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Negative regulation of Drosophila JAK-STAT signalling by endocytic trafficking.

ABSTRACT: Appropriate regulation of signal transduction pathways is essential for normal development and is often disrupted in disease. Therefore, many regulatory mechanisms and feedback loops have evolved to ensure appropriate signalling. One mechanism previously suggested to modulate a range of signal transduction pathways involves the internalisation and destruction of transmembrane receptors by the endocytic trafficking machinery. Strikingly, a recent report has suggested that the endocytic trafficking of the Drosophila JAK-STAT pathway receptor Domeless (Dome) does not act to downregulate pathway activity, but rather is necessary for in vivo signalling. Here, we examine this relationship to address the interaction of Drosophila JAK-STAT pathway signalling and endocytic trafficking. We show that Dome is trafficked through clathrin-mediated endocytosis and a directed RNAi screen identified several components of the endocytic machinery as negative regulators of pathway signalling. We demonstrate that Dome signals both from the plasma membrane and internalised vesicles and show, using knockdown experiments, that endocytic components negatively regulate JAK-STAT signalling in vivo. As such, disruption in endocytic trafficking represents a potent negative regulator of the disease relevant JAK-STAT signalling cascade.

SUBMITTER: Vidal OM

PROVIDER: S-EPMC2951467 | biostudies-other | 2010 Oct

REPOSITORIES: biostudies-other

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Negative regulation of Drosophila JAK-STAT signalling by endocytic trafficking.

Vidal Oscar Marino OM Stec Wojciech W Bausek Nina N Smythe Elizabeth E Zeidler Martin P MP

Journal of cell science 20100914 Pt 20

Appropriate regulation of signal transduction pathways is essential for normal development and is often disrupted in disease. Therefore, many regulatory mechanisms and feedback loops have evolved to ensure appropriate signalling. One mechanism previously suggested to modulate a range of signal transduction pathways involves the internalisation and destruction of transmembrane receptors by the endocytic trafficking machinery. Strikingly, a recent report has suggested that the endocytic traffickin ...[more]

PMID: 20841381

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Project description:The posterior signalling centre (PSC), a small group of specialised cells, controls hemocyte (blood cell) homeostasis in the Drosophila larval hematopoietic organ, the lymph gland. This role of the PSC is very reminiscent of the "niche," the micro-environment of hematopoietic stem cells in vertebrates. We have recently shown that the PSC acts in a non-cell-autonomous manner to maintain janus tyrosine kinase/signal transducers and activators of transcription (JAK/STAT) signalling in hematopoietic progenitors (prohemocytes), thereby preserving the multipotent character necessary for their differentiation into lamellocytes, a cryptic and dedicated immune cell type required to fight specific immune threats such as wasp parasitism. In this report, on the basis of a knock out generated by homologous recombination, we show that a short type I cytokine-related receptor CG14225/Latran is required for switching off JAK/STAT signalling in prohemocytes. This is a prerequisite to massive differentiation of lamellocytes upon wasp parasitisation. In vivo and cell culture assays indicate that Latran forms heteromers with Domeless, the Drosophila type I cytokine signalling receptor related to mammalian GP130, and antagonises Domeless activity in a dose-dependent manner. Our analysis further shows that a primary immune response to wasp parasitism is a strong decrease in cytokine mRNA levels in the lymph gland, followed by an increase in the latran/domeless ratio. We propose that this sequence of events culminates in the complete inhibition of residual JAK/STAT signalling by Latran. JAK/STAT activity has been associated with several human diseases including leukaemia while knock-out studies in mice point to a central role of this pathway in hematopoiesis and regulation of immune functions. The specific function of Drosophila Latran is, to our knowledge, the first in vivo example of a role for a nonsignalling receptor in controlling a dedicated immune response, and thus raises the question of whether short, nonsignalling receptors also control specific aspects of vertebrate cellular immunity.

Project description:BACKGROUND:Due to the lack of effective therapies and poor prognosis in TNBC (triple-negative breast cancer) patients, there is a strong need to develop effective novel targeted therapies for this subtype of breast cancer. Inhibition of heat shock protein 90 (HSP90), a conserved molecular chaperone that is involved in the regulation of oncogenic client proteins, has shown to be a promising therapeutic approach for TNBC. However, both intrinsic and acquired resistance to HSP90 inhibitors (HSP90i) limits their effectiveness in cancer patients. METHODS:We developed models of acquired resistance to HSP90i by prolonged exposure of TNBC cells to HSP90i (ganetespib) in vitro. Whole transcriptome profiling and a 328-compound bioactive small molecule screen were performed on these cells to identify the molecular basis of acquired resistance to HSP90i and potential therapeutic approaches to overcome resistance. RESULTS:Among a panel of seven TNBC cell lines, the most sensitive cell line (Hs578T) to HSP90i was selected as an in vitro model to investigate acquired resistance to HSP90i. Two independent HSP90i-resistant clones were successfully isolated which both showed absence of client proteins degradation, apoptosis induction and G2/M cell cycle arrest after treatment with HSP90i. Gene expression profiling and pathway enrichment analysis demonstrate significant activation of the survival JAK-STAT signalling pathway in both HSP90i-resistant clones, possibly through IL6 autocrine signalling. A bioactive small molecule screen also demonstrated that the HSP90i-resistant clones showed selective sensitivity to JAK2 inhibition. Inhibition of JAK and HSP90 caused higher induction of apoptosis, despite prior acquired resistance to HSP90i. CONCLUSIONS:Acquired resistance to HSP90i in TNBC cells is associated with an upregulated JAK-STAT signalling pathway. A combined inhibition of the JAK-STAT signalling pathway and HSP90 could overcome this resistance. The benefits of the combined therapy could be explored further for the development of effective targeted therapy in TNBC patients.

Dataset Information

Negative regulation of Drosophila JAK-STAT signalling by endocytic trafficking.

Publications

Negative regulation of Drosophila JAK-STAT signalling by endocytic trafficking.

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