TOR (target of rapamycin), an evolutionarily-conserved serine/threonine kinase, acts as a central regulator of cell growth, proliferation and survival in response to nutritional status, growth factor, and stress signals. It plays a crucial role in coordinating the balance between cell growth and cell death, depending on cellular conditions and needs. As such, TOR has been identified as a key modulator of autophagy for more than a decade, and several deregulations of this pathway have been implicated in a variety of pathological disorders, including cancer. At the molecular level, autophagy regulates several survival or death signaling pathways that may decide the fate of cancer cells; however, the relationship between autophagy pathways and cancer are still nascent. In this review, we discuss the recent cellular signaling pathways regulated by TOR, their interconnections to autophagy, and the clinical implications of TOR inhibitors in cancer.
Highlights d AMPK and FLCN regulate TFEB/TFE3-mediated innate immunity and pathogen resistance d Loss of FLCN or activation of AMPK induces TFEB/TFE3dependent pro-inflammatory profile d FLCN depletion in macrophages enhances their energy metabolism and phagocytosis d LPS treatment induces acute ATP reduction followed by AMPK and TFEB activation
TFEB and TFE3 are transcriptional regulators of the innate immune response, but the mechanisms regulating their activation upon pathogen infection are poorly elucidated. Using C. elegans and mammalian models, we report that the master metabolic modulator 5'-AMPactivated protein kinase (AMPK) and its negative regulator Folliculin (FLCN) act upstream of TFEB/TFE3 in the innate immune response, independently of the mTORC1 signaling pathway.In nematodes, loss of FLCN or overexpression of AMPK conferred pathogen resistance via activation of TFEB/TFE3-dependent antimicrobial genes, while ablation of total AMPK activity abolished this phenotype. Similarly, in mammalian cells, loss of FLCN or pharmacological activation of AMPK induced TFEB/TFE3-dependent pro-inflammatory cytokine expression.Importantly, a rapid reduction in cellular ATP levels in murine macrophages was observed upon lipopolysaccharide (LPS) treatment accompanied by an acute AMPK activation and TFEB nuclear localization. These results uncover an ancient, highly conserved and pharmacologically actionable mechanism coupling energy status with innate immunity. translocation ( Figure 3E). These findings suggest that loss of FLCN drives HLH-30/TFEB/TFE3
SUMMARYThe fact that some organisms are able to regenerate organs of the correct shape and size following amputation is particularly fascinating, but the mechanism by which this occurs remains poorly understood. The zebrafish (Danio rerio) caudal fin has emerged as a model system for the study of bone development and regeneration. The fin comprises 16 to 18 bony rays, each containing multiple joints along its proximodistal axis that give rise to segments. Experimental observations on fin ray growth, regeneration and joint formation have been described, but no unified theory has yet been put forward to explain how growth and joint patterns are controlled. We present a model for the control of fin ray growth during development and regeneration, integrated with a model for joint pattern formation, which is in agreement with published, as well as new, experimental data. We propose that fin ray growth and joint patterning are coordinated through the interaction of three morphogens. When the model is extended to incorporate multiple rays across the fin, it also accounts for how the caudal fin acquires its shape during development, and regains its correct size and shape following amputation.
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