Yeast ARV1 is required for efficient delivery of an early GPI intermediate to the first mannosyltransferase during GPI assembly and controls lipid flow from the endoplasmic reticulum

Glycosylphosphatidylinositol (GPI), covalently attached to many eukaryotic proteins, not only acts as a membrane anchor but is also thought to be a sorting signal for GPI-anchored proteins that are associated with sphingolipid and sterol-enriched domains. GPI anchors contain a core structure conserved among all species. The core structure is synthesized in two topologically distinct stages on the leaflets of the endoplasmic reticulum (ER). Early GPI intermediates are assembled on the cytoplasmic side of the ER and then are flipped into the ER lumen where a complete GPI precursor is synthesized and transferred to protein. The flipping process is predicted to be mediated by a protein referred as flippase; however, its existence has not been proven. Here we show that yeast Arv1p is an important protein required for the delivery of an early GPI intermediate, GlcN-acylPI, to the first mannosyltransferase of GPI synthesis in the ER lumen. We also provide evidence that ARV1 deletion and mutations in other proteins involved in GPI anchor synthesis affect inositol phosphorylceramide synthesis as well as the intracellular distribution and amounts of sterols, suggesting a role of GPI anchor synthesis in lipid flow from the ER.     

血栓调节蛋白在胚胎肺及肺癌中的表达

目的研究血栓调节蛋白(thrombomodulin,TM)在胚胎肺、正常肺组织及肺癌组织中的表达。方法以不同周龄的胚胎肺组织、正常成人肺组织、肺癌组织为研究对象,应用免疫组织化学SP法检测TM的存在。结果8、15、18、21、24、27、29周人胎肺组织中,TM在气管纤毛柱状上皮细胞、I型和Ⅱ型肺泡上皮细胞及软骨、结缔组织均呈阴性表达,围绕肺泡上皮细胞团周围的血管内皮细胞阳性表达。正常成人支气管纤毛柱状上皮细胞、肺泡上皮细胞不表达,但在血管内皮细胞呈阳性表达。TM在鳞状上皮不典型增生的细胞膜和细胞问桥表达,在肺鳞癌表达,阳性率为97．3％(34／35),在癌细胞膜和细胞问桥阳性表达,但腺癌、小细胞癌癌细胞不表达。结论TM在胚胎肺以及成人肺仅见于血管内皮细胞,在支气管上皮、肺泡上皮不表达。与其它的血管内皮细胞标记物不同,TM的表达在肺鳞癌与腺癌表扶明显不同．右助于鉴别肺鳞癌与肺腺癌．     

A rice brassinosteroid-deficient mutant, ebisu dwarf (d2), is caused by a loss of function of a new member of cytochrome P450

We characterized a rice dwarf mutant, ebisu dwarf (d2). It showed the pleiotropic abnormal phenotype similar to that of the rice brassinosteroid (BR)-insensitive mutant, d61. The dwarf phenotype of d2 was rescued by exogenous brassinolide treatment. The accumulation profile of BR intermediates in the d2 mutants confirmed that these plants are deficient in late BR biosynthesis. We cloned the D2 gene by map-based cloning. The D2 gene encoded a novel cytochrome P450 classified in CYP90D that is highly similar to the reported BR synthesis enzymes. Introduction of the wild D2 gene into d2-1 rescued the abnormal phenotype of the mutants. In feeding experiments, 3-dehydro-6-deoxoteasterone, 3-dehydroteasterone, and brassinolide effectively caused the lamina joints of the d2 plants to bend, whereas more upstream compounds did not cause bending. Based on these results, we conclude that D2/CYP90D2 catalyzes the steps from 6-deoxoteasterone to 3-dehydro-6-deoxoteasterone and from teasterone to 3-dehydroteasterone in the late BR biosynthesis pathway.     

The heterogeneity of dermatan sulfate and heparan sulfate in rat liver and a shift in the glycosaminoglycan contents in carbon tetrachloride-damaged liver

The glycosaminoglycan of rat liver can be separated into five distinct fractions; a hyaluronic acid franction, a heparan sulfate fraction with a molar ratio of sulfate to hexosamine (S/HexN) around 0.7, a heparan sulfate fraction with a S/HexN ratio around 1.4, a dermatan sulfate fraction with a S/HexN ratio near unity, and a dermatan sulfate fraction with a S/HexN ratio around 1.3.Enzymatic analysis of the two dermatan sulfate fractions indicates that they differ significantly in that the high sulfated fraction contains relatively more N-acetylgalactosamine 4,6-bissulfate units (about 26% of the total hexosamine). In experimental injury produced by carbon tetrachloride, the low sulfated fraction increases as much as 9-fold on a dry weight basis, bearing no linear relationship to the amount of the high sulfated fraction which increases only 2-fold. A significant shift is also observed in the levels of the two heparan sulfate fractions. In this case, however, the high sulfated fraction shows a much more pronounced increase than does the low sulfated fraction. On the basis of these observations, it is suggested that for each of the dermatan sulfate and heparan sulfate classes are at least two pools, distinguished by sulfation degree and perhaps by turnover rate and physiological function.     

A new species of the genus <Emphasis Type=Italic>Stathmopoda</Emphasis> (Lepidoptera: Stathmopodidae) closely related to the persimmon pest, <Emphasis Type=Italic>S. masinissa</Emphasis>, from Ryukyu Islands,Japan

A new species of the genus Stathmopoda from the Ryukyu Islands, Japan, is described. The new species is associated with Diospyros maritima Blume and is very similar to S. masinissa Meyrick, which is a notorious pest of persimmon, D. kaki L., in Japan and Korea. The adult external features, wing venation, and male and female genitalia of both species are illustrated and compared in detail.     

Extracellular and Intracellular Mechanisms of Mechanotransduction in Three-Dimensionally Embedded Rat Chondrocytes

Purpose

Articular cartilage homeostasis involves modulation of chondrocyte matrix synthesis in response to mechanical stress (MS). We studied extracellular and intracellular mechanotransduction pathways mediating this response.

Methods

We first confirmed rapid up-regulation of the putative chondro-protective cytokine, interleukin (IL)-4, as an immediate response to MS. We then studied the role of IL-4 by investigating responses to exogenous IL-4 or a specific IL-4 inhibitor, combined with MS. Next we investigated the intracellular second messengers. Since chondrocyte phenotype alters according to the extracellular environment, we characterized the response to mechanotransduction in 3-dimensionally embedded chondrocytes.

Results

Expression of aggrecan and type II collagen was significantly up-regulated by exogenous IL-4 whereas MS-induced matrix synthesis was inhibited by an IL-4 blocker. Further, MS-induced matrix synthesis was completely blocked by a p38 MAPK inhibitor, while it was only partially blocked by inhibitors of other putative second messengers.

Conclusion

IL-4 mediates an extracellular pathway of mechanotransduction, perhaps via an autocrine/paracrine loop, while p38 mediates an intracellular pathway prevalent only in a 3-dimensional environment.