Browsing by Subject "PHOSPHATIDYLSERINE"

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  • Najumudeen, A. K.; Jaiswal, A.; Lectez, B.; Oetken-Lindholm, C.; Guzman, C.; Siljamaki, E.; Posada, I. M. D.; Lacey, E.; Aittokallio, T.; Abankwa, D. (2016)
    Cancer stem cells (CSCs) are considered to be responsible for treatment relapse and have therefore become a major target in cancer research. Salinomycin is the most established CSC inhibitor. However, its primary mechanistic target is still unclear, impeding the discovery of compounds with similar anti-CSC activity. Here, we show that salinomycin very specifically interferes with the activity of K-ras4B, but not H-ras, by disrupting its nanoscale membrane organization. We found that caveolae negatively regulate the sensitivity to this drug. On the basis of this novel mechanistic insight, we defined a K-ras-associated and stem cell-derived gene expression signature that predicts the drug response of cancer cells to salinomycin. Consistent with therapy resistance of CSC, 8% of tumor samples in the TCGA-database displayed our signature and were associated with a significantly higher mortality. Using our K-ras-specific screening platform, we identified several new candidate CSC drugs. Two of these, ophiobolin A and conglobatin A, possessed a similar or higher potency than salinomycin. Finally, we established that the most potent compound, ophiobolin A, exerts its K-ras4B-specific activity through inactivation of calmodulin. Our data suggest that specific interference with the K-ras4B/calmodulin interaction selectively inhibits CSC.
  • Lombardi, Elisabetta; Matte, Alessandro; Risitano, Antonio M.; Ricklin, Daniel; Lambris, John D.; De Zanet, Denise; Jokiranta, Sakari T.; Martinelli, Nicola; Scambi, Cinzia; Salvagno, Gianluca; Bisoffi, Zeno; Colato, Chiara; Siciliano, Angela; Bortolami, Oscar; Mazzuccato, Mario; Zorzi, Francesco; De Marco, Luigi; De Franceschi, Lucia (2019)
    Sickle cell disease is an autosomal recessive genetic red cell disorder with a worldwide distribution. Growing evidence suggests a possible involvement of complement activation in the severity of clinical complications of sickle cell disease. In this study we found activation of the alternative complement pathway with microvascular deposition of C5b-9 on skin biopsies from patients with sickle cell disease. There was also deposition of C3b on sickle red cell membranes, which is promoted locally by the exposure of phosphatidylserine. In addition, we showed for the first time a peculiar "stop-and-go" motion of sickle cell red blood cells on tumor factor-alpha-activated vascular endothelial surfaces. Using the C3b/iC3b binding plasma protein factor H as an inhibitor of C3b cell-cell interactions, we found that factor H and its domains 19-20 prevent the adhesion of sickle red cells to the endothelium, normalizing speed transition times of red cells. We documented that factor H acts by preventing the adhesion of sickle red cells to P-selectin and/or the Mac-1 receptor (CD11b/CD18), supporting the activation of the alternative pathway of complement as an additional mechanism in the pathogenesis of acute sickle cell related vaso-occlusive crises. Our data provide a rationale for further investigation of the potential contribution of factor H and other modulators of the alternative complement pathway with potential implications for the treatment of sickle cell disease.
  • Venditti, Rossella; Rega, Laura Rita; Masone, Maria Chiara; Santoro, Michele; Polishchuk, Elena; Sarnataro, Daniela; Paladino, Simona; D'Auria, Sabato; Varriale, Antonio; Olkkonen, Vesa M.; Di Tullio, Giuseppe; Polishchuk, Roman; De Matteis, Maria Antonietta (2019)
    ER-TGN contact sites (ERTGoCS) have been visualized by electron microscopy, but their location in the crowded perinuclear area has hampered their analysis via optical microscopy as well as their mechanistic study. To overcome these limits we developed a FRET-based approach and screened several candidates to search for molecular determinants of the ERTGoCS. These included the ER membrane proteins VAPA and VAPB and lipid transfer proteins possessing dual (ER and TGN) targeting motifs that have been hypothesized to contribute to the maintenance of ERTGoCS, such as the ceramide transfer protein CERT and several members of the oxysterol binding proteins. We found that VAP proteins, OSBP1, ORP9, and ORP10 are required, with OSBP1 playing a redundant role with ORP9, which does not involve its lipid transfer activity, and ORP10 being required due to its ability to transfer phosphatidylserine to the TGN. Our results indicate that both structural tethers and a proper lipid composition are needed for ERTGoCS integrity.