Inhibition of ezrin phosphorylation by NSC305787 attenuates procaterol-stimulated ciliary beating in airway cilia

Ciliary beating in the airway epithelium plays an important role in preventing infection by eliminating small particles and pathogens. Stimulation of β2 adrenergic receptor (β2AR) increases [cAMP]i levels and strongly activates this ciliary beating. β2AR is localized to the apical membrane of the airways by indirectly binding to ezrin, an actin-binding protein. Ezrin takes active phosphorylated and inactive dephosphorylated states at Thr-567. Previously we showed that procaterol-stimulated ciliary beating was impaired in the ezrin-knockdown mice. In this study, we examined the roles of ezrin and its phosphorylation in regulating ciliary beating by using NSC305787, an ezrin inhibitor, in normal human airway epithelial cells (NHBE). We found that NSC305787 inhibits the phosphorylation of ezrin with an IC50 of 50 μM in NHBE. Treatment with NSC305787 for 4 h or more decreased the expression of β2AR in the cell membrane and induced vesicle- or dot-like expression of ezrin and β2AR inside the cell. As a result, inhibition of ezrin phosphorylation by NSC305787 attenuated the effect of procaterol-induced activation of ciliary beating in both frequency and distance indices.

Talin mechanotransduction in disease

Talin protein (Talin 1/2) is a mechanosensitive cytoskeleton protein. The unique structure of the Talin plays a vital role in transmitting mechanical forces. Talin proteins connect the extracellular matrix to the cytoskeleton by linking to integrins and actin, thereby mediating the conversion of mechanical signals into biochemical signals and influencing disease progression as potential diagnostic indicators, therapeutic targets, and prognostic indicators of various diseases. Most studies in recent years have confirmed that mechanical forces also have a crucial role in the development of disease, and Talin has been found to play a role in several diseases. Still, more studies need to be done on how Talin is involved in mechanical signaling in disease. This review focuses on the mechanical signaling of Talin in disease, aiming to summarize the mechanisms by which Talin plays a role in disease and to provide references for further studies.

Ezrin knockdown reduces procaterol-stimulated ciliary beating without morphological changes in mouse airway cilia

The mucociliary clearance, which is conducted by the beating cilia cooperating with the surface mucous layer, is a major host defense mechanism of the airway epithelium. Ezrin, a crosslinker between membrane proteins and actin cytoskeleton, is located in microvilli and around the basal bodies in airway ciliary cells. It is also likely that ezrin may play the important role of apical localization of β2-adrenergic receptor (β2AR) in airway ciliary cells. Here we studied the physiological roles of ezrin by using the trachea and airway epithelial cells prepared from the ezrin-knockdown (Vil2kd/kd) mice. The trachea and airway ciliary cells of Vil2kd/kd mice represented normal morphology and basal body orientation, suggesting that ezrin is not directly involved in development and planer cell polarity of cilia. Procaterol stimulates ciliary beating (frequency and amplitude) via β2AR in the airway ciliary cells. In the Vil2kd/kd mice, airway ciliary beating stimulated with procaterol was partly inhibited due to the impairment of cell surface expression of β2AR. These results suggest that ezrin regulates the beating of airway ciliary cells by promoting the apical surface localization of β2AR.

Development of an expression system in Tetrahymena inner arm dyneins and motile properties of the single-headed subspecies (Dyh8p and Dyh12p)

Diverse inner arm dyneins cooperate with outer arm dyneins to produce ciliary beating. This study demonstrates an expression system for inner arm dyneins in Tetrahymena. The motor domain of inner arm dynein (Dyh8p or Dyh12p) was fused with the tail of outer arm dynein (Dyh3p) and expressed in viable DYH3-knockout (vKO-DYH3) cells. The chimeric dyneins were observed in the oral apparatus and cilia on the cell bodies, and did not change the swimming speed of vKO-DYH3 cells. In a gliding assay, the motor domains of Dyh8p and Dyh12p moved toward the minus ends of microtubules at 0.8 and 0.3 μm/s, respectively. The gliding velocities of Dyh8p and Dyh12p were decreased in 5 mM ATP but not increased in 0.1 or 0.5 mM ADP. This expression system will be useful for molecular studies on diverse inner arm dyneins.

Two-Dimensional Gel Electrophoresis Combined with Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Analysis of Eye Lens to Identify Biomarkers of Age-Related Cataract

This chapter describes the application of two-dimensional gel electrophoresis (2DGE) combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in the analysis of rat eye lens proteins. The main purpose was to identify proteins that may serve as potential biomarkers in age-related cataract formation. This includes the family of proteins known as the crystallins. Structural proteins and enzymes involved antioxidant activities. In addition, we also analyzed lenses from other species to illustrate the potential of using this technique in clinical and preclinical biomarker studies.

The cytoskeletal protein Zyxin interacts with the zinc-finger transcription factor Zic1 and plays the role of a scaffold for Gli1 and Zic1 interactions during early development of Xenopus laevis

We have shown recently that the cytoskeletal protein Zyxin participates in the fine tuning of the neural plate pattering in Xenopus laevis embryos by modulating activity of one of the effectors of Hedgehog (Shh) signaling cascade, the transcription factor Gli1. In the present work, we show that Zyxin can also interact with the potential modulator of the Shh pathway, the transcription factor Zic1. The interaction of proteins occurs primarily by mean of the zinc-finger domain of Zic1 and 2nd LIM domain of Zyxin. Moreover, we have also revealed the ability of the Zyxin, Zic1 and Gli1 to form a ternary complex. The activity of this complex resembles that of the previously described by other authors protein complex formed by Gli1 and Zic1, amplifying effect of the latter. The data obtained provide evidence for the scaffolding role of Zyxin for Gli1 and Zic1 interactions and confirm its role in the regulation of Shh signaling cascade.

Functional characterization of lethal P-loop mutations in Tetrahymena outer arm dynein (Dyh3p)

Mutational analyses of axonemal dyneins are useful for elucidating the molecular mechanism of ciliary motility. This study demonstrates a mutation system for characterizing lethal P-loop mutations in Tetrahymena outer arm dynein (Dyh3p). The viable DYH3-knockout (vKO-DYH3) cells isolated in this study enabled the examination of lethal mutations in P-loops 1 and 2. The P1 mutant dynein localized in the oral apparatus and the proximal region of the cilia, and the P2 mutant dynein localized only in the oral apparatus. Both results are different from the localization of wild-type Dyh3p. In addition, a co-precipitation assay showed that the P1 and P2 mutant dyneins did not dissociate from microtubules in ATP plus vanadate or in no-ATP conditions, in contrast to wild-type Dyh3p. This mutation system is useful for further molecular studies of axonemal dyneins and ciliary motility.

SP600125 blocks the proteolysis of cytoskeletal proteins in apoptosis induced by gas signaling molecule (NO) via decreasing the activation of caspase-3 in rabbit chondrocytes

NO plays a key role in the pathological mechanisms of articular diseases. As cytoskeletal proteins are responsible for the polymerization, stabilization, and dynamics of the cytoskeleton network, we investigated whether cytoskeletal proteins are the intracellular pathological targets of NO. We aimed at clarifying whether the cytoskeleton perturbations involved in apoptosis are induced in rabbit articular chondrocytes by NO, which can be liberated by sodium nitroprusside (SNP) treatment. The first passage rabbit articular chondrocytes were cultured as monolayer for the experiments, and the effects of NO were tested in the presence of JNK-specific inhibitor, SP600125. SNP treatment of cultured chondrocytes caused significant apoptosis in a concentration-dependent manner (time and dose), as evaluated by TUNEL assay and Annexin V flow cytometry, while the apoptosis was reduced by the SP600125 addition 30 min before SNP treatment. Besides, SP600125 decreased significantly the protein expression of total caspase-3 and the intracellular gene expression of caspase-3, measured by Western blot analysis and PCR. SP600125 also increased the cytoskeletal protein expressions. These results suggested that JNK pathway plays a critical role in the NO-induced chondrocyte apoptosis, and SP600125 treatment blocks the dissolution of the cytoskeletal proteins via activation of caspase-3 pathways.

Establishment of a mutation system in Tetrahymena outer arm dynein and P-loop functions of the alpha heavy chain (Dyh3p)

Axonemal dyneins are large AAA+ type motor proteins that exhibit unique motor properties during ciliary beating. This study established a mutation system for Tetrahymena outer arm dynein and characterized four nucleotide-binding loops (P-loops; P1-P4) in the alpha heavy chain (Dyh3p). Macronuclear transformation of the mutant DYH3 genes in DYH3-knockout (KO-DYH3) cells enabled P-loop mutations that abolish the ability of nucleotide binding to be stably maintained in the polyploid genome. This mutation system revealed that the P3 and P4 mutant dyneins rescued lethality in macronuclear KO-DYH3 cells and exhibited normal ciliary localization. Intriguingly, however, an in vitro motility assay showed that the P3 mutation abolished the motor activity of Dyh3p, whereas the P4 mutation did not affect the gliding velocity or gliding index of Dyh3p. In contrast, no P1 or P2 mutant cells were isolated from the KO-DYH3 cells, which suggests that nucleotide binding at the P1 and P2 sites is required for the intracellular function of Dyh3p. This mutation system will be useful for further molecular studies of diverse axonemal dyneins and ciliary motility.

[Effects of wild-type PTEN overexpression and its mutation on F-actin in activated hepatic stellate cells]

Objective: To investigate the effect of overexpression of wild-type phosphatase and tensin homolog (PTEN) deleted on chromosome 10 and its mutant G129E (exhibiting the activity of protein phosphatase and losing the activity of lipid phosphatase) on F-actin in activated hepatic stellate cells (HSCs) cultured in vitro. Methods: The activated hepatic stellate cell-T6 (HSC-T6) cells were cultured in vitro, and activated HSCs were transfected with adenovirus that carried wild-type PTEN gene and G129E gene using transient transfection. The HSCs were divided into the following groups: control group, which was transfected with DMEM medium instead of virus solution; Ad-GFP group, which was transfected with the empty adenovirus vector with the expression of green fluorescent protein (GFP); Ad-PTEN group, which was transfected with the recombinant adenovirus with wild-type PTEN gene and GFP expression; Ad-G129E group, which was transfected with the recombinant adenovirus with G129E gene and GFP expression. Western blot and quantitative real-time PCR were used to measure the protein and mRNA expression of PTEN in activated HSCs; under a laser scanning confocal microscope (LSCM), phalloidine labeled with the fluorescein tetramethylrhodamine isothiocyanate (TRITC) was used to observe the morphology of HSCs, distribution and fluorescence intensity of F-actin, and changes in pseudopodia and stress fibers, and a calcium fluorescence probe (Rhod-2/AM) was used to measure the changes in Ca(2+) concentration in HSCs. A one-way analysis of variance was used for comparison between multiple groups, and the least significant difference test was used for comparison between two groups. Results: Wild-type PTEN and G129E genes were highly expressed in activated HSCs. In the control group and the Ad-GFP group, HSCs had a starlike or polygonal shape, F-actin was reconfigured and formed a large number of stress fibers which stretched across the whole cell, and layered pseudopodia were seen around the cell. In the Ad-PTEN group and the Ad-G129E group, the HSCs had a fusiform shape, F-actin was mainly seen around the cell, a small number of stress fibers were seen inside the cell, and layered pseudopodia around the cell disappeared. The Ad-PTEN group and the Ad-G129E group had significant reductions in the fluorescence intensity of F-actin compared with the control group and the Ad-GFP group (357.67±13.39/377.25±14.55 vs 961.87±27.33/954.68±20.71, F = 1783.486, P < 0.05), while there were no significant differences between the Ad-PTEN group and the Ad-G129E group, as well as between the control group and the Ad-GFP group (P > 0.05). The Ad-PTEN group and the Ad-G129E group had significant reductions in the relative concentration of Ca(2+) compared with the control group and the Ad-GFP group (251.60±90.88/352.18±146.01 vs 1953.95±132.99/1937.57±115.17, F = 834.988, P < 0.05), while there were no significant differences between the Ad-PTEN group and the Ad-G129E group, as well as between the control group and the Ad-GFP group (P > 0.05). Conclusion: The overexpressed wild-type PTEN and its mutant G129E can significantly inhibit the formation and reconfiguration of cytoskeletal protein F-actin and reduce the concentration of Ca2+ in activated HSCs in vitro. In addition, there are no significant differences in the above effects between wild-type PTEN and G129E.

Identification of a novel stress regulated FERM domain containing cytosolic protein having PTP activity in Setaria cervi, a bovine filarial parasite

A 67 kDa cytosolic FERM domain containing protein having significant protein tyrosine phosphatases activity (PTPL) has been purified to homogeneity from Setaria cervi, a bovine filarial parasite. The MALDI-MS/MS analysis of the purified protein revealed 16 peptide peaks showing nearest match to Brugia malayi Moesin/ezrin/radixin homolog 1 protein and one peptide showing significant similarity with a region lying in the catalytic domain of human PTPD1. PTPL showed significant cross reactivity with the human PTP1B antibody and colocalize with actin in the coelomyrian cells of hypodermis in the parasite. PTPL was stress regulated as it showed marked decrease in the expression when exposed to Aspirin, an antifilarial drug and Phenylarsine Oxide, PTP inhibitor.

Deficiency of the 15-kDa selenoprotein led to cytoskeleton remodeling and non-apoptotic membrane blebbing through a RhoA/ROCK pathway

The 15-kDa selenoprotein (Sep15) has been implicated in etiology of some types of cancer. Herein, inducible RNAi cell lines were established and cell morphology and motility were analyzed. The majority of Sep15-deficient cells (>95%) formed membrane blebs in a dynamic manner. Blebbing cells transformed cell morphology from a normal flat spindle shape to a spherical morphology. In blebbing cells, actin fibers moved to the cell periphery, covering and obscuring visualization of α-tubulin. Bleb formation was suppressed by the inhibitors of Rho-associated protein kinase (ROCK), RhoA or myosin light chain (MLC), restoring blebbing cells to wild-type morphology. RhoA activation and phosphorylation of myosin phosphatase target subunit 1 was induced by Sep15 knockdown. Sep15-deficient cells were non-apoptotic, and displayed a distinct relative localization of F-actin and α-tubulin from typical apoptotic blebbing cells. Our data suggest that Sep15 in Chang liver cells regulates the pathway that antagonizes RhoA/ROCK/MLC-dependent non-apoptotic bleb formation.

Motor domain-based motility system and motile properties of alpha heavy chain in Tetrahymena outer arm dynein

Axonemal dynein plays an essential role in ciliary motility, and impaired ciliary motility causes human diseases such as primary ciliary dyskinesia (PCD). The motor domain of axonemal dynein powers ciliary motility and its function is regulated by several accessary proteins bound to the tail region. Therefore, to understand the essential properties of dynein motility, examining the motile properties of the motor domain without the tail is necessary. In this study, the functional motor domain of the alpha heavy chain in Tetrahymena outer arm dynein was purified, and its motile properties were examined using an in vitro motility system. The purified protein caused microtubules to glide at a velocity of 5.0μm/s with their minus-end trailing, and motility was inhibited in an ATP concentration-dependent manner, which is in contrast with kinesin1. This method could be applicable to other axonemal dyneins and will enable further molecular studies on diverse axonemal dyneins and ciliary motility.

The functional expression and motile properties of recombinant outer arm dynein from Tetrahymena

Cilia and flagella are motile organelles that play various roles in eukaryotic cells. Ciliary movement is driven by axonemal dyneins (outer arm and inner arm dyneins) that bind to peripheral microtubule doublets. Elucidating the molecular mechanism of ciliary movement requires the genetic engineering of axonemal dyneins; however, no expression system for axonemal dyneins has been previously established. This study is the first to purify recombinant axonemal dynein with motile activity. In the ciliated protozoan Tetrahymena, recombinant outer arm dynein purified from ciliary extract was able to slide microtubules in a gliding assay. Furthermore, the recombinant dynein moved processively along microtubules in a single-molecule motility assay. This expression system will be useful for investigating the unique properties of diverse axonemal dyneins and will enable future molecular studies on ciliary movement.