Browse
Submit Data
Databases
API
Help

Dataset Information

19 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Dictyostelium myosin II mechanochemistry promotes active behavior of the cortex on long time scales.

ABSTRACT: Cell cortices rearrange dynamically to complete cytokinesis, crawlin response to chemoattractant, build tissues, and make neuronal connections. Highly enriched in the cell cortex, actin, myosin II, and actin crosslinkers facilitate cortical movements. Because cortical behavior is the consequence of nanoscale biochemical events, it is essential to probe the cortex at this level. Here, we use high-resolution laser-based particle tracking to examine how myosin II mechanochemistry and dynacortin-mediated actin crosslinking control cortex dynamics in Dictyostelium. Consistent with its low duty ratio, myosin II does not directly drive active bead motility. Instead, myosin II and dynacortin antagonistically regulate other active processes in the living cortex.

SUBMITTER: Girard KD

PROVIDER: S-EPMC1413706 | biostudies-literature | 2006 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Dictyostelium myosin II mechanochemistry promotes active behavior of the cortex on long time scales.

Girard Kristine D KD Kuo Scot C SC Robinson Douglas N DN

Proceedings of the National Academy of Sciences of the United States of America 20060203 7

Cell cortices rearrange dynamically to complete cytokinesis, crawlin response to chemoattractant, build tissues, and make neuronal connections. Highly enriched in the cell cortex, actin, myosin II, and actin crosslinkers facilitate cortical movements. Because cortical behavior is the consequence of nanoscale biochemical events, it is essential to probe the cortex at this level. Here, we use high-resolution laser-based particle tracking to examine how myosin II mechanochemistry and dynacortin-med ...[more]

PMID: 16461463

Similar Datasets

Allosteric communication in Dictyostelium myosin II.

Project description:Myosin's affinities for nucleotides and actin are reciprocal. Actin-binding substantially reduces the affinity of ATP for myosin, but the effect of actin on myosin's ADP affinity is quite variable among myosin isoforms, serving as the principal mechanism for tuning the actomyosin system to specific physiological purposes. To understand the structural basis of this variable relationship between actin and ADP binding, we studied several constructs of the catalytic domain of Dictyostelium myosin II, varying their length (from the N-terminal origin) and cysteine content. The constructs varied considerably in their actin-activated ATPase activity and in the effect of actin on ADP affinity. Actin had no significant effect on ADP affinity for a single-cysteine catalytic domain construct, a double-cysteine construct partially restored the actin-dependence of ADP binding, and restoration of all native Cys restored it further, but full restoration of function (similar to that of skeletal muscle myosin II) was obtained only by adding all native Cys and an artificial lever arm extension. Pyrene-actin fluorescence confirmed these effects on ADP binding to actomyosin. We conclude that myosin's Cys content and lever arm both allosterically modulate the reciprocal affinities of myosin for ADP and actin, a key determinant of the biological functions of myosin isoforms.

| S-EPMC3600821 | biostudies-literature

A role for myosin II clusters and membrane energy in cortex rupture for Dictyostelium discoideum.

Project description:Blebs, pressure driven protrusions of the cell membrane, facilitate the movement of eukaryotic cells such as the soil amoeba Dictyostelium discoideum, white blood cells and cancer cells. Blebs initiate when the cell membrane separates from the underlying cortex. A local rupture of the cortex, has been suggested as a mechanism by which blebs are initiated. However, much clarity is still needed about how cells inherently regulate rupture of the cortex in locations where blebs are expected to form. In this work, we examine the role of membrane energy and the motor protein myosin II (myosin) in facilitating the cell driven rupture of the cortex. We perform under-agarose chemotaxis experiments, using Dictyostelium discoideum cells, to visualize the dynamics of myosin and calculate changes in membrane energy in the blebbing region. To facilitate a rapid detection of blebs and analysis of the energy and myosin distribution at the cell front, we introduce an autonomous bleb detection algorithm that takes in discrete cell boundaries and returns the coordinate location of blebs with its shape characteristics. We are able to identify by microscopy naturally occurring gaps in the cortex prior to membrane detachment at sites of bleb nucleation. These gaps form at positions calculated to have high membrane energy, and are associated with areas of myosin enrichment. Myosin is also shown to accumulate in the cortex prior to bleb initiation and just before the complete disassembly of the cortex. Together our findings provide direct spatial and temporal evidence to support cortex rupture as an intrinsic bleb initiation mechanism and suggests that myosin clusters are associated with regions of high membrane energy where its contractile activity leads to a rupture of the cortex at points of maximal energy.

| S-EPMC9037949 | biostudies-literature

Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium.

Project description:Blebbistatin, a cell-permeable inhibitor of class-II myosins, was developed to provide a tool for studying the biologic roles of myosin II. Consistent with this use, we find that blebbistatin inhibits three myosin II-dependent processes in Dictyostelium (growth in suspension culture, capping of Con A receptors, and development to fruiting bodies) and does not inhibit growth on plates, which does not require myosin II. As expected, macropinocytosis (myosin I-dependent), contractile vacuole activity (myosin V-dependent), and phagocytosis (myosin VII-dependent), none of which requires myosin II, are not inhibited by blebbistatin in myosin II-null cells, but, unexpectedly, blebbistatin does inhibit macropinocytosis and phagocytosis by cells expressing myosin II. Expression of catalytically inactive myosin II in myosin II-null cells also inhibits macropinocytosis and phagocytosis. Both blebbistatin-inhibited myosin II and catalytically inactive myosin II form cytoplasmic aggregates, which may be why they inhibit myosin II-independent processes, but neither affects the distribution of actin filaments in vegetative cells or actin and myosin distribution in dividing or polarized cells. Blebbistatin also inhibits cell streaming and plaque expansion in myosin II-null cells. Our results are consistent with myosin II being the only Dictyostelium myosin that is inhibited by blebbistatin but also show that blebbistatin-inactivated myosin II inhibits some myosin II-independent processes and that blebbistatin inhibits other activities in the absence of myosin II.

| S-EPMC547870 | biostudies-other

Dictyostelium huntingtin controls chemotaxis and cytokinesis through the regulation of myosin II phosphorylation.

Project description:Abnormalities in the huntingtin protein (Htt) are associated with Huntington's disease. Despite its importance, the function of Htt is largely unknown. We show that Htt is required for normal chemotaxis and cytokinesis in Dictyostelium discoideum. Cells lacking Htt showed slower migration toward the chemoattractant cAMP and contained lower levels of cortical myosin II, which is likely due to defects in dephosphorylation of myosin II mediated by protein phosphatase 2A (PP2A). htt(-) cells also failed to maintain myosin II in the cortex of the cleavage furrow, generating unseparated daughter cells connected through a thin cytoplasmic bridge. Furthermore, similar to Dictyostelium htt(-) cells, siRNA-mediated knockdown of human HTT also decreased the PP2A activity in HeLa cells. Our data indicate that Htt regulates the phosphorylation status of myosin II during chemotaxis and cytokinesis through PP2A.

| S-EPMC3128529 | biostudies-literature

Novel myosin heavy chain kinase involved in disassembly of myosin II filaments and efficient cleavage in mitotic dictyostelium cells.

Project description:We have cloned a full-length cDNA encoding a novel myosin II heavy chain kinase (mhckC) from Dictyostelium. Like other members of the myosin heavy chain kinase family, the mhckC gene product, MHCK C, has a kinase domain in its N-terminal half and six WD repeats in the C-terminal half. GFP-MHCK C fusion protein localized to the cortex of interphase cells, to the cleavage furrow of mitotic cells, and to the posterior of migrating cells. These distributions of GFP-MHCK C always corresponded with that of myosin II filaments and were not observed in myosin II-null cells, where GFP-MHCK C was diffusely distributed in the cytoplasm. Thus, localization of MHCK C seems to be myosin II-dependent. Cells lacking the mhckC gene exhibited excessive aggregation of myosin II filaments in the cleavage furrows and in the posteriors of the daughter cells once cleavage was complete. The cleavage process of these cells took longer than that of wild-type cells. Taken together, these findings suggest MHCK C drives the disassembly of myosin II filaments for efficient cytokinesis and recycling of myosin II that occurs during cytokinesis.

| S-EPMC138637 | biostudies-literature

Identification of a new mechanism for targeting myosin II heavy chain phosphorylation by Dictyostelium myosin heavy chain kinase B.

Project description:BackgroundHeavy chain phosphorylation plays a central role in regulating myosin II bipolar filament assembly in Dictyostelium, as well as in higher eukaryotic nonmuscle cells. Our previous work has demonstrated that the WD-repeat domain of Dictyostelium myosin II heavy chain kinase B (MHCK-B), unlike its counterpart in MHCK-A, is not absolutely required for targeting of the kinase to phosphorylate MHC. Thus, we tested the hypothesis that an asparagine-rich and structurally disordered region that is unique to MHCK-B can by itself function in substrate targeting.FindingsBiochemical assays comparing the activities of full-length MHCK-B, a truncation lacking only the WD-repeat domain (B-Delta-WD), and a truncation lacking both the N-rich region and the WD-repeat domain (B-Delta-N-WD) revealed that the N-rich region targets MHCK-B to phosphorylate MHC in a manner that leads to bipolar filament disassembly. This targeting is physiologically relevant since cellular over-expression of the B-Delta-WD truncation, but not the B-Delta-N-WD truncation, leads to dramatically reduced levels of myosin II filament assembly and associated defects in cytokinesis and multicellular development.ConclusionsThe results presented here demonstrate that an intrinsically unstructured, and asparagine-rich, region of a MHCK-B can mediate specific targeting of the kinase to phosphorylate myosin II heavy chain. This targeting involves a direct binding interaction with myosin II filaments. In terms of regulating myosin bipolar filament assembly, our results suggest that factors affecting the activity of this unique region of MHCK-B could allow for regulation of MHCK-B in a manner that is distinct from the other MHCKs in Dictyostelium.

| S-EPMC2838905 | biostudies-literature

Myosin light chain kinase-driven myosin II turnover regulates actin cortex contractility during mitosis.

Project description:Force generation by the molecular motor myosin II (MII) at the actin cortex is a universal feature of animal cells. Despite its central role in driving cell shape changes, the mechanisms underlying MII regulation at the actin cortex remain incompletely understood. Here we show that myosin light chain kinase (MLCK) promotes MII turnover at the mitotic cortex. Inhibition of MLCK resulted in an alteration of the relative levels of phosphorylated regulatory light chain (RLC), with MLCK preferentially creating a short-lived pRLC species and Rho-associated kinase (ROCK) preferentially creating a stable ppRLC species during metaphase. Slower turnover of MII and altered RLC homeostasis on MLCK inhibition correlated with increased cortex tension, driving increased membrane bleb initiation and growth, but reduced bleb retraction during mitosis. Taken together, we show that ROCK and MLCK play distinct roles at the actin cortex during mitosis; ROCK activity is required for recruitment of MII to the cortex, while MLCK activity promotes MII turnover. Our findings support the growing evidence that MII turnover is an essential dynamic process influencing the mechanical output of the actin cortex.

| S-EPMC8684764 | biostudies-literature

Myosin II-interacting guanine nucleotide exchange factor promotes bleb retraction via stimulating cortex reassembly at the bleb membrane.

Project description:Blebs are involved in various biological processes such as cell migration, cytokinesis, and apoptosis. While the expansion of blebs is largely an intracellular pressure-driven process, the retraction of blebs is believed to be driven by RhoA activation that leads to the reassembly of the actomyosin cortex at the bleb membrane. However, it is still poorly understood how RhoA is activated at the bleb membrane. Here, we provide evidence demonstrating that myosin II-interacting guanine nucleotide exchange factor (MYOGEF) is implicated in bleb retraction via stimulating RhoA activation and the reassembly of an actomyosin network at the bleb membrane during bleb retraction. Interaction of MYOGEF with ezrin, a well-known regulator of bleb retraction, is required for MYOGEF localization to retracting blebs. Notably, knockout of MYOGEF or ezrin not only disrupts RhoA activation at the bleb membrane, but also interferes with nonmuscle myosin II localization and activation, as well as actin polymerization in retracting blebs. Importantly, MYOGEF knockout slows down bleb retraction. We propose that ezrin interacts with MYOGEF and recruits it to retracting blebs, where MYOGEF activates RhoA and promotes the reassembly of the cortical actomyosin network at the bleb membrane, thus contributing to the regulation of bleb retraction.

| S-EPMC6004584 | biostudies-literature

Optimizing agent behavior over long time scales by transporting value.

Project description:Humans prolifically engage in mental time travel. We dwell on past actions and experience satisfaction or regret. More than storytelling, these recollections change how we act in the future and endow us with a computationally important ability to link actions and consequences across spans of time, which helps address the problem of long-term credit assignment: the question of how to evaluate the utility of actions within a long-duration behavioral sequence. Existing approaches to credit assignment in AI cannot solve tasks with long delays between actions and consequences. Here, we introduce a paradigm where agents use recall of specific memories to credit past actions, allowing them to solve problems that are intractable for existing algorithms. This paradigm broadens the scope of problems that can be investigated in AI and offers a mechanistic account of behaviors that may inspire models in neuroscience, psychology, and behavioral economics.

| S-EPMC6864102 | biostudies-literature

Mechanochemistry: one bond at a time.

Project description:Single-molecule force-clamp spectroscopy offers a novel platform for mechanically denaturing proteins by applying a constant force to a polyprotein. A powerful emerging application of the technique is that, by introducing a disulfide bond in each protein module, the chemical kinetics of disulfide bond cleavage under different stretching forces can be probed at the single-bond level. Even at forces much lower than that which can rupture the chemical bond, the breaking of the S-S bond at the presence of various chemical reducing agents is significantly accelerated. Our previous work demonstrated that the rate of thiol/disulfide exchange reaction is force-dependent and well-described by an Arrhenius term of the form r = A(exp((FΔx(r) - E(a))/k(B)T)[nucleophile]). From Arrhenius fits to the force dependency of the reduction rate, we measured the bond elongation parameter, Δx(r), along the reaction coordinate to the transition state of the S(N)2 reaction cleaved by different nucleophiles and enzymes, never before observed by any other technique. For S-S cleavage by various reducing agents, obtaining the Δx(r) value can help depicting the energy landscapes and elucidating the mechanisms of the reactions at the single-molecule level. Small nucleophiles, such as 1,4-dl-dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP), and l-cysteine, react with the S-S bond with monotonically increasing rates under the applied force, while thioredoxin enzymes exhibit both stretching-favored and -resistant reaction-rate regimes. These measurements demonstrate the power of the single-molecule force-clamp spectroscopy approach in providing unprecedented access to chemical reactions.

| S-EPMC2891658 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data