Dual-specificity phosphatase 5 regulates nuclear ERK activity and suppresses skin cancer by inhibiting mutant Harvey-Ras (HRas ^Q61L )-driven SerpinB2 expression

Abstract

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...

Dual-specificity phosphatase 5 controls the localized inhibition, propagation, and transforming potential of ERK signaling

“…S1B) and DUSP5 expression (Fig. 1C), suggesting that DUSP5 may be responsible for the nuclear accumulation and dephosphorylation of ERK (21,22). In agreement with this hypothesis, Dusp5 deletion both reduced the N:C ERK ratio and elevated nuclear p-ERK levels ( Fig.…”

“…We have previously demonstrated that DUSP5 causes both nuclear accumulation and dephosphorylation of ERK in MEFs when stimulated with the phorbol ester TPA (22). These localized effects were revealed using confocal and high-content microscopy (HCM) (22).…”

“…We recently established that Dusp5 knockout (KO) mice are sensitized to HRAS Q61L -driven DMBA/TPA (7,12-dimethylbenz[a] anthracene/12-O-tetra-decanoylphorbol-13-acetate)-initiated skin carcinogenesis, due to increased nuclear ERK activity and ERK-dependent SerpinB2 expression (22). Furthermore, the downregulation of DUSP5 in gastric and prostate cancers is also associated with a poor prognosis (23,24), suggesting that DUSP5 can function as a tumor suppressor.…”

“…1 A and B) may arise because DUSP5 is induced by ERK activity (19,20). To test this prediction, we rescued DUSP5 expression in Dusp5 KO MEFs using adenovirus (Ad) vectors containing an ERK-responsive 1.2-kb EGR1 immediate early gene promoter to drive DUSP5-Myc expression (22). Low-titer (0.3 pfu/nL) Ad DUSP5-Myc restored transient DUSP5 expression (Fig.…”

“…S1C). Negative control experiments using Ad to express an R53/54A kinase interaction motif (KIM) mutant of DUSP5-Myc that is unable to bind to ERK and driven by the EGR1 promoter (21,22) failed to influence ERK responses at any titer, indicating the necessity of DUSP5 association with ERK to influence ERK signaling ( Fig. 1B and Fig.…”