Dimeric PKD regulates membrane fission to form transport carriers at the TGN

Protein kinase D (PKD) is recruited to the trans-Golgi network (TGN) through interaction with diacylglycerol (DAG) and is required for the biogenesis of TGN to cell surface transport carriers. We now provide definitive evidence that PKD has a function in membrane fission. PKD depletion by siRNA inhibits trafficking from the TGN, whereas expression of a constitutively active PKD converts TGN into small vesicles. These findings demonstrate that PKD regulates membrane fission and this activity is used to control the size of transport carriers, and to prevent uncontrolled vesiculation of TGN during protein transport

CP110 Suppresses Primary Cilia Formation through Its Interaction with CEP290, a Protein Deficient in Human Ciliary Disease

SummaryPrimary cilia are nonmotile organelles implicated in signaling and sensory functions. Understanding how primary cilia assemble could shed light on the many human diseases caused by mutations in ciliary proteins. The centrosomal protein CP110 is known to suppress ciliogenesis through an unknown mechanism. Here, we report that CP110 interacts with CEP290— a protein whose deficiency is implicated in human ciliary disease—in a discrete complex separable from other CP110 complexes involved in regulating the centrosome cycle. Ablation of CEP290 prevents ciliogenesis without affecting centrosome function or cell-cycle progression. Interaction with CEP290 is absolutely required for the ability of CP110 to suppress primary cilia formation. Furthermore, CEP290 and CP110 interact with Rab8a, a small GTPase required for cilia assembly. Depletion of CEP290 interferes with localization of Rab8a to centrosomes and cilia. Our results suggest that CEP290 cooperates with Rab8a to promote ciliogenesis and that this function is antagonized by CP110

The Deubiquitylase MATH-33 Controls DAF-16 Stability and Function in Metabolism and Longevity

SummaryFOXO family transcription factors are downstream effectors of Insulin/IGF-1 signaling (IIS) and major determinants of aging in organisms ranging from worms to man. The molecular mechanisms that actively promote DAF16/FOXO stability and function are unknown. Here we identify the deubiquitylating enzyme MATH-33 as an essential DAF-16 regulator in IIS, which stabilizes active DAF-16 protein levels and, as a consequence, influences DAF-16 functions, such as metabolism, stress response, and longevity in C. elegans. MATH-33 associates with DAF-16 in cellulo and in vitro. MATH-33 functions as a deubiquitylase by actively removing ubiquitin moieties from DAF-16, thus counteracting the action of the RLE-1 E3-ubiquitin ligase. Our findings support a model in which MATH-33 promotes DAF-16 stability in response to decreased IIS by directly modulating its ubiquitylation state, suggesting that regulated oscillations in the stability of DAF-16 protein play an integral role in controlling processes such as metabolism and longevity

Modulation of RNA splicing enhances response to BCL2 inhibition in leukemia.

Therapy resistance is a major challenge in the treatment of cancer. Here, we performed CRISPR-Cas9 screens across a broad range of therapies used in acute myeloid leukemia to identify genomic determinants of drug response. Our screens uncover a selective dependency on RNA splicing factors whose loss preferentially enhances response to the BCL2 inhibitor venetoclax. Loss of the splicing factor RBM10 augments response to venetoclax in leukemia yet is completely dispensable for normal hematopoiesis. Combined RBM10 and BCL2 inhibition leads to mis-splicing and inactivation of the inhibitor of apoptosis XIAP and downregulation of BCL2A1, an anti-apoptotic protein implicated in venetoclax resistance. Inhibition of splicing kinase families CLKs (CDC-like kinases) and DYRKs (dual-specificity tyrosine-regulated kinases) leads to aberrant splicing of key splicing and apoptotic factors that synergize with venetoclax, and overcomes resistance to BCL2 inhibition. Our findings underscore the importance of splicing in modulating response to therapies and provide a strategy to improve venetoclax-based treatments

Etude de nouveaux partenaires protéiques du facteur de croissance fibroblastique 2 humain (translokine et FIB)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Measurement of fine root tissue density: a comparison of three methods reveals the potential of root dry matter content

15 pages, 3 figures, 2 tables, 57 references.Aims Root tissue density (RTD, the ratio of root dry mass to root volume) is a fundamental trait in comparative root ecology, being increasingly used as an indicator of plant species’ resource use strategy. However, the lack of standardized method to measure this trait makes comparisons tricky. This study aims to compare three methods commonly used for determining fine RTD and to test whether root dry matter content (RDMC, the ratio between root drymass and root freshmass) could be used as a surrogate of fine root tissue density. Methods RTD of 163 fine root samples was determined using (i) Archimedes’ method, (ii) image analysis (WinRHIZO software), and (iii) using the root dry matter content as a proxy. Root samples belonged to different herbaceous species grown in different conditions. Results RTD measured with Archimedes’ method was positively correlated with RTD estimated with image analysis and with RDMC. However we demonstrated that RTD measured with Archimedes’ method was better predicted by RDMC (R2=0.90) than by RTD measured with image analysis (R2=0.56). The performance and limitations of each method were discussed. Conclusion RDMCis a quick, cheap and relatively easy measurable root attribute; we thus recommended its measurement as a proxy of fine root tissue density.The research was supported by the FRB RESPIRS CT 054045 grant, from the “Fondation de la Recherche sur la Biodiversité”.Peer reviewe

Interleukin-8 expression is regulated by histone deacetylases through the nuclear factor-kappaB pathway in breast cancer.

International audienceWe have reported recently that the chemokine interleukin 8 (IL-8)/CXCL8 was overexpressed in invasive estrogen receptor (ERalpha)-negative breast cancer cells compared with ERalpha-positive breast cancer cells. We now demonstrate that histone deacetylases (HDACs) play an essential role in the regulation of IL-8 gene expression in ERalpha-positive MCF-7 breast cancer cells. Treatment of MCF-7 cells with the HDAC inhibitor trichostatin A (TSA) led to a strong up-regulation of IL-8 protein and RNA levels in MCF-7 cells. The up-regulation of IL-8 in MCF-7 cells was time- and concentration-dependent. Moreover, run-on and transfection experiments demonstrated that IL-8 induction by HDAC inhibitors was transcriptional and involved mainly the nuclear factor-kappaB (NF-kappaB) site of the IL-8 promoter. These observations are corroborated by an up-regulation of NF-kappaB activity in MCF-7 cells in the presence of TSA. In addition, blocking NF-kappaB pathway by adenoviral delivery of a dominant-negative IkappaBorIkappaB kinase complex 2 (IKK2) mutant abolished IL-8 gene induction by histone deacetylase inhibitors. HDAC inhibitors triggered IKK phosphorylation and up-regulated p65 nuclear translocation, although they decreased the protein levels of IkappaBalpha, which accounts for NF-kappaB activation. TSA increased binding of acetylated histone 3 to the IL-8 gene promoter. In summary, our results demonstrate that NF-kappaB pathway repression by HDAC is responsible for the low expression of IL-8 in ERalpha-positive breast cancer cells