Acox2 is a regulator of lysine crotonylation that mediates hepatic metabolic homeostasis in mice.

Acyl-CoA oxidase 2 (Acox2) is an enzyme involved in peroxisomal bile acid synthesis and branched-chain fatty acid degradation. Acox2 knockout (-/-) mice spontaneously developed liver cancer with marked lymphocytic infiltrate. Tandem-affinity purification coupled with mass spectrometry analysis revealed that Acox2 interacted with methylcrotonoyl-CoA carboxylase followed by co-immunoprecipitation confirmation. Here we reported that non-histone lysine crotonylation (Kcr) levels were downregulated in Acox2-/- mice livers. Interestingly, Kcr signals were concentrated in the nucleus of tumor cells but mostly located in the cytoplasm of adjacent normal liver cells of Acox2-/- mice. Quantitative analysis of the global crotonylome further revealed that 54% (27/50) of downregulated non-histone Kcr sites were located in mitochondrial (11/50) and peroxisomal (17/50) enzymes including Ehhadh, Scp2, Hsd17b4, Crot, Etfa, Cpt1a, Eci1/2, Hadha, Etfdh, and Idh2. Subsequent site-directed mutagenesis and transcriptome analysis revealed that Ehhadh K572cr might have site-specific regulatory roles by downregulating TOP3B expression that lead to increased DNA damage in vitro. Our findings suggested Acox2 is a regulator of Kcr that might play critical role on hepatic metabolic homeostasis.

Dusp3 deletion in mice promotes experimental lung tumour metastasis in a macrophage dependent manner.

Vaccinia-H1 Related (VHR) dual-specificity phosphatase, or DUSP3, plays an important role in cell cycle regulation and its expression is altered in several human cancers. In mouse model, DUSP3 deletion prevents neo-angiogenesis and b-FGF-induced microvessel outgrowth. Considering the importance of angiogenesis in metastasis formation, our study aimed to investigate the role of DUSP3 in tumour cell dissemination. Using a Lewis Lung carcinoma (LLC) experimental metastasis model, we observed that DUSP3-/- mice developed larger lung metastases than littermate controls. DUSP3-/- bone marrow transfer to lethally irradiated DUSP3+/+ mice was sufficient to transfer the phenotype to DUSP3+/+ mice, indicating that hematopoietic cells compartment was involved in the increased tumour cell dissemination to lung tissues. Interestingly, we found a higher percentage of tumour-promoting Ly6Cint macrophages in DUSP3-/- LLC-bearing lung homogenates that was at least partially due to a better recruitment of these cells. This was confirmed by 1) the presence of higher number of the Ly6Bhi macrophages in DUSP3-/- lung homogenates and by 2) the better migration of DUSP3-/- bone marrow sorted monocytes, peritoneal macrophages and bone marrow derived macrophages (BMDMs), compared to DUSP3+/+ monocytes, macrophages and BMDMs, in response to LLC-conditioned medium. Our study demonstrates that DUSP3 phosphatase plays a key role in metastatic growth through a mechanism involving the recruitment of macrophages towards LLC-bearing lungs.

DUSP3 Genetic Deletion Confers M2-like Macrophage-Dependent Tolerance to Septic Shock.

DUSP3 is a small dual-specificity protein phosphatase with an unknown physiological function. We report that DUSP3 is strongly expressed in human and mouse monocytes and macrophages, and that its deficiency in mice promotes tolerance to LPS-induced endotoxin shock and to polymicrobial septic shock after cecal ligation and puncture. By using adoptive transfer experiments, we demonstrate that resistance to endotoxin is macrophage dependent and transferable, and that this protection is associated with a striking increase of M2-like macrophages in DUSP3(-/-) mice in both the LPS and cecal ligation and puncture models. We show that the altered response of DUSP3(-/-) mice to sepsis is reflected in decreased TNF production and impaired ERK1/2 activation. Our results demonstrate that DUSP3 plays a key and nonredundant role as a regulator of innate immune responses by mechanisms involving the control of ERK1/2 activation, TNF secretion, and macrophage polarization.

Fine-tuning the intensity of the PKB/Akt signal enables diverse physiological responses.

The PI3K/PDK1/PKB signaling pathway plays essential roles in regulating neuronal survival, differentiation and plasticity in response to neurotrophic factors, neurotransmitters and ion channels. Both PDK1 and PKB can interact at the plasma membrane with a phosphoinositide synthesized by PI3K, the second messenger PtdIns(3,4,5)P3, enabling PDK1 to phosphorylate and activate PKB. In the PDK1 K465E knock-in mice expressing a mutant form of PDK1 incapable of phosphoinositide binding, activation of PKB was markedly affected, but not totally abolished. It has been recently proposed that in the absence of PtdIns(3,4,5)P3 binding, PDK1 can still moderately activate PKB due to a docking site-mediated interaction of these 2 kinases. A recent report has uncovered that in the PDK1 K465E mice neurons, a PKB signal threshold was sufficient to support neuronal survival responses, whereas neuritogenesis, neuronal polarization and axon outgrowth were severely impaired. We propose here that the low-efficiency mechanism of PKB activation observed in the PDK1 K465E mice might represent the ancestral mechanism responsible for the essential functions of this pathway, while the phosphoinositide-dependent activation should be considered an evolutionary innovation that enabled the acquisition of novel functions.

DUSP3/VHR is a pro-angiogenic atypical dual-specificity phosphatase.

BACKGROUND: DUSP3 phosphatase, also known as Vaccinia-H1 Related (VHR) phosphatase, encoded by DUSP3/Dusp3 gene, is a relatively small member of the dual-specificity protein phosphatases. In vitro studies showed that DUSP3 is a negative regulator of ERK and JNK pathways in several cell lines. On the other hand, DUSP3 is implicated in human cancer. It has been alternatively described as having tumor suppressive and oncogenic properties. Thus, the available data suggest that DUSP3 plays complex and contradictory roles in tumorigenesis that could be cell type-dependent. Since most of these studies were performed using recombinant proteins or in cell-transfection based assays, the physiological function of DUSP3 has remained elusive. RESULTS: Using immunohistochemistry on human cervical sections, we observed a strong expression of DUSP3 in endothelial cells (EC) suggesting a contribution for this phosphatase to EC functions. DUSP3 downregulation, using RNA interference, in human EC reduced significantly in vitro tube formation on Matrigel and spheroid angiogenic sprouting. However, this defect was not associated with an altered phosphorylation of the documented in vitro DUSP3 substrates, ERK1/2, JNK1/2 and EGFR but was associated with an increased PKC phosphorylation. To investigate the physiological function of DUSP3, we generated Dusp3-deficient mice by homologous recombination. The obtained DUSP3-/- mice were healthy, fertile, with no spontaneous phenotype and no vascular defect. However, DUSP3 deficiency prevented neo-vascularization of transplanted b-FGF containing Matrigel and LLC xenograft tumors as evidenced by hemoglobin (Hb) and FITC-dextran quantifications. Furthermore, we found that DUSP3 is required for b-FGF-induced microvessel outgrowth in the aortic ring assay. CONCLUSIONS: All together, our data identify DUSP3 as a new important player in angiogenesis.

Interaction of PDK1 with phosphoinositides is essential for neuronal differentiation but dispensable for neuronal survival.

3-Phosphoinositide-dependent protein kinase 1 (PDK1) operates in cells in response to phosphoinositide 3-kinase activation and phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P(3)] production by activating a number of AGC kinases, including protein kinase B (PKB)/Akt. Both PDK1 and PKB contain pleckstrin homology (PH) domains that interact with the PtdIns(3,4,5)P(3) second messenger. Disrupting the interaction of the PDK1 PH domain with phosphoinositides by expressing the PDK1 K465E knock-in mutation resulted in mice with reduced PKB activation. We explored the physiological consequences of this biochemical lesion in the central nervous system. The PDK1 knock-in mice displayed a reduced brain size due to a reduction in neuronal cell size rather than cell number. Reduced BDNF-induced phosphorylation of PKB at Thr308, the PDK1 site, was observed in the mutant neurons, which was not rate limiting for the phosphorylation of those PKB substrates governing neuronal survival and apoptosis, such as FOXO1 or glycogen synthase kinase 3 (GSK3). Accordingly, the integrity of the PDK1 PH domain was not essential to support the survival of different embryonic neuronal populations analyzed. In contrast, PKB-mediated phosphorylation of PRAS40 and TSC2, allowing optimal mTORC1 activation and brain-specific kinase (BRSK) protein synthesis, was markedly reduced in the mutant mice, leading to impaired neuronal growth and differentiation.