Role of RNA-Binding Proteins in MAPK Signal Transduction Pathway

Mitogen-activated protein kinases (MAPKs), which are found in all eukaryotes, are signal transducing enzymes playing a central role in diverse biological processes, such as cell proliferation, sexual differentiation, and apoptosis. The MAPK signaling pathway plays a key role in the regulation of gene expression through the phosphorylation of transcription factors. Recent studies have identified several RNA-binding proteins (RBPs) as regulators of MAPK signaling because these RBPs bind to the mRNAs encoding the components of the MAPK pathway and regulate the stability of their transcripts. Moreover, RBPs also serve as targets of MAPKs because MAPK phosphorylate and regulate the ability of RBPs to bind and stabilize target mRNAs, thus controlling various cellular functions. In this review, we present evidence for the significance of the MAPK signaling in the regulation of RBPs and their target mRNAs, which provides additional information about the regulatory mechanism underlying gene expression. We further present evidence for the clinical importance of the posttranscriptional regulation of mRNA stability and its implications for drug discovery

C2C12筋管細胞においてモリンはデキサメタゾン誘導性の酸化ストレスと筋萎縮を抑制する

Glucocorticoids are the drugs most commonly used to manage inflammatory diseases. However, they are prone to inducing muscle atrophy by increasing muscle proteolysis and decreasing protein synthesis. Various studies have demonstrated that antioxidants can mitigate glucocorticoid-induced skeletal muscle atrophy. Here, we investigated the effect of a potent antioxidative natural flavonoid, morin, on the muscle atrophy and oxidative stress induced by dexamethasone (Dex) using mouse C2C12 skeletal myotubes. Dex (10 μM) enhanced the production of reactive oxygen species (ROS) in C2C12 myotubes via glucocorticoid receptor. Moreover, Dex administration reduced the diameter and expression levels of the myosin heavy chain protein in C2C12 myotubes, together with the upregulation of muscle atrophy-associated ubiquitin ligases, such as muscle atrophy F-box protein 1/atrogin-1, muscle ring finger protein-1, and casitas B-lineage lymphoma proto-oncogene-b. Dex also significantly decreased phosphorylated Foxo3a and increased total Foxo3a expression. Interestingly, Dex-induced ROS accumulation and Foxo3a expression were inhibited by morin (10 μM) pretreatment. Morin also prevented the Dex-induced reduction of myotube thickness, together with muscle protein degradation and suppression of the upregulation of atrophy-associated ubiquitin ligases. In conclusion, our results suggest that morin effectively prevents glucocorticoid-induced muscle atrophy by reducing oxidative stress

Negative feedback regulation of calcineurin-dependent Prz1 transcription factor by the CaMKK-CaMK1 axis in fission yeast

Calcium signals trigger the translocation of the Prz1 transcription factor from the cytoplasm to the nucleus. The process is regulated by the calciumactivated phosphatase calcineurin, which activates Prz1 thereby maintaining active transcription during calcium signalling. When calcium signalling ceases, Prz1 is inactivated by phosphorylation and exported to the cytoplasm. In budding yeast and mammalian cells, different kinases have been reported to counter calcineurin activity and regulate nuclear export. Here, we show that the Ca2+/calmodulin-dependent kinase Cmk1 is first phosphorylated and activated by the newly identified kinase CaMKK2 homologue, Ckk2, in response to Ca2+. Then, active Cmk1 binds, phosphorylates and inactivates Prz1 transcription activity whilst at the same time cmk1 expression is enhanced by Prz1 in response to Ca2+. Furthermore, Cdc25 phosphatase is also phosphorylated by Cmk1, inducing cell cycle arrest in response to an increase in Ca2+. Moreover, cmk1 deletion shows a high tolerance to chronic exposure to Ca2+, due to the lack of cell cycle inhibition and elevated Prz1 activity. This work reveals that Cmk1 kinase activated by the newly identified Ckk2 counteracts calcineurin function by negatively regulating Prz1 activity which in turn is involved in activating cmk1 gene transcription. These results are the first insights into Cmk1 and Ckk2 function in Schizosaccharomyces pombe

テツ ケツボウセイ ヒンケツ ジャクネン ジョシ ノ ケッショウ ガンリュウ アミノサンチ

鉄欠乏性貧血は生体中の鉄が欠乏している状態であるが,鉄以外の栄養素にも異常があるのではないかという考えのもとに種々の検討を行ってきた。今回は血漿アミノ酸を測定し,同時に血清B_6値の測定も行った。B_6はすでに鉄欠乏性貧血では低下していることを報告してあるが,B_6はアミノ酸代謝においてアミノ基転移や,アミノ基離脱反応に大きな働きをしているので,B_6不足状態は血漿アミノ酸の異常をきたすのではないかどうかの検討をおこなった。ヘモグロビンが10.5g/dl以下の若年女性28人に,治療前と鉄剤を1カ月服用後に,研究目的を説明して了解を得てから採血をした。研究開始時に2日間の食物摂取調査をした。対照者は28人の同年代の女性である。貧血者の血漿アミノ酸値はTaurine,Cystine,Methioninの含硫アミノ酸とGlutamic acidが有意に低下していた。鉄剤服用後はCystine,Taurine,Glutamic acid,Valine,Isoleusine,Ornithineが有意に増加した。鉄投与によってCystine値が最も上昇した。またB_6値が低下していた例ほどCystine値が低かった。貧血者のアミノ酸で有意に上昇していたのはAspartic acid,Glutamine,Proline,Tryptophanである。食事調査の結果は貧血群ではタンパク質,カルシウム,カロチン,ビタミンD,B_6の摂取量が少なかった。以上から鉄欠乏性貧血者は鉄の補給のみではなくて,含硫アミノ酸やB_6の多い食品を積極的に摂取することが勧められる成績を得た

シソアブラ ト オリーブシソアブラ セッシュ ガ ケッセイ シシツ カサンカ シシツ ギョウコセンヨウケイ ニ オヨボス エイキョウ

血清脂質改善作用があるn-9系多価不飽和脂肪酸のオレイン酸はオリーブ油に多く含まれ,また同作用をもつn-3系多価不飽和脂肪酸のα-リノレン酸はしそ油に多く含まれている。これらの脂肪酸が,年々増え続ける生活習慣病において有効な役割を果たすかどうかの検討をした。オレイン酸とα-リノレン酸の混合油であるオリーブしそ油とα-リノレン酸を主とするしそ油を,それぞれ別々の期間で毎日20gずつ14日間若年女性11名に摂取させて,過酸化脂質,血清脂質,動脈硬化因子であるトリグリセライド(triglyceride : 以下TG)との関わりが注目されている血液凝固線溶系への影響を比較検討した。その結果,しそ油では血中線維素原であるフィブリノーゲンの低下作用及び摂取後14日目でのTG低下作用を確認した。さらにTGと血液凝固抑制作用のあるt-PA,フィブリノーゲンと血栓形成作用のあるPAI-1,フィブリノーゲンとPAI-1,フィブリノーゲンとt-PA,t-PAとPAI-1間で正相関がみられた。オリーブしそ油ではしそ油よりも強い血清脂質改善作用とフィブリノーゲンの抑制作用,t-PAの増加作用が認められ,さらにTGとフィブリノーゲン,TGとPAI-1,TGとt-PA,フィブリノーゲンとPAI-1,フィブリノーゲンとt-PA,t-PAとPAI-1間で正相関がみられた。このように,各油摂取による血液への影響をそれぞれ確認し,n-3系とn-3+n-9系脂肪酸の重要性がわかった

Oral Rehydration Solutionに関する歴史的・文献的考察と今後の問題点

Oral rehydration therapy(以下、ORT)は、成人コレラ患者の治療法として普及後、乳児下痢症による脱水症の治療法としての効果も認められ、特にWHOやUNICEFの指導と推進により発展途上国で多くの乳児を救命している。また、ORTは脱水症の予防としても有効である。このORTに用いる溶液であるoral rehydration solution(以下、ORS)は、水、糖、電解質の混合液であり、腸粘膜における糖とナトリウム(以下、Na)吸収のメカニズムが理論的に立証されている。ここでは、ORSが発展してきた背景を歴史的および文献的に考察し、今後の問題点や将来の展望を述べることとする

Structure of MSPL–inhibitor complex

Infection of certain influenza viruses is triggered when its HA is cleaved by host cell proteases such as proprotein convertases and type II transmembrane serine proteases (TTSP). HA with a monobasic motif is cleaved by trypsin-like proteases, including TMPRSS2 and HAT, whereas the multibasic motif found in high pathogenicity avian influenza HA is cleaved by furin, PC5/6, or MSPL. MSPL belongs to the TMPRSS family and preferentially cleaves [R/K]-K-K-R↓ sequences. Here, we solved the crystal structure of the extracellular region of human MSPL in complex with an irreversible substrate-analog inhibitor. The structure revealed three domains clustered around the C-terminal α-helix of the SPD. The inhibitor structure and its putative model show that the P1-Arg inserts into the S1 pocket, whereas the P2-Lys and P4-Arg interacts with the Asp/Glu-rich 99-loop that is unique to MSPL. Based on the structure of MSPL, we also constructed a homology model of TMPRSS2, which is essential for the activation of the SARS-CoV-2 spike protein and infection. The model may provide the structural insight for the drug development for COVID-19

PKN3 is the major regulator of angiogenesis and tumor metastasis in mice

PKN, a conserved family member related to PKC, was the first protein kinase identified as a target of the small GTPase Rho. PKN is involved in various functions including cytoskeletal arrangement and cell adhesion. Furthermore, the enrichment of PKN3 mRNA in some cancer cell lines as well as its requirement in malignant prostate cell growth suggested its involvement in oncogenesis. Despite intensive research efforts, physiological as well as pathological roles of PKN3 in vivo remain elusive. Here, we generated mice with a targeted deletion of PKN3. The PKN3 knockout (KO) mice are viable and develop normally. However, the absence of PKN3 had an impact on angiogenesis as evidenced by marked suppressions of micro-vessel sprouting in ex vivo aortic ring assay and in vivo corneal pocket assay. Furthermore, the PKN3 KO mice exhibited an impaired lung metastasis of melanoma cells when administered from the tail vein. Importantly, PKN3 knock-down by small interfering RNA (siRNA) induced a glycosylation defect of cell-surface glycoproteins, including ICAM-1, integrin β1 and integrin α5 in HUVECs. Our data provide the first in vivo genetic demonstration that PKN3 plays critical roles in angiogenesis and tumor metastasis, and that defective maturation of cell surface glycoproteins might underlie these phenotypes