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 Rtn1p Is Involved in Structuring the Cortical Endoplasmic Reticulum

2006 ◽  
Vol 17 (7) ◽  
pp. 3009-3020 ◽  
Author(s):  
Johan-Owen De Craene ◽  
Jeff Coleman ◽  
Paula Estrada de Martin ◽  
Marc Pypaert ◽  
Scott Anderson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Cell Cortex ◽  
Proteomic Screen ◽  
Wide Range ◽  
Membrane Spanning ◽  
Green Fluorescent ◽  
Hydrophilic Loop ◽  
Yeast Mutants

The endoplasmic reticulum (ER) contains both cisternal and reticular elements in one contiguous structure. We identified rtn1Δ in a systematic screen for yeast mutants with altered ER morphology. The ER in rtn1Δ cells is predominantly cisternal rather than reticular, yet the net surface area of ER is not significantly changed. Rtn1-green fluorescent protein (GFP) associates with the reticular ER at the cell cortex and with the tubules that connect the cortical ER to the nuclear envelope, but not with the nuclear envelope itself. Rtn1p overexpression also results in an altered ER structure. Rtn proteins are found on the ER in a wide range of eukaryotes and are defined by two membrane-spanning domains flanking a conserved hydrophilic loop. Our results suggest that Rtn proteins may direct the formation of reticulated ER. We independently identified Rtn1p in a proteomic screen for proteins associated with the exocyst vesicle tethering complex. The conserved hydophilic loop of Rtn1p binds to the exocyst subunit Sec6p. Overexpression of this loop results in a modest accumulation of secretory vesicles, suggesting impaired exocyst function. The interaction of Rtn1p with the exocyst at the bud tip may trigger the formation of a cortical ER network in yeast buds.

scholarly journals Microtubules Orient the Mitotic Spindle in Yeast through Dynein-dependent Interactions with the Cell Cortex

1997 ◽  
Vol 138 (3) ◽  
pp. 629-641 ◽  
Author(s):  
Janet L. Carminati ◽  
Tim Stearns
Keyword(s):  
Mitotic Spindle ◽  
Fluorescent Protein ◽  
Dynamic Instability ◽  
Dynamic Properties ◽  
Yeast Cells ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Animal Cells ◽  
Green Fluorescent ◽  
Mutant Cells

Proper orientation of the mitotic spindle is critical for successful cell division in budding yeast. To investigate the mechanism of spindle orientation, we used a green fluorescent protein (GFP)–tubulin fusion protein to observe microtubules in living yeast cells. GFP–tubulin is incorporated into microtubules, allowing visualization of both cytoplasmic and spindle microtubules, and does not interfere with normal microtubule function. Microtubules in yeast cells exhibit dynamic instability, although they grow and shrink more slowly than microtubules in animal cells. The dynamic properties of yeast microtubules are modulated during the cell cycle. The behavior of cytoplasmic microtubules revealed distinct interactions with the cell cortex that result in associated spindle movement and orientation. Dynein-mutant cells had defects in these cortical interactions, resulting in misoriented spindles. In addition, microtubule dynamics were altered in the absence of dynein. These results indicate that microtubules and dynein interact to produce dynamic cortical interactions, and that these interactions result in the force driving spindle orientation.

scholarly journals Daip1, a Dictyostelium Homologue of the Yeast Actin-Interacting Protein 1, Is Involved in Endocytosis, Cytokinesis, and Motility

1999 ◽  
Vol 146 (2) ◽  
pp. 453-464 ◽  
Author(s):  
Angelika Konzok ◽  
Igor Weber ◽  
Evelyn Simmeth ◽  
Ulrike Hacker ◽  
Markus Maniak ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Fluid Phase ◽  
Gene Replacement ◽  
Cell Cortex ◽  
Filamentous Actin ◽  
Cortical Actin ◽  
Interacting Protein ◽  
Phagocytic Cups ◽  
Green Fluorescent

The 64-kD protein DAip1 from Dictyostelium contains nine WD40-repeats and is homologous to the actin-interacting protein 1, Aip1p, from Saccharomyces cerevisiae, and to related proteins from Caenorhabditis, Physarum, and higher eukaryotes. We show that DAip1 is localized to dynamic regions of the cell cortex that are enriched in filamentous actin: phagocytic cups, macropinosomes, lamellipodia, and other pseudopodia. In cells expressing green fluorescent protein (GFP)-tagged DAip1, the protein rapidly redistributes into newly formed cortical protrusions. Functions of DAip1 in vivo were assessed using null mutants generated by gene replacement, and by overexpressing DAip1. DAip1-null cells are impaired in growth and their rates of fluid-phase uptake, phagocytosis, and movement are reduced in comparison to wild-type rates. Cytokinesis is prolonged in DAip1-null cells and they tend to become multinucleate. On the basis of similar results obtained by DAip1 overexpression and effects of latrunculin-A treatment, we propose a function for DAip1 in the control of actin depolymerization in vivo, probably through interaction with cofilin. Our data suggest that DAip1 plays an important regulatory role in the rapid remodeling of the cortical actin meshwork.

scholarly journals Saccharomyces cerevisiae Aqr1 Is an Internal-Membrane Transporter Involved in Excretion of Amino Acids

2004 ◽  
Vol 3 (6) ◽  
pp. 1492-1503 ◽  
Author(s):  
Isabel Velasco ◽  
Sandra Tenreiro ◽  
Isabel L. Calderon ◽  
Bruno André
Keyword(s):  
Amino Acids ◽  
Reverse Genetics ◽  
Fluorescent Protein ◽  
Negative Control ◽  
Yeast Cells ◽  
Green Fluorescent Protein Fusion ◽  
Protein Fusion ◽  
Membrane Structures ◽  
Internal Membrane ◽  
Green Fluorescent

ABSTRACT Excretion of amino acids by yeast cells was reported long ago but has not been characterized in molecular terms. It is typically favored by overproduction of the amino acid and/or impairment of its uptake. Here we describe the construction of a yeast strain excreting threonine and homoserine. Using this excretor strain, we then applied a reverse-genetics approach and found that the transporter encoded by the YNL065w/AQR1 gene, a protein thought to mediate H+ antiport, is involved in homoserine and threonine excretion. Furthermore, overexpression of AQR1 led to increased excretion of several amino acids (alanine, aspartate, and glutamate) known to be relatively abundant in the cytosol. Transcription of the AQR1 gene is induced severalfold by a number of amino acids and appears to be under the negative control of Gcn4. An Aqr1-green fluorescent protein fusion protein is located in multiple internal membrane structures and appears to cycle continuously between these compartments and the plasma membrane. The Aqr1 sequence is significantly similar to the vesicular amine transporters of secretory vesicles of neuronal cells. We propose that Aqr1 catalyzes transport of excess amino acids into vesicles, which then release them in the extracellular space by exocytosis.

scholarly journals Induction of Distinct [URE3] Yeast Prion Strains

2001 ◽  
Vol 21 (20) ◽  
pp. 7035-7046 ◽  
Author(s):  
Martin Schlumpberger ◽  
Stanley B. Prusiner ◽  
Ira Herskowitz
Keyword(s):  
Fluorescent Protein ◽  
Regulatory Region ◽  
Type A ◽  
Full Length ◽  
Yeast Cells ◽  
Type B ◽  
Protein Fusion ◽  
Inactive Form ◽  
Colony Color ◽  
Green Fluorescent

ABSTRACT [URE3] is a non-Mendelian genetic element inSaccharomyces cerevisiae, which is caused by a prion-like, autocatalytic conversion of the Ure2 protein (Ure2p) into an inactive form. The presence of [URE3] allows yeast cells to take up ureidosuccinic acid in the presence of ammonia. This phenotype can be used to select for the prion state. We have developed a novel reporter, in which the ADE2 gene is controlled by the DAL5 regulatory region, which allows monitoring of Ure2p function by a colony color phenotype. Using this reporter, we observed induction of different [URE3] prion variants (“strains”) following overexpression of the N-terminal Ure2p prion domain (UPD) or full-length Ure2p. Full-length Ure2p induced two types of [URE3]: type A corresponds to conventional [URE3], whereas the novel type B variant is characterized by relatively high residual Ure2p activity and efficient curing by coexpression of low amounts of a UPD-green fluorescent protein fusion protein. Overexpression of UPD induced type B [URE3] but not type A. Both type A and B [URE3] strains, as well as weak and strong isolates of type A, were shown to stably maintain different prion strain characteristics. We suggest that these strain variants result from different modes of aggregation of similar Ure2p monomers. We also demonstrate a procedure to counterselect against the [URE3] state.

scholarly journals Interactions and Nuclear Import of the N and P Proteins of Sonchus Yellow Net Virus, a Plant Nucleorhabdovirus

2001 ◽  
Vol 75 (19) ◽  
pp. 9393-9406 ◽  
Author(s):  
Michael M. Goodin ◽  
Jennifer Austin ◽  
Renée Tobias ◽  
Miki Fujita ◽  
Christina Morales ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nuclear Localization ◽  
Nuclear Import ◽  
Fluorescent Protein ◽  
Yeast Cells ◽  
Protein Fusion ◽  
N Protein ◽  
Subnuclear Localization ◽  
P Proteins ◽  
Green Fluorescent

ABSTRACT We have characterized the interaction and nuclear localization of the nucleocapsid (N) protein and phosphoprotein (P) of sonchus yellow net nucleorhabdovirus. Expression studies with plant and yeast cells revealed that both N and P are capable of independent nuclear import. Site-specific mutagenesis and deletion analyses demonstrated that N contains a carboxy-terminal bipartite nuclear localization signal (NLS) located between amino acids 465 and 481 and that P contains a karyophillic region between amino acids 40 and 124. The N NLS was fully capable of functioning outside of the context of the N protein and was able to direct the nuclear import of a synthetic protein fusion consisting of green fluorescent protein fused to glutathioneS-transferase (GST). Expression and mapping studies suggested that the karyophillic domain in P is located within the N-binding domain. Coexpression of N and P drastically affected their localization patterns relative to those of individually expressed proteins and resulted in a shift of both proteins to a subnuclear region. Yeast two-hybrid and GST pulldown experiments verified the N-P and P-P interactions, and deletion analyses have identified the N and P interacting domains. N NLS mutants were not transported to the nucleus by import-competent P, presumably because N binding masks the P NLS. Taken together, our results support a model for independent entry of N and P into the nucleus followed by associations that mediate subnuclear localization.

scholarly journals Cloning and Characterization of an Ovine Intracellular Seven Transmembrane Receptor for Progesterone that Mediates Calcium Mobilization

Endocrinology ◽  
2006 ◽  
Vol 147 (9) ◽  
pp. 4151-4159 ◽  
Author(s):  
R. L. Ashley ◽  
C. M. Clay ◽  
T. A. Farmerie ◽  
G. D. Niswender ◽  
T. M. Nett
Keyword(s):  
Endoplasmic Reticulum ◽  
Cho Cells ◽  
Cellular Localization ◽  
Fluorescent Protein ◽  
Specific Binding ◽  
Protein Fusion ◽  
Acid Protein ◽  
Modulation Of Gene Expression ◽  
Hydroxy Progesterone ◽  
Green Fluorescent

Classically, progesterone has been thought to act only through the well-known genomic pathway involving hormone binding to nuclear receptors (nPR) and subsequent modulation of gene expression. However, there is increasing evidence for rapid, nongenomic effects of progesterone in a variety of tissues in mammals, and it seems likely that a membrane PR (mPR) is causing these events. The objective of this study was to isolate and characterize an ovine mPR distinct from the nPR. A cDNA clone was isolated from ovine genomic DNA by PCR. The ovine mPR is a 350-amino acid protein that, based on computer hydrophobicity analysis, possesses seven transmembrane domains and is distinct from the nPR. Message for the ovine mPR was detected in hypothalamus, pituitary, uterus, ovary, and corpus luteum by RT-PCR. In CHO cells that overexpressed a mPR-green fluorescent protein fusion protein, the ovine mPR was localized to the endoplasmic reticulum and not the plasma membrane. Specific binding of 3H-progesterone to membrane fractions was demonstrated in CHO cells that expressed the ovine mPR but not in nontransfected cells. Furthermore, progesterone and 17α-hydroxy-progesterone stimulated intracellular Ca2+ mobilization in CHO cells that expressed ovine mPR in Ca2+-free medium (P < 0.05) but not in CHO cells transfected with empty vector. This rise in intracellular Ca2+ is believed to be from the endoplasmic reticulum as intracellular Ca2+ mobilization is absent when mPR transfected cells are first treated with thapsigargin to deplete Ca2+ stores from the endoplasmic reticulum. Isolation, identification, tissue distribution, cellular localization, steroid binding, and a functional response for a unique intracellular mPR in the sheep are presented.

scholarly journals Evidence of a Continuous Endoplasmic Reticulum in the Protozoan Parasite Entamoeba histolytica

2008 ◽  
Vol 7 (7) ◽  
pp. 1222-1226 ◽  
Author(s):  
Jose E. Teixeira ◽  
Christopher D. Huston
Keyword(s):  
Endoplasmic Reticulum ◽  
Green Fluorescent Protein ◽  
Fusion Protein ◽  
Entamoeba Histolytica ◽  
Fluorescent Protein ◽  
Protozoan Parasite ◽  
Green Fluorescent Protein Fusion ◽  
Protein Fusion ◽  
Green Fluorescent

ABSTRACT Entamoeba histolytica, the cause of amebiasis, is believed to have no continuous endoplasmic reticulum (ER), with ER functions occurring in vesicles. Here, using an ER-targeted green fluorescent protein fusion protein and fluorescence loss in photobleaching, we have unambiguously demonstrated the presence of a continuous ER compartment in living E. histolytica trophozoites.

Organization of transport from endoplasmic reticulum to Golgi in higher plants

2000 ◽  
Vol 28 (4) ◽  
pp. 505-512 ◽  
Author(s):  
A. V. Andreeva ◽  
H. Zheng ◽  
C. M. Saint-Jore ◽  
M. A. Kutuzov ◽  
D. E. Evans ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Fluorescent Protein ◽  
Higher Plants ◽  
Plant Cells ◽  
Yeast Cells ◽  
Green Fluorescent

In plant cells, the organization of the Golgi apparatus and its interrelationships with the endoplasmic reticulum differ from those in mammalian and yeast cells. Endoplasmic reticulum and Golgi apparatus can now be visualized in plant cells in vivo with green fluorescent protein (GFP) specifically directed to these compartments. This makes it possible to study the dynamics of the membrane transport between these two organelles in the living cells. The GFP approach, in conjunction with a considerable volume of data about proteins participating in the transport between endoplasmic reticulum and Golgi in yeast and mammalian cells and the identification of their putative plant homologues, should allow the establishment of an experimental model in which to test the involvement of the candidate proteins in plants. As a first step towards the development of such a system, we are using Sar1, a small G-protein necessary for vesicle budding from the endoplasmic reticulum. This work has demonstrated that the introduction of Sar1 mutants blocks the transport from endoplasmic reticulum to Golgi in vivo in tobacco leaf epidermal cells and has therefore confirmed the feasibility of this approach to test the function of other proteins that are presumably involved in this step of endo-membrane trafficking in plant cells.

scholarly journals Synaptotagmins at the endoplasmic reticulum–plasma membrane contact sites maintain diacylglycerol homeostasis during abiotic stress

2021 ◽  
Author(s):  
Noemi Ruiz-Lopez ◽  
Jessica Pérez-Sancho ◽  
Alicia Esteban del Valle ◽  
Richard P Haslam ◽  
Steffen Vanneste ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Abiotic Stress ◽  
Fluorescent Protein ◽  
Mechanical Damage ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Green Fluorescent

Abstract Endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased plasma membrane (PM) integrity under multiple abiotic stresses such as freezing, high salt, osmotic stress and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild type while the levels of most glycerolipid species remain unchanged. Additionally, the SYT1-green fluorescent protein (GFP) fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.

Sign in / Sign up

Export Citation Format

Share Document