Takanori Hattori

Ezrin, a membrane cytoskeletal cross-linker, is essential for the regulation of phosphate and calcium homeostasis

Ezrin cross-links plasma membrane proteins with the actin cytoskeleton. In the kidney, ezrin mainly localizes at the brush border membrane of proximal tubules with the scaffolding protein, Na(+)/H(+) exchanger regulatory factor (NHERF) 1. NHERF1 interacts with the sodium/phosphate cotransporter, Npt2a. Defects in NHERF1 or Npt2a in mice cause hypophosphatemia. Here we studied the physiological role of ezrin in renal phosphate reabsorption using ezrin knockdown mice (Vil2). These mice exhibit hypophosphatemia, hypocalcemia, and osteomalacia. The reduced plasma phosphate concentrations were ascribed to defects in urinary phosphate reabsorption. Immunofluorescence and immunoblotting indicated a marked reduction in renal Npt2a and NHERF1 expression at the apical membrane of proximal tubules in the knockdown mice. On the other hand, urinary loss of calcium was not found in Vil2 mice. Plasma concentrations of 1,25-dihydroxyvitamin D were elevated following reduced plasma phosphate levels, and mRNA of the vitamin D-dependent TRPV6 calcium channel were significantly increased in the duodenum of knockdown mice. Expression of TRPV6 at the apical membrane, however, was significantly decreased. Furthermore, tibial bone mineral density was significantly lower in both the adult and young Vil2 mice. These results suggest that ezrin is required for the regulation of systemic phosphate and calcium homeostasis in vivo.

Comprehensive proteome analysis of brush border membrane fraction of ileum of ezrin knockdown mice.

Ezrin is an actin binding protein which cross-links membrane proteins with cytoskeleton directly or indirectly via PDZ domain-containing scaffold proteins. It is mainly expressed at the brush border membrane (BBM) of gastrointestinal tracts, and is involved in the construction of microvilli structure and the functional expression of membrane protein complexes at the cell surface. To precisely study the roles of ezrin on the expression of membrane proteins at the cell surface, here we prepared the BBM fractions of ileums from the wild-type and ezrin-knockdown (Vil2(kd/kd)) mice, analyzed them by mass spectrometry, and compared their proteomic patterns. Totally 313 proteins were identified in the BBM fractions. Several transport proteins, cytoskeleton-associated proteins, and trafficking proteins were up- or down-regulated in the BBM fraction of the ileum in the Vil2(kd/kd) mice. Among them, the expressions of i) Na(+)/H(+) exchanger regulatory factor 1 (a PDZ domain-containing scaffold protein), ii) sodium monocarboxylate transporter 1, which contains a PDZ domain-binding motif at their carboxy-terminal, and iii) chloride intracellular channel protein 5 were down-regulated at the BBM fraction of the ileum in the Vil2(kd/kd) mice, suggesting that ezrin is involved in their expression in the BBM.

9 – Role of Immunohistochemical Expression of Beta-Catenin and Mucin in Stomach Cancer

This chapter discusses the role of immunohistochemical (IHC) expression of beta-catenin and mucin in stomach cancer. Beta-catenin plays an important role in the cell-cell adhesion system and in the wingless/wnt cell-cell signalling system. Beta-catenin acts as E-cadherin binding protein mostly on the cell membrane. Abnormally accumulated beta-catenin causes cell proliferation and carcinogenesis. Intracellular levels of beta-catenin are mainly regulated by degradation that is probably initiated, by interaction, with the adenomatous polyposis coli (APC) protein and glycogen synthase kinase (GSK)-3 beta. Abnormality in exon3 of the beta-catenin gene result in accumulation of beta-catenin or phosphorylation of these residues may inhibit degradation. Beta-catenin mutations and expression are analyzed in various common cancers. The relationship between beta-catenin expression and phenotype of group C lesion is analyzed. Mutations of the APC gene occur and are detected during the early stages of gastric adenoma development. The beta-catenin expression does not always reflect the malignant transformation in the early stage of gastric tumorigenesis and beta-catenin abnormality is only one particular aspect of malignant transformation.

Carcinoid Tumor of the Cecum with Expression of p53 Gene Product.

消化管内分泌細胞腫瘍は生物学的性状の極めて異なる低悪性度の古典的カルチノイドと高悪性度の内分泌癌 (endocrine cell carcinoma;ECC) に分類されている. 両者の鑑別は組織学的異型度の相違に基づいて行われるが, しばしば困難である. ECCはしばしば十二指腸, 直腸や胆道系に発生するが, 盲腸原発は極めてまれである. 我々は, 盲腸に原発したと思われるECCの1症例を経験した. 症例は, 70歳の女性. 既往歴は虫垂炎にて虫垂切除術を施行されていた. イレウス症状にて来院し, 注腸にて盲腸に3cm大のapple core signを認め, 右半結腸切除術を施行した. 病理組織学的には, endocrinecell carcinoma, mixed type, combined oat cell carcinoma with squamous cell and adenocarcinomaと診断された. また, p53遺伝子蛋白の染色は, 古典的カルチノイド7例がすべて陰性であったのに対して, 本症例は強陽性を示した. ECCの診断においてp53蛋白染色が有用である可能性が示唆された.

Clinicopathological and Mucin-histochemical Study of Gastric Cancer of the Residual Stomach and upper Portion of the Stomach.

解剖学的にほぼ同じ位置より発生する残胃癌 (12例15病変) と胃上部癌 (39例41病変) の相違点を, 臨床病理学的および粘液組織化学的に検討した.組織型では残胃癌は未分化型 (60.0%) が, 胃上部癌は分化型 (82.9%) が多かった.早期癌では残胃癌は隆起型を, 胃上部癌は陥凹型もしくは混合型を, 進行癌になると残胃癌は浸潤型を, 胃上部癌は限局型を呈した.腸上皮化生は残胃癌で75.0%, 胃上部癌で64.1%であったが, gastritis cystica polyposa (GCP) は残胃癌で50.0%, 胃上部癌7.7%と, 残胃癌に高頻度であった.Galactose oxidase-shiff染色, concanavalin-A-paradoxical法III型粘液染色, High iron diamine-alcianblue染色により癌の上皮型を, 胃型, 腸型, 混合型に分類すると, 分化型早期癌において, 残胃癌は胃型 (66.7%) が, 胃上部癌では腸型 (71.4%) が多かった.残胃という特殊な環境での発癌は通常の胃癌発生と機序を異にする可能性が示唆された.

Cancer risk in the operated stomach.

は じめに 私どもはこれらの問題を動物実験で検索してきたの 胃の良性疾患で胃切除された残胃に発生した癌を欧 で ,そ の成績を報告する。 米ではgastric stump carcinoma,本邦では残胃癌 と 材料および方法 よんでいる。残胃癌は,胃 癌の発生頻度の高いわが国 1.実 験動物 では従来少ないと言われていたが,近 年増加傾向にあ Wistar系 雄性ラットを用いた。 りまれではなくなっている。また,欧 米では胃癌がい 2.発 癌物質の投与 ちじるしく減少する中で,残 胃癌だけは増加している N・ methyl‐N′‐nitro‐N‐nitrosoguanidine(以 後 と報告されている。残胃癌の発生率は,消 化管再建法 MNNGと 略す)500mgを 10′の飲料水に溶解 し,ア ル がビルロー ト1法 より2法 に高 く,そ の原因として十 ミ 箔で遮光 したポ リエチ レン給水瓶 に分注 し,ad 二指腸液の胃内逆流が挙げられている。さらに,消 化 libitumに 飲用させた。 性漬瘍の手術は,胃切除後障害をできるだけ防ごうと, 3.胃 癌判定基準 近年迷走神経切断術の導入により, 胃切除を行わない MNNG投 与による発癌実験での,胃 癌の半」定基準 か,あ るいは行っても小範囲にとどめるようになって は 腺胃に肉眼的に腫瘍を認め,組 織学的に異型腺増生 お り, このような手術では残胃粘膜が広いだけに胃癌 が 粘膜筋板を破 り,粘 膜下層以下に浸潤増殖するもの の発生率が高まらないかとの危倶が生じている。 を 癌 とした。