Brain region-specific synaptic function of FUS underlies the FTLD-linked behavioural disinhibition.

Synaptic dysfunction is one of the earliest pathological processes that contribute to the development of many neurological disorders, including Alzheimer's disease and frontotemporal lobar degeneration. However, the synaptic function of many disease-causative genes and their contribution to the pathogenesis of the related diseases remain unclear. In this study, we investigated the synaptic role of fused in sarcoma, an RNA-binding protein linked to frontotemporal lobar degeneration and amyotrophic lateral sclerosis, and its potential pathological role in frontotemporal lobar degeneration using pyramidal neuron-specific conditional knockout mice (FuscKO). We found that FUS regulates the expression of many genes associated with synaptic function in a hippocampal subregion-specific manner, concomitant with the frontotemporal lobar degeneration-linked behavioural disinhibition. Electrophysiological study and molecular pathway analyses further reveal that fused in sarcoma differentially regulates synaptic and neuronal properties in the ventral hippocampus and medial prefrontal cortex, respectively. Moreover, fused in sarcoma selectively modulates the ventral hippocampus-prefrontal cortex projection, which is known to mediate the anxiety-like behaviour. Our findings unveil the brain region- and synapse-specific role of fused in sarcoma, whose impairment might lead to the emotional symptoms associated with frontotemporal lobar degeneration.

An essential function for beta-arrestin 2 in the inhibitory signaling of natural killer cells.

The inhibitory signaling of natural killer (NK) cells is crucial in the regulation of innate immune responses. Here we show that the association of KIR2DL1, an inhibitory receptor of NK cells, with beta-arrestin 2 mediated recruitment of the tyrosine phosphatases SHP-1 and SHP-2 to KIR2DL1 and facilitated 'downstream' inhibitory signaling. Consequently, the cytotoxicity of NK cells was higher in beta-arrestin 2-deficient mice but was inhibited in beta-arrestin 2-transgenic mice. Moreover, beta-arrestin 2-deficient mice were less susceptible than wild-type mice to mouse cytomegalovirus infection, an effect that was abolished by depletion of NK cells. Our findings identify a previously unknown mechanism by which the inhibitory signaling in NK cells is regulated.

Molecular identification and functional characterization of a Drosophila dual-specificity phosphatase DMKP-4 which is involved in PGN-induced activation of the JNK pathway.

MAP (Mitogen-activated protein) kinases play an important role in regulating many critical cellular processes. The inactivation of MAP kinases is always accomplished by a family of dual-specificity phosphatases, termed MAPK phosphatases (MKPs). Here, we have identified a novel MKP-like protein, designated DMKP-4, from the Drosophila genome. DMKP-4 is a protein of 387 amino acids, with a dual-specificity phosphatase (DSP) catalytic domain. Recombinant protein DMKP-4 retains intrinsic phosphatase activity against chromogenic substrate pNPP. Overexpression of DMKP-4 inhibited the activation of ERK, JNK and p38 by H(2)O(2), sorbitol and heat shock in HEK293-T cells, and JNK activation in Drosophila S2 cells under PGN stimuli. "Knockdown" of DMKP-4 expression by RNAi significantly enhanced the PGN-stimulated activation of JNK, but not ERK nor p38. Further study revealed that DMKP-4 interacted specifically with JNK via its DSP domain. Mutation of Cys-126 to serine in the DSP domain of DMKP-4 not only eliminated its interaction with JNK, but also markedly reduced its phosphatase activity. Thus, DMKP-4 is a Drosophila homologue of mammalian MKPs, and may play important roles in the regulation of various developmental processes.

Potent antitumor efficacy of ST13 for colorectal cancer mediated by oncolytic adenovirus via mitochondrial apoptotic cell death.

ST13 is a cofactor of heat shock protein 70 (Hsp70). To date, all data since the discovery of ST13 in 1993 until more recent studies in 2007 have proved that ST13 is downregulated in tumors and it was proposed to be a tumor suppressor gene, but no work reported its antitumor effect and apoptotic mechanism. In the work described in this paper, ST13 was inserted into ZD55, an oncolytic adenovirus with the E1B 55-kDa gene deleted, to form ZD55-ST13, which exerts an excellent antitumor effect in vitro and in an animal model of colorectal carcinoma SW620 xenograft. ZD55-ST13 inhibited tumor cells 100-fold more than Ad-ST13 and ZD55-EGFP in vitro. However, ZD55-ST13 showed no damage of normal fibroblast MRC5 cells. In exploring the mechanism of ZD55-ST13 in tumor cell killing, we found that ZD55-ST13-infected SW620 cells formed apoptotic bodies and presented obvious apoptosis phenomena. ZD55-ST13 induced the upregulation of Hsp70, the downregulation of antiapoptotic gene Bcl-2, and the release of cytochrome c. Cytochrome c triggered apoptosis by activating caspase-9 and caspase-3, which cleave the enzyme poly(ADP-ribose) polymerase in ZD55-ST13-infected SW620 cells. In summary, overexpressed ST13 as mediated by oncolytic adenovirus could exert potent antitumor activity via the intrinsic apoptotic pathway and has the potential to become a novel therapeutic for colorectal cancer gene therapy.

Feedback control of MKP-1 expression by p38.

Mitogen-activated protein (MAP) kinases play a critical role in innate immune responses to microbial infection through eliciting the biosynthesis of proinflammatory cytokines. MAP phosphatases (MKP)-1 is an archetypical member of the dual-specificity phosphatase family that deactivates MAP kinases. Induction of MKP-1 has been implicated in attenuating the lipopolysaccharide (LPS) and Peptidoglycan (PGN) responses, but how the expression of the MKP-1 is regulated is still not fully understood. Here, we show that inhibition of p38 MAP kinase by specific inhibitor SB 203580 or RNA interference (RNAi) markedly reduced the expression of MKP-1 in LPS or PGN-treated macrophages, which is correlated with prolonged activation of p38 and JNK. Depletion of MAPKAP kinase 2 (MK2), a downstream substrate of p38, by RNAi also inhibited the expression of MKP-1. The mRNA level of MKP-1 is not affected by inhibition of p38, but the expression of MKP-1 is inhibited by treatment of cycloheximide. Thus, p38 MAPK plays a critical role in mediating expression of MKP-1 at a post-transcriptional level. Furthermore, inhibition of p38 by SB 203580 prevented the expression of MKP-1 in LPS-tolerized macrophages, restored the activation of MAP kinases after LPS restimulation. These results indicate a critical role of p38-MK2-dependent induction of MKP-1 in innate immune responses.

Regulation of Drosophila p38 activation by specific MAP2 kinase and MAP3 kinase in response to different stimuli.

The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in cellular responses to inflammatory stimuli and environmental stress. Activation of p38 is mediated through phosphorylation by upstream MAPKK, which in turn is activated by MAPKKK. However, the mechanism of how different upstream MAP2Ks and MAP3Ks specifically contribute to p38 activation in response to different stimuli is still not clearly understood. By using double-stranded RNA-mediated interference (RNAi) in Drosophila cells, we demonstrate that D-MKK3 is a major MAP2K responsible for D-p38 activation by UV, heat shock, NaCl or peptiodglycan (PGN). Stimulation of UV and PGN activates D-p38 through D-MEKK1, heat shock-induced activation of D-p38 signals through both D-MEKK1 and D-ASK1. On the other hand, maximal activation of D-p38 by NaCl requires the expression of four MAP3Ks.

Drosophila TAB2 is required for the immune activation of JNK and NF-kappaB.

The TAK1 plays a pivotal role in the innate immune response of Drosophila by controlling the activation of JNK and NF-kappaB. Activation of TAK1 in mammals is mediated by two TAK1-binding proteins, TAB1 and TAB2, but the role of the TAB proteins in the immune response of Drosophila has not yet been established. Here, we report the identification of a TAB2-like protein in Drosophila called dTAB2. dTAB2 can interact with dTAK1, and stimulate the activation of the JNK and NF-kB signaling pathway. Furthermore, we have found that silencing of dTAB2 expression by dsRNAi inhibits JNK activation by peptidoglycans (PGN), but not by NaCl or sorbitol. In addition, suppression of dTAB2 blocked PGN-induced expression of antibacterial peptide genes, a function normally mediated by the activation of NF-kappaB signaling pathway. No significant effect on p38 activation by dTAB2 was found. These results suggest that dTAB2 is specifically required for PGN-induced activation of JNK and NF-kappaB signaling pathways.

Association of supervillin with KIR2DL1 regulates the inhibitory signaling of natural killer cells.

Inhibitory signaling is crucial in the regulation of the cytotoxicity of natural killer (NK) cells. Here, we show that KIR2DL1, an inhibitory receptor of NK cells, associates with supervillin, an F-actin binding protein. Interaction of supervillin with KIR2DL1 is dependent on the KIR2DL1 receptor stimulation and requires the phosphorylation of tyrosines in both ITIM motifs. "Knockdown" of expression of supervillin by RNA interference (RNAi) restores the KIR2DL1-suppressed cytotoxicity of NK cells. Inhibition of supervillin by RNAi also enhances the polarization of cytolytic granules (both granzyme B and perforin) to the synapse formed between YTS-GFP-KIR2DL1 NK cells and 721.221-HLA-Cw4 target cells. Further study reveals that supervillin is required for KIR2DL1-mediated inhibition of Vav1 and ERK phoshorylation. Moreover, we have found that binding of supervillin with KIR2DL1 facilitates the recruitment of SHPs especially SHP-2 to KIR2DL1 receptor. Thus, our findings demonstrate that supervillin is a novel molecule that associates with KIR2DL1 receptor and regulates the inhibitory signaling in NK cells.