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Sophia Frentzas, Eve Simoneau, Victoria L Bridgeman, Peter B Vermeulen, Shane Foo, Eleftherios Kostaras, Mark R Nathan, Andrew Wotherspoon, Zu-Hua Gao, Yu Shi, Gert Van den Eynden, Frances Daley, Clare Peckitt, Xianming Tan, Ayat Salman, Anthoula Lazaris, Patrycja Gazinska, Tracy J Berg, Zak Eltahir, Laila Ritsma, Jacco van Rheenen, Alla Khashper, Gina Brown, Hanna Nyström, Malin Sund, Steven Van Laere, Evelyne Loyer, Luc Dirix, David Cunningham, Peter Metrakos, Andrew R Reynolds
The efficacy of angiogenesis inhibitors in cancer is limited by resistance mechanisms that are poorly understood. Notably, instead of through the induction of angiogenesis, tumor vascularization can occur through the nonangiogenic mechanism of vessel co-option. Here we show that vessel co-option is associated with a poor response to the anti-angiogenic agent bevacizumab in patients with colorectal cancer liver metastases. Moreover, we find that vessel co-option is also prevalent in human breast cancer liver metastases, a setting in which results with anti-angiogenic therapy have been disappointing...
October 17, 2016: Nature Medicine
Xenia Naj, Stefan Linder
The spirochete Borrelia burgdorferi is the causative agent of Lyme disease, a multisystemic disorder affecting primarily skin, nervous system, and joints. If an infection with Borrelia proceeds unchecked, the disease can also enter a chronic stage, leading to the development of neuroborreliosis or cardiac arrhythmia. Successful elimination of B. burgdorferi by the host immune system is thus decisive for the positive outcome of a respective infection. Accordingly, host immune cells such as macrophages and dendritic cells have to be able to efficiently internalize and degrade infecting spirochetes...
October 16, 2016: Current Topics in Microbiology and Immunology
Bryan F Singer, Nancy Bubula, Magdalena M Przybycien-Szymanska, Dongdong Li, Paul Vezina
Drug-paired stimuli rapidly enlarge dendritic spines in the nucleus accumbens (NAcc). While increases in spine size and shape are supported by rearrangement of the actin cytoskeleton and facilitate the synaptic expression of AMPA-type glutamate receptors, it remains unclear whether drug-related stimuli can influence signaling pathways known to regulate these changes in spine morphology. These pathways were studied in rats trained on a discrimination learning paradigm using subcellular fractionation and protein immunoblotting to isolate proteins within dendritic spine compartments in the NAcc shell...
October 6, 2016: European Neuropsychopharmacology: the Journal of the European College of Neuropsychopharmacology
Joanna R Watson, Darerca Owen, Helen R Mott
The small GTPase, Cdc42, is a key regulator of actin dynamics, functioning to connect multiple signals to actin polymerization through effector proteins of the Wiskott-Aldrich syndrome protein (WASP) and Transducer of Cdc42-dependent actin assembly (TOCA) families. WASP family members serve to couple Cdc42 with the actin nucleator, the Arp2/3 complex, via direct interactions. The regulation of these proteins in the context of actin dynamics has been extensively studied. Studies on the TOCA family, however, are more limited and relatively little is known about their roles and regulation...
August 11, 2016: Small GTPases
Andrew S Moore, Yvette C Wong, Cory L Simpson, Erika L F Holzbaur
Mitochondria form interconnected networks that dynamically remodel in response to cellular needs. Using live-cell imaging, we investigate the role of the actin cytoskeleton in regulating mitochondrial fission and fusion. We identify cycling of actin filaments onto and off of subsets of cellular mitochondria. The association of actin filaments with mitochondrial subpopulations is transient; actin quickly disassembles, then reassembles around a distinct subpopulation, efficiently cycling through all cellular mitochondria within 14 min...
2016: Nature Communications
Xenia Snetkov, Ina Weisswange, Julia Pfanzelter, Ashley C Humphries, Michael Way
During its egress, vaccinia virus transiently recruits AP-2 and clathrin after fusion with the plasma membrane. This recruitment polarizes the viral protein A36 beneath the virus, enhancing actin polymerization and the spread of infection. We now demonstrate that three NPF motifs in the C-terminus of A36 recruit AP-2 and clathrin by interacting directly with the Epsin15 homology domains of Eps15 and intersectin-1. A36 is the first identified viral NPF motif containing protein shown to interact with endocytic machinery...
2016: Nature Microbiology
Ellen G Allwood, Joe J Tyler, Agnieszka N Urbanek, Iwona I Smaczynska-de Rooij, Kathryn R Ayscough
Actin nucleation is the key rate limiting step in the process of actin polymerization, and tight regulation of this process is critical to ensure actin filaments form only at specific times and at defined regions of the cell. Arp2/3 is a well-characterised protein complex that can promote nucleation of new filaments, though its activity requires additional nucleation promotion factors (NPFs). The best recognized of these factors are the WASP family of proteins that contain binding motifs for both monomeric actin and for Arp2/3...
2016: PloS One
Erin F Spence, Daniel J Kanak, Benjamin R Carlson, Scott H Soderling
UNLABELLED: Dendritic filopodia are actin-rich structures that are thought to contribute to early spine synapse formation; however, the actin regulatory proteins important for early synaptogenesis are poorly defined. Using organotypic hippocampal slice cultures and primary neuron hippocampal cultures from Arp2/3 conditional knock-out mice, we analyze the roles of the Arp2/3 complex, an actin regulator that creates branched actin networks, and demonstrate it is essential for distinct stages of both structural and functional maturation of excitatory spine synapses...
September 14, 2016: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Pin Lv, Fan Zhang, Ya-Juan Yin, Yu-Can Wang, Min Gao, Xiao-Li Xie, Li-Li Zhao, Li-Hua Dong, Yan-Ling Lin, Ya-Nan Shu, Dan-Dan Zhang, Gui-Xia Liu, Mei Han
We previously demonstrated that smooth muscle (SM) 22α promotes the migration activity in contractile vascular smooth muscle cells (VSMCs). Based on the varied functions exhibited by SM22α in different VSMC phenotypes, we investigated the effect of SM22α on VSMC migration under pathological conditions. The results demonstrated that SM22α overexpression in synthetic VSMCs inhibited platelet-derived growth factor (PDGF)-BB-induced cell lamellipodium formation and migration, which was different from its action in contractile cells...
September 14, 2016: American Journal of Physiology. Cell Physiology
Daniel Andritschke, Sabrina Dilling, Mario Emmenlauer, Tobias Welz, Fabian Schmich, Benjamin Misselwitz, Pauli Rämö, Klemens Rottner, Eugen Kerkhoff, Teiji Wada, Josef M Penninger, Niko Beerenwinkel, Peter Horvath, Christoph Dehio, Wolf-Dietrich Hardt
Salmonella Typhimurium (S. Tm) is a leading cause of diarrhea. The disease is triggered by pathogen invasion into the gut epithelium. Invasion is attributed to the SPI-1 type 3 secretion system (T1). T1 injects effector proteins into epithelial cells and thereby elicits rearrangements of the host cellular actin cytoskeleton and pathogen invasion. The T1 effector proteins SopE, SopB, SopE2 and SipA are contributing to this. However, the host cell factors contributing to invasion are still not completely understood...
2016: PloS One
Chenchang Xu, Xiuping Fu, Shaoxia Zhu, Jia-Jia Liu
Retrolinkin, a neuronal membrane protein, coordinates with endophilin A1 and mediates early endocytic trafficking and signal transduction of the ligand-receptor complex formed between brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin related Kinase B (TrkB), in dendrites of CNS (CNS) neurons. Here we report that retrolinkin interacts with the CYFIP1/2 subunit of the WAVE1 complex, a member of the WASP/WAVE family of nucleation promoting factors (NPF) that binds and activates the Arp2/3 complex to promote branched actin polymerization...
September 7, 2016: Molecular Biology of the Cell
Olivia Muriel, Alejandra Tomas, Cameron C Scott, Jean Gruenberg
We have used in vivo and in vitro strategies to study the mechanisms of multivesicular endosomes biogenesis. We found that, while annexinA2 and Arp2/3 mediate F-actin nucleation and branching, respectively, the ERM protein moesin supports the formation of F-actin networks on early endosomes. We also found that moesin plays no role during endocytosis and recycling to the plasma membrane, but is absolutely required, much like actin, for early-to-late endosome transport and multivesicular endosome formation. Both actin network formation in vitro and early-to-late endosome transport in vivo also depend on the F-actin binding protein cortactin...
September 7, 2016: Molecular Biology of the Cell
Javier Pizarro-Cerdá, Dror Shlomo Chorev, Benjamin Geiger, Pascale Cossart
The Arp2/3 complex has so far been considered to be a single seven-subunit protein complex required for actin nucleation and actin filament polymerization in diverse critical cellular functions including phagocytosis, vesicular trafficking and lamellipodia extension. The Arp2/3 complex is also exploited by bacterial pathogens and viruses during cellular infectious processes. Recent studies suggest that some subunits of the complex are dispensable in specific cellular contexts, pointing to the existence of alternative 'hybrid Arp2/3 complexes' containing other components such as vinculin or α-actinin, as well as different isoforms or phosphorylation variants of canonical Arp2/3 subunits...
August 29, 2016: Trends in Cell Biology
Geun-Young Kim, Jin-Hee Park, Hanna Kim, Hyun-Joung Lim, Hyun-Young Park
Coronin 1B is an actin-binding protein that regulates various cellular processes including cell motility. However, the role of coronin 1B in vascular cell migration remains controversial. Here, we examined the function of coronin 1B in vascular endothelial growth factor (VEGF)-induced migration of human umbilical vein endothelial cells (HUVECs) and investigated the mechanism by which coronin 1B regulates this cellular process. We found that depletion of coronin 1B increased the VEGF-induced migration of HUVECs...
December 2016: Cellular Signalling
Marco Biondini, Amel Sadou-Dubourgnoux, Perrine Paul-Gilloteaux, Giulia Zago, Melis D Arslanhan, François Waharte, Etienne Formstecher, Maud Hertzog, Jinchao Yu, Raphael Guerois, Alexis Gautreau, Giorgio Scita, Jacques Camonis, Maria Carla Parrini
Coordination between membrane trafficking and actin polymerization is fundamental in cell migration, but a dynamic view of the underlying molecular mechanisms is still missing. The Rac1 GTPase controls actin polymerization at protrusions by interacting with its effector, the Wave regulatory complex (WRC). The exocyst complex, which functions in polarized exocytosis, has been involved in the regulation of cell motility. Here, we show a physical and functional connection between exocyst and WRC. Purified components of exocyst and WRC directly associate in vitro, and interactions interfaces are identified...
October 15, 2016: Journal of Cell Science
Etsuko Koike, Keiichi Iwaya, Akinori Watanabe, Shinji Miyake, Eiichi Sato, Takashi Ishikawa
OBJECTIVE: To determine the associations between breast cancer recurrence and cytological findings of fine-needle aspiration cytology (FNAC). STUDY DESIGN: The study included 117 women who had undergone a modified radical mastectomy for invasive ductal carcinoma of the breast. FNAC samples of these patients were reexamined, and cytological findings, such as cellular dissociation, nuclear pleomorphism, nuclear atypia, chromatin pattern, and nuclear size, were scored...
September 1, 2016: Acta Cytologica
Björn Häupl, Christian H Ihling, Andrea Sinz
We investigated the interaction network of human PKD2 in the cytosol and in Golgi-enriched subcellular protein fractions by an affinity enrichment strategy combined with chemical cross-linking/mass spectrometry (MS). Analysis of the subproteomes revealed the presence of distinct proteins in the cytosolic and Golgi fractions. The covalent fixation of transient or weak interactors by chemical cross-linking allowed capturing interaction partners that might otherwise disappear during conventional pull-down experiments...
October 7, 2016: Journal of Proteome Research
Pankaj Dubey, Seema Shirolikar, Krishanu Ray
Spermatogenesis occurs inside a somatic cell enclosure. Sperm release, the most important final step and a target for contraceptives, has been extensively studied in fixed tissue preparations. Here, we provide a time-lapse description of the release process in Drosophila testis ex vivo. We show that the spermatid tails exit the somatic enclosure and enter the testicular duct first, followed by the spermatid heads. Prior to this, individual spermatid heads attempt to invade the head cyst cell, and on each occasion they are repelled by a rapid and local F-actin polymerization response from the head cyst cell...
September 12, 2016: Developmental Cell
R F Sommese, R F Hariadi, K Kim, M Liu, M J Tyska, S Sivaramakrishnan
DNA nanostructures have become an important and powerful tool for studying protein function over the last five years. One of the challenges, though, has been the development of universal methods for patterning protein complexes on DNA nanostructures. Herein, we present a new approach for labeling DNA nanostructures by functionalizing them with a GFP-nanobody. We demonstrate the ability to precisely control protein attachment via our nanobody linker using two enzymatic model systems, namely adenylyl cyclase activity and myosin motility...
August 18, 2016: Protein Science: a Publication of the Protein Society
Jesper Johansen, Gabriel Alfaro, Christopher T Beh
Polarized growth is maintained by both polarized exocytosis, which transports membrane components to specific locations on the cell cortex, and endocytosis, which retrieves these components before they can diffuse away. Despite functional links between these two transport pathways, they are generally considered to be separate events. Using live cell imaging, in vivo and in vitro protein binding assays, and in vitro pyrene-actin polymerization assays, we show that the yeast Rab GTPase Sec4p couples polarized exocytosis with cortical actin polymerization, which induces endocytosis...
August 2016: PLoS Biology
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