scholarly journals The important role of actinin-like protein (AcnA) in cytokinesis and apical dominance of hyphal cells in Aspergillus nidulans

Microbiology ◽  
2009 ◽  
Vol 155 (8) ◽  
pp. 2714-2725 ◽  
Author(s):  
Jinjun Wang ◽  
Hongqin Hu ◽  
Sha Wang ◽  
Jie Shi ◽  
Shaochun Chen ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Apical Dominance ◽  
Actin Binding ◽  
Expansion Phase ◽  
Capping Proteins ◽  
Dependent Polarization ◽  
Isotropic Expansion ◽  
Actin Capping

The actin cytoskeleton is involved in many processes in eukaryotic cells, including interaction with a wide variety of actin-binding proteins such as the actin-capping proteins, the actin filament nucleators and the actin cross-linking proteins. Here, we report the identification and characterization of an actinin-like protein (AcnA) from the filamentous fungus Aspergillus nidulans. Not only did the depletion of AcnA by alcA(p) promoter repression or the deletion of AcnA result in explicit abnormalities in septation and conidiation, but also the acnA mutants induced a loss of apical dominance in cells with dichotomous branching, in which a new branch was formed by splitting the existing tip in two. Consequently, the colony showed flabellate edges. Moreover, we found that the localization of the GFP–AcnA fusion was quite dynamic. In the isotropic expansion phase of the germinated spore, GFP–AcnA was organized as cortical patches with cables lining the cell wall. Subsequently, GFP–AcnA was localized to the actively growing hyphal tips and to the sites of septation in the form of combined double contractile rings. Our data suggest that AcnA plays an important role in cytokinesis and apical dominance of hyphal cells, possibly via actin-dependent polarization maintenance and medial ring establishment in A. nidulans. This is the first report, to our knowledge, of the function of an actinin-like protein in filamentous fungi.

scholarly journals Capping protein regulates endosomal trafficking by controlling F-actin density around endocytic vesicles and recruiting RAB5 effectors

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Dawei Wang ◽  
Zuodong Ye ◽  
Wenjie Wei ◽  
Jingting Yu ◽  
Lihong Huang ◽  
...  
Keyword(s):  
Actin Binding ◽  
Binding Motif ◽  
Endosomal Trafficking ◽  
Capping Protein ◽  
Capping Proteins ◽  
Early Endosomes ◽  
Endocytic Vesicles ◽  
Actin Capping ◽  
Heterodimeric Protein Complex

Actin filaments (F-actin) have been implicated in various steps of endosomal trafficking, and the length of F-actin is controlled by actin capping proteins, such as CapZ, which is a stable heterodimeric protein complex consisting of a and β subunits. However, the role of these capping proteins in endosomal trafficking remains elusive. Here, we found that CapZ docks to endocytic vesicles via its C-terminal actin-binding motif. CapZ knockout significantly increases the F-actin density around immature early endosomes, and this impedes fusion between these vesicles, manifested by the accumulation of small endocytic vesicles in CapZ-knockout cells. CapZ also recruits several RAB5 effectors, such as Rabaptin-5, to RAB5-positive early endosomes via its N-terminal domain, and this further activates RAB5. Collectively, our results indicate that CapZ regulates endosomal trafficking by controlling actin density around early endosomes and recruiting RAB5 effectors.

Characterization of the Role of the FluG Protein in Asexual Development of Aspergillus nidulans

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 1027-1036 ◽  
Author(s):  
Cletus A D'Souza ◽  
Bee Na Lee ◽  
Thomas H Adams
Keyword(s):  
Aspergillus Nidulans ◽  
Negative Influence ◽  
Asexual Development ◽  
Wild Type ◽  
Significant Similarity ◽  
Developmental Defects ◽  
Asexual Sporulation ◽  
Type Strains

Abstract We showed previously that a ΔfluG mutation results in a block in Aspergillus nidulans asexual sporulation and that overexpression of fluG activates sporulation in liquid-submerged culture, a condition that does not normally support sporulation of wild-type strains. Here we demonstrate that the entire N-terminal region of FluG (∼400 amino acids) can be deleted without affecting sporulation, indicating that FluG activity resides in the C-terminal half of the protein, which bears significant similarity with GSI-type glutamine synthetases. While FluG has no apparent role in glutamine biosynthesis, we propose that it has an enzymatic role in sporulation factor production. We also describe the isolation of dominant suppressors of ΔfluG(dsg) that should identify components acting downstream of FluG and thereby define the function of FluG in sporulation. The dsgA1 mutation also suppresses the developmental defects resulting from ΔflbA and dominant activating fadA mutations, which both cause constitutive induction of the mycelial proliferation pathway. However, dsgA1 does not suppress the negative influence of these mutations on production of the aflatoxin precursor, sterigmatocystin, indicating that dsgA1 is specific for asexual development. Taken together, our studies define dsgA as a novel component of the asexual sporulation pathway.

scholarly journals Physiological role of actin regulation in male fertility: Insight into actin capping proteins in spermatogenic cells

2020 ◽  
Vol 19 (2) ◽  
pp. 120-127
Author(s):  
Tetsuji Soda ◽  
Yasushi Miyagawa ◽  
Shinichiro Fukuhara ◽  
Hiromitsu Tanaka
Keyword(s):  
Male Fertility ◽  
Physiological Role ◽  
Spermatogenic Cells ◽  
Capping Proteins ◽  
Actin Capping ◽  
Insight Into

scholarly journals The structure of the actin filament uncapping complex mediated by twinfilin

2021 ◽  
Vol 7 (5) ◽  
pp. eabd5271
Author(s):  
Dennis M. Mwangangi ◽  
Edward Manser ◽  
Robert C. Robinson
Keyword(s):  
Actin Filament ◽  
Protein Interactions ◽  
Protein Complex ◽  
Actin Filaments ◽  
Actin Binding ◽  
Capping Protein ◽  
Binding Surface ◽  
Actin Capping Protein ◽  
Actin Capping

Uncapping of actin filaments is essential for driving polymerization and depolymerization dynamics from capping protein–associated filaments; however, the mechanisms of uncapping leading to rapid disassembly are unknown. Here, we elucidated the x-ray crystal structure of the actin/twinfilin/capping protein complex to address the mechanisms of twinfilin uncapping of actin filaments. The twinfilin/capping protein complex binds to two G-actin subunits in an orientation that resembles the actin filament barbed end. This suggests an unanticipated mechanism by which twinfilin disrupts the stable capping of actin filaments by inducing a G-actin conformation in the two terminal actin subunits. Furthermore, twinfilin disorders critical actin-capping protein interactions, which will assist in the dissociation of capping protein, and may promote filament uncapping through a second mechanism involving V-1 competition for an actin-binding surface on capping protein. The extensive interactions with capping protein indicate that the evolutionary conserved role of twinfilin is to uncap actin filaments.

scholarly journals Identification and Characterization of Genes Required for Hyphal Morphogenesis in the Filamentous Fungus Aspergillus nidulans

Genetics ◽  
1999 ◽  
Vol 151 (3) ◽  
pp. 1015-1025 ◽  
Author(s):  
Steven D Harris ◽  
Amy F Hofmann ◽  
Hugo W Tedford ◽  
Maurice P Lee
Keyword(s):  
Aspergillus Nidulans ◽  
Filamentous Fungus ◽  
Spore Germination ◽  
Temperature Sensitive ◽  
Normal Pattern ◽  
Hyphal Morphogenesis ◽  
Tube Emergence ◽  
Identification And Characterization

Abstract In the filamentous fungus Aspergillus nidulans, germination of an asexual conidiospore results in the formation of a hyphal cell. A key feature of spore germination is the switch from isotropic spore expansion to polarized apical growth. Here, temperature-sensitive mutations are used to characterize the roles of five genes (sepA, hypA, podB-podD) in the establishment and maintenance of hyphal polarity. Evidence that suggests that the hypA, podB, and sepA genes are required for multiple aspects of hyphal morphogenesis is presented. Notably, podB and sepA are needed for organization of the cytoskeleton at sites of polarized growth. In contrast, podC and podD encode proteins that appear to be specifically required for the establishment of hyphal polarity during spore germination. The role of sepA and the pod genes in controlling the spatial pattern of polarized morphogenesis in germinating spores is also described. Results obtained from these experiments indicate that the normal pattern of germ-tube emergence is dependent upon the integrity of the actin cytoskeleton.

scholarly journals From filopodia to synapses: the role of actin-capping and anti-capping proteins

2011 ◽  
Vol 34 (10) ◽  
pp. 1655-1662 ◽  
Author(s):  
Elisabetta Menna ◽  
Giuliana Fossati ◽  
Giorgio Scita ◽  
Michela Matteoli
Keyword(s):  
Capping Proteins ◽  
Actin Capping

scholarly journals Contribution of Ena/VASP Proteins to Intracellular Motility ofListeriaRequires Phosphorylation and Proline-rich Core but Not F-Actin Binding or Multimerization

2002 ◽  
Vol 13 (7) ◽  
pp. 2383-2396 ◽  
Author(s):  
Marcus Geese ◽  
Joseph J. Loureiro ◽  
James E. Bear ◽  
Jürgen Wehland ◽  
Frank B. Gertler ◽  
...  
Keyword(s):  
Bacterial Motility ◽  
Actin Binding ◽  
Rich Region ◽  
Bacterial Surface ◽  
Identification And Characterization ◽  
Actin Binding Site ◽  
Intracellular Motility ◽  
Proline Rich Region

The Listeria model system has been essential for the identification and characterization of key regulators of the actin cytoskeleton such as the Arp2/3 complex and Ena/vasodilator-stimulated phosphoprotein (VASP) proteins. Although the role of Ena/VASP proteins in Listeria motility has been extensively studied, little is known about the contributions of their domains and phosphorylation state to bacterial motility. To address these issues, we have generated a panel of Ena/VASP mutants and, upon expression in Ena/VASP-deficient cells, evaluated their contribution to Ena/VASP function in Listeria motility. The proline-rich region, the putative G-actin binding site, and the Ser/Thr phosphorylation of Ena/VASP proteins are all required for efficientListeria motility. Surprisingly, the interaction of Ena/VASP proteins with F-actin and their potential ability to form multimers are both dispensable for their involvement in this process. Our data suggest that Ena/VASP proteins contribute toListeria motility by regulating both the nucleation and elongation of actin filaments at the bacterial surface.

scholarly journals Vinculin–actin interaction couples actin retrograde flow to focal adhesions, but is dispensable for focal adhesion growth

2013 ◽  
Vol 202 (1) ◽  
pp. 163-177 ◽  
Author(s):  
Ingo Thievessen ◽  
Peter M. Thompson ◽  
Sylvain Berlemont ◽  
Karen M. Plevock ◽  
Sergey V. Plotnikov ◽  
...  
Keyword(s):  
Focal Adhesions ◽  
Leading Edge ◽  
Flow Speed ◽  
Actin Binding ◽  
Retrograde Flow ◽  
Actin Assembly ◽  
Filamentous Actin ◽  
Primary Fibroblasts

In migrating cells, integrin-based focal adhesions (FAs) assemble in protruding lamellipodia in association with rapid filamentous actin (F-actin) assembly and retrograde flow. How dynamic F-actin is coupled to FA is not known. We analyzed the role of vinculin in integrating F-actin and FA dynamics by vinculin gene disruption in primary fibroblasts. Vinculin slowed F-actin flow in maturing FA to establish a lamellipodium–lamellum border and generate high extracellular matrix (ECM) traction forces. In addition, vinculin promoted nascent FA formation and turnover in lamellipodia and inhibited the frequency and rate of FA maturation. Characterization of a vinculin point mutant that specifically disrupts F-actin binding showed that vinculin–F-actin interaction is critical for these functions. However, FA growth rate correlated with F-actin flow speed independently of vinculin. Thus, vinculin functions as a molecular clutch, organizing leading edge F-actin, generating ECM traction, and promoting FA formation and turnover, but vinculin is dispensible for FA growth.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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