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Marcus W Stepp, Mark A Doll, Samantha M Carlisle, J Christopher States, David W Hein
Arylamine N-acetyltransferase 1 (NAT1) expression is reported to affect proliferation, invasiveness, and growth of cancer cells. MDA-MB-231 breast cancer cells were engineered such that NAT1 expression was elevated or suppressed, or treated with a small molecule inhibitor of NAT1. The MDA-MB-231 human breast cancer cell lines were engineered with a scrambled shRNA, a NAT1 specific shRNA or a NAT1 overexpression cassette stably integrated into a single flippase recognition target (FRT) site facilitating incorporation of these different genetic elements into the same genomic location...
January 9, 2018: Molecular Carcinogenesis
Lukasz M Solanko, David P Sullivan, Yves Y Sere, Maria Szomek, Anita Lunding, Katarzyna A Solanko, Azra Pizovic, Lyubomir D Stanchev, Thomas Günther Pomorski, Anant K Menon, Daniel Wüstner
Transbilayer lipid asymmetry is a fundamental characteristic of the eukaryotic cell plasma membrane (PM). While PM phospholipid asymmetry is well documented, the transbilayer distribution of PM sterols such as mammalian cholesterol and yeast ergosterol is not reliably known. We now report that sterols are asymmetrically distributed across the yeast PM, with the majority (~80%) located in the cytoplasmic leaflet. By exploiting the sterol-auxotrophic hem1Δ yeast strain we obtained cells in which endogenous ergosterol was quantitatively replaced with dehydroergosterol (DHE), a closely related fluorescent sterol that functionally and accurately substitutes for ergosterol in vivo...
December 28, 2017: Traffic
Katumori Segawa, Sachiko Kurata, Shigekazu Nagata
Flippases are enzymes that translocate phosphatidylserine (PtdSer) and phosphatidyl- ethanolamine (PtdEtn) from the outer to the inner leaflet in the lipid bilayer of the plasma membrane, leading to the asymmetric distribution of aminophospholipids in the membrane. One mammalian phospholipid flippase at the plasma membrane is ATP11C, a type IV P-type ATPase (P4-ATPase) that forms a hetero-complex with the transmembrane protein CDC50A. However, the structural features in CDC50A that support the function of ATP11C and other P4-ATPases have not been characterized...
December 24, 2017: Journal of Biological Chemistry
M S Jensen, S R Costa, A S Duelli, P A Andersen, L R Poulsen, L D Stanchev, P Gourdon, M Palmgren, T Günther Pomorski, R L López-Marqués
P4 ATPase flippases translocate phospholipids across biomembranes, thus contributing to the establishment of transmembrane lipid asymmetry, a feature important for multiple cellular processes. The mechanism by which such phospholipid flipping occurs remains elusive as P4 ATPases transport a giant substrate very different from that of other P-type ATPases such as Na+/K+- and Ca2+-ATPases. Based on available crystal structures of cation-transporting P-type ATPases, we generated a structural model of the broad-specificity flippase ALA10...
December 15, 2017: Scientific Reports
Małgorzata Marczak, Andrzej Mazur, Piotr Koper, Kamil Żebracki, Anna Skorupska
Rhizobia dwell and multiply in the soil and represent a unique group of bacteria able to enter into a symbiotic interaction with plants from the Fabaceae family and fix atmospheric nitrogen inside de novo created plant organs, called nodules. One of the key determinants of the successful interaction between these bacteria and plants are exopolysaccharides, which represent species-specific homo- and heteropolymers of different carbohydrate units frequently decorated by non-carbohydrate substituents. Exopolysaccharides are typically built from repeat units assembled by the Wzx/Wzy-dependent pathway, where individual subunits are synthesized in conjunction with the lipid anchor undecaprenylphosphate (und-PP), due to the activity of glycosyltransferases...
December 1, 2017: Genes
Zhongxin Guo, Xian-Bing Wang, Ying Wang, Wan-Xiang Li, Amit Gal-On, Shou-Wei Ding
Small interfering RNAs (siRNAs) processed from virus-specific dsRNA direct antiviral RNA interference (RNAi) in diverse eukaryotic hosts. We have recently performed a sensitized genetic screen in Arabidopsis thaliana and identified two related phospholipid flippases required for antiviral RNAi and the amplification of virus-derived siRNAs by plant RNA-dependent RNA polymerase 1 (RDR1) and RDR6. Here we report the identification and cloning of ANTIVIRAL RNAI-DEFECTIVE 2 (AVI2) from the same genetic screen. AVI2 encodes a multi-span transmembrane protein broadly conserved in plants and animals with two homologous human proteins known as magnesium transporters...
November 28, 2017: Plant Physiology
Sheila Ingemann Jensen, Alex Toftgaard Nielsen
Lambda Red recombineering is an easy and efficient method for generating genetic modifications in Escherichia coli. For gene deletions, lambda Red recombineering is combined with the use of selectable markers, which are removed through the action of, e.g., flippase (Flp) recombinase. This PCR-based engineering method has also been applied to a number of other bacteria. In this chapter, we describe a recently developed one plasmid-based method as well as the use of a strain with genomically integrated recombineering genes, which significantly speeds up the engineering of strains with multiple genomic alterations...
2018: Methods in Molecular Biology
Gail G Hardy, Evelyn Toh, Cécile Berne, Yves V Brun
Attachment is essential for microorganisms to establish interactions with both biotic and abiotic surfaces. Stable attachment of Caulobacter crescentus to surfaces requires an adhesive polysaccharide holdfast, but the exact composition of holdfast is unknown. The holdfast is anchored to the cell envelope by outer membrane proteins HfaA, HfaB and HfaD. Holdfast anchor gene mutations result in holdfast shedding and reduced cell adherence. Translocation of HfaA and HfaD to the cell surface requires HfaB. The Wzx homolog, HfsF, is predicted to be a bacterial polysaccharide flippase...
November 20, 2017: Journal of Bacteriology
Hiroyuki Takatsu, Masahiro Takayama, Tomoki Naito, Naoto Takada, Kazuya Tsumagari, Yasushi Ishihama, Kazuhisa Nakayama, Hye-Won Shin
We and others showed that ATP11A and ATP11C, members of the P4-ATPase family, translocate phosphatidylserine (PS) and phosphatidylethanolamine from the exoplasmic to the cytoplasmic leaflets at the plasma membrane. PS exposure on the outer leaflet of the plasma membrane in activated platelets, erythrocytes, and apoptotic cells was proposed to require the inhibition of PS-flippases, as well as activation of scramblases. Although ATP11A and ATP11C are cleaved by caspases in apoptotic cells, it remains unclear how PS-flippase activity is regulated in non-apoptotic cells...
November 10, 2017: Nature Communications
Tatsuyuki Matsudaira, Kojiro Mukai, Taishin Noguchi, Junya Hasegawa, Tomohisa Hatta, Shun-Ichiro Iemura, Tohru Natsume, Norio Miyamura, Hiroshi Nishina, Jun Nakayama, Kentaro Semba, Takuya Tomita, Shigeo Murata, Hiroyuki Arai, Tomohiko Taguchi
Yes-associated protein (YAP) is a recently discovered growth-promoting transcription coactivator that has been shown to regulate the malignancy of various cancers. How YAP is regulated is not fully understood. Here, we show that one of the factors regulating YAP is phosphatidylserine (PS) in recycling endosomes (REs). We use proximity biotinylation to find proteins proximal to PS. Among these proteins are YAP and multiple proteins related to YAP signalling. Knockdown of ATP8A1 (an RE PS-flippase) or evectin-2 (an RE-resident protein) and masking of PS in the cytoplasmic leaflet of membranes, all suppress nuclear localization of YAP and YAP-dependent transcription...
November 1, 2017: Nature Communications
Karl-Heinz Tomaszowski, Nadja Hellmann, Viviane Ponath, Hiroyuki Takatsu, Hye-Won Shin, Bernd Kaina
The DNA repair protein O (6)-methylguanine-DNA-methyltransferase (MGMT) is a key determinant of cancer resistance. The MGMT inhibitors O (6)-benzylguanine (O(6)BG) and O (6)-(4-bromothenyl)guanine (O(6)BTG) failed to enhance the therapeutic response due to toxic side effects when applied in combination with alkylating chemotherapeutics, indicating a need of inhibitor targeting. We assessed MGMT targeting that relies on conjugating the inhibitors O(6)BG and O(6)BTG to ß-D-glucose, resulting in O(6)BG-Glu and O(6)BTG-Glu, respectively...
October 24, 2017: Scientific Reports
Yue Niu, Dong Qian, Baiyun Liu, Jianchao Ma, Dongshi Wan, Xinyu Wang, Wenliang He, Yun Xiang
Maintaining lipid membrane integrity is an essential aspect of plant tolerance to high temperature. P4-type ATPases are responsible for flipping and stabilizing asymmetric phospholipids in membrane systems, though their functions in stress tolerance are not entirely clear. Aminophospholipid ATPase6 (ALA6) is a member of the P4-type ATPase family, which has 12 members in Arabidopsis thaliana. Here, we show that a loss-of-function mutant of ALA6 (ala6) exhibits clear sensitivity to heat stress, including both basal and acquired thermotolerance treatments...
2017: Frontiers in Plant Science
Stephen R Thom, Veena M Bhopale, Kevin Yu, Weiliang Huang, Maureen A Kane, David J Margolis
Microparticles are lipid bilayer-enclosed vesicles produced by cells under oxidative stress. MP production is elevated in patients with diabetes, but the underlying cellular mechanisms are poorly understood. We hypothesized that raising glucose above the physiological level of 5.5 mm would stimulate leukocytes to produce MPs and activate the nucleotide-binding domain, leucine-rich repeat pyrin domain-containing 3 (NLRP3) inflammasome. We found that when incubated in buffer with up to 20 mm glucose, human and murine neutrophils, but not monocytes, generate progressively more MPs with high interleukin (IL)-1β content...
November 3, 2017: Journal of Biological Chemistry
Karthik R Chamakura, Lok-To Sham, Rebecca M Davis, Lorna Min, Hongbaek Cho, Natividad Ruiz, Thomas G Bernhardt, Ry Young
For bacteriophage infections, the cell walls of bacteria, consisting of a single highly polymeric molecule of peptidoglycan (PG), pose a major problem for the release of progeny virions. Phage lysis proteins that overcome this barrier can point the way to new antibacterial strategies (1) , especially small lytic single-stranded DNA (the microviruses) and RNA phages (the leviviruses) that effect host lysis using a single non-enzymatic protein (2) . Previously, the A2 protein of levivirus Qβ and the E protein of the microvirus ϕX174 were shown to be 'protein antibiotics' that inhibit the MurA and MraY steps of the PG synthesis pathway (2-4) ...
November 2017: Nature Microbiology
Rasmus H Gantzel, Louise S Mogensen, Stine A Mikkelsen, Bente Vilsen, Robert S Molday, Anna L Vestergaard, Jens P Andersen
Phospholipid flippases (P4-ATPases) translocate specific phospholipids from the exoplasmic to the cytoplasmic leaflet of membranes. While there is good evidence that the overall molecular structure of flippases is similar to that of P-type ATPase ion-pumps, the transport pathway for the "giant" lipid substrate has not been determined. ATP8A2 is a flippase with selectivity toward phosphatidylserine (PS), possessing a net negatively charged head group, whereas ATP8B1 exhibits selectivity toward the electrically neutral phosphatidylcholine (PC)...
September 5, 2017: Scientific Reports
Bhupender Sharma, Shamsher S Kanwar
Cancer is a leading cause of mortality and morbidity globally. Many prominent cancer-associated molecules have been identified over the recent years which include EGFR, CD44, TGFbRII, HER2, miR-497, NMP22, BTA, Fibrin/FDP etc. These biomarkers are often used for screening, detection, diagnosis, prognosis, prediction and monitoring of cancer development. Phosphatidylserine (PS) is an essential component in all human cells which is present on the inner leaflet of the cell membrane. The oxidative stress causes exposure of PS on the surface of the vascular endothelium in the cancer cells (lung, breast, pancreatic, bladder, skin, brain metastasis, rectal adenocarcinoma etc...
September 1, 2017: Seminars in Cancer Biology
Wei Mi, Yanyan Li, Sung Hwan Yoon, Robert K Ernst, Thomas Walz, Maofu Liao
Lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria is critical for the assembly of their cell envelopes. LPS synthesized in the cytoplasmic leaflet of the inner membrane is flipped to the periplasmic leaflet by MsbA, an ATP-binding cassette transporter. Despite substantial efforts, the structural mechanisms underlying MsbA-driven LPS flipping remain elusive. Here we use single-particle cryo-electron microscopy to elucidate the structures of lipid-nanodisc-embedded MsbA in three functional states...
September 14, 2017: Nature
John Chu, Xavier Vila-Farres, Daigo Inoyama, Ricardo Gallardo-Macias, Mark Jaskowski, Shruthi Satish, Joel S Freundlich, Sean F Brady
The flippase MurJ is responsible for transporting the cell wall intermediate lipid II from the cytoplasm to the outside of the cell. While essential for the survival of bacteria, it remains an underexploited target for antibacterial therapy. The humimycin antibiotics are lipid II flippase (MurJ) inhibitors that were synthesized on the basis of bioinformatic predictions derived from secondary metabolite gene clusters found in the human microbiome. Here, we describe an SAR campaign around humimycin A that produced humimycin 17S...
September 11, 2017: ACS Infectious Diseases
Lin Zhang, Yeming Yang, Shujin Li, Shanshan Zhang, Xiong Zhu, Zhengfu Tai, Mu Yang, Yuqing Liu, Xinzheng Guo, Bo Chen, Zhilin Jiang, Fang Lu, Xianjun Zhu
Phosphatidylserine (PS) is asymmetrically distributed between the outer and inner leaflets of the plasma membrane in eukaryotic cells. PS asymmetry on the plasma membrane depends on the activities of P4-ATPases, and disruption of PS distribution can lead to various disease conditions. Folding and transporting of P4-ATPases to their cellular destination requires the β subunit TMEM30A proteins. However, the in vivo functions of Tmem30a remain unknown. To this end, we generated retinal-specific Tmem30a-knockout mice to investigate its roles in vivo for the first time...
August 24, 2017: Scientific Reports
Archita Srivastava, Shabnam Sircaik, Farha Husain, Edwina Thomas, Shivani Ror, Sumit Rastogi, Darakshan Alim, Priyanka Bapat, David R Andes, Clarissa J Nobile, Sneh L Panwar
Fungal pathogens such as Candida albicans exhibit several survival mechanisms to evade attack by antifungals and colonise host tissues. Rta3, a member of the Rta1-like family of lipid-translocating exporters has a 7-transmembrane domain topology, similar to the G-protein-coupled receptors and is unique to the fungal kingdom. Our findings point towards a role for the plasma membrane localised Rta3 in providing tolerance to miltefosine, an analogue of alkylphosphocholine, by maintaining mitochondrial energetics...
December 2017: Cellular Microbiology
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