Febs Letters

doi: 10.1016/0014-5793(95)90079-9pmid: N/A

doi: 10.1016/0014-5793(95)90081-0pmid: N/A

Kojima, Naoya; Yoshida, Yukiko; Kurosawa, Nobuyuki; Lee, Young-Choon; Tsuji, Shuichi

doi: 10.1016/0014-5793(95)00059-Ipmid: 7875291

We have detected sialyltransferase activity of recombinant mouse STX, which was cloned from rat brain as a new member of the sialyltransferase family, but sialyltransferase activity of which had not been detected previously [Livingston and Paulson, J. Biol. Chem. (1993) 268, 11504–11507]. The activity of mouse STX was specific toward sialylated glycoproteins. N‐Glycanase treatment and linkage‐specific sialidase treatment of glycoproteins revealed that STX transfers sialic acids through α2,8‐linkages to only N‐linked oligosaccharides of glycoproteins. However, polymerase activity for polysialic acid synthesis was not detected for this sialyltransferase. Since this α2,8‐sialyltransferase gene is highly restricted in fetal and newborn brain, it may be involved in the polysialylation of glycoproteins, especially of N‐CAM.

Tanaka, Toshihisa; Iqbal, Khalid; Trenkner, Ekkhart; Dong Jie Liu, ; Grundke-Iqbal, Inge

doi: 10.1016/0014-5793(95)00061-Dpmid: 7875300

In Alzheimer disease (AD) the microtubule associated protein (MAP) tau is hyperphosphorylated at several sites. In the present study, like AD tau, tau in the human neuroblastoma SH‐SY5Y was found to be hyperphosphorylated, at Ser‐199/202, Thr‐231, Ser‐396 and Ser‐404. However, in contrast to AD, the tau in SY5Y cells was not hyperphosphorylated at Ser‐235 and there was only one tau isoform. Quantitative analysis revealed that approximately 80% of the SY5Y‐ tau was phosphorylated at Ser‐199/202. The phosphorylated tau was deposited in perikarya and processes of the cells whereas most of the unphosphorylated (at Ser‐199/202) tau was localized in the nucleus. Tau from the cell lysates did not bind to taxol‐stabilized microtubules. In contrast, MAP1b and MAP2 from cell lysates bound to stabilized microtubules in vitro and were associated to the microtubule network in situ. Phosphorylation of tau at high levels, its inactivity with microtubules and its accumulation in SY5Y cells provide for the first time a cell model of cytoskeletal changes seen in AD.

Kuo, Paul C.; Abe, Keith Y.

doi: 10.1016/0014-5793(95)00067-Jpmid: 7533105

To investigate the role of the cytochrome P‐450 system in NO synthesis, cytochrome P‐450IIIA, IIE and IA activities were specifically inhibited by cimetidine (IIIA), clotrimazole (IIIA), benzoflavone (IA) and disulfiram (IIE) in a model of cultured rat hepatocytes. Cytokine‐induced NO synthesis was significantly decreased in the presence of cimetidine and clotrimazole. Kinetic analysis revealed a non‐competitive mode of inhibition (K i = 21 mM, cimetidine; K i = 13 μM, clotrimazole). Reverse transcriptase‐PCR and immunoblot analysis revealed no significant change in steady state levels of iNOS mRNA and protein expression with P‐450IIIA inhibition. Purified iNOS enzyme activity was not altered. These data suggest that cytokinemediated hepatocyte synthesis of NO is dependent upon P‐450IIIA activity, which functions in a post‐translational capacity.

Domoney, C.; Welham, T.; Sidebottom, C.; Firmin, J.L.

doi: 10.1016/0014-5793(95)00070-Ppmid: 7875292

Characterization of Pisum (pea) seed trypsin inhibitors (TI) and their corresponding cDNAs indicates that the pea TI gene family contains two genes. The existence of multiple TI isoforms can be attributed to post‐translational modifications of primary gene products. Post‐translational processing at the C‐terminus during the desiccation stage of seed development results in the appearance of TI isoforms with increased affinity for the target enzyme, trypsin.

Chandler, Simon P.; Fox, Keith R.

doi: 10.1016/0014-5793(95)00069-Lpmid: 7875293

We have used DNase I footprinting to examine the formation of intermolecular triple helices at a fragment containing the target sequence A11(AT)6 · (AT)6T11, using oligonucleotides designed to form parallel T · AT and G · TA triplets. We find that, although (TG)6 does not form a complex with (AT)6 · (AT)6, T11(TG)6 forms a stable structure producing a clear footprint which includes the (AT)6 portion of the target site. This complex is not formed in the presence of magnesium, but can be stabilised by either manganese or a triplex‐binding ligand.

Kikuchi, Haruhito; Akasaka, Yoshikiyo; Kurosawa, Yoshihiro; Yoneyama, Hiroshi; Kato, Shingo; Hata, Jun-ichi

doi: 10.1016/0014-5793(95)00071-Gpmid: 7875294

The WT1 gene is a tumor suppresser gene for Wilms' tumor (WT). Inactivation of both alleles has been proposed as the cause of WT. We encountered a patient with Denys‐Drash syndrome associated with WT whose WT1 gene had a homozygous point mutation not only in WT but also in renal tissue adjacent to the WT and in the germline. These findings indicate that factor(s) other than the loss of WT1 are required for WT to develop.

Barahmand-pour, Fariba; Meinke, Andreas; Eilers, Andreas; Gouilleux, Fabrice; Groner, Bernd; Decker, Thomas

doi: 10.1016/0014-5793(95)00072-Hpmid: 7875295

The Jak‐Stat pathway of intracellular signals is used by growth factor‐ and cytokine receptors to induce gene transcription. We have recently reported that differentiation of myeloid cells, induced by phorbol ester, interferon‐γ (IFN‐γ) or colony‐stimulating factor‐1 (CSF‐1) is accompanied by the activation of the differentiation‐induced factor (DIF). Activated DIF specifically associates with a subclass of gamma‐interferon activation site (GAS)‐like DNA elements. We now report that GM‐CSF, which like CSF‐1 promotes the generation of mature macrophages, activates DIF. No activation was observed after treatment with the granulocyte growth and differentiation factor G‐ CSF. Antibodies raised against a Stat family protein, designated mammary gland factor‐Stat 5 (MGF‐Stat 5), reacted with DIF induced by either CSF‐1, GM‐CSF or IFN‐γ. Antisera to other known Stats were without effect on the DIF complex in electrophoretic mobility shift assays (EMSA). A 112 kDa protein could be isolated from either GM‐CSF‐ or IFN‐γ‐treated cells by GAS oligonucleotide precipitation. This protein reacted with antibodies to both MGF‐Stat 5 and phosphotyrosine. MGF‐Stat 5 and closely related proteins thus define a subfamily of Stat transcription factors that are present in a variety of cell types and are required for the onset of immediate gene expression in response to differentiating stimuli.

Green, Paula J.; Ferguson, Michael A.J.; Robinson, Peter J.; Feizi, Ten

doi: 10.1016/0014-5793(95)00050-Jpmid: N/A

The cation‐independent mannose‐6‐phosphate/insulin‐like growth factor II receptor has been observed to bind to soluble forms of glycosyl‐phosphatidylinositol‐linked molecules, one of mammalian origin (rat Thy‐1) and two of protozoan origins. Of the two phosphate groups found on the soluble forms of the protozoan glycosyl‐phosphatidylinositol‐linked molecules: (i) the internal mannose‐6‐phosphate diester (which forms a part of the ethanolamine bridge) and (ii) the inositol‐1,2 cyclic phosphate group (which arises after cleavage of the membrane associated form with phosphatidylinositol‐specific phospholipase C), only the former appears to be recognized by the mannose‐6‐phosphate/insulin‐like growth factor II receptor, as mild acid hydrolysis which destroys the latter has been observed not to affect the receptor binding site.