Mitochondrial clearance by the STK38 kinase supports oncogenic Ras-induced cell transformation.

Oncogenic Ras signalling occurs frequently in many human cancers. However, no effective targeted therapies are currently available to treat patients suffering from Ras-driven tumours. Therefore, it is imperative to identify downstream effectors of Ras signalling that potentially represent promising new therapeutic options. Particularly, considering that autophagy inhibition can impair the survival of Ras-transformed cells in tissue culture and mouse models, an understanding of factors regulating the balance between autophagy and apoptosis in Ras-transformed human cells is needed. Here, we report critical roles of the STK38 protein kinase in oncogenic Ras transformation. STK38 knockdown impaired anoikis resistance, anchorage-independent soft agar growth, and in vivo xenograft growth of Ras-transformed human cells. Mechanistically, STK38 supports Ras-driven transformation through promoting detachment-induced autophagy. Even more importantly, upon cell detachment STK38 is required to sustain the removal of damaged mitochondria by mitophagy, a selective autophagic process, to prevent excessive mitochondrial reactive oxygen species production that can negatively affect cancer cell survival. Significantly, knockdown of PINK1 or Parkin, two positive regulators of mitophagy, also impaired anoikis resistance and anchorage-independent growth of Ras-transformed human cells, while knockdown of USP30, a negative regulator of PINK1/Parkin-mediated mitophagy, restored anchorage-independent growth of STK38-depleted Ras-transformed human cells. Therefore, our findings collectively reveal novel molecular players that determine whether Ras-transformed human cells die or survive upon cell detachment, which potentially could be exploited for the development of novel strategies to target Ras-transformed cells

ATG5 is essential for ATG8-dependent autophagy and mitochondrial homeostasis in Leishmania major

Macroautophagy has been shown to be important for the cellular remodelling required for Leishmania differentiation. We now demonstrate that L. major contains a functional ATG12-ATG5 conjugation system, which is required for ATG8-dependent autophagosome formation. Nascent autophagosomes were found commonly associated with the mitochondrion. L. major mutants lacking ATG5 (Δatg5) were viable as promastigotes but were unable to form autophagosomes, had morphological abnormalities including a much reduced flagellum, were less able to differentiate and had greatly reduced virulence to macrophages and mice. Analyses of the lipid metabolome of Δatg5 revealed marked elevation of phosphatidylethanolamines (PE) in comparison to wild type parasites. The Δatg5 mutants also had increased mitochondrial mass but reduced mitochondrial membrane potential and higher levels of reactive oxygen species. These findings indicate that the lack of ATG5 and autophagy leads to perturbation of the phospholipid balance in the mitochondrion, possibly through ablation of membrane use and conjugation of mitochondrial PE to ATG8 for autophagosome biogenesis, resulting in a dysfunctional mitochondrion with impaired oxidative ability and energy generation. The overall result of this is reduced virulence

mTOR independent regulation of macroautophagy by Leucine Rich Repeat Kinase 2 via Beclin-1

Leucine rich repeat kinase 2 is a complex enzyme with both kinase and GTPase activities, closely linked to the pathogenesis of several human disorders including Parkinson’s disease, Crohn’s disease, leprosy and cancer. LRRK2 has been implicated in numerous cellular processes; however its physiological function remains unclear. Recent reports suggest that LRRK2 can act to regulate the cellular catabolic process of macroautophagy, although the precise mechanism whereby this occurs has not been identi ed. To investigate the signalling events through which LRRK2 acts to in uence macroautophagy, the mammalian target of rapamycin (mTOR)/Unc-51-like kinase 1 (ULK1) and Beclin-1/phosphatidylinositol 3-kinase (PI3K) pathways were evaluated in astrocytic cell models in the presence and absence of LRRK2 kinase inhibitors. Chemical inhibition of LRRK2 kinase activity resulted in the stimulation of macroautophagy in a non-canonical fashion, independent of mTOR and ULK1, but dependent upon the activation of Beclin 1-containing class III PI3-kinase

Os custos da inatividade física no mundo: estudo de revisão

Resumo Os benefícios da atividade física e do exercício físico para a manutenção da saúde e a prevenção de doenças estão bem esclarecidos na literatura científica. Entretanto, estudos associando os custos da utilização de serviços de saúde e com os da inatividade física ainda são poucos. Pesquisas internacionais quantificaram estes custos e apresentaram associações com a prática de atividade física e/ou comportamento sedentário. Assim, o objetivo desta revisão foi, a partir destas informações, analisar os custos mundiais relacionados à inatividade física nas últimas décadas. Foram utilizados os resultados de 24 artigos originais, conduzidos em nove países, incluindo o Brasil. Os resultados mostraram que a inatividade física, independente do método de classificação, é onerosa à economia da saúde em todo o mundo e diretamente responsável pelo alto gasto com medicamentos, internação hospitalar e consultas clínicas. Os gastos com a parcela da população fisicamente inativa, acometida por doenças crônicas,estão entre os principais integrantes dos custos totais em saúde pública

Autophagy is defective in collagen VI muscular dystrophies and its reactivation rescues myofiber degeneration

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The mTOR inhibitor, everolimus (RAD001), overcomes resistance to imatinib in quiescent Ph-positive acute lymphoblastic leukemia cells

In Ph-positive (Ph+) leukemia, the quiescent cell state is one of the reasons for resistance to the BCR-ABL-kinase inhibitor, imatinib. In order to examine the mechanisms of resistance due to quiescence and the effect of the mammalian target of rapamycin inhibitor, everolimus, for such a resistant population, we used Ph+ acute lymphoblastic leukemia patient cells serially xenotransplanted into NOD/SCID/IL2rγnull (NOG) mice. Spleen cells from leukemic mice showed a higher percentage of slow-cycling G0 cells in the CD34+CD38− population compared with the CD34+CD38+ and CD34− populations. After ex vivo imatinib treatment, more residual cells were observed in the CD34+CD38− population than in the other populations. Although slow-cycling G0 cells were insensitive to imatinib in spite of BCR-ABL and CrkL dephosphorylation, combination treatment with everolimus induced substantial cell death, including that of the CD34+CD38− population, with p70-S6 K dephosphorylation and decrease of MCL-1 expression. The leukemic non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mouse system with the in vivo combination treatment with imatinib and everolimus showed a decrease of tumor burden including CD34+ cells. These results imply that treatment with everolimus can overcome resistance to imatinib in Ph+ leukemia due to quiescence

Molecular definitions of autophagy and related processes

Over the past two decades, the molecular machinery that underlies autophagic responses has been characterized with ever increasing precision in multiple model organisms. Moreover, it has become clear that autophagy and autophagy-related processes have profound implications for human pathophysiology. However, considerable confusion persists about the use of appropriate terms to indicate specific types of autophagy and some components of the autophagy machinery, which may have detrimental effects on the expansion of the field. Driven by the overt recognition of such a potential obstacle, a panel of leading experts in the field attempts here to define several autophagy-related terms based on specific biochemical features. The ultimate objective of this collaborative exchange is to formulate recommendations that facilitate the dissemination of knowledge within and outside the field of autophagy research. © 2017 The Author