MAST-like protein kinase IREH1 from Arabidopsis thaliana co-localizes with the centrosome when expressed in animal cells.

MAIN CONCLUSION: The similarity of IREH1 (Incomplete Root Hair Elongation 1) and animal MAST kinases was confirmed; IREH1cDNA was cloned while expressing in cultured animal cells co-localized with the centrosome. In mammals and fruit flies, microtubule-associated serine/threonine-protein kinases (MAST) are strongly involved in the regulation of the microtubule system. Higher plants also possess protein kinases homologous to MASTs, but their function and interaction with the cytoskeleton remain unclear. Here, we confirmed the sequence and structural similarity of MAST-related putative protein kinase IREH1 (At3g17850) and known animal MAST kinases. We report the first cloning of full-length cDNA of the IREH1 from Arabidopsis thaliana. Recombinant GFP-IREH1 protein was expressed in different cultured animal cells. It revealed co-localization with the centrosome without influencing cell morphology and microtubule arrangement. Structural N-terminal region of the IREH1 molecule co-localized with centrosome as well.

Involvement of Inositol Biosynthesis and Nitric Oxide in the Mediation of UV-B Induced Oxidative Stress.

The involvement of NO-signaling in ultraviolet B (UV-B) induced oxidative stress (OS) in plants is an open question. Inositol biosynthesis contributes to numerous cellular functions, including the regulation of plants tolerance to stress. This work reveals the involvement of inositol-3-phosphate synthase 1 (IPS1), a key enzyme for biosynthesis of myo-inositol and its derivatives, in the response to NO-dependent OS in Arabidopsis. Homozygous mutants deficient for IPS1 (atips1) and wild-type plants were transformed with a reduction- grx1-rogfp2 and used for the dynamic measurement of UV-B-induced and SNP (sodium nitroprusside)-mediated oxidative stresses by confocal microscopy. atips1 mutants displayed greater tissue-specific resistance to the action of UV-B than the wild type. SNP can act both as an oxidant or repairer depending on the applied concentration, but mutant plants were more tolerant than the wild type to nitrosative effects of high concentration of SNP. Additionally, pretreatment with low concentrations of SNP (10, 100 µM) before UV-B irradiation resulted in a tissue-specific protective effect that was enhanced in atips1. We conclude that the interplay between nitric oxide and inositol signaling can be involved in the mediation of UV-B-initiated oxidative stress in the plant cell.

Nitric oxide signalling via cytoskeleton in plants.

Nitric oxide (NO) in plant cell mediates processes of growth and development starting from seed germination to pollination, as well as biotic and abiotic stress tolerance. However, proper understanding of the molecular mechanisms of NO signalling in plants has just begun to emerge. Accumulated evidence suggests that in eukaryotic cells NO regulates functions of proteins by their post-translational modifications, namely tyrosine nitration and S-nitrosylation. Among the candidates for NO-downstream effectors are cytoskeletal proteins because of their involvement in many processes regulated by NO. This review discusses new insights in plant NO signalling focused mainly on the involvement of cytoskeleton components into NO-cascades. Herein, examples of NO-related post-translational modifications of cytoskeletal proteins, and also indirect NO impact, are discussed. Special attention is paid to plant α-tubulin tyrosine nitration as an emerging topic in plant NO research.

Immunohistochemical analysis of S6K1 and S6K2 expression in endometrial adenocarcinomas.

AIM: The aim of this study was to analyze the levels 70 kDa ribosomal protein S6 kinase 1 (S6K1) and 70 kDa ribosomal protein S6 kinase 2 (S6K2) expression and S6 ribosomal protein phosphorylation in endometrial adenocarcinomas. METHODS: S6K1/2 expression and phosphorylated ribosomal S6 protein (phS6) content have been detected in formalin fixed, paraffin embedded sections of 50 human endometrial adenocarcinomas with different grade of differentiation and in 13 normal endometrial tissues using immunohistochemical approach with following semiquantitative analysis. RESULTS: In normal endometrial epithelial cells both S6K1 and S6K2 were expressed on the low level. S6K1 and S6K2 has been detected predominantly in stromal elements. Increased phS6 level was found in superficial epithelial cells. In deeper parts of endometrial glands and vessels phS6 was discovered occasionally. In endometrial adenocarcinoma's tissues, overexpression of S6K1 was found in cytoplasm and nuclei in 8.0% of cases, overexpression of S6K2--in cytoplasm in 12.0% of cases and in nuclei in 18.0% of cases. Overexpression of S6K1 in endothelial cells of vessels was discovered in 58% of cases. Positive correlation has been determined between: 1) tumor stage and intensity of stromal staining for S6K1 (p = 0.027); 2) tumor differentiation grade and intensity of cytoplasm staining of cancer cells for S6K1 (p = 0.039); 3) intensity of stromal staining and vessel's staining for S6K1 (p = 0.019); 4) vessel's staining for S6K1 and staining for phS6 (p = 0.028). CONCLUSION: Overexpression of S6K1 and S6K2 is a characteristic feature of parenchyma and vessels of endometrial adenocarcinomas. Phosphorylation of ribosomal S6 protein is not dependent from expression level of S6K1 and S6K2.