor de Insulina/genética , Transducción de Señal/genética , Transducción de Señal/fisiologíaRESUMEN
Degradation of cytoplasmic material by autophagy plays a key role in protein homeostasis and metabolic control, as well as in the removal of intracellular protein aggregates, pathogens and damaged organelles. The concept of up- or down-regulating this pathway pharmacologically in neurodegenerative diseases, infections, inflammation and cancer is therefore attractive. Among the key pharmacological targets in regulation of autophagy are the phosphoinositide 3-kinases (PI3Ks), which mediate the phosphorylation of phosphatidylinositol (PtdIns) or PtdIns 4,5-bisphosphate in the 3-position of the (phospho)inositol headgroup. The catalytic products, PtdIns 3-phosphate (PtdIns3P) and PtdIns 3,4,5-trisphosphate [PtdIns(3,4,5)P3 ], respectively, have opposing roles in autophagy. PtdIns3P, the product of class II and III PI3Ks, mediates the recruitment of specific autophagic effectors to the sites of origin of autophagic membranes and thereby plays an essential role in canonical autophagy. By contrast, PtdIns(3,4,5)P3 , the product of class I PI3Ks, triggers the target of rapamycin signalling pathway, which inhibits autophagy. In this review, we discuss the functions of class I, II and III PI3Ks in autophagy and describe the protein effectors of PtdIns3P and PtdIns(3,4,5)P3 that promote or inhibit autophagy, respectively. We also provide examples of how PI3K-mediated control of autophagy is relevant to an understanding of tumour suppression and progression.
Asunto(s)
Autofagia , Fosfatidilinositol 3-Quinasas/metabolismo , Transducción de Señal , Animales , HumanosRESUMEN
Drosophila PNS sense organs arise from single sensory organ precursor (SOP) cells through a series of asymmetric divisions. In a mis-expression screen for factors affecting PNS development, we identified string and dappled as being important for the proper formation of adult external sensory (ES) organs. string is a G2 regulator. dappled has no described function but is implicated in tumorigenesis. The mis-expression effect from string was analysed using timed over expression during adult ES-organ and, for comparison, embryonic Chordotonal (Ch) organ formation. Surprisingly, string mis-expression prior to SOP division gave the greatest effect in both systems. In adult ES-organs, this lead to cell fate transformations producing structural cells, whilst in the embryo organs were lost, hence differences within the lineages exist. Mis-expression of dappled, lead to loss and duplications of entire organs in both systems, potentially affecting SOP specification, in addition to affecting neuronal guidance.
Asunto(s)
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriología , Metaloproteínas/metabolismo , Organogénesis , Sistema Nervioso Periférico/embriología , Proteínas Tirosina Fosfatasas/metabolismo , Órganos de los Sentidos/embriología , Animales , Proteínas Portadoras , Ciclo Celular/genética , Proteínas de Ciclo Celular , Proteínas de Drosophila/análisis , Proteínas de Drosophila/genética , Drosophila melanogaster/citología , Drosophila melanogaster/metabolismo , Femenino , Masculino , Metaloproteínas/genética , Mutación , Organogénesis/genética , Sistema Nervioso Periférico/citología , Sistema Nervioso Periférico/metabolismo , Proteínas Tirosina Fosfatasas/análisis , Proteínas Tirosina Fosfatasas/genética , Órganos de los Sentidos/citología , Órganos de los Sentidos/metabolismoRESUMEN
During Drosophila embryogenesis, timely and orderly asymmetric cell divisions ensure the correct number of each cell type that make up the sensory organs of the larval PNS. We report a role of scraps, Drosophila Anillin, during these divisions. Anillin, a constitutive member of the contractile ring is essential for cytokinesis in Drosophila and vertebrates. During embryogenesis we find that zygotically transcribed scraps is required specifically for the unequal cell divisions, those in which cytokinesis occurs in an "off-centred" manner, of the pIIb and pIIIb neuronal precursor cells, but not the equal cell divisions of the lineage related precursor cells. Complementation and genetic rescue studies demonstrate this effect results from zygotic scraps and leads to polyploidy, ectopic mitosis, and loss of the neuronal precursor daughter cells. The net result of which is the formation of incomplete sense organs and embryonic lethality.
Asunto(s)
Proteínas Contráctiles/metabolismo , Citocinesis/fisiología , Drosophila melanogaster/embriología , Drosophila melanogaster/fisiología , Desarrollo Embrionario/fisiología , Nervios Periféricos/citología , Nervios Periféricos/embriología , Animales , División Celular/fisiología , Células Cultivadas , Nervios Periféricos/fisiologíaRESUMEN
Drosophila Dappled (DPLD) is a member of the RBCC/TRIM superfamily, a protein family involved in numerous diverse processes such as developmental timing and asymmetric cell divisions. DPLD belongs to the LIN-41 subclade, several members of which are micro RNA (miRNA) regulated. We re-examined the LIN-41 subclade members and their relation to other RBCC/TRIMs and dpld paralogs, and identified a new Drosophila muscle specific RBCC/TRIM: Another B-Box Affiliate, ABBA. In silico predictions of candidate miRNA regulators of dpld identified let-7 as the strongest candidate. Overexpression of dpld led to abnormal eye development, indicating that strict regulation of dpld mRNA levels is crucial for normal eye development. This phenotype was sensitive to let-7 dosage, suggesting let-7 regulation of dpld in the eye disc. A cell-based assay verified let-7 miRNA down-regulation of dpld expression by means of its 3'-untranslated region. Thus, dpld seems also to be miRNA regulated, suggesting that miRNAs represent an ancient mechanism of LIN-41 regulation.
Asunto(s)
Proteínas de Drosophila/genética , Drosophila/genética , Regulación del Desarrollo de la Expresión Génica , Metaloproteínas/genética , MicroARNs/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas Portadoras , Células Cultivadas , Drosophila/clasificación , Drosophila/embriología , Proteínas de Drosophila/metabolismo , Inmunohistoquímica , Hibridación in Situ , Metaloproteínas/metabolismo , MicroARNs/metabolismo , Modelos Genéticos , Datos de Secuencia Molecular , Filogenia , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido NucleicoRESUMEN
Mutants of L-type pyruvate kinase with modified peptide sequence around the Ser-12 phosphorylation site were prepared and kinetics of their phosphorylation by protein kinase A was studied. The profile of substrate specificity obtained for these proteins was compared with the kinetic data of phosphorylation of short peptide substrates. Alterations made in protein structure caused weaker effects than the corresponding alterations made in peptides, while the amino acid preferences and the overall specificity pattern remained similar in the both cases. Thus, similar consensus motif holds for both protein and peptide substrates, but is less critical for recognition of proteins if compared with short peptides.