Selective suppression of stress‐activated protein kinase pathway by protein phosphatase 2C in mammalian cells

Hanada, Masahito; Kobayashi, Toshihide; Ohnishi, Motoko; Ikeda, Shoko; Wang, Hong; Katsura, Koji; Yanagawa, Yuchio; Hiraga, Akira; Kanamaru, Ryunosuke; Tamura, Shinji

doi:10.1016/s0014-5793(98)01229-0

Cited by 97 publications

(96 citation statements)

References 34 publications

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“…We have recently reported that ectopic expression of mouse PP2C␣ or PP2C␤-1 inhibited the stress-activated MKK3/6-p38 and MKK4/7-JNK pathways but not the mitogen-activated MKK1-ERK1 pathway. Thus, negative regulation by PP2C␣ and PP2C␤-1 is selective for different SAPK pathways (17). Essentially the same results were obtained in studies of human PP2C␣-1 and -2 in mammalian cells (14).…”

supporting

confidence: 68%

Regulation of the TAK1 Signaling Pathway by Protein Phosphatase 2C

Hanada

Ninomiya‐Tsuji

Komaki

et al. 2001

Journal of Biological Chemistry

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135

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supporting

confidence: 68%

Regulation of the TAK1 Signaling Pathway by Protein Phosphatase 2C

Hanada

Ninomiya‐Tsuji

Komaki

et al. 2001

Journal of Biological Chemistry

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135

123

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“…12,13 The extent and specificity of JNK activation serve as important signals for promoting the stabilization and transcriptional activity of JNK substrates, which then mediate cell survival and/or apoptosis. Although phosphatases capable of dephosphorylating JNK cascade substrates have been deemed the primary negative regulators of JNK signaling, 14,15 several other proteins inhibit mitogen-activated kinase kinases (MAPKKs) signaling by interacting physically with various cascade components. [16][17][18] Thus, the precise molecular mechanism(s) that modulate JNK activation have yet to be completely elucidated.…”

mentioning

confidence: 99%

RASSF7 negatively regulates pro-apoptotic JNK signaling by inhibiting the activity of phosphorylated-MKK7

et al. 2010

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Members of the Ras-association domain family (RASSF) of proteins influence apoptosis and cell cycling but little is known about the mechanisms. Here, we show that RASSF7 interacts with N-Ras and mitogen-activated protein kinase kinase 7 (MKK7) to negatively regulate c-Jun N-terminal kinase (JNK) signaling. Stress-induced JNK activation and apoptosis were markedly enhanced in cells depleted of RASSF7 or N-Ras by RNAi knockdown. An interaction with RASSF7 promoted the phosphorylated state of MKK7 but inhibited this kinase's ability to activate JNK. RASSF7 required its RA domain for both interaction with GTP-bound N-Ras and the anti-apoptotic response to stress stimuli. Following prolonged stress, however, RASSF7's antiapoptotic effect was eliminated because of degradation of RASSF7 protein via the ubiquitin-proteasome pathway. Our results indicate that RASSF7 acts in concert with N-Ras to constitute a stress-sensitive temporary mechanism of apoptotic regulation. With initial stress, RASSF7/N-Ras promotes cell survival by inhibiting the MKK7/JNK pathway. However, with prolonged stress, RASSF7 protein undergoes degradation that allows cell death signaling to proceed. Our findings may account for the association of elevated RASSF7 with tumorigenesis. Members of the Ras-association domain family (RASSF) share a conserved motif called the RalGDS/AF6-type Ras association (RA) domain. 1-3 The vertebrate RASSF comprises the classical RASSF members, RASSF1-6, and the more recently identified N-terminal (NT) RASSF members, RASSF7-10. 1-3 Epigenetic silencing of most of RASSF genes has been observed at high frequencies in various tumor types. 1,2 In contrast, upregulation of RASSF7 has been noted in pancreatic, endometrial and ovarian cancers, 4-8 although no direct evidence exists indicating that RASSF7 promotes tumorigenesis.RASSF7 was originally identified as HRAS cluster 1 (HRC1), located within a cluster of genes situated about 32-kb upstream of HRAS1 on human chromosome 11p15. In Xenopus, knockdown of the RASSF7 homolog prevented cells from completing mitosis and caused a striking loss of tissue architecture in the neural tube. 9 However, the physiological functions of RASSF7 in mammals are unknown, and the signaling pathways in which RASSF7 participates remain a mystery.The c-Jun N-terminal kinase (JNK) enzymes function primarily in stress-activated signaling and are important as both positive and negative modulators of apoptosis, depending on the cellular context. 10,11 In response to cell stresses, such as heat shock, ultraviolet (UV) irradiation, hyperosmolarity and ischemia/reperfusion injury, MAP kinase kinase kinases (MAPKKKs) are activated. These enzymes then activate MAP kinase kinase 4 (MKK4; also known as SEK1) and/or MKK7, which in turn activate JNKs. 12,13 The extent and specificity of JNK activation serve as important signals for promoting the stabilization and transcriptional activity of JNK substrates, which then mediate cell survival and/or apoptosis. Although phosphatases capable of dephosphorylating ...

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“…Marley et al (38) reported that deletion of the C-terminal residues (including Arg 174 ) results in a completely inactive protein. In addition, replacement of Arg 179 (corresponding to Arg 174 of PP2C␣) with Gly in PP2C␤ results in a nearly complete loss of enzymatic activity (18). Therefore, Arg 174 may be necessary for the phosphatase activity of the protein.…”

Section: Discussionmentioning

confidence: 99%

“…Generation of Mutant PP2C␣ and Preparation of Recombinant Adenovirus-The recombinant vector containing HA-tagged mouse PP2C␣ cDNA was generated as described previously (18). A QuikChange sitedirected mutagenesis kit (Stratagene, La Jolla, CA) was used for mutagenesis.…”

Section: Methodsmentioning

confidence: 99%

Protein Phosphatase-2Cα as a Positive Regulator of Insulin Sensitivity through Direct Activation of Phosphatidylinositol 3-Kinase in 3T3-L1 Adipocytes

Yoshizaki

Maegawa

Egawa

et al. 2004

Journal of Biological Chemistry

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During differentiation, expression of protein phosphatase-2C␣ (PP2C␣) is increased in 3T3-L1 adipocytes.To elucidate the role of PP2C␣ in insulin signaling, we overexpressed wild-type (WT) PP2C␣ by adenovirus-mediated gene transfer in 3T3-L1 adipocytes. Overexpression of PP2C␣-WT enhanced the insulin sensitivity of glucose uptake without any changes in the early steps of insulin signaling. Infection with adenovirus 5 expressing PP2C␣-WT increased phosphatidylinositol 3-kinase (PI3K) activities in the immunoprecipitate using antibody against the p85 or p110 subunit under both basal and insulin-stimulated conditions, followed by activation of downstream steps in the PI3K pathway, such as phosphorylation of Akt, glycogen synthase kinase-3, and atypical protein kinase C. In contrast, overexpression of the phosphatase-defective mutant PP2C␣(R174G) did not produce such effects. Furthermore, overexpression of PP2C␣-WT (but not PP2C␣(R174G)) decreased the 32 P-labeled phosphorylation state as well as the gel mobility shift of the p85 subunit, suggesting that dephosphorylation of the p85 subunit by PP2C␣ activation might stimulate PI3K catalytic activity. Moreover, knockdown of PP2C␣ by transfection of small interfering RNA led to a significant decrease in Akt phosphorylation. In addition, microinjection of anti-PP2C␣ antibody or PP2C␣ small interfering RNA led to decreased insulin-stimulated GLUT4 translocation. In conclusion, PP2C␣ is a new positive regulator of insulin sensitivity that acts through a direct activation of PI3K in 3T3-L1 adipocytes.Phosphorylation state is regulated by both protein kinase and protein phosphatase and is critical for the regulation of cellular functions such as cell growth, differentiation, and metabolism (1, 2). The protein phosphatases of eukaryotic cells are structurally and functionally diverse enzymes that can be divided into two distinct families (serine/threonine phosphatases and protein-tyrosine phosphatases) based on their specificities for phosphoamino acids (3, 4). Serine/threonine phosphatases are further classified into four major groups (protein phosphatase (PP) 1 -1, PP2A, PP2B, and PP2C␣) depending on their substrate specificities, bivalent cation dependences, and sensitivities to various inhibitor molecules such as protein inhibitor-1 and -2 and the tumor promoter okadaic acid (3, 5).The role of protein-tyrosine phosphatases in insulin signaling has been well characterized in several recent studies (6 -11). As does tyrosine phosphorylation, serine/threonine phosphorylation plays important roles in insulin signal transduction. A major role in the negative regulation of insulin action is attributed to agents that enhance serine/threonine phosphorylation of the receptor itself or its downstream effectors such as insulin receptor substrate-1 (IRS-1). Serine/threonine phosphorylation of such molecules induces insulin resistance. Furthermore, Akt and atypical protein kinase C (PKC ) are serine/threonine kinases, and their kinase activities are regulated through the serine/threo...

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Selective suppression of stress‐activated protein kinase pathway by protein phosphatase 2C in mammalian cells

Cited by 97 publications

References 34 publications

Regulation of the TAK1 Signaling Pathway by Protein Phosphatase 2C

Regulation of the TAK1 Signaling Pathway by Protein Phosphatase 2C

RASSF7 negatively regulates pro-apoptotic JNK signaling by inhibiting the activity of phosphorylated-MKK7

Protein Phosphatase-2Cα as a Positive Regulator of Insulin Sensitivity through Direct Activation of Phosphatidylinositol 3-Kinase in 3T3-L1 Adipocytes

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