scholarly journals ATP depletion: a novel method to study junctional properties in epithelial tissues. I. Rearrangement of the actin cytoskeleton

1994 ◽  
Vol 107 (12) ◽  
pp. 3301-3313 ◽  
Author(s):  
R. Bacallao ◽  
A. Garfinkel ◽  
S. Monke ◽  
G. Zampighi ◽  
L.J. Mandel
Keyword(s):  
Tight Junction ◽  
Actin Cytoskeleton ◽  
Three Dimensional ◽  
Atp Depletion ◽  
Ultrastructural Changes ◽  
Junctional Complex ◽  
Actin Network ◽  
Cortical Actin ◽  
Actin Ring ◽  
Dimensional Reconstruction

The effect of cellular injury caused by depletion of intracellular ATP stores was studied in the Madin-Darby canine kidney (MDCK) and JTC cell lines. In prior studies, it was shown that ATP depletion uncouples the gate and fence functions of the tight junction. This paper extends these observations by studying the changes in the actin cytoskeleton and tight junction using electron microscopy and confocal fluorescence microscopy in combination with computer-aided three-dimensional reconstruction. Marked regional differences in the sensitivity to the effects of ATP depletion were observed in the actin cytoskeleton. Actin depolymerization appears to first affect the cortical actin network running along the apical basal axis of the cell. The next actin network that is disrupted is the stress fibers found at the basal surface of the cell. Finally, the actin ring at the level of the zonulae occludens and adherens is compromised. The breakup of the actin ring correlates with ultrastructural changes in tight junction strands and the loss of the tight junction's role as a molecular fence. During the process of actin network dissolution, polymerized actin aggregates form in the cytoplasm. The changes in the junctional complexes and the potential to reverse the ATP depletion suggest that this may be a useful method to study junctional complex formation and its relationship to the actin cytoskeletal network.

Cofilin mediates ATP depletion-induced endothelial cell actin alterations

2006 ◽  
Vol 290 (6) ◽  
pp. F1398-F1407 ◽  
Author(s):  
Maria V. Suurna ◽  
Sharon L. Ashworth ◽  
Melanie Hosford ◽  
Ruben M. Sandoval ◽  
Sarah E. Wean ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Actin Cytoskeleton ◽  
Fluorescent Protein ◽  
Cell Damage ◽  
Fluorescent Imaging ◽  
Atp Depletion ◽  
Stress Fibers ◽  
Cortical Actin ◽  
Lim Kinase ◽  
Actin Stress Fibers

Ischemia and sepsis lead to endothelial cell damage, resulting in compromised microvascular flow in many organs. Much remains to be determined regarding the intracellular structural events that lead to endothelial cell dysfunction. To investigate potential actin cytoskeletal-related mechanisms, ATP depletion was induced in mouse pancreatic microvascular endothelial cells (MS1). Fluorescent imaging and biochemical studies demonstrated a rapid and progressive increase in F-actin along with a decrease in G-actin at 60 min. Confocal microscopic analysis showed ATP depletion resulted in destruction of actin stress fibers and accumulation of F-actin aggregates. We hypothesized these actin alterations were secondary to dephosphorylation/activation of actin-depolymerizing factor (ADF)/cofilin proteins. Cofilin, the predominant isoform expressed in MS1 cells, was rapidly dephosphorylated/activated during ATP depletion. To directly investigate the role of cofilin activation on the actin cytoskeleton during ischemia, MS1 cells were infected with adenoviruses containing the cDNAs for wild-type Xenopus laevis ADF/cofilin green fluorescent protein [XAC(wt)-GFP], GFP, and the constitutively active and inactive isoforms XAC(S3A)-GFP and XAC(S3E)-GFP. The rate and extent of cortical actin destruction and actin aggregate formation were increased in ATP-depleted XAC(wt)-GFP- and XAC(S3A)-GFP-expressing cells, whereas increased actin stress fibers were observed in XAC(S3E)-GFP-expressing cells. To investigate the upstream signaling pathway of ADF/cofilin, LIM kinase 1-GFP (LIMK1-GFP) was expressed in MS1 cells. Cells expressing LIMK1-GFP protein had higher levels of phosphorylated ADF/cofilin, increased stress fibers, and delayed F-actin cytoskeleton destruction during ATP depletion. These results strongly support the importance of cofilin regulation in ischemia-induced endothelial cell actin cytoskeleton alterations leading to cell damage and microvascular dysfunction.

scholarly journals Disruption of the Actin Cytoskeleton Can Complement the Ability of Nef To Enhance Human Immunodeficiency Virus Type 1 Infectivity

2004 ◽  
Vol 78 (11) ◽  
pp. 5745-5755 ◽  
Author(s):  
Edward M. Campbell ◽  
Rafael Nunez ◽  
Thomas J. Hope
Keyword(s):  
Human Immunodeficiency Virus ◽  
Actin Cytoskeleton ◽  
Leukemia Virus ◽  
Actin Network ◽  
Cortical Actin ◽  
Immunodeficiency Virus ◽  
Cytoskeleton Disruption ◽  
Amphotropic Envelope ◽  
Cytoskeleton Rearrangements

ABSTRACT The human immunodeficiency virus (HIV) protein Nef has been shown to increase the infectivity of HIV at an early point during infection. Since Nef is known to interact with proteins involved in actin cytoskeleton rearrangements, we tested the possibility that Nef may enhance HIV infectivity via a mechanism that involves the actin cytoskeleton. We find that disruption of the actin cytoskeleton complements the Nef infectivity defect. The ability of disruption of the actin cytoskeleton to complement the Nef defect was specific to envelopes that fuse at the cell surface, including a variety of HIV envelopes and the murine leukemia virus amphotropic envelope. In contrast, the infectivity of HIV virions pseudotyped to enter cells via endocytosis, which is known to complement the HIV Nef infectivity defect and can naturally penetrate the cortical actin barrier, was not altered by actin cytoskeleton disruption. The results presented here suggest that Nef functions to allow the HIV genome to penetrate the cortical actin network, a known barrier for intracellular parasitic organisms.

scholarly journals Exogenous Expression of the Amino-Terminal Half of the Tight Junction Protein Zo-3 Perturbs Junctional Complex Assembly

2000 ◽  
Vol 151 (4) ◽  
pp. 825-836 ◽  
Author(s):  
Erika S. Wittchen ◽  
Julie Haskins ◽  
Bruce R. Stevenson
Keyword(s):  
Tight Junction ◽  
Actin Cytoskeleton ◽  
Mdck Cells ◽  
Dominant Negative ◽  
Tight Junction Protein ◽  
Junctional Complex ◽  
Amino Terminal ◽  
Junction Protein ◽  
Exogenous Expression ◽  
E Cadherin

The functional characteristics of the tight junction protein ZO-3 were explored through exogenous expression of mutant protein constructs in MDCK cells. Expression of the amino-terminal, PSD95/dlg/ZO-1 domain-containing half of the molecule (NZO-3) delayed the assembly of both tight and adherens junctions induced by calcium switch treatment or brief exposure to the actin-disrupting drug cytochalasin D. Junction formation was monitored by transepithelial resistance measurements and localization of junction-specific proteins by immunofluorescence. The tight junction components ZO-1, ZO-2, endogenous ZO-3, and occludin were mislocalized during the early stages of tight junction assembly. Similarly, the adherens junction proteins E-cadherin and β-catenin were also delayed in their recruitment to the cell membrane, and NZO-3 expression had striking effects on actin cytoskeleton dynamics. NZO-3 expression did not alter expression levels of ZO-1, ZO-2, endogenous ZO-3, occludin, or E-cadherin; however, the amount of Triton X-100–soluble, signaling-active β-catenin was increased in NZO-3–expressing cells during junction assembly. In vitro binding experiments showed that ZO-1 and actin preferentially bind to NZO-3, whereas both NZO-3 and the carboxy-terminal half of the molecule (CZO-3) contain binding sites for occludin and cingulin. We hypothesize that NZO-3 exerts its dominant-negative effects via a mechanism involving the actin cytoskeleton, ZO-1, and/or β-catenin.

Molecular structure and assembly of the tight junction

1998 ◽  
Vol 274 (1) ◽  
pp. F1-F9 ◽  
Author(s):  
Bradley M. Denker ◽  
Sanjay K. Nigam
Keyword(s):  
Tight Junction ◽  
Transmembrane Protein ◽  
Atp Depletion ◽  
Junctional Complex ◽  
Permeability Barrier ◽  
Epithelial Tissue ◽  
Heterotrimeric G Proteins ◽  
Toxic Injury ◽  
Intracellular Ca ◽  
Protein Components

Polarized epithelial cells separate two extremely different cellular milieus. The tight junction (TJ) is the most apical component of the junctional complex and serves as the permeability barrier between these environments. The tight junctional complex appears to be a dynamic and regulated structure. Some of its protein components have been identified and include the transmembrane protein occludin. Nontransmembrane proteins on the cytosolic leaflet including ZO-1, ZO-2, cingulin, 7H6, and several unidentified phosphoproteins are also believed to be part of the TJ. Interactions of some of these proteins with the actin cytoskeleton are a major determinant of TJ structure and may also play a role in the regulation of TJ assembly. Recent progress using the “calcium switch” and the “ATP depletion-repletion” model of TJ formation offers new insight regarding how these structures form. TJ biogenesis appears to be regulated, in part, by classic signal transduction pathways involving heterotrimeric G proteins, release of intracellular Ca2+, and activation of protein kinase C. Although many of the details of the signaling pathways have yet to be defined, these observations may provide insight into how TJs form during tubular development. Furthermore, it may be possible to suggest potential therapeutic targets for intervention in a variety of diseases (e.g., ischemia, toxic injury to the kidney and other epithelial tissue) where TJ integrity has been compromised and reassembly is required.

Three-dimensional reconstruction of the actin cytoskeleton from stereo images

2000 ◽  
Vol 33 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Yuan Cheng ◽  
Christopher A. Hartemink ◽  
John H. Hartwig ◽  
C. Forbes Dewey
Keyword(s):  
Actin Cytoskeleton ◽  
Three Dimensional ◽  
Three Dimensional Reconstruction ◽  
Stereo Images ◽  
Dimensional Reconstruction

F-actin ring formation and the role of F-actin cables in the fission yeastSchizosaccharomyces pombe

2002 ◽  
Vol 115 (5) ◽  
pp. 887-898 ◽  
Author(s):  
Ritsuko Arai ◽  
Issei Mabuchi
Keyword(s):  
Three Dimensional ◽  
Spindle Pole ◽  
Ring Formation ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Wild Type ◽  
Actin Ring ◽  
Medial Region ◽  
Dimensional Reconstruction ◽  
Actin Cables

Cells of the fission yeast Schizosaccharomyces pombe divide by the contraction of the F-actin ring formed at the medial region of the cell. We investigated the process of F-actin ring formation in detail using optical sectioning and three-dimensional reconstruction fluorescence microscopy. In wild-type cells, formation of an aster-like structure composed of F-actin cables and accumulation of F-actin cables were recognized at the medial cortex of the cell during prophase to metaphase. The formation of the aster-like structure seemed to initiate from branching of the longitudinal F-actin cables at a site near the spindle pole bodies, which had been duplicated but not yet separated. A single cable extended from the aster and encircled the cell at the equator to form a primary F-actin ring during metaphase. During anaphase,the accumulated F-actin cables were linked to the primary F-actin ring, and then all of these structures seemed to be packed to form the F-actin ring. These observations suggest that formation of the aster-like structure and the accumulation of the F-actin cables at the medial region of the cell during metaphase may be required to initiate the F-actin ring formation. In the nda3 mutant, which has a mutation in ß-tubulin and has been thought to be arrested at prophase, an F-actin ring with accumulated F-actin cables similar to that of anaphase wild-type cells was formed at a restrictive temperature. Immediately after shifting to a permissive temperature, this structure changed into a tightly packed ring. This suggests that the F-actin ring formation progresses beyond prophase in the nda3 cells once the cells enter prophase. We further examined F-actin structures in both cdc12 and cdc15 early cytokinesis mutants. As a result,Cdc12 seemed to be required for the primary F-actin ring formation during prophase, whereas Cdc15 may be involved in both packing the F-actin cables to form the F-actin ring and rearrangement of the F-actin after anaphase. In spg1, cdc7 and sid2 septum initiation mutants, the F-actin ring seemed to be formed in order.

scholarly journals Ponticulin plays a role in the positional stabilization of pseudopods.

1995 ◽  
Vol 131 (6) ◽  
pp. 1495-1506 ◽  
Author(s):  
D C Shutt ◽  
D Wessels ◽  
K Wagenknecht ◽  
A Chandrasekhar ◽  
A L Hitt ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Time Course ◽  
Three Dimensional ◽  
Computer Assisted ◽  
Spatial Gradient ◽  
Actin Network ◽  
Wild Type ◽  
Cortical Actin ◽  
High Affinity

Ponticulin is a 17-kD glycoprotein that represents a major high affinity link between the plasma membrane and the cortical actin network of Dictyostelium. To assess the role of ponticulin in pseudopod extension and retraction, the motile behavior of two independently generated mutants lacking ponticulin was analyzed using computer-assisted two- and three-dimensional motion analysis systems. More than half of the lateral pseudopods formed off the substratum by ponticulin-minus cells slipped relative to the substratum during extension and retraction. In contrast, all pseudopods formed off the substratum by wild-type cells were positionally fixed in relation to the substratum. Ponticulin-minus cells also formed a greater proportion of both anterior and lateral pseudopods off the substratum and absorbed a greater proportion of lateral pseudopods into the uropod than wild-type cells. In a spatial gradient of cAMP, ponticulin-minus cells were less efficient in tracking the source of chemoattractant. Since ponticulin-minus cells extend and retract pseudopods with the same time course as wild-type cells, these behavioral defects in ponticulin-minus cells appear to be the consequence of pseudopod slippage. These results demonstrate that pseudopods formed off the substratum by wild-type cells are positionally fixed in relation to the substratum, that ponticulin is required for positional stabilization, and that the loss of ponticulin and the concomitant loss of positional stability of pseudopods correlate with a decrease in the efficiency of chemotaxis.

scholarly journals VASP mediated actin dynamics activate and recruit a filopodia myosin

2021 ◽  
Author(s):  
Ashley L Arthur ◽  
Amy Crawford ◽  
Anne Houdusse ◽  
Margaret A Titus
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
The State ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Network ◽  
Cortical Actin ◽  
Close Collaboration ◽  
Actin Binding Protein ◽  
Dynamic Regions

Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in Dictyostelium requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network, that activates the MF myosin and together they shape the actin network to promote extension of parallel bundles during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin binding protein, the state of the actin cytoskeleton and MF myosin activity.

scholarly journals VASP mediated actin dynamics activate and recruit a filopodia myosin

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ashley L Arthur ◽  
Amy Crawford ◽  
Anne Houdusse ◽  
Margaret A Titus
Keyword(s):  
Actin Cytoskeleton ◽  
Actin Polymerization ◽  
The State ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Actin Network ◽  
Cortical Actin ◽  
Close Collaboration ◽  
Actin Binding Protein ◽  
Dynamic Regions

Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in Dictyostelium requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network that activates myosin and together they shape the actin network to promote extension of parallel bundles of actin during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin binding protein, the state of the actin cytoskeleton and MF myosin activity.

Heat stress ameliorates ATP depletion-induced sublethal injury in mouse proximal tubule cells

1997 ◽  
Vol 272 (3) ◽  
pp. F347-F355 ◽  
Author(s):  
S. C. Borkan ◽  
Y. H. Wang ◽  
W. Lieberthal ◽  
P. R. Burke ◽  
J. H. Schwartz
Keyword(s):  
Heat Stress ◽  
Tight Junction ◽  
Actin Cytoskeleton ◽  
Proximal Tubule ◽  
Lucifer Yellow ◽  
Atp Depletion ◽  
Stress Fibers ◽  
Protective Effects ◽  
Proximal Tubule Cells ◽  
Tubule Cells

The role of prior heat stress (HS) in ameliorating changes in the actin cytoskeleton and the loss of tight junction integrity that accompany ATP depletion was examined. Mouse proximal tubule cells in primary culture were exposed to sodium cyanide (CN) in the absence of dextrose for 1 h, a maneuver that produced equivalent degrees of ATP depletion in control and in HS cells. After ATP depletion, actin stress fibers were completely disrupted in control cells. In contrast, HS cells with elevated HSP-72 content showed preservation of stress fibers after CN exposure. ATP depletion in control and HS cells produced similar and reversible depletion of the G-actin pool without altering total actin content. Integrity of the tight junction was assessed by transepithelial electrical resistance (TER) and unidirectional flux of lucifer yellow (LY, mol wt 482). After CN alone, the nadir in TER was lower than that of HS + CN cells (51.6 +/- 2.5 vs. 96.2 +/- 3.2 omega x cm2, respectively; P < 0.05). After 30-min recovery, TER of HS + CN recovered to control values (277 +/- 7.2 vs. 227 +/- 6.6 omega x cm2; P > 0.05), whereas CN did not (165 +/- 7.3 vs. 227 +/- 6.6 omega x cm2; P < 0.05). Changes in LY flux paralleled those in TER. HS is associated with preservation of the actin cytoskeleton and improved integrity of the tight junction after sublethal ATP depletion injury. These protective effects may contribute to the preservation of epithelial cell polarity and function following an ischemic insult.

Sign in / Sign up

Export Citation Format

Share Document