Changes in S-type lectin localization in neuroblastoma cells (N1E115) upon differentiation

The distribution of a 14.4 kDa S-type lectin was examined in murine neuroblastoma cells, either undifferentiated or after differentiation induced by dibutyryl-cyclic adenosine monophosphate. In undifferentiated cells the immunoreactivity was detected extracellularly, associated with the plasma membrane and in bulges released into the extracellular milieu. Important modifications of the lectin localization were associated with the differentiation process that induced an increased cytosolic expression and a decreased externalization. Possible functions for the lectin expressed intracellularly in the differentiated cells are also considered.     

Evidence of Coat Color Variation Sheds New Light on Ancient Canids

We have used a paleogenetics approach to investigate the genetic landscape of coat color variation in ancient Eurasian dog and wolf populations. We amplified DNA fragments of two genes controlling coat color, Mc1r (Melanocortin 1 Receptor) and CBD103 (canine-β-defensin), in respectively 15 and 19 ancient canids (dogs and wolf morphotypes) from 14 different archeological sites, throughout Asia and Europe spanning from ca. 12 000 B.P. (end of Upper Palaeolithic) to ca. 4000 B.P. (Bronze Age). We provide evidence of a new variant (R301C) of the Melanocortin 1 receptor (Mc1r) and highlight the presence of the beta-defensin melanistic mutation (CDB103-K locus) on ancient DNA from dog-and wolf-morphotype specimens. We show that the dominant K^B allele (CBD103), which causes melanism, and R301C (Mc1r), the variant that may cause light hair color, are present as early as the beginning of the Holocene, over 10 000 years ago. These results underline the genetic diversity of prehistoric dogs. This diversity may have partly stemmed not only from the wolf gene pool captured by domestication but also from mutations very likely linked to the relaxation of natural selection pressure occurring in-line with this process.     

Ceramide increases mitochondrial free calcium levels via caspase 8 and Bid: role in initiation of cell death

We investigated how the mitochondrial phase of ceramide-mediated cell death is initiated in nerve growth factor (NGF)-differentiated PC12 cells. We distinguished three independent effects of ceramide: free radical production; a transient increase in cytosolic free calcium; and a long-lasting increase in mitochondrial free calcium. Only the latter led to cell death, which could be prevented by buffering of mitochondrial calcium with the calcium binding protein calbindin D-28K ectopically expressed in mitochondria. We showed that mitochondrial calcium did not increase as a result of the increase in cytosolic free calcium levels. Rather, it appears to derive from the endoplasmic reticulum (ER) since dantrolene, which inhibits release of calcium from ER into cytosol through ryanodine receptors, prevented the increase in cytosolic free calcium but potentiated the increase in mitochondrial free calcium. This suggests that a transfer of calcium occurs directly, or very locally, between the two organelles. This transfer implicated activation of caspase 8 and cleavage of its substrate Bid, a previously unknown function of these cell death intermediaries. The increase in mitochondrial free calcium was also responsible for the release of cytochrome c into the cytosol, underlining the critical role it plays in ceramide-mediated cell death.     

Engineering soluble proteins for structural genomics

Structural genomics has the ambitious goal of delivering three-dimensional structural information on a genome-wide scale. Yet only a small fraction of natural proteins are suitable for structure determination because of bottlenecks such as poor expression, aggregation, and misfolding of proteins, and difficulties in solubilization and crystallization. We propose to overcome these bottlenecks by producing soluble, highly expressed proteins that are derived from and closely related to their natural homologs. Here we demonstrate the utility of this approach by using a green fluorescent protein (GFP) folding reporter assay to evolve an enzymatically active, soluble variant of a hyperthermophilic protein that is normally insoluble when expressed in Escherichia coli, and determining its structure by X-ray crystallography. Analysis of the structure provides insight into the substrate specificity of the enzyme and the improved solubility of the variant.     

Very-Long-Chain Fatty Acids Are Involved in Polar Auxin Transport and Developmental Patterning in Arabidopsis

Very-long-chain fatty acids (VLCFAs) are essential for many aspects of plant development and necessary for the synthesis of seed storage triacylglycerols, epicuticular waxes, and sphingolipids. Identification of the acetyl-CoA carboxylase PASTICCINO3 and the 3-hydroxy acyl-CoA dehydratase PASTICCINO2 revealed that VLCFAs are important for cell proliferation and tissue patterning. Here, we show that the immunophilin PASTICCINO1 (PAS1) is also required for VLCFA synthesis. Impairment of PAS1 function results in reduction of VLCFA levels that particularly affects the composition of sphingolipids, known to be important for cell polarity in animals. Moreover, PAS1 associates with several enzymes of the VLCFA elongase complex in the endoplasmic reticulum. The pas1 mutants are deficient in lateral root formation and are characterized by an abnormal patterning of the embryo apex, which leads to defective cotyledon organogenesis. Our data indicate that in both tissues, defective organogenesis is associated with the mistargeting of the auxin efflux carrier PIN FORMED1 in specific cells, resulting in local alteration of polar auxin distribution. Furthermore, we show that exogenous VLCFAs rescue lateral root organogenesis and polar auxin distribution, indicating their direct involvement in these processes. Based on these data, we propose that PAS1 acts as a molecular scaffold for the fatty acid elongase complex in the endoplasmic reticulum and that the resulting VLCFAs are required for polar auxin transport and tissue patterning during plant development.     

Role of very-long-chain fatty acids in plant development,when chain length does matter

Very long chain fatty acids (VLCFAs) are essential components for eukaryotes. They are elongated by the elongase complex in the endoplasmic reticulum and are incorporated into four major lipid pools (triacylglycerols, waxes, phospholipids, complex sphingolipids). Functional analysis of several components of the elongase complex demonstrated the essential role of VLCFAs in plants, invertebrates and vertebrates. Although VLCFAs changes in the triacylglycerol pool has no consequence for plant development, modifications of the nature and levels of VLCFAs in waxes, phospholipids and complex sphingolipids have, collectively, profound effects on embryo, leaf, root and flower development. VLCFAs levels in epicuticular waxes are critical for the regulation of epidermal fusions during organogenesis. VLCFAs phospholipids and sphingolipids are involved in membrane structure and dynamics regulating cell size but also division and differentiation. This review summarizes the recent findings in plants but also in other organisms, highlighting the importance of very long acyl chain length during development.     

Antitumoral effects of cyclin-dependent kinases inhibitors CR8 and MR4 on chronic myeloid leukemia cell lines

Background

Although Imatinib mesylate has revolutionized the treatment of chronic myeloid leukemia, some patients develop resistance with progression of leukemia. Alternative or additional targeting of signalling pathways deregulated in Bcr-Abl-driven chronic myeloid leukemia may provide a feasible option for improving clinical response and overcoming resistance.

Results

In this study, we investigate ability of CR8 isomers (R-CR8 and S-CR8) and MR4, three derivatives of the cyclin-dependent kinases (CDKs) inhibitor Roscovitine, to exert anti-leukemic activities against chronic myeloid leukemia in vitro and then, we decipher their mechanisms of action. We show that these CDKs inhibitors are potent inducers of growth arrest and apoptosis of both Imatinib-sensitive and –resistant chronic myeloid leukemia cell lines. CR8 and MR4 induce dose-dependent apoptosis through mitochondrial pathway and further caspases 8/10 and 9 activation via down-regulation of short-lived survival and anti-apoptotic factors Mcl-1, XIAP and survivin which are strongly implicated in survival of Bcr-Abl transformed cells.

Conclusions

These results suggest that CDK inhibitors may constitute a complementary approach to treat chronic myeloid leukemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0163-x) contains supplementary material, which is available to authorized users.     

Sphingolipids involvement in plant endomembrane differentiation: the BY2 case

Sphingolipids play an essential role in the functioning of the secretory pathway in eukaryotic organisms. Their importance in the functional organization of plant cells has not been studied in any detail before. The sphingolipid synthesis inhibitor fumonisin B1 (FB1), a mycotoxin acting as a specific inhibitor of ceramide synthase, was tested for its effects on cell growth, cell polarity, cell shape, cell cycle and on the ultrastructure of BY2 cells. We used cell lines expressing different GFP-tagged markers for plant cell compartments, as well as a Golgi marker fused to the photoconvertible protein Kaede. Light and electron microscopy, combined with flow cytometry, were applied to analyse the morphodynamics and architecture of compartments of the secretory pathway. The results indicate that FB1 treatment had severe effects on cell growth and cell shape, and induced a delay in cell division processes. The cell changes were accompanied by the formation of the endoplasmic reticulum (ER)-derived tubular aggregates (FB1-induced compartments), together with an inhibition of cargo transport from the ER to the Golgi apparatus. A change in polar localization of the auxin transporter PIN1 was also observed, but endocytic processes were little affected. Electron microscopy studies confirmed that molecular FB1 targets were distinct from brefeldin A (BFA) targets. We propose that the reported effects of inhibition of ceramide biosynthesis reflect the importance of sphingolipids during cell growth and establishment of cell polarity in higher plant cells, notably through their contribution to the functional organization of the ER or its differentiation into distinct compartments.