scholarly journals The Abl-related gene (Arg) requires its F-actin–microtubule cross-linking activity to regulate lamellipodial dynamics during fibroblast adhesion

2004 ◽  
Vol 165 (3) ◽  
pp. 407-420 ◽  
Author(s):  
Ann L. Miller ◽  
Yinxiang Wang ◽  
Mark S. Mooseker ◽  
Anthony J. Koleske
Keyword(s):  
Molecular Mechanisms ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Physical Contact ◽  
Actin Binding ◽  
Cross Linking ◽  
Cell Periphery ◽  
Related Gene ◽  
Filamentous Actin ◽  
Protein Fusion

Microtubules (MTs) help establish and maintain cell polarity by promoting actin-dependent membrane protrusion at the leading edge of the cell, but the molecular mechanisms that mediate cross-talk between actin and MTs during this process are unclear. We demonstrate that the Abl-related gene (Arg) nonreceptor tyrosine kinase is required for dynamic lamellipodial protrusions after adhesion to fibronectin. arg−/− fibroblasts exhibit reduced lamellipodial dynamics as compared with wild-type fibroblasts, and this defect can be rescued by reexpression of an Arg-yellow fluorescent protein fusion. We show that Arg can bind MTs with high affinity and cross-link filamentous actin (F-actin) bundles and MTs in vitro. MTs concentrate and insert into Arg-induced F-actin–rich cell protrusions. Arg requires both its F-actin–binding domains and its MT-binding domain to rescue the defects in lamellipodial dynamics of arg−/− fibroblasts. These findings demonstrate that Arg can mediate physical contact between F-actin and MTs at the cell periphery and that this cross-linking activity is required for Arg to regulate lamellipodial dynamics in fibroblasts.

scholarly journals Microtubule-dependent distribution of mRNA in adult cardiocytes

2008 ◽  
Vol 294 (3) ◽  
pp. H1135-H1144 ◽  
Author(s):  
Dimitri Scholz ◽  
Catalin F. Baicu ◽  
William J. Tuxworth ◽  
Lin Xu ◽  
Harinath Kasiganesan ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Fluorescent Protein ◽  
Average Distance ◽  
Yellow Fluorescent Protein ◽  
Pressure Overload ◽  
Structural Protein ◽  
Protein Fusion ◽  
Microtubule Depolymerization ◽  
Microtubule Network ◽  
Hypertrophic Growth

Synthesis of myofibrillar proteins in the diffusion-restricted adult cardiocyte requires microtubule-based active transport of mRNAs as part of messenger ribonucleoprotein particles (mRNPs) to translation sites adjacent to nascent myofibrils. This is especially important for compensatory hypertrophy in response to hemodynamic overloading. The hypothesis tested here is that excessive microtubule decoration by microtubule-associated protein 4 (MAP4) after cardiac pressure overloading could disrupt mRNP transport and thus hypertrophic growth. MAP4-overexpressing and pressure-overload hypertrophied adult feline cardiocytes were infected with an adenovirus encoding zipcode-binding protein 1-enhanced yellow fluorescent protein fusion protein, which is incorporated into mRNPs, to allow imaging of these particles. Speed and distance of particle movement were measured via time-lapse microscopy. Microtubule depolymerization was used to study microtubule-based transport and distribution of mRNPs. Protein synthesis was assessed as radioautographic incorporation of [3H]phenylalanine. After microtubule depolymerization, mRNPs persist only perinuclearly and apparent mRNP production and protein synthesis decrease. Reestablishing microtubules restores mRNP production and transport as well as protein synthesis. MAP4 overdecoration of microtubules via adenovirus infection in vitro or following pressure overloading in vivo reduces the speed and average distance of mRNP movement. Thus cardiocyte microtubules are required for mRNP transport and structural protein synthesis, and MAP4 decoration of microtubules, whether directly imposed or accompanying pressure-overload hypertrophy, causes disruption of mRNP transport and protein synthesis. The dense, highly MAP4-decorated microtubule network seen in severe pressure-overload hypertrophy both may cause contractile dysfunction and, perhaps even more importantly, may prevent a fully compensatory growth response to hemodynamic overloading.

Barrier role of actin filaments in regulated mucin secretion from airway goblet cells

2005 ◽  
Vol 288 (1) ◽  
pp. C46-C56 ◽  
Author(s):  
Camille Ehre ◽  
Andrea H. Rossi ◽  
Lubna H. Abdullah ◽  
Kathleen De Pestel ◽  
Sandra Hill ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Filaments ◽  
Fluorescent Protein ◽  
Secretory Granules ◽  
Yellow Fluorescent Protein ◽  
Goblet Cells ◽  
Actin Binding ◽  
Secretory Cells ◽  
Cortical Actin ◽  
Mucin Secretion

Airway goblet cells secrete mucin onto mucosal surfaces under the regulation of an apical, phospholipase C/Gq-coupled P2Y2receptor. We tested whether cortical actin filaments negatively regulate exocytosis in goblet cells by forming a barrier between secretory granules and plasma membrane docking sites as postulated for other secretory cells. Immunostaining of human lung tissues and SPOC1 cells (an epithelial, mucin-secreting cell line) revealed an apical distribution of β- and γ-actin in ciliated and goblet cells. In goblet cells, actin appeared as a prominent subplasmalemmal sheet lying between granules and the apical membrane, and it disappeared from SPOC1 cells activated by purinergic agonist. Disruption of actin filaments with latrunculin A stimulated SPOC1 cell mucin secretion under basal and agonist-activated conditions, whereas stabilization with jasplakinolide or overexpression of β- or γ-actin conjugated to yellow fluorescent protein (YFP) inhibited secretion. Myristoylated alanine-rich C kinase substrate, a PKC-activated actin-plasma membrane tethering protein, was phosphorylated after agonist stimulation, suggesting a translocation to the cytosol. Scinderin (or adseverin), a Ca2+-activated actin filament severing and capping protein was cloned from human airway and SPOC1 cells, and synthetic peptides corresponding to its actin-binding domains inhibited mucin secretion. We conclude that actin filaments negatively regulate mucin secretion basally in airway goblet cells and are dynamically remodeled in agonist-stimulated cells to promote exocytosis.

Identity of the renin cell is mediated by cAMP and chromatin remodeling: an in vitro model for studying cell recruitment and plasticity

2008 ◽  
Vol 294 (2) ◽  
pp. H699-H707 ◽  
Author(s):  
Ellen Steward Pentz ◽  
Maria Luisa S. Sequeira Lopez ◽  
Magali Cordaillat ◽  
R. Ariel Gomez
Keyword(s):  
Chromatin Remodeling ◽  
In Vitro Model ◽  
Molecular Mechanisms ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Histone H4 Acetylation ◽  
Renin Gene ◽  
Vitro Model

The renin-angiotensin system (RAS) regulates blood pressure and fluid-electrolyte homeostasis. A key step in the RAS cascade is the regulation of renin synthesis and release by the kidney. We and others have shown that a major mechanism to control renin availability is the regulation of the number of cells capable of making renin. The kidney possesses a pool of cells, mainly in its vasculature but also in the glomeruli, capable of switching from smooth muscle to endocrine renin-producing cells when homeostasis is threatened. The molecular mechanisms governing the ability of these cells to turn the renin phenotype on and off have been very difficult to study in vivo. We, therefore, developed an in vitro model in which cells of the renin lineage are labeled with cyan fluorescent protein and cells actively making renin mRNA are labeled with yellow fluorescent protein. The model allowed us to determine that it is possible to culture cells of the renin lineage for numerous passages and that the memory to express the renin gene is maintained in culture and can be reenacted by cAMP and chromatin remodeling (histone H4 acetylation) at the cAMP-responsive element in the renin gene.

scholarly journals Oligomeric Sensor Kinase DcuS in the Membrane of Escherichia coli and in Proteoliposomes: Chemical Cross-linking and FRET Spectroscopy

2010 ◽  
Vol 192 (13) ◽  
pp. 3474-3483 ◽  
Author(s):  
Patrick D. Scheu ◽  
Yun-Feng Liao ◽  
Julia Bauer ◽  
Holger Kneuper ◽  
Thomas Basché ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Living Cells ◽  
Full Length ◽  
Cross Linking ◽  
Oligomeric State ◽  
Bacterial Membranes ◽  
Chemical Cross Linking

ABSTRACT DcuS is the membrane-integral sensor histidine kinase of the DcuSR two-component system in Escherichia coli that responds to extracellular C4-dicarboxylates. The oligomeric state of full-length DcuS was investigated in vitro and in living cells by chemical cross-linking and by f luorescence r esonance e nergy t ransfer (FRET) spectroscopy. The FRET results were quantified by an improved method using background-free spectra of living cells for determining FRET efficiency (E) and donor fraction {fD = (donor)/[(donor) + (acceptor)]}. Functional fusions of cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) variants of green fluorescent protein to DcuS were used for in vivo FRET measurements. Based on noninteracting membrane proteins and perfectly interacting proteins (a CFP-YFP fusion), the results of FRET of cells coexpressing DcuS-CFP and DcuS-YFP were quantitatively evaluated. In living cells and after reconstitution of purified recombinant DcuS in proteoliposomes, DcuS was found as a dimer or higher oligomer, independent of the presence of an effector. Chemical cross-linking with disuccinimidyl suberate showed tetrameric, in addition to dimeric, DcuS in proteoliposomes and in membranes of bacteria, whereas purified DcuS in nondenaturing detergent was mainly monomeric. The presence and amount of tetrameric DcuS in vivo and in proteoliposomes was not dependent on the concentration of DcuS. Only membrane-embedded DcuS (present in the oligomeric state) is active in (auto)phosphorylation. Overall, the FRET and cross-linking data demonstrate the presence in living cells, in bacterial membranes, and in proteoliposomes of full-length DcuS protein in an oligomeric state, including a tetramer.

scholarly journals Endoplasmic Reticulum Dynamics, Inheritance, and Cytoskeletal Interactions in Budding Yeast

2002 ◽  
Vol 13 (3) ◽  
pp. 854-865 ◽  
Author(s):  
K. L. Fehrenbacher ◽  
D. Davis ◽  
M. Wu ◽  
I. Boldogh ◽  
Liza A. Pon
Keyword(s):  
Endoplasmic Reticulum ◽  
Fluorescent Protein ◽  
Yeast Cells ◽  
Cell Cortex ◽  
Filamentous Actin ◽  
Protein Fusion ◽  
Directed Movement ◽  
Apical Bud ◽  
M Phase ◽  
Green Fluorescent

The endoplasmic reticulum (ER) in Saccharomyces cerevisiae consists of a reticulum underlying the plasma membrane (cortical ER) and ER associated with the nuclear envelope (nuclear ER). We used a Sec63p-green fluorescent protein fusion protein to study motility events associated with inheritance of cortical ER and nuclear ER in living yeast cells. During M phase before nuclear migration, we observed thick, apparently rigid tubular extensions emanating from the nuclear ER that elongate, undergo sweeping motions along the cell cortex, and shorten. Two findings support a role for microtubules in this process. First, extension of tubular structures from the nuclear ER is inhibited by destabilization of microtubules. Second, astral microtubules, structures that undergo similar patterns of extension, cortical surveillance and retraction, colocalize with nuclear ER extensions. During S and G2 phases of the cell cycle, we observed anchorage of the cortical ER at the site of bud emergence and apical bud growth. Thin tubules of the ER that extend from the anchored cortical ER display undulating, apparently random movement and move into the bud as it grows. Finally, we found that cortical ER morphology is sensitive to a filamentous actin–destabilizing drug, latrunculin-A, and to mutations in the actin-encoding ACT1 gene. Our observations support 1) different mechanisms and cytoskeletal mediators for the inheritance of nuclear and cortical ER elements and 2) a mechanism for cortical ER inheritance that is cytoskeleton dependent but relies on anchorage, not directed movement.

scholarly journals Dynamic localization of two tobamovirus ORF6 proteins involves distinct organellar compartments

2013 ◽  
Vol 94 (1) ◽  
pp. 230-240 ◽  
Author(s):  
Vladimir A. Gushchin ◽  
Nina I. Lukhovitskaya ◽  
Dmitri E. Andreev ◽  
Kathryn M. Wright ◽  
Michael E. Taliansky ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Tobacco Rattle Virus ◽  
Tomato Mosaic Virus ◽  
Protein Fusion ◽  
Orf6 Gene ◽  
Orf6 Protein

ORF6 is a small gene that overlaps the movement and coat protein genes of subgroup 1a tobamoviruses. The ORF6 protein of tomato mosaic virus (ToMV) strain L (L-ORF6), interacts in vitro with eukaryotic elongation factor 1α, and mutation of the ORF6 gene of tobacco mosaic virus (TMV) strain U1 (U1-ORF6) reduces the pathogenicity in vivo of TMV, whereas expression of this gene from two other viruses, tobacco rattle virus (TRV) and potato virus X (PVX), increases their pathogenicity. In this work, the in vivo properties of the L-ORF6 and U1-ORF6 proteins were compared to identify sequences that direct the proteins to different subcellular locations and also influence virus pathogenicity. Site-specific mutations in the ORF6 protein were made, hybrid ORF6 proteins were created in which the N-terminal and C-terminal parts were derived from the two proteins, and different subregions of the protein were examined, using expression either from a recombinant TRV vector or as a yellow fluorescent protein fusion from a binary plasmid in Agrobacterium tumefaciens. L-ORF6 caused mild necrotic symptoms in Nicotiana benthamiana when expressed from TRV, whereas U1-ORF6 caused severe symptoms including death of the plant apex. The difference in symptoms was associated with the C-terminal region of L-ORF6, which directed the protein to the endoplasmic reticulum (ER), whereas U1-ORF6 was directed initially to the nucleolus and later to the mitochondria. Positively charged residues at the N terminus allowed nucleolar entry of both U1-ORF6 and L-ORF6, but hydrophobic residues at the C terminus of L-ORF6 directed this protein to the ER.

scholarly journals The Spectraplakin Short Stop Is an Actin–Microtubule Cross-Linker That Contributes to Organization of the Microtubule Network

2010 ◽  
Vol 21 (10) ◽  
pp. 1714-1724 ◽  
Author(s):  
Derek A. Applewhite ◽  
Kyle D. Grode ◽  
Darby Keller ◽  
Alireza Dehghani Zadeh ◽  
Kevin C. Slep ◽  
...  
Keyword(s):  
Cross Talk ◽  
Function Analysis ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Cross Linking ◽  
Cell Periphery ◽  
Cellular Functions ◽  
Microtubule Organization ◽  
Microtubule Network ◽  
Cross Linker

The dynamics of actin and microtubules are coordinated in a variety of cellular and morphogenetic processes; however, little is known about the molecules mediating this cytoskeletal cross-talk. We are studying Short stop (Shot), the sole Drosophila spectraplakin, as a model actin–microtubule cross-linking protein. Spectraplakins are an ancient family of giant cytoskeletal proteins that are essential for a diverse set of cellular functions; yet, we know little about the dynamics of spectraplakins and how they bridge actin filaments and microtubules. In this study we describe the intracellular dynamics of Shot and a structure–function analysis of its role as a cytoskeletal cross-linker. We find that Shot interacts with microtubules using two different mechanisms. In the cell interior, Shot binds growing plus ends through an interaction with EB1. In the cell periphery, Shot associates with the microtubule lattice via its GAS2 domain, and this pool of Shot is actively engaged as a cross-linker via its NH2-terminal actin-binding calponin homology domains. This cross-linking maintains microtubule organization by resisting forces that produce lateral microtubule movements in the cytoplasm. Our results provide the first description of the dynamics of these important proteins and provide key insight about how they function during cytoskeletal cross-talk.

scholarly journals A Herpes Simplex Virus gD-YFP Fusion Glycoprotein Is Transported Separately from Viral Capsids in Neuronal Axons

2007 ◽  
Vol 81 (15) ◽  
pp. 8337-8340 ◽  
Author(s):  
Aleksandra Snyder ◽  
Birgitte Bruun ◽  
Helena M. Browne ◽  
David C. Johnson
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Pseudorabies Virus ◽  
Fluorescent Protein ◽  
Yellow Fluorescent Protein ◽  
Protein Fusion ◽  
Anterograde Transport ◽  
Viral Capsids ◽  
Antibody Staining ◽  
Simplex Virus

ABSTRACT Two models describing how alphaherpesviruses exit neurons differ with respect to whether nucleocapsids and envelope glycoproteins travel toward axon termini separately or as assembled enveloped virions. Recently, a pseudorabies virus glycoprotein D (gD)-green fluorescent protein fusion was found to colocalize with viral capsids, supporting anterograde transport of enveloped virions. Previous antibody staining experiments demonstrated that herpes simplex virus (HSV) glycoproteins and capsids are separately transported in axons. Here, we generated an HSV expressing a gD-yellow fluorescent protein (YFP) fusion and found that gD-YFP and capsids were transported separately in neuronal axons. Anti-gD antibodies colocalized with gD-YFP, indicating that gD-YFP behaves like wild-type HSV gD.

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