A computationally engineered RAS rheostat reveals RAS-ERK signaling dynamics.

Synthetic protein switches controlled with user-defined inputs are powerful tools for studying and controlling dynamic cellular processes. To date, these approaches have relied primarily on intermolecular regulation. Here we report a computationally guided framework for engineering intramolecular regulation of protein function. We utilize this framework to develop chemically inducible activator of RAS (CIAR), a single-component RAS rheostat that directly activates endogenous RAS in response to a small molecule. Using CIAR, we show that direct RAS activation elicits markedly different RAS-ERK signaling dynamics from growth factor stimulation, and that these dynamics differ among cell types. We also found that the clinically approved RAF inhibitor vemurafenib potently primes cells to respond to direct wild-type RAS activation. These results demonstrate the utility of CIAR for quantitatively interrogating RAS signaling. Finally, we demonstrate the general utility of our approach in design of intramolecularly regulated protein tools by applying it to the Rho family of guanine nucleotide exchange factors

Inside and out: the activities of senescence in cancer.

The core aspect of the senescent phenotype is a stable state of cell cycle arrest. However, this is a disguise that conceals a highly active metabolic cell state with diverse functionality. Both the cell-autonomous and the non-cell-autonomous activities of senescent cells create spatiotemporally dynamic and context-dependent tissue reactions. For example, the senescence-associated secretory phenotype (SASP) provokes not only tumour-suppressive but also tumour-promoting responses. Senescence is now increasingly considered to be an integrated and widespread component that is potentially important for tumour development, tumour suppression and the response to therapy.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nrc377

'Doubling down' on the autophagy pathway to suppress tumor growth.

In this issue of Genes & Development, Wei and colleagues (pp. 1204-1216) use elegant genetic approaches to simultaneously delete the essential autophagy gene FIP200 (FAK family-interacting protein of 200 kDa) and the signaling adaptor p62/SQSTM1 within established murine tumors, which reveals an unexpected synergism between the autophagy pathway and p62 in driving tumor growth. Intriguingly, these observations suggest that the combined targeting of autophagy and p62 may serve as an effective approach to treat specific cancers

'Doubling down' on the autophagy pathway to suppress tumor growth.

In this issue of Genes & Development, Wei and colleagues (pp. 1204-1216) use elegant genetic approaches to simultaneously delete the essential autophagy gene FIP200 (FAK family-interacting protein of 200 kDa) and the signaling adaptor p62/SQSTM1 within established murine tumors, which reveals an unexpected synergism between the autophagy pathway and p62 in driving tumor growth. Intriguingly, these observations suggest that the combined targeting of autophagy and p62 may serve as an effective approach to treat specific cancers

Drosophila Cup is an eIF4E-binding protein that functions in Smaug-mediated translational repression

Translational regulation plays an essential role in development and often involves factors that interact with sequences in the 3′ untranslated region (UTR) of specific mRNAs. For example, Nanos protein at the posterior of the Drosophila embryo directs posterior development, and this localization requires selective translation of posteriorly localized nanos mRNA. Spatial regulation of nanos translation requires Smaug protein bound to the nanos 3′ UTR, which represses the translation of unlocalized nanos transcripts. While the function of 3′ UTR-bound translational regulators is, in general, poorly understood, they presumably interact with the basic translation machinery. Here we demonstrate that Smaug interacts with the Cup protein and that Cup is an eIF4E-binding protein that blocks the binding of eIF4G to eIF4E. Cup mediates an indirect interaction between Smaug and eIF4E, and Smaug function in vivo requires Cup. Thus, Smaug represses translation via a Cup-dependent block in eIF4G recruitment

Autophagy-Dependent Shuttling of TBC1D5 Controls Plasma Membrane Translocation of GLUT1 and Glucose Uptake.

Autophagy traditionally sustains metabolism in stressed cells by promoting intracellular catabolism and nutrient recycling. Here, we demonstrate that in response to stresses requiring increased glycolytic demand, the core autophagy machinery also facilitates glucose uptake and glycolytic flux by promoting cell surface expression of the glucose transporter GLUT1/Slc2a1. During metabolic stress, LC3+ autophagic compartments bind and sequester the RabGAP protein TBC1D5 away from its inhibitory interactions with the retromer complex, thereby enabling retromer recruitment to endosome membranes and GLUT1 plasma membrane translocation. In contrast, TBC1D5 inhibitory interactions with the retromer are maintained in autophagy-deficient cells, leading to GLUT1 mis-sorting into endolysosomal compartments. Furthermore, TBC1D5 depletion in autophagy-deficient cells rescues retromer recruitment to endosomal membranes and GLUT1 surface recycling. Hence, TBC1D5 shuttling to autophagosomes during metabolic stress facilitates retromer-dependent GLUT1 trafficking. Overall, our results illuminate key interconnections between the autophagy and endosomal pathways dictating GLUT1 trafficking and extracellular nutrient uptake

Autophagy-Dependent Production of Secreted Factors Facilitates Oncogenic RAS-Driven Invasion

The tumor promoting functions of autophagy are primarily attributed to its ability to promote cancer cell survival. However, emerging evidence suggests that autophagy plays other roles during tumorigenesis. Here, we uncover that autophagy promotes oncogenic RAS-driven invasion. In epithelial cells transformed with oncogenic RAS, depletion of autophagy-related genes suppresses invasion in three-dimensional culture, decreases cell motility, and reduces pulmonary metastases in vivo. Treatment with conditioned media from autophagy-competent cells rescues the invasive capacity of autophagy-deficient cells, indicating these cells fail to secrete factors required for RAS-driven invasion. Reduced autophagy diminishes the secretion of the pro-migratory cytokine IL6, which is necessary to restore invasion of autophagy-deficient cells. Moreover, autophagy-deficient cells exhibit reduced levels of MMP2 and WNT5A. These results support a previously unrecognized function for autophagy in promoting cancer cell invasion via the coordinate production of multiple secreted factors