Cot/tpl2-MKK1/2-Erk1/2 controls mTORC1-mediated mRNA translation in Toll-like receptor-activated macrophages

Cot/tpl2 is the only MAP3K that activates MKK1/2-Erk1/2 in Toll-like receptor–activated macrophages. Here we show that Cot/tpl2 regulates RSK, S6 ribosomal protein, and 4E-BP phosphorylation after stimulation of bone marrow–derived macrophages with lipopolysaccharide (LPS), poly I:C, or zymosan. The dissociation of the 4E-BP–eIF4E complex, a key event in the cap-dependent mRNA translation initiation, is dramatically reduced in LPS-stimulated Cot/tpl2-knockout (KO) macrophages versus LPS-stimulated wild-type (Wt) macrophages. Accordingly, after LPS activation, increased cap-dependent translation is observed in Wt macrophages but not in Cot/tpl2 KO macrophages. In agreement with these data, Cot/tpl2 increases the polysomal recruitment of the 5´ TOP eEF1α and eEF2 mRNAs, as well as of inflammatory mediator gene–encoding mRNAs, such as tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and KC in LPS-stimulated macrophages. In addition, Cot/tpl2 deficiency also reduces total TNFα, IL-6, and KC mRNA expression in LPS-stimulated macrophages, which is concomitant with a decrease in their mRNA half-lives. Macrophages require rapid fine control of translation to provide an accurate and not self-damaging response to host infection, and our data show that Cot/tpl2 controls inflammatory mediator gene–encoding mRNA translation in Toll-like receptor–activated macrophages.     

Position-dependent effects of hnRNP A1/A2 in SMN1/2 exon7 splicing

Heterogeneous nuclear ribonucleoprotein A1 and A2 (hnRNP A1/2) is a ubiquitously expressed RNA binding protein known to bind intronic or exonic splicing silencer. Binding of hnRNP A1/2 to survival of motor neuron gene (SMN1/2) exon 7 and flanking sequences strongly inhibits the inclusion of exon 7, which causes spinal muscular atrophy, a common genetic disorder. However, the role of hnRNP A1/2 on the side away from exon 7 is unclear. Here using antisense oligonucleotides, we fished an intronic splicing enhancer (ISE) near the 3′-splice site (SS) of intron 7 of SMN1/2. Mutagenesis identified the efficient motif of the ISE as “UAGUAGG”, coupled with RNA pull down and protein overexpression, we proved that hnRNP A1/2 binding to the ISE promotes the inclusion of SMN1/2 exon 7. Using MS2-tethering array and “UAGGGU” motif walking, we further uncovered that effects of hnRNP A1/2 on SMN1/2 exon 7 splicing are position-dependent: exon 7 inclusion is inhibited when hnRNP A1/2 binds proximal to the 5′SS of intron 7, promoted when its binds proximal to the 3′SS. These data provide new insights into the splicing regulatory mechanism of SMN1/2.     

Unbalanced activation of ERK1/2 and MEK1/2 in apigenin-induced HeLa cell death

Apigenin, a dietary bioflavonoid with anticarcinogenic properties, was highly cytotoxic for HeLa cells (incubated with 0.5% FBS). This effect was accompanied with a marked increase in ERK1/2 but not MEK1/2 phosphorylation. The cytotoxic effects of apigenin were attenuated by the stimulation of these cells with 10% FBS, which provoked an increase in the phosphorylation levels of MEK1/2 and ERK1/2. The steps in the ERK1/2 pathway relevant to the cytotoxic effects of apigenin, as well as the contribution of other signaling pathways, were investigated. The activation of the pathway by transfection with the constitutively active Ras mutant (RasV12) conferred protection to serum-starved HeLa cells against apigenin, whereas the constitutively active MEK(E) mutant did not. MEK inhibitors (PD098059 or U0126) blocked ERK1/2 phosphorylation induced by apigenin and conferred partial protection against this flavonoid. The effects of apigenin did not involve p38-MAPK or JNK1/2, and were not simply due to inhibition of PI3kinase or protein kinase CK2. These data suggest that the deregulation of the ERK1/2 pathway, due to the potentiation of ERK1/2 phosphorylation without increasing MEK1/2 phosphorylation, is involved in apigenin-induced HeLa cell death.     

M-1/M-2 macrophages and the Th1/Th2 paradigm

Evidence is provided that macrophages can make M-1 or M-2 responses. The concept of M-1/M-2 fomented from observations that macrophages from prototypical Th1 strains (C57BL/6, B10D2) are more easily activated to produce NO with either IFN-gamma or LPS than macrophages from Th2 strains (BALB/c, DBA/2). In marked contrast, LPS stimulates Th2, but not Th1, macrophages to increase arginine metabolism to ornithine. Thus, M-1/M-2 does not simply describe activated or unactivated macrophages, but cells expressing distinct metabolic programs. Because NO inhibits cell division, while ornithine can stimulate cell division (via polyamines), these results also indicate that M-1 and M-2 responses can influence inflammatory reactions in opposite ways. Macrophage TGF-beta1, which inhibits inducible NO synthase and stimulates arginase, appears to play an important role in regulating the balance between M-1 and M-2. M-1/M-2 phenotypes are independent of T or B lymphocytes because C57BL/6 and BALB/c NUDE or SCID macrophages also exhibit M-1/M-2. Indeed, M-1/M-2 proclivities are magnified in NUDE and SCID mice. Finally, C57BL/6 SCID macrophages cause CB6F1 lymphocytes to increase IFN-gamma production, while BALB/c SCID macrophages increase TGF-beta production. Together, the results indicate that M-1- or M-2-dominant macrophage responses can influence whether Th1/Th2 or other types of inflammatory responses occur.     

Mxi2 sustains ERK1/2 phosphorylation in the nucleus by preventing ERK1/2 binding to phosphatases

ERK1/2 (extracellular-signal-regulated kinase 1/2) MAPKs (mitogen-activated protein kinases) are tightly regulated by the cellular microenvironment in which they operate. Mxi2 is a p38α splice isoform capable of binding to ERK1/2 and ensuring their translocation to the nucleus. Therein Mxi2 sustains ERK1/2 phosphorylation levels and, as a consequence, ERK1/2 nuclear signals are enhanced. However, the molecular mechanisms underlying this process are still unclear. In the present study, we show that Mxi2 prevents nuclear but not cytoplasmic phosphatases from binding to and dephosphorylating ERK1/2, disclosing an unprecedented mechanism for the spatial regulation of ERK1/2 activation. We also demonstrate that the kinetics of ERK1/2 extranuclear signals can be significantly altered by artificially tethering Mxi2 to the cytoplasm. In this case, Mxi2 abolishes ERK1/2 inactivation by cytoplasmic phosphatases and potentiates ERK1/2 functions at this compartment. These results highlight Mxi2 as a key spatial regulator of ERK1/2 functions, playing a pivotal role in the balance between ERK1/2 nuclear and cytoplasmic signals.     

SirT1 inhibition reduces IGF-I/IRS-2/Ras/ERK1/2 signaling and protects neurons

Sirtuins are known to protect cells and extend life span, but our previous studies indicated that S. cerevisiae Sir2 can also increase stress sensitivity and limit life-span extension. Here we provide evidence for a role of the mammalian Sir2 ortholog SirT1 in the sensitization of neurons to oxidative damage. SirT1 inhibition increased acetylation and decreased phosphorylation of IRS-2; it also reduced activation of the Ras/ERK1/2 pathway, suggesting that SirT1 may enhance IGF-I signaling in part by deacetylating IRS-2. Either the inhibition of SirT1 or of Ras/ERK1/2 was associated with resistance to oxidative damage. Markers of oxidized proteins and lipids were reduced in the brain of old SirT1-deficient mice, but the life span of the homozygote knockout mice was reduced under both normal and calorie-restricted conditions. These results are consistent with findings in S. cerevisiae and other model systems, suggesting that mammalian sirtuins can play both protective and proaging roles.     

人脑胶质瘤中的IDH1/2突变

胶质母细胞瘤的基因组突变分析中发现的异柠檬酸脱氢酶(isocitrate dehydrogenase,IDH1)突变对胶质瘤的认识具有突破性意义。随后,在胶质瘤中发现了IDH1的R132碱基和IDH2的R172碱基突变。IDH1突变较多的发生在WHOII-III级胶质瘤和继发胶质母细胞瘤中。这种突变改变了异柠檬酸脱氢酶的结构,从而使将异柠檬酸转化为a-酮戊二酸的能力丧失,而获得将a-酮戊二酸转化为2-羟基戊二酸这一新的酶活性。在临床中,IDH1和IDH2突变已经显示对胶质瘤患者有诊断和预后意义。同时,现今也发展了一些检测方法。     

Pkh1/2-Pil1信号调节酵母细胞内吞

酵母细胞中Pkh1/2信号影响细胞内吞功能.Pil1因与Pkh1/2形成复合物并可被 其磷酸化引起关注.新近发现一个大分子复合物eisosome 是内吞的标志性位点， 而Pil1是其主要成分.前期研究发现，Pil1的磷酸化状态对eisosome结构完整至关 重要.本研究通过检测Pkh1/2突变菌的生长和萤光黄（LY） 染料在空泡聚集情况 ，发现由于Pkh1/2突变导致的生长抑制和液相内吞功能丧失,可部分由过表达的 Pil1补偿，得出结论是Pkh1/2-Pil1信号在一定程度上调节细胞内吞.     

GM1 Induced the inflammatory response related to the Raf-1/MEK1/2/ERK1/2 pathway in co-culture of pig mesenchymal stem cells with RAW264.7

Pig-human xenotransplantation can trigger cell-mediated immune responses. We explored the role of gangliosides in inflammation related to immune rejection in xenotransplantation. Co-culture of xenogeneic cells (pig-MSCs and RAW264.7) was used to emulate xenotransplantation conditions. MTT assay results indicated that cell viability was significantly decreased in pADMSCs co-cultured with RAW264.7 cells. GM1 and GM3 were highly expressed in pADMSCs co-cultured with RAW264.7 cells. pADMSCs co-cultured with RAW264.7 cells strongly expressed pro-inflammatory proteins such as COX-2, iNOS, p50, p65, pIκBα, and TNF-α. GM1-knockdown pADMSCs co-cultured with RAW 264.7 cells did not show significantly altered cell viability, but pro-inflammatory proteins were markedly inhibited. Co-culture of pADMSCs with RAW264.7 cells induced significant phosphorylation (p) of JNK1/2 and pERK1/2. However, pERK1/2 and pJNK1/2 were decreased and MEK1/2 and Raf1 were suppressed in GM1-knockdown pADMSCs co-cultured with RAW264.7 cells. Thus, the Raf-1/MEK1/2/ERK1/2 and JNK1/2 pathways were significantly upregulated in response to increases of GM1 in co-cultured xenogeneic cells. However, the inflammatory response was suppressed in co-culture of GM1-knockdown pADMSCs with RAW264.7 cells via down-regulation of the Raf-1/MEK1/2/ERK1/2 and JNK1/2 pathways. Therefore, the ganglioside GM1 appears to play a major role in the inflammatory response in xenotransplantation via the Raf-1/MEK1/2/ERK1/2 and JNK1/2 pathways.     

Generation of 'humanized' hCYP1A1_1A2_Cyp1a1/1a2(-/-) mouse line

Human/rodent CYP1A1 and CYP1A2 orthologs are well known to exhibit species-specific differences in substrate preferences and rates of metabolism. This lab previously characterized a BAC-transgenic mouse carrying the human CYP1A1_CYP1A2 locus; in this line, human dioxin-inducible CYP1A1 and basal vs dioxin-inducible CYP1A2 have been shown to be expressed normally (with regard to mRNAs, proteins and three enzyme activities) in every one of nine mouse tissues studied. The mouse Cyp1a1 and Cyp1a2 genes are oriented head-to-head and share a bidirectional promoter region of 13,954 bp. Using Cre recombinase and loxP sites inserted 3' of the stop codons of both genes, we show here a successful interchromosomal excision of 26,173 bp that ablated both genes on the same allele. The Cyp1a1/1a2(-) double-knockout allele was bred with the "humanized" line; the final product is the hCYP1A1_1A2_Cyp1a1/1a2(-/-) line on a theoretically >99.8% C57BL/6J genetic background-having both human genes replacing the mouse orthologs. This line will be valuable for human risk assessment studies involving any environmental toxicant or drug that is a substrate for CYP1A1 or CYP1A2.     

ERK1/2和p-ERK1/2在肺癌组织中的表达及意义

目的研究细胞外信号调节激酶1/2（extracellular regulated kinase 1/2,ERK1/2）及其磷酸化状态（p-ERK1/2）在不同分化程度肺癌中的表达情况,探讨二者与肺癌侵袭、转移的关系。方法采用免疫组化（Envision）法,检测79例肺癌组织及l2例癌旁正常肺组织中ERK1/2和p-ERK1/2的表达。结果ERK1/2在高、中、低分化组表达率分别为13.6%,39.4%,66.7%,p-ERK1/2在高、中、低分化组表达率分别14.3%,27.3%,79.2%（P〈0.05）;无淋巴结转移者阳性率为20%,有淋巴结转移者阳性率为50.1%（P〈0.05）。ERK1/2和p-ERK1/2的表达在不同年龄、性别、肿瘤大小、肿瘤病理类型无显著性差异,而与分化程度有关,其中p-ERK1/2的表达还与有无淋巴结转移有关。结论ERK1/2和p-ERK1/2在肺癌组织中高表达且与分化程度有关。     

HMGB1/2 can target DNA for illegitimate cleavage by the RAG1/2 complex

Background  

V(D)J recombination is initiated in antigen receptor loci by the pairwise cleavage of recombination signal sequences (RSSs) by the RAG1 and RAG2 proteins via a nick-hairpin mechanism. The RSS contains highly conserved heptamer (consensus: 5'-CACAGTG) and nonamer (consensus: 5'-ACAAAAACC) motifs separated by either 12- or 23-base pairs of poorly conserved sequence. The high mobility group proteins HMGB1 and HMGB2 (HMGB1/2) are highly abundant architectural DNA binding proteins known to promote RAG-mediated synapsis and cleavage of consensus recombination signals in vitro by facilitating RSS binding and bending by the RAG1/2 complex. HMGB1/2 are known to recognize distorted DNA structures such as four-way junctions, and damaged or modified DNA. Whether HMGB1/2 can promote RAG-mediated DNA cleavage at sites lacking a canonical RSS by targeting or stabilizing structural distortions is unclear, but is important for understanding the etiology of chromosomal translocations involving antigen receptor genes and proto-oncogene sequences that do not contain an obvious RSS-like element.     

Akt1K64/276与SUMO1结合激活ERK1/2-Elk1-BDNF信号通路

本研究主要从蛋白质结构分析Akt1 SUMO化的位点及位点的突变对其结构与功能的影响。采用多种软件分析Akt1 SUMO化位点和Akt1野生型(Akt1wt)及Akt1K64/276R的理化性质、亲/疏水性及二/三级结构;分析结果显示,Akt1K64/276R较Akt1wt,亲/疏水性未改变,α-螺旋和β-折叠都有少量的不同。三级结构分析显示,与野生型组相比,Akt1K64R氢键增多。以Myc-Akt1wt-pcDNA3.1为模板,采用PCR定点突变技术扩增出Myc-Akt1K64/276R。DNA序列分析结果显示,Myc-Akt1K64/276R基因序列编码赖氨酸(K)的密码子AAG被成功突变为精氨酸(R)密码子AGG。免疫沉淀和免疫印迹结果显示,不共转PIAS3,Akt1也能与SUMO1结合;Myc-Akt1wt和Myc-Akt1K64/276R均可在HEK293细胞中高效表达;转染Myc-Akt1K64/276R组SUMO化水平降低了70%左右(P<0.05)。免疫印迹结果显示,在小鼠海马神经细胞HT22中,Myc-Akt1wt组ERK1/2磷酸化水平及BDNF蛋白水平是突...     

On the reversibility of the B1 2r−B1 2s couple in cobalamins

The cobalt(II)—cobalt(I) interconversion in a number of vitamin B_{1 2} derivatives was investigated by cyclic voltammetry. Particular attention was focused on the factors determining whether the interconversion is reversible. When the lower axial coordination position is occupied by a strong ligand, such as the benzimidazole nucleotide in “base on” cobalamins, the cobalt(II)—cobalt(I) interconversion is irreversible due to a slow reduction of the cobalt(II). However, when the lower axial coordination position is free of a strong ligand, as in most cobinamides or in “base off” cobalamins, the cobalt(II)—cobalt(I) interconversion is nearly perfectly reversible. Possible implications of the observations to B_{1 2}-dependent enzymes are briefly discussed.