• Parasites, Hosts and Diseases
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• 제36권4호
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• pp.227-234
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• 1998

쥐와포자충의 운동에 관여하는 구조에 대하여 다른 구충류에서와 마찬가지로 알려진 바가 없다. 이 연구에서는 쥐와포자충에서 microfilament와 그 결합단백질의 분포를 관찰하여 이 기생충의 운동기전에 대한 이해를 돕고자 하였다. Actin의 분포를 보기 위해 두 종류의 actin, 즉 닭 골격근과 평활근의 actin에 대한 항체를 사용하였고, tropomyosin의 관찰을 위해서는 닭 골격근의 tropomyosin에 대한 항체를 이용하여 면역황금표지법으로 관찰하였다. 관찰된 모든 발육단계의 쥐와포자충이 actin과 tropomyosin을 가지고 있었는데 두 종류의 actin은 서로 다른 부위에서 관찰되었다. 즉, 골격근에 대한 항체는 주로 세포질과 세포막 구조에 표지되었고, 평활근에 대한 항체는 feeder organelle과 숙주세포 사이의 섬유질 구조 (filamentous cytoplasm)에 주로 표지되어 서로 다른 actin이 상이하게 분포하고 있음을 알 수 있었다. 분포 위치로 미루어 볼 때 골격근형 actin은 기생충의 세포질 내 여러 가지 현상에, 평활근형 actin은 쥐와포자충과 숙주세포 부착을 유지시키는데 주요 역할을 할 것으로 생각된다. Tropomyosin은 쥐와포자충 모든 발육단계에서 관찰되었는데 세포막에 주로 분포하였고 세포질 내의 소공포 (vacuole) 막 주위 및 핵 주위에서도 관찰되었다. Tropomyosin은 쥐와포자충의 발육단계가 변함에 따라 끊임없이 분포를 달리하는 것으로 생각되며 특히 막구조에 다수 분포하므로 항원으로서 숙주세포를 자극할 가능성이 있는 것으로 보인다.

• Fisheries and Aquatic Sciences
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• 제12권2호
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• pp.90-97
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• 2009

The cytoskeletal $\beta$-actin gene and its 5'-upstream region were isolated and characterized in the rockbream (Oplegnathus fasciatus). Complementary DNA of the rockbream $\beta$-actin represented a 1,125 bp of an open reading frame encoding 375 amino acids, and the rockbream $\beta$-actin cDNA and deduced amino acid sequences were highly homologous to those of other vertebrate orthologs. At the genomic level, the $\beta$-actin gene also exhibited an organization typical of vertebrate cytoskeletal actin genes (2,159 bp composed of five translated exons interrupted by four introns) with a conserved GT/AG exon-intron splicing rule. The putative non-translated exon predicted in the rockbream $\beta$-actin gene was much more homologous with those of teleostean $\beta$-actin genes than those of mammals. The 5'-upstream regulatory region isolated by genome walking displayed conserved and essential elements such as TATA, CArG and CAAT boxes in its proximal part, while several other immune- or stress-related motifs such as those for NF-kappa B, USF, HNF, AP-1 and C/EBP were in the distal part. Semi-quantitative RT-PCR assay results demonstrated that the rockbream $\beta$-actin transcripts were ubiquitously but different-tially expressed across the tissues of juveniles.

• BMB Reports
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• 제33권6호
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• pp.531-536
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• 2000

Tropomyosin (TM) is an important actin binding protein involved in regulation of muscle contraction. Unacetylated striated tropomyosin failed to bind to actin whereas unacetylated smooth tropomyosin bound well to actin. It has been demonstrated that high actin affinity of unacetylated ${\alpha}-tropomyosin$ was ascribed to the carboxyl terminal amino acid residues. In order to define the role of the carboxyl terminal residues of tropomyosin molecule on actin binding, two mutant tropomyosins were constructed. TM11 is identical to the striated tropomyosin except that the carboxyl terminal last three amino acids was replaced with $^{282}NNM^{284}$ whereas in TM14 $^{276}HA^{277}$ was substituted with smooth specific $^{276}QT^{277}$. TM11 and TM14 were overproduced in Escherichia coli and analyzed for actin affinity. The apparent binding constants (Kapp) of unacetylated tropomyosins were $2.2{\times}10^6M^{-1}$ for sm9, $1.03{\times}10^6M^{-1}$ for TM14, $0.19{\times}10^6M^{-1}$ for TM11, $>0.1{\times}10^6M^{-1}$ for striated, respectively. This result indicated that higher actin affinity of the unacetylated smooth tropomyosin was primarily attributed to the presence of QT residues in the smooth sequence. In case of the Ala-Ser (AS) dipeptide extension of the amino terminus of tropomyosin, Kapp were $21.1{\times}10^6M^{-1}$ for AS-sm9, $8.0{\times}10^6M^{-1}$ for AS-11, $4.7{\times}10^6M^{-1}$ for AS-14, $3.8{\times}10^6M^{-1}$ for AS-striated. AS-TM11 showed considerably higher actin affinity than AS-TM14, implying that interaction of Ala-Ser of the amino terminus with the carboxyl terminal residues. Since Kapp of AS-TM11 was significantly lower than that of AS-sm9, the presence of QT might be required for restoration of high actin affinity of the smooth ${\alpha}-tropomyosin$. These results suggested that the carboxyl terminal amino acid residues Glutamine275-Threonine276 are important for actin affinity of the recombinant smooth ${\alpha}-tropomyosin$, particularly of unacetylated smooth ${\alpha}-tropomyosin$.

• BMB Reports
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• 제35권6호
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• pp.562-567
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• 2002

In order to find the cellular interaction factors of the Heliothis armigera nuclear polyhedrosis virus capsid protein VP39, a Heliothis armigera cell cDNA library was constructed. Then VP39 was used as bait. The host actin gene was isolated from the cDNA library with the yeast two-hybrid system. This demonstrated that VP39 could interact with its host actin in yeast. In order to corroborate this interaction in vivo, the vp39 gene was fused with the green fluorescent protein gene in plasmid pEGFP39. The fusion protein was expressed in the Hz-AM1 cells under the control of the Autographa californica multiple nucleopolyhedrovirus immediate early gene promoter. The host actin was labeled specifically by the red fluorescence substance, tetramethy rhodamine isothicyanete-phalloidin. Observation under a fluorescence microscopy showed that VP39, which was indicated by green fluorescence, began to appear in the cells 6 h after being transfected with pEGFP39. Red actin cables were also formed in the cytoplasm at the same time. Actin was aggregated in the nucleus 9 h after the transfection. The green and red fluorescence always appeared in the same location of the cells, which demonstrated that VP39 could combine with the host actin. Such a combination would result in the actin skeleton rearrangement.

• Parasites, Hosts and Diseases
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• 제44권4호
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• pp.331-341
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• 2006

Actin binding proteins play key roles in cell structure and movement particularly as regulators of the assembly, stability and localization of actin filaments in the cytoplasm. In the present study, a cDNA clone encoding an actin bundling protein named as AhABP was isolated from Acanthamoeba healyi, a causative agent of granulomatous amebic encephalitis. This clone exhibited high similarity with genes of Physarum polycephalum and Dictyostelium discoideum, which encode actin bundling proteins. Domain search analysis revealed the presence of essential conserved regions, i.e., an active actin binding site and 2 putative calcium binding EF-hands. Transfected amoeba cells demonstrated that AhABP is primarily localized in phagocytic cups, peripheral edges, pseudopods, and in cortical cytoplasm where actins are most abundant. Moreover, AhABP after the deletion of essential regions formed ellipsoidal inclusions within transfected cells. High-speed co-sedimentation assays revealed that AhABP directly interacted with actin in the presence of up to $10{\mu}M$ of calcium. Under the electron microscope, thick parallel bundles were formed by full length AhABP, in contrast to the thin actin bundles formed by constructs with deletion sites. In the light of these results, we conclude that AhABP is a novel actin bundling protein that is importantly associated with actin filaments in the cytoplasm.

• BMB Reports
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• 제29권5호
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• pp.474-480
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• 1996

We present a study of evolutionary changes in expression of actin genes among closely related sea urchin species that exhibit different modes of early development. For this purpose, polyclonal antisera raised against peptides from the carboxyl terminus of the HeCyI cytoskeletal actin of Heliocidaris erythrogramma were used. H. erythrogramma is a direct developing sea urchin that proceeds from embryonic to adult stages without an intervening feeding larval stage. Expression patterns of the CyI actin isoform were compared with those of Heliocidaris tuberculata and to a related sea urchin Strongylocentrotus purpuratus, which both produce a feeding pluteus larval stage. The CyI actin of all three species is expressed in the same cell types. However, its expression patterns have been changed with reorganization of early cell lineage differentiation, which is apparent among the three species. Thus. evolutionary changes in CyI actin gene expression patterns are correlated with not only phylogenetic relationship, but developmental mode. The implication of this observation is that evolutionary changes in expression patterns of histospecific genes may underlie the emergence of novel developmental processes.

• BMB Reports
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• 제51권3호
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• pp.151-156
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• 2018

The Hippo signaling pathway controls nuclear accumulation and stability of the transcriptional coregulator YAP and its paralog TAZ. The activity of Hippo-YAP signaling is influenced not only by biochemical signals, but also by cell shape and mechanical tension transmitted through cell-cell junctions and cell-matrix adhesions. Data accumulated thus far indicates that the actin cytoskeleton is a key mediator of the regulation of Hippo-YAP signaling by means of a variety of biochemical and mechanical cues. In this review, we have outlined the role of actin dynamics and actin-associated proteins in the regulation of Hippo-YAP signaling. In addition, we discuss actin-mediated regulation of YAP/TAZ activity independent of the core Hippo kinases MST and LATS. Although our understanding of the link between Hippo-YAP signaling and the actin cytoskeleton is progressing rapidly, many open questions remain.

• Journal of Photoscience
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• 제9권2호
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• pp.326-328
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• 2002

In many plant cells, the positions of chloroplasts change in response to changes in light conditions. In the epidermal cells of the aquatic angiosperm Vallisneria gigantea, the avoidance response of chloroplasts is induced specifically by irradiation with blue light of high intensity. Possible roles of actin cytoskeleton in the blue-light-induced avoidance response of chloroplasts were investigated by partial irradiation and phalloidin staining. We showed that the blue-light-dependent redistribution of chloroplasts was induced only in the limited area, where exposed to blue light, even in individual cells. In addition. in the exposed area, the configuration of actin filaments strikingly changed compared with that before the irradiation. Short and thick bundles of actin filaments surrounding the chloroplasts changed to much longer and thinner bundles with a more stretched array. In contrast, in the unexposed area, neither the distribution of chloroplasts nor the configuration of actin filaments exhibited any changes. Cytochalasin D and latrunculin B inhibited the avoidance response of chloroplasts concomitantly with the fragmentation of actin filaments. These results indicate that the reorganization of actin filaments plays a crucial role in the induction of avoidance response of chloroplasts.

• Toxicological Research
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• 제17권
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• pp.105-108
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• 2001

Several marine toxins with macrolide structure have been found to act on actin. One of these toxins is mycalolide B isolated from the genus Mycale. This compound belongs to macrolide antibiotics and consists of tris-oxazole with strong cytotoxic activity ($IC_{50}$: 10-50 nM for growth of L1210 murine leukemia cells). This compound was found to be an actin-depolymerizing agent with the mode of action distinct from that of the known actin inhibitor, cytochalasin D. Tolytoxin, a macrolide isolated from cyano-bacteria with similar chemical structure to mycalolide B, seems to have similar effect. Another macrolide compound, aplyronine A, showed the effects similar to those of mycalolide B. Although bistheonellide A, a dimeric macrolide, did not show a severing effect, it de polymerized F-actin and sequestered G-actin by forming 1 : 2 complex with G-actins. Swinholide A has a structure and effects similar to those of bistheonel-lide A. In conclusion, mycalolide B, tolytoxin, aplyronine A, bistheonellide A and swinholide A are the members of "actin de polymerizing macrolide" the mechanism of which is different from that of cytochalasin D.halasin D.

• Animal cells and systems
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• 제5권3호
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• pp.205-209
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• 2001

Mesenchymal cells from the leg buds of stage 24-chick embryos differentiated into chondrocytes when plated at high density. Treatment of high density micromass culture of chick mesenchymal cells with cytochalasin D(CD, 2 $\mu$M for 24 h) resulted in inhibition of chondrogenesis. CD treatment was found to affect the expression of the contractile protein $\alpha$-smooth muscle actin ($\alpha$-SM actin). In control cultures, $\alpha$-SM actin uniformly expressed from culture day 2, but the CD-treated cells induced expression of $\alpha$-SM actin from the first day of culture followed by a continuous increase. Expression of pan-cadherin (P-cadherin) decreased as chondrogenesis proceeded in the control culture, whereas the CD-treated cells showed sustained expression. These results propose a close connection of chondrogenic differentiation with expression of $\alpha$-SM actin and P-cadherin.