Deletion of the Dual Specific Phosphatase-4 (DUSP-4) Gene Reveals an Essential Non-redundant Role for MAP Kinase Phosphatase-2 (MKP-2) in Proliferation and Cell Survival

Abstract

Mitogen-activated protein kinase phosphatase-2 (MKP-2The amplitude and duration of MAP kinase signaling within a specific subcellular compartment are key features in the integration of extracellular stimuli and their effects on cellular (1). Three main MAP kinase groups, the ERKs, JNK, and p38 MAP kinases, are involved in regulating functions such as proliferation, apoptosis, and differentiation in response to growth factors, peptide hormones, stress, and infection (2). Perturbations in MAP kinase signaling are features of several different types of diseases including several types of cancers (3), diabetes (4), atherosclerosis (5, 6), and immune disorders.The kinetics of MAP kinase activation are strictly controlled principally by the mitogen-activated protein kinase phosphatases (MKPs), 3 a family of at least 10 dual specific phosphatases (DUSPs) that function to terminate MAP kinase signaling within a defined subcellular location (7). They share a common C-terminal catalytic domain and an N-terminal non-catalytic domain containing the MAP kinase interaction motif (8). Each isoform has unique yet overlapping features including substrate specificity, subcellular distribution, and factors regulating induction. For example, MKP-1 is a nuclear DUSP of the type 1 class and selective for all three major MAP kinases in vitro, whereas MKP-3, a type II DUSP, is a cytosolic phosphatase selective solely for ERK over the other kinases (7). Due to effects upon MAP kinase signaling, pertubations in the MKPs have been implicated principally in cancer (9). However, more recently, a role has been established in inflammation (10) and some cardiovascular disorders (11).One poorly studied MKP is MKP-2 (12). This DUSP (DUSP-4) is a member of the type 1 family and has been shown to be induced in response to a number of stimuli including phorbol esters and growth hormones (12-14). Nuclear targeting is regulated by two distinct nuclear targeting sequences (15). Substrate specificity for ERK and JNK was originally demonstrated in vitro (16); however, selective inhibition of JNK has been implicated in cellular studies (17,18). Although MKP-2 has been recently regarded as a surrogate for the more well described MKP-1, recent cellular studies demonstrate a role in protection against apoptosis (17) and in senescence (19). However, there is still a lack of information describing the function of DUSP-4 in different cell types, in particular regarding substrate selectivity in vivo.We have recently developed a DUSP-4 deletion mouse model and demonstrated a novel immunological phenotype in vivo (20). Using embryonic fibroblasts from DUSP-4 deletion mice, we now examine the effect of deletion upon MAP kinase signaling and growth parameters. We find that despite very moderate increases in ERK and JNK activity, MKP-2 deletion has profound effects upon cellular proliferation. In particular, we identify a role for MKP-2 in G 2 /M phase transition and demonstrate that MKP-2 plays a role in cell survival in response to the apo-* This work was supporte...

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“…However, this proved problematic using any commercial antibodies which could not detect a band which corresponded unequivocally to human MKP-2 either in resting cells or cells stimulated with appropriate agonists (not shown). This strongly contrasts with multiple studies including our own which show increased expression of MKP-2 in mouse cells in response to a number of agonists 19,20 .…”

“…A number of studies have established that MKP-2 plays an essential, significant role in ERK dephosphorylation 21,22 , however this is usually established using over expression of MKP-2 or mouse KO cells 19,20 and the current study is one of the first using knockdown of human DUSP-4 to demonstrate a role for MKP-2 in regulating the kinetics of ERK activation. How this translates into oncogenic potential is unclear.…”

“…In contrast, MKP-2 has been described as a mediator of oxidative damage-induced apoptosis through inhibition of ERK activation 11 . A recent study indicated a crucial role of MKP-2 in cell cycle progression; fibroblasts from DUSP-4 -/ -mice were more liable to arrest in G2/M-phase compared to wild type cells 12 . However there are few equivalent studies in human cells assessing cellular function in conditions of MKP-2 knockdown.…”

Linking JNK Activity to the DNA Damage Response

“…[59][60][61] The authors proposed a model whereby JNK translocation into the nucleus, where it meets its H2AX substrate, is a core event in the process, leading to UV-induced cell death. Moreover, Lawan and colleagues 62 have shown that UV-induced H2AX phosphorylation and apoptosis are increased in mouse embryonic fibroblasts (MEFs) deficient for the dualspecificity phosphatase MKP-2. Interestingly, MKP-2 is localized specifically in the nucleus, pinpointing the suggestion that specific nuclear activity of JNK is central in JNK-induced apoptosis.…”

Discovery of Novel DUSP4 Inhibitors through the Virtual Screening with Docking Simulations

“…6 Thus, the inhibition of DUSP4 activity can be a promising strategy for the development of anti-cancer medicines.…”