Ectopic expression of dual-specificity phosphatase 5 (DUSP5), an inducible mitogen-activated protein (MAP) kinase phosphatase, specifically inactivates and anchors extracellular signal-regulated kinase (ERK)1/2 in the nucleus. However, the role of endogenous DUSP5 in regulating the outcome of Ras/ERK kinase signaling under normal and pathological conditions is unknown. Here we report that mice lacking DUSP5 show a greatly increased sensitivity to mutant Harvey-Ras (HRas Q61L )-driven papilloma formation in the 7,12-Dimethylbenz[a]anthracene/12-O-tetradecanoylphorbol-13-acetate (DMBA/TPA) model of skin carcinogenesis. Furthermore, mouse embryo fibroblasts (MEFs) from DUSP5 −/− mice show increased levels of nuclear phospho-ERK immediately after TPA stimulation and fail to accumulate total ERK in the nucleus compared with DUSP5 +/+ cells. Surprisingly, a microarray analysis reveals that only a small number of Ras/ERK-dependent TPA-responsive transcripts are up-regulated on deletion of DUSP5 in MEFs and mouse skin. The most up-regulated gene on DUSP5 loss encodes SerpinB2, an inhibitor of extracellular urokinase plasminogen activator and deletion of DUSP5 acts synergistically with mutant HRas Q61L and TPA to activate ERK-dependent SerpinB2 expression at the transcriptional level. SerpinB2 has previously been implicated as a mediator of DMBA/TPA-induced skin carcinogenesis. By analyzing DUSP5−/− double knockout mice, we demonstrate that deletion of SerpinB2 abrogates the increased sensitivity to papilloma formation seen on DUSP5 deletion. We conclude that DUSP5 performs a key nonredundant role in regulating nuclear ERK activation, localization, and gene expression. Furthermore, our results suggest an in vivo role for DUSP5 as a tumor suppressor by modulating the oncogenic potential of activated Ras in the epidermis.is one of four mammalian inducible, nuclear mitogen-activated protein kinase (MAPK) phosphatases (MKPs) (1). However, DUSP5 is unique within this group in targeting only the classical extracellular signal-regulated kinases 1 and 2 (referred to hereafter as ERK) (2). This, coupled with the finding that ERK activation is required for inducible DUSP5 expression, indicates that it acts as a negative feedback regulator of nuclear Ras/ERK signaling (3). DUSP5 overexpression also leads to nuclear accumulation of endogenous ERK (2), suggesting that DUSP5 may also act as a nuclear anchor, thus regulating both the spatial organization and activity of the pathway (4).Ras/ERK signaling is frequently deregulated in human cancers due to activating mutations in pathway components such as growth factor receptors, Ras GTPases, and the MAPK kinase kinase, BRaf (5). BRaf is mutated in 40-60% of malignant melanomas as well as in thyroid, colorectal, and lung tumors, underscoring the importance of this pathway and making it a focus of anticancer drug development (6). Whereas mechanisms of Ras/MAPK pathway activation in cancer are understood, little is known about how negative feedback controls influence tumorigenesis (7). Stud...

The authors wish to note the following: "Since the publication of our paper, we have become aware that the quantitative data presented in Fig. 1B do not represent the full raw data set provided in the supporting information deposited online at https://doi.org/ 10.15125/BATH-00317. We are therefore publishing a corrected version of Fig. 1 in which the graphs in panel B have been replaced by those generated from the complete online dataset. The result and the conclusions drawn are unchanged. A minor correction has also been made to the figure legend to reflect the altered P values that result from use of the complete dataset." The corrected Fig. 1 and its corrected legend appear below.

The mechanistic Target of Rapamycin complex 1 (mTORC1) senses intracellular amino acid levels through an intricate machinery, which includes the Rag GTPases, Ragulator and vacuolar ATPase (V-ATPase). The membrane-associated E3 ubiquitin ligase ZNRF2 is released into the cytosol upon its phosphorylation by Akt. In this study, we show that ZNRF2 interacts with mTOR on membranes, promoting the amino acid-stimulated translocation of mTORC1 to lysosomes and its activation in human cells. ZNRF2 also interacts with the V-ATPase and preserves lysosomal acidity. Moreover, knockdown of ZNRF2 decreases cell size and cell proliferation. Upon growth factor and amino acid stimulation, mTORC1 phosphorylates ZNRF2 on Ser145, and this phosphosite is dephosphorylated by protein phosphatase 6. Ser145 phosphorylation stimulates vesicle-to-cytosol translocation of ZNRF2 and forms a novel negative feedback on mTORC1. Our findings uncover ZNRF2 as a component of the amino acid sensing machinery that acts upstream of Rag-GTPases and the V-ATPase to activate mTORC1.DOI: http://dx.doi.org/10.7554/eLife.12278.001

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