scholarly journals A SAC phosphoinositide phosphatase controls rice development via hydrolyzing phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate

2019 ◽  
Author(s):  
Tao Guo ◽  
Hua-Chang Chen ◽  
Zi-Qi Lu ◽  
Min Diao ◽  
Ke Chen ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Membrane Lipids ◽  
Dependent Manner ◽  
Cytoskeleton Organization ◽  
Cellular Processes ◽  
Phosphoinositide Phosphatase ◽  
Actin Cytoskeleton Organization ◽  
Phosphatidylinositol 4 ◽  
Related Proteins

AbstractPhosphoinositides (PIs) as regulatory membrane lipids play essential roles in multiple cellular processes. Although the exact molecular targets of PIs-dependent modulation remain largely elusive, the effects of disturbed PIs metabolism could be employed to propose regulatory modules associated with particular downstream targets of PIs. Here, we identified the role of GRAIN NUMBER AND PLANT HEIGHT 1 (GH1), which encodes a suppressor of actin (SAC) domain-containing phosphatase with unknown function in rice. Endoplasmic reticulum-localized GH1 specifically dephosphorylated and hydrolyzed phosphatidylinositol 4-phosphate (PI4P) and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Inactivation of GH1 resulted in massive accumulation of both PI4P and PI(4,5)P2, while excessive GH1 caused their depletion. Notably, superabundant PI4P and PI(4,5)P2 could both disrupt actin cytoskeleton organization and suppress cell elongation. Interestingly, both PI4P and PI(4,5)P2 inhibited actin-related proteins 2 and 3 (Arp2/3) complex-nucleated actin branching networks in vitro, whereas PI(4,5)P2 showed more dramatic effect in a dose-dependent manner. Overall, the overaccumulation of PI(4,5)P2 resulted from dysfunction of SAC phosphatase possibly perturbs Arp2/3 complex-mediated actin polymerization, thereby disordering the cell development. These findings imply that Arp2/3 complex might be the potential molecular target of PI(4,5)P2-dependent modulation in eukaryotes, thereby providing new insights into the relationship between PIs homeostasis and plants growth and development.

scholarly journals Regulation of the Actin Cytoskeleton Organization in Yeast by a Novel Serine/Threonine Kinase Prk1p

1999 ◽  
Vol 144 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Guisheng Zeng ◽  
Mingjie Cai
Keyword(s):  
Actin Cytoskeleton ◽  
Asymmetric Distribution ◽  
Wild Type ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Cytoskeleton Organization ◽  
Actin Cytoskeleton Organization ◽  
Related Proteins ◽  
Regulation Of Actin Cytoskeleton

Normal actin cytoskeleton organization in budding yeast requires the function of the Pan1p/ End3p complex. Mutations in PAN1 and END3 cause defects in the organization of actin cytoskeleton and endocytosis. By screening for mutations that can suppress the temperature sensitivity of a pan1 mutant (pan1-4), a novel serine/threonine kinase Prk1p is now identified as a new factor regulating the actin cytoskeleton organization in yeast. The suppression of pan1-4 by prk1 requires the presence of mutant Pan1p. Although viable, the prk1 mutant is unable to maintain an asymmetric distribution of the actin cytoskeleton at 37°C. Consistent with its role in the regulation of actin cytoskeleton, Prk1p localizes to the regions of cell growth and coincides with the polarized actin patches. Overexpression of the PRK1 gene in wild-type cells leads to lethality and actin cytoskeleton abnormalities similar to those exhibited by the pan1 and end3 mutants. In vitro phosphorylation assays demonstrate that Prk1p is able to phosphorylate regions of Pan1p containing the LxxQxTG repeats, including the region responsible for binding to End3p. Based on these findings, we propose that the Prk1 protein kinase regulates the actin cytoskeleton organization by modulating the activities of some actin cytoskeleton-related proteins such as Pan1p/End3p.

scholarly journals Sac1 Lipid Phosphatase and Stt4 Phosphatidylinositol 4-Kinase Regulate a Pool of Phosphatidylinositol 4-Phosphate That Functions in the Control of the Actin Cytoskeleton and Vacuole Morphology

2001 ◽  
Vol 12 (8) ◽  
pp. 2396-2411 ◽  
Author(s):  
Michelangelo Foti ◽  
Anjon Audhya ◽  
Scott D. Emr
Keyword(s):  
Actin Cytoskeleton ◽  
Temperature Sensitive ◽  
Primary Role ◽  
Cytoskeleton Organization ◽  
Phosphoinositide Phosphatase ◽  
Actin Cytoskeleton Organization ◽  
Sensitive Allele ◽  
Phosphatidylinositol 4 ◽  
Mutant Cells

Synthesis and turnover of phosphoinositides are tightly regulated processes mediated by a set of recently identified kinases and phosphatases. We analyzed the primary role of the phosphoinositide phosphatase Sac1p in Saccharomyces cerevisiae with the use of a temperature-sensitive allele of this gene. Our analysis demonstrates that inactivation of Sac1p leads to a specific increase in the cellular levels of phosphatidylinositol 4-phosphate (PtdIns(4)P), accompanied by changes in vacuole morphology and an accumulation of lipid droplets. We have found that the majority of Sac1p localizes to the endoplasmic reticulum, and this localization is crucial for the efficient turnover of PtdIns(4)P. By generating double mutant strains harboring the sac1tsallele and one of two temperature-sensitive PtdIns 4-kinase genes,stt4tsor pik1ts, we have demonstrated that the bulk of PtdIns(4)P that accumulates insac1 mutant cells is generated by the Stt4 PtdIns 4-kinase, and not Pik1p. Consistent with these findings, inactivation of Sac1p partially rescued defects associated withstt4tsbut notpik1tsmutant cells. To analyze potential overlapping functions between Sac1p and other homologous phosphoinositide phosphatases, sac1tsmutant cells lacking various other synaptojanin-like phosphatases were generated. These double and triple mutants exacerbated the accumulation of intracellular phosphoinositides and caused defects in Golgi function. Together, our results demonstrate that Sac1p primarily turns over Stt4p-generated PtdIns(4)P and that the membrane localization of Sac1p is important for its function in vivo. Regulation of this PtdIns(4)P pool appears to be crucial for the maintenance of vacuole morphology, regulation of lipid storage, Golgi function, and actin cytoskeleton organization.

SH3 domain-containing proteins and the actin cytoskeleton in yeast

2005 ◽  
Vol 33 (6) ◽  
pp. 1247-1249 ◽  
Author(s):  
G. Mirey ◽  
A. Soulard ◽  
C. Orange ◽  
S. Friant ◽  
B. Winsor
Keyword(s):  
Actin Cytoskeleton ◽  
Protein Interactions ◽  
Membrane Trafficking ◽  
Actin Polymerization ◽  
Protein Protein Interactions ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sh3 Domains ◽  
Cytoskeleton Organization ◽  
Actin Cytoskeleton Organization

SH3 (Src homology-3) domains are involved in protein–protein interactions through proline-rich domains. Many SH3-containing proteins are implicated in actin cytoskeleton organization. The aim of our ongoing work is to study the functions of the SH3-containing proteins in actin cytoskeleton regulation. The yeast Saccharomyces cerevisiae proteome includes 29 SH3 domains distributed in 25 proteins. We have examined the direct involvement of these SH3 domains in actin polymerization using an in vitro polymerization assay on GST (glutathione S-transferase)–SH3-coated beads. As expected, not all SH3 domains show polymerization activity, and many recruit distinct partners as assessed by microscopy and pull-down experiments. One such partner, Las17p, the yeast homologue of WASP (Wiskott–Aldrich syndrome protein), was assayed because it stimulates actin nucleation via the Arp2/3 (actin-related protein 2/3) complex. Ultimately, proteins involved in specific biological processes, such as membrane trafficking, may also be recruited by some of these SH3 domains, shedding light on the SH3-containing proteins and actin cytoskeleton functions in these processes.

scholarly journals Multiple repeat elements within the FAM21 tail link the WASH actin regulatory complex to the retromer

2012 ◽  
Vol 23 (12) ◽  
pp. 2352-2361 ◽  
Author(s):  
Da Jia ◽  
Timothy S. Gomez ◽  
Daniel D. Billadeau ◽  
Michael K. Rosen
Keyword(s):  
Actin Polymerization ◽  
Isothermal Calorimetry ◽  
Actin Dynamics ◽  
Bacterial Invasion ◽  
Dependent Manner ◽  
Repeat Elements ◽  
Cellular Processes ◽  
Regulatory Complex ◽  
Syndrome Protein

Wiskott–Aldrich syndrome protein (WASPs) control actin dynamics in cellular processes, including cell motility, receptor-mediated endocytosis, bacterial invasion, and vesicular trafficking. We demonstrated that WASH, a recently identified WASP family protein, colocalizes on endosomal subdomains with the cargo-selective complex (CSC) of the retromer, where it regulates retrograde sorting from endosomes in an actin-dependent manner. However, the mechanism of WASH recruitment to these retromer-enriched endosomal subdomains is unclear. Here we show that a component of the WASH regulatory complex (SHRC), FAM21, which contains 21 copies of a novel L-F-[D/E]3-10-L-F motif, directly interacts with the retromer CSC protein VPS35. Endosomal localization of FAM21 is VPS35 dependent and relies on multivalency of FAM21 repeat elements. Using a combination of pull-down assays and isothermal calorimetry, we demonstrate that individual repeats can bind CSC, and binding affinity varies among different FAM21 repeats. A high-affinity repeat can be converted into a low-affinity one by mutation of a hydrophobic residue within the motif. These in vitro data mirror the localization of FAM21 to retromer-coated vesicles in cells. We propose that multivalency enables FAM21 to sense the density of retromer on membranes, allowing coordination of SHRC recruitment, and consequent actin polymerization, with retromer sorting domain organization/maturation.

scholarly journals The Fibrinogen Globe of Tenascin-C Promotes Basic Fibroblast Growth Factor-induced Endothelial Cell Elongation

1999 ◽  
Vol 10 (9) ◽  
pp. 2933-2943 ◽  
Author(s):  
Susanne Schenk ◽  
Ruth Chiquet-Ehrismann ◽  
Edouard J. Battegay
Keyword(s):  
Endothelial Cells ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Basic Fibroblast Growth Factor ◽  
Fibroblast Growth ◽  
Aortic Endothelial Cells ◽  
Tenascin C ◽  
Cytoskeleton Organization ◽  
Actin Cytoskeleton Organization

To investigate the potential role of tenascin-C (TN-C) on endothelial sprouting we used bovine aortic endothelial cells (BAECs) as an in vitro model of angiogenesis. We found that TN-C is specifically expressed by sprouting and cord-forming BAECs but not by nonsprouting BAECs. To test whether TN-C alone or in combination with basic fibroblast growth factor (bFGF) can enhance endothelial sprouting or cord formation, we used BAECs that normally do not sprout and, fittingly, do not express TN-C. In the presence of bFGF, exogenous TN-C but not fibronectin induced an elongated phenotype in nonsprouting BAECs. This phenotype was due to altered actin cytoskeleton organization. The fibrinogen globe of the TN-C molecule was the active domain promoting the elongated phenotype in response to bFGF. Furthermore, we found that the fibrinogen globe was responsible for reduced cell adhesion of BAECs on TN-C substrates. We conclude that bFGF-stimulated endothelial cells can be switched to a sprouting phenotype by the decreased adhesive strength of TN-C, mediated by the fibrinogen globe.

scholarly journals Functional analyses of phosphatidylserine/PI(4)P exchangers with diverse lipid species and membrane contexts set unanticipated rules on lipid transfer

2021 ◽  
Author(s):  
Souade Ikhlef ◽  
Nicolas-Frédéric Lipp ◽  
Vanessa Delfosse ◽  
Nicolas Fuggetta ◽  
William Bourguet ◽  
...  
Keyword(s):  
Lipid Transfer ◽  
Oxysterol Binding Protein ◽  
Lipid Exchange ◽  
Exchange Processes ◽  
Lipid Species ◽  
Acyl Chains ◽  
Phosphatidylinositol 4 ◽  
Functional Analyses ◽  
Related Proteins

Several members of the oxysterol-binding protein-related proteins (ORPs)/oxysterol-binding homology (Osh) family exchange phosphatidylserine (PS) and phosphatidylinositol 4-phosphate (PI(4)P) at the endoplasmic reticulum/plasma membrane (PM) interface. It is unclear whether they preferentially exchange PS and PI(4)P with specific acyl chains to tune the features of the PM, whether they use phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) instead of PI(4)P for exchange processes and whether their activity is influenced by the association of PS with sterol in the PM. Here, we measured in vitro how the yeast Osh6p and human ORP8 transported diverse PS and PI(4)P subspecies, including major cellular species, between membranes. We established how their activity is impacted by the length and unsaturation degree of these lipids. Surprisingly, the speed at which they individually transfer these ligands inversely depends on their affinity for them. To be fast, the transfer of high-affinity ligands requires an exchange with a counterligand of equivalent affinity. Besides, we determined that Osh6p and ORP8 cannot use PI(4,5)P2 for intracellular lipid exchange, as they have a low affinity for this lipid compared to PI(4)P, and do not transfer more PS into sterol-rich membranes. This study provides insights into PS/PI(4)P exchangers and sets unanticipated rules on how the activity of lipid transfer proteins relates to their affinity for ligands.

Small-Molecule Screen Identifies ROS as Key Regulators of Actin Dynamics in Neutrophils

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4641-4641
Author(s):  
Hidenori Hattori ◽  
Kulandayan K Subramanian ◽  
Hongbo R. Luo
Keyword(s):  
Small Molecule ◽  
Actin Polymerization ◽  
Neutrophil Migration ◽  
Physiological Role ◽  
Leading Edge ◽  
Actin Dynamics ◽  
Functional Screening ◽  
Cellular Processes

Abstract Precise spatial and temporal control of actin polymerization and depolymerization is essential for mediating various cellular processes such as migration, phagocytosis, vesicle trafficking and adhesion. In this study, we used a small-molecule functional screening approach to identify novel regulators of actin dynamics during neutrophil migration. Here we show that NADPH-oxidase dependent Reactive Oxygen Species act as negative regulators of actin polymerization. Neutrophils with pharmacologically inhibited oxidase or isolated from Chronic Granulomatous Disease (CGD) patient and mice displayed enhanced F-actin polymerization, multiple pseudopods formation and impaired chemotaxis. ROS localized to pseudopodia and inhibited actin polymerization by driving actin glutathionylation at the leading edge of migrating cells. Consistent with these in vitro results, adoptively transferred CGD murine neutrophils also showed impaired in vivo recruitment to sites of inflammation. Together, these results present a novel physiological role for ROS in regulation of action polymerization and shed new light on the pathogenesis of CGD.

scholarly journals Recruitment and membrane interactions of host cell proteins during attachment of enteropathogenic and enterohaemorrhagic Escherichia coli

2012 ◽  
Vol 445 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Diana Munera ◽  
Eric Martinez ◽  
Svetlana Varyukhina ◽  
Arvind Mahajan ◽  
Jesus Ayala-Sanmartin ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Actin Polymerization ◽  
Attachment Site ◽  
Bacterial Attachment ◽  
Dependent Manner ◽  
Cellular Processes ◽  
Host Cell Proteins ◽  
Enterohaemorrhagic Escherichia Coli ◽  
Attachment Sites ◽  
Infected Cells

EPEC (enteropathogenic Escherichia coli) and EHEC (enterohaemorrhagic Escherichia coli) are attaching and effacing pathogens frequently associated with infectious diarrhoea. EPEC and EHEC use a T3SS (type III secretion system) to translocate effectors that subvert different cellular processes to sustain colonization and multiplication. The eukaryotic proteins NHERF2 (Na+/H+ exchanger regulatory factor 2) and AnxA2 (annexin A2), which are involved in regulation of intestinal ion channels, are recruited to the bacterial attachment sites. Using a stable HeLa-NHERF2 cell line, we found partial co-localization of AnxA2 and NHERF2; in EPEC-infected cells, AnxA2 and NHERF2 were extensively recruited to the site of bacterial attachment. We confirmed that NHERF2 dimerizes and found that NHERF2 interacts with AnxA2. Moreover, we found that AnxA2 also binds both the N- and C-terminal domains of the bacterial effector Tir through its C-terminal domain. Immunofluorescence of HeLa cells infected with EPEC showed that AnxA2 is recruited to the site of bacterial attachment in a Tir-dependent manner, but independently of Tir-induced actin polymerization. Our results suggest that AnxA2 and NHERF2 form a scaffold complex that links adjacent Tir molecules at the plasma membrane forming a lattice that could be involved in retention and dissemination of other effectors at the bacterial attachment site.

scholarly journals Mislocalization of CDK11/PITSLRE, a regulator of the G2/M phase of the cell cycle, in Alzheimer disease

2011 ◽  
Vol 16 (3) ◽  
Author(s):  
Vladan Bajić ◽  
Bo Su ◽  
Hyoung-Gon Lee ◽  
Wataru Kudo ◽  
Sandra Siedlak ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Alzheimer Disease ◽  
Expression Patterns ◽  
Vital Role ◽  
Dependent Manner ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Cellular Processes ◽  
M Phase

AbstractPost-mitotic neurons are typically terminally differentiated and in a quiescent status. However, in Alzheimer disease (AD), many neurons display ectopic re-expression of cell cycle-related proteins. Cyclin-dependent kinase 11 (CDK11) mRNA produces a 110-kDa protein (CDK11p110) throughout the cell cycle, a 58-kDa protein (CDK11p58) that is specifically translated from an internal ribosome entry site and expressed only in the G2/M phase of the cell cycle, and a 46-kDa protein (CDK11p46) that is considered to be apoptosis specific. CDK11 is required for sister chromatid cohesion and the completion of mitosis. In this study, we found that the expression patterns of CDK11 vary such that cytoplasmic CDK11 is increased in AD cellular processes, compared to a pronounced nuclear expression pattern in most controls. We also investigated the effect of amyloid precursor protein (APP) on CDK11 expression in vitro by using M17 cells overexpressing wild-type APP and APP Swedish mutant phenotype and found increased CDK11 expression compared to empty vector. In addition, amyloid-β25–35 resulted in increased CDK11 in M17 cells. These data suggest that CDK11 may play a vital role in cell cycle re-entry in AD neurons in an APP-dependent manner, thus presenting an intriguing novel function of the APP signaling pathway in AD.

scholarly journals Organization of Associating or Crosslinked Actin Filaments in Confinement

2019 ◽  
Author(s):  
Maral Adeli Koudehi ◽  
David M. Rutkowski ◽  
Dimitrios Vavylonis
Keyword(s):  
Actin Filaments ◽  
Brownian Dynamics ◽  
Persistence Length ◽  
Monomer Concentration ◽  
Ring Formation ◽  
Short Range Potential ◽  
Cytoskeleton Organization ◽  
Key Factor ◽  
Actin Cytoskeleton Organization

AbstractA key factor of actin cytoskeleton organization in cells is the interplay between the dynamical properties of actin filaments and cell geometry, which restricts, confines and directs their orientation. Crosslinking interactions among actin filaments, together with geometrical cues and regulatory proteins can give rise to contractile rings in dividing cells and actin rings in neurons. Motivated by recent in vitro experiments, in this work we performed computer simulations to study basic aspects of the interplay between confinement and attractive interactions between actin filaments. We used a spring-bead model and Brownian dynamics to simulate semiflexible actin filaments that polymerize in a confining sphere with a rate proportional to the monomer concentration. We model crosslinking, or attraction through the depletion interaction, implicitly as an attractive short-range potential between filament beads. In confining geometries smaller than the persistence length of actin filaments, we show rings can form by curving of filaments of length comparable to, or longer than the confinement diameter. Rings form for optimal ranges of attractive interactions that exist in between open bundles, irregular loops, aggregated and unbundled morphologies. The probability of ring formation is promoted by attraction to the confining sphere boundary and decreases for large radii and initial monomer concentrations, in agreement with prior experimental data. The model reproduces ring formation along the flat axis of oblate ellipsoids.

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