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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
Arkadi Shwartz, Nagaraju Dhanyasi, Eyal D Schejter, Ben-Zion Shilo
Actin-based thin filament arrays constitute a fundamental core component of muscle sarcomeres. We have used formation of the Drosophila indirect flight musculature for studying the assembly and maturation of thin-filament arrays in a skeletal muscle model system. Employing GFP-tagged actin monomer incorporation, we identify several distinct phases in the dynamic construction of thin-filament arrays. This sequence includes assembly of nascent arrays after an initial period of intensive microfilament synthesis, followed by array elongation, primarily from filament pointed-ends, radial growth of the arrays via recruitment of peripheral filaments and continuous barbed-end turnover...
October 12, 2016: ELife
Cho-Yin Lee, Jizhong Lou, Kuo-Kuang Wen, Melissa McKane, Suzanne G Eskin, Peter A Rubenstein, Shu Chien, Shoichiro Ono, Cheng Zhu, Larry V McIntire
The dynamic turnover of the actin cytoskeleton is regulated cooperatively by force and biochemical signaling. We previously demonstrated that actin depolymerization under force is governed by catch-slip bonds mediated by force-induced K113:E195 salt-bridges. Yet, the biochemical regulation as well as the functional significance of actin catch bonds has not been elucidated. Using AFM force-clamp experiments, we show that formin controlled by RhoA switches the actin catch-slip bonds to slip-only bonds. SMD simulations reveal that the force does not induce the K113:E195 interaction when formin binds to actin K118 and E117 residues located at the helical segment extending to K113...
October 12, 2016: Scientific Reports
Takehiko Ueyama, Yuzuru Ninoyu, Shin-Ya Nishio, Takushi Miyoshi, Hiroko Torii, Koji Nishimura, Kazuma Sugahara, Hideaki Sakata, Dean Thumkeo, Hirofumi Sakaguchi, Naoki Watanabe, Shin-Ichi Usami, Naoaki Saito, Shin-Ichiro Kitajiri
DIAPH1 encodes human DIA1, a formin protein that elongates unbranched actin. The c.3634+1G>T DIAPH1 mutation causes autosomal dominant nonsyndromic sensorineural hearing loss, DFNA1, characterized by progressive deafness starting in childhood. The mutation occurs near the C-terminus of the diaphanous autoregulatory domain (DAD) of DIA1, which interacts with its N-terminal diaphanous inhibitory domain (DID), and may engender constitutive activation of DIA1. However, the underlying pathogenesis that causes DFNA1 is unclear...
October 5, 2016: EMBO Molecular Medicine
J Y Wang, Z H Li, M Ye, Q Feng, Z M Chen, X S Ye, Z G Wu, B Wang, L Liu, J Yao
Biliary atresia (BA) is a destructive bile duct disease occurring in newborn children within a few weeks after birth. In this study, the effect of miR-29c and miR-129-5p on epithelial-mesenchymal transition (EMT) in experimental BA was explored by constructing BA mouse models via Rhesus rotavirus vaccine infection. miR-29c and miR-129-5p expression was analyzed by real-time quantitative polymerase chain reaction. EMT was established by induction with transforming growth factor (TGF)-β1. miR-29c and miR-129-5p were overexpressed and inhibited, respectively, by Lipofectamine transfection...
September 2, 2016: Genetics and Molecular Research: GMR
Daniel D Shaye, Iva Greenwald
The C. elegans excretory cell (EC) is a powerful model for tubulogenesis, a conserved process that requires precise cytoskeletal regulation. EXC-6, an ortholog of the disease-associated formin INF2, coordinates cell outgrowth and lumen formation during EC tubulogenesis by regulating F-actin at the tip of the growing canal and the dynamics of basolateral microtubules. EXC-6 functions in parallel to EXC-5/FGD, a predicted activator of the Rho GTPase Cdc42. Here we identify the parallel pathway: EXC-5 functions through CDC-42 to regulate two other formins: INFT-2, another INF2 ortholog, and CYK-1, the sole ortholog of mammalian Diaphanous (mDia)...
October 3, 2016: Development
David Pruyne
Formins are a widespread family of eukaryotic cytoskeleton-organizing proteins. Many species encode multiple formin isoforms, and for animals, much of this reflects the presence of multiple conserved subtypes. Earlier phylogenetic analyses identified seven major formin subtypes in animals (DAAM, DIAPH, FHOD, FMN, FMNL, INF, and GRID2IP/delphilin), but left a handful of formins, particularly from nematodes, unassigned. In this new analysis drawing from genomic data from a wider range of taxa, nine formin subtypes are identified that encompass all the animal formins analyzed here...
2016: PloS One
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
Chunxing Yang, Eric W Danielson, Tao Qiao, Jake Metterville, Robert H Brown, John E Landers, Zuoshang Xu
Mutations in the profilin 1 (PFN1) gene cause amyotrophic lateral sclerosis (ALS), a neurodegenerative disease caused by the loss of motor neurons leading to paralysis and eventually death. PFN1 is a small actin-binding protein that promotes formin-based actin polymerization and regulates numerous cellular functions, but how the mutations in PFN1 cause ALS is unclear. To investigate this problem, we have generated transgenic mice expressing either the ALS-associated mutant (C71G) or wild-type protein. Here, we report that mice expressing the mutant, but not the wild-type, protein had relentless progression of motor neuron loss with concomitant progressive muscle weakness ending in paralysis and death...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
Caroline Laplante, Fang Huang, Irene R Tebbs, Joerg Bewersdorf, Thomas D Pollard
Cytokinesis in animals, fungi, and amoebas depends on the constriction of a contractile ring built from a common set of conserved proteins. Many fundamental questions remain about how these proteins organize to generate the necessary tension for cytokinesis. Using quantitative high-speed fluorescence photoactivation localization microscopy (FPALM), we probed this question in live fission yeast cells at unprecedented resolution. We show that nodes, protein assembly precursors to the contractile ring, are discrete structural units with stoichiometric ratios and distinct distributions of constituent proteins...
October 4, 2016: Proceedings of the National Academy of Sciences of the United States of America
Xuhui Gao, Xuelian Wang, Kaican Cai, Wujun Wang, Qun Ju, Xiyao Yang, Haofei Wang, Hua Wu
In this study, we investigated the expression patterns and functional roles of microRNA 127 (miR-127) and its target gene Formin-Like 3 (FMNL3) in human esophageal squamous cell carcinoma (ESCC). Quantitative RT-PCR (qRT-PCR) was used to compare miR-127 expression between ESCC cell lines and normal esophageal epithelium cell line, as well as paired ESCC tumors and adjacent normal esophageal tissues in 33 patients. We found miR-127 was aberrantly downregulated in both ESCC cell lines and human ESCC tumors. In ESCC cell lines TE-1 and ECA109 cells, lentiviral-induced miR-127 upregulation markedly inhibited cancer proliferation and migration in vitro, and tumorigenicity in vivo...
September 17, 2016: European Journal of Pharmacology
Zhaofei Fan, Zhihao Wu, Lijuan Wang, Yuxia Zou, Peijun Zhang, Feng You
Olive flounder Paralichthys olivaceus is an important commercially cultured marine flatfish in China, Korea, and Japan. Gynogenesis, via meiogynogenesis and mitogynogenesis, shows advantages in breeding and sex control, but the low survival rate, especially for mitogynogenesis, limits its application. In this study, we sequenced the embryo transcriptomes of gynogenetic haploid, meiogynogenetic diploid, mitogynogenetic diploid, and common diploid flounder and investigated their respective genetic characteristics by analyzing differentiated expressed genes...
September 17, 2016: Marine Biotechnology
Khatuna Kachlishvili, Kapil Dave, Martin Gruebele, Harold Abraham Scheraga, Gia G Maisuradze
Intermediate states in protein folding may slow folding, and sometimes can provide a starting point for aggregation. Recently, the FBP28 WW domain of the formin-binding protein was used as a model for a computational study of the origin and prevention of intermediate-state formation, and local hydrophobic interactions of Leu26 were implicated. Here, we combine new simulations over a broad temperature range with experimental temperature-jump data to study this site in more detail. We replace Leu26 by Asp26 or Trp26 to alter the folding scenario from three-state folding towards two-state or downhill folding at temperatures below the melting point, whereas the wild type shows two-state behavior only near its melting temperature...
September 1, 2016: Journal of Physical Chemistry. B
Christine Péladeau, Allan Heibein, Melissa T Maltez, Sarah J Copeland, John W Copeland
BACKGROUND: Formins are a highly conserved family of cytoskeletal remodeling proteins. A growing body of evidence suggests that formins play key roles in the progression and spread of a variety of cancers. There are 15 human formin proteins and of these the Diaphanous-Related Formins (DRFs) are the best characterized. Included in the DRFs are the Formin-Like proteins, FMNL1, 2 & 3, each of which have been strongly implicated in driving tumorigenesis and metastasis of specific tumors. In particular, increased FMNL2 expression correlates with increased invasiveness of colorectal cancer (CRC) in vivo and for a variety of CRC cell-lines in vitro...
2016: BMC Cell Biology
Peter J Wen, Staffan Grenklo, Gianvito Arpino, Xinyu Tan, Hsien-Shun Liao, Johanna Heureaux, Shi-Yong Peng, Hsueh-Cheng Chiang, Edaeni Hamid, Wei-Dong Zhao, Wonchul Shin, Tuomas Näreoja, Emma Evergren, Yinghui Jin, Roger Karlsson, Steven N Ebert, Albert Jin, Allen P Liu, Oleg Shupliakov, Ling-Gang Wu
Vesicle fusion is executed via formation of an Ω-shaped structure (Ω-profile), followed by closure (kiss-and-run) or merging of the Ω-profile into the plasma membrane (full fusion). Although Ω-profile closure limits release but recycles vesicles economically, Ω-profile merging facilitates release but couples to classical endocytosis for recycling. Despite its crucial role in determining exocytosis/endocytosis modes, how Ω-profile merging is mediated is poorly understood in endocrine cells and neurons containing small ∼30-300 nm vesicles...
2016: Nature Communications
Yunfan Yang, Jinfeng Zhao, Yongqing Li
The investigation of excited-state intramolecular proton transfer (ESIPT) has been carried out via the density functional theory (DFT) and the time-dependent density functional theory (TDDFT) method for natural product quercetin in dichloromethane (DCM) solvent. For distinguishing different types of intramolecular interaction, the reduced density gradient (RDG) function also has been used. In this study, we have clearly clarified the viewpoint that two kinds of tautomeric forms (K1, K2)originated from ESIPT processconsist inthe first electronic excited state (S1)...
2016: Scientific Reports
Jie Jin, Yu Wang, Yang Xu, Xu Zhou, Yu Liu, Xiang Li, Jin Wang
BACKGROUND: In this study, we explored the functional roles of microRNA-144 (miR-144) upregulation and downregulation in human acute lymphoblastic leukemia (ALL). METHOD: Gene expression of miR-144 was examined by qRT-PCR in both ALL cell lines and T-leukemic cells of ALL patients. In ALL cell lines Molt-3 and Jurkat cells, miR-144 was either upregulated or downregulated through lentiviral transduction. The subsequent effects of miR-144 upregulation or downregulation on ALL proliferation, cell-cycle transition, and in vivo xenograft were assessed...
August 24, 2016: Journal of Gene Medicine
Hailong Lu, Patricia M Fagnant, Elena B Krementsova, Kathleen M Trybus
Mutations in vascular smooth muscle α-actin (SM α-actin), encoded by ACTA2, are the most common cause of familial thoracic aortic aneurysms that lead to dissection (TAAD). The R179H mutation has a poor patient prognosis, and is unique in causing multisystemic smooth muscle dysfunction (1). Here we characterize this mutation in expressed human SM α-actin. R179H actin shows severe polymerization defects, with a 40-fold higher critical concentration for assembly than WT SM α-actin, driven by a high disassembly rate...
August 22, 2016: Journal of Biological Chemistry
Maria Gardberg, Vanina D Heuser, Ilkka Koskivuo, Mari Koivisto, Olli Carpén
While most early (stage I-II) melanomas are cured by surgery, recurrence is not uncommon. Prognostication by current clinicopathological parameters does not provide sufficient means for identifying patients who are at risk of developing metastases and in need of adjuvant therapy. Actin-regulating formins may account for invasive properties of cancer cells, including melanoma. Here, we studied formin-like protein 2 and 3 (FMNL2 and FMNL3) in melanoma by analysing their role in the invasive properties of melanoma cells and by evaluating whether FMNL2 expression is associated with melanoma outcome...
January 2016: Journal of Pathology. Clinical Research
Thomas E Sladewski, Elena B Krementsova, Kathleen M Trybus
A hallmark of the well-studied vertebrate class Va myosin is its ability to take multiple steps on actin as a single molecule without dissociating, a feature called "processivity." Therefore, it was surprising when kinetic and single-molecule assays showed that human myosin Vc (MyoVc) was not processive on single-actin filaments [1-3]. We explored the possibility that MyoVc is processive only under conditions that resemble its biological context. Recently, it was shown that zymogen vesicles are transported on actin "superhighways" composed of parallel actin cables nucleated by formins from the plasma membrane [4]...
August 22, 2016: Current Biology: CB
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