The human Smoothened inhibitor PF-04449913 induces exit from quiescence and loss of multipotent Drosophila hematopoietic progenitor cells

The oncoprotein BCR-ABL1 triggers Chronic Myeloid Leukemia. It is clear that the disease relies on the constitutive BCR-ABL1 kinase activity, but not all the interactors and regulators of the oncoprotein are known. We describe and validate a Drosophila leukemia model based on inducible human BCR-ABL1 expression controlled by tissue specific promoters and thought as a versatile tool to perform genetic screens. BCR-ABL1 expression in the developing eye interferes with ommatidia differentiation and expression in the hematopoietic precursors increases the number of circulating blood cells. We show that BCR-ABL1 interferes with the pathway of endogenous dAbl with which it shares the target protein Ena. Loss of function of ena or Dab, an upstream regulator of dAbl, respectively suppresses or enhances both the BCR-ABL1 dependent phenotypes. Importantly, in patients with leukemia decrease of human Dab1 and Dab2 expression correlates with a more severe disease and Dab1 expression reduces the proliferation of leukemia cells. Globally, these observations validate our Drosophila model that promises to be an excellent system to perform unbiased genetic screens aimed at identifying new BCR-ABL1 interactors and regulators to better elucidate the mechanism of leukemia onset and progression.

Pathological mutations in the LRRK2 gene are the major genetic cause of Parkinson’s disease (PD). Although several animal models with either LRRK2 down- or over-expression have been developed, the physiological function of LRRK2 remains elusive. LRRK2 is constitutively expressed in various tissues including neurons and glial cells, but importantly, it is expressed at low levels in dopaminergic neurons, further contributing to the cryptic function of LRRK2. Significant levels of LRRK2 protein and mRNA have been detected in peripheral blood mononuclear cells, lymph nodes, the spleen, and primary microglia, strongly suggesting the contribution of inflammatory cells to neuronal degeneration. In this research article, using Drosophila LRRK2 models, we were able to demonstrate a significant contribution of glial cells to the LRRK2 pathological phenotype. Furthermore, in Drosophila, neurodegeneration is associated with a significant and important increase in specific inflammatory peptides. Finally, levetiracetam, a compound widely used in human therapy to treat epilepsy, was able to rescue both neuronal degeneration and neuroinflammation.

Parkinson’s disease (PD) is a fatal neurodegenerative disease for which there are no still effective treatments able to stop or slow down neurodegeneration. To date, pathological mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have been identified as the major genetic cause of PD, although the molecular mechanism responsible for the loss of dopaminergic neurons is still cryptic. In this review, we explore the contribution of Drosophila models to the elucidation of LRRK2 function in different cellular pathways in either neurons or glial cells. Importantly, recent studies have shown that LRRK2 is highly expressed in immunocompetent cells, including astrocytes and microglia in the brain, compared to neuronal expression. LRRK2 mutations are also strongly associated with the development of inflammatory diseases and the production of inflammatory molecules. Using Drosophila models, this paper shows that a genetic reduction of the inflammatory response protects flies from the neurodegeneration induced by LRRK2 pathological mutant expression.

Pathological mutations in leucine-rich repeat kinase 2 (LRRK2) gene are the major genetic cause of Parkinson’s disease (PD). Multiple lines of evidence link LRRK2 to the control of vesicle dynamics through phosphorylation of a subset of RAB proteins. However, the molecular mechanisms underlying these processes are not fully elucidated. We have previously demonstrated that LRRK2 increases the exocyst complex assembly by Sec8 interaction, one of the eight members of the exocyst complex, and that Sec8 over-expression mitigates the LRRK2 pathological effect in PC12 cells. Here, we extend this analysis using LRRK2 drosophila models and show that the LRRK2-dependent exocyst complex assembly increase is downstream of RAB phosphorylation. Moreover, exocyst complex inhibition rescues mutant LRRK2 pathogenic phenotype in cellular and drosophila models. Finally, prolonged exocyst inhibition leads to a significant reduction in the LRRK2 protein level, overall supporting the role of the exocyst complex in the LRRK2 pathway. Taken together, our study suggests that modulation of the exocyst complex may represent a novel therapeutic target for PD.