• Proceedings of the Zoological Society Korea Conference
• /
• 1999.10b
• /
• pp.182.1-182
• /
• 1999

No Abstract, See Full Text

• Biomedical Science Letters
• /
• v.14 no.3
• /
• pp.179-186
• /
• 2008

Matrix metalloproteinases (MMPs), also designated matrixins, hydrolyze components of the extracellular matrix. These proteinases playa central role in many biological processes, such as embryogenesis, normal tissue remodeling, wound healing, and angiogenesis, and in diseases such as atheroma, arthritis, cancer, and tissue ulceration. In previous data, disruption of the actin cytoskeleton by cytochalasin D (CD) inhibited NO-induced apoptosis, dedifferentiation, cyclooxygenase (COX)-2 expression, and prostaglandin $E_2$ production in chondrocytes cultured on plastic or during cartilage explants culture. In this study, we investigated the effects of the actin cytoskeleton architecture on MMP-2 expression and dedifferentiation by CD in rabbit articular chondrocytes. Rabbit articular chondrocytes were prepared from cartilage slices of 2-weeks-old New Zealand white rabbits by enzymatic digestion. CD was used as a disruptor of actin cytoskeleton. In this experiments measuring CD dose response, primary chondrocytes were treated with various concentrations of CD for 24h. The actin disruption was determined by immunostaining. MMP-2 expression levels were determined by immunoblot analysis and Reverse transcriptase-Polymerase chain reaction (RT-PCR) and MMP-2 activity was determined by gelatin zymography. We found that cell morphological change and up-regulation of MMP-2 expression by CD as determined via immunostaining, gelatin zymography and immunoblotting. Moreover, CD induced MMP-2 transcription was detected by RT-PCR. Also, CD-induced type II collagen expression was inhibited by MMP-2 inhibitor I treatment. Our results indicate that CD up-regulated MMP-2 activation causes dedifferentiation of articular chondrocyte.

• Journal of Life Science
• /
• v.21 no.10
• /
• pp.1401-1406
• /
• 2011

Morphological changes in immune cells occur due to pathogen infection and natural circulation. T cells produce uropod, filopodia, lamellipodia, and microvilli for inflammation, immunosurvelliance, migration, and diapedesis. Short finger-like microvilli cover the surfaces of circulating mammalian immune cells. The surface features of monocytes and neutrophils are quite different, containing membrane ruffles as their predominant structure. In this study, we present the involvement of actin cytoskeleton regarding T lymphocyte microvilli. From analysis of scanning electron micrographs, Jurkat T lymphocyte microvilli was observed to rapidly disassemble when exposed to the actin-sequestering molecule, cytochalasin D. In contrast to cytochalasin D treatment, we found that median microvillar thickness was enlarged on Jurkat T lymphocytes treated with PMA via Lin-11, Isl-1, Mec-3 Kinase (LIMK) and cofilin signaling. In addition, actin cytoskeleton was involved in polarity formation in EL4 T lymphocytes. These results suggest that microvilli formation or polarity of T lymphocytes are involved in actin cytoskeleton dynamics.

• Toxicological Research
• /
• v.17
• /
• pp.105-108
• /
• 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.

• The Korean Journal of Physiology
• /
• v.20 no.2
• /
• pp.209-217
• /
• 1986

The functional molecular weight of band 4.5 polypeptide was measured by applying the classical target theory to radiation inactivation data of the cytochalasin B binding. Band 4.5 polypeptides purified from human erythrocyte membranes were irradiated at -45 to $-50^{\circ}C$ with an increasing dose of 1.5 MeV electron beam, and after thawing, cytochalasin B binding activities were assayed. Each activity measured was reduced as a simple exponential function of radiation dose. $D_{37}$, dose appeared to be 6.7 mega rads, from which the target size (radiation sensitive mass) of band 4.5 polypeptide was calculated to be 95,500 daltons. This result with other informations available in literature suggests that band 4.5 polypeptide may exist as a dimer in human erythrocytes.

• Proceedings of the Zoological Society Korea Conference
• /
• 1998.10b
• /
• pp.236.2-236
• /
• 1998

No Abstract, See Full Text

• 한국전자현미경학회:학술대회논문집
• /
• 1998.05a
• /
• pp.23-24
• /
• 1998

• Biomedical Science Letters
• /
• v.15 no.1
• /
• pp.55-60
• /
• 2009

Insect cells such as Spodoptera frugiperda Clone 9 (Sf9) cells are widely chosen as the host for heterologous expression of a mammalian sugar transport protein using the baculovirus expression system. Characterization of the expressed protein is expected to include assay of its function, including its ability to transport sugars and to bind inhibitory ligands such as cytochalasin B. It is therefore very important first to establish the transport characteristics and other properties of the endogenous sugar transport proteins of the host insect cells. However, very little is known of the transport characteristics of Sf9 cells, although their ability to grow on TC-100 medium strongly suggested the presence of endogenous glucose transport system. In order to investigate the substrate and inhibitor recognition properties of the Sf9 cell transporter, the ability of pentoses to inhibit 2-deoxy-D-glucose (2dGlc) transport was investigated by measuring inhibition constants $(K_i)$. To determine the time period over which of sugar into the Sf cells was linear, the uptake of 2dGlc 0.1mM extracellular concentration was measured over periods ranging from 30 seconds to 30 minutes. The uptake was linear for at least 2 minutes at the concentration, implying that uptake made over a 1 minute time course would reflect initial rates of the sugar uptake. The data have also revealed the existence of a saturable transport system for pentose uptake by the insect cells. The transport was inhibited by D-xylose and D-ribose, although not as effective as hexoses. However, L-xylose had a little effect on 2dGlc transport in the Sf9 cells, indicating that the transport is stereoselective. Unlike the human erythrocyte-type glucose transport system, D-ribose had a somewhat greater apparent affinity for the Sf9 cell transporter than D-xylose. It is therefore concluded that Sf9 cells contain an endogenous sugar transport activity that in some aspects resembled the human erythrocyte-type counterpart, although the Sf9 and human transport systems do differ in their affinity for cytochalasin B.

• Biomedical Science Letters
• /
• v.11 no.3
• /
• pp.327-332
• /
• 2005

Sf21 cells become popular as the host permissive cell line to support the baculovirus AcNPV replication and protein synthesis. The cells grow well on TC-100 medium that contains $0.1\%$ D-glucose as the major carbon source, strongly suggesting the presence of endogenous glucose transporters. However, unlike human glucose transporters, very little is known about the characteristics of the endogenoussugar transporter(s) in Sf21 cells. Thus, some kinetic properties of the sugar transport system were investigated, involving the uptake of 2-deoxy-D-glucose (2dG1c). In order to obtain a true measure of the initial rate of uptake, the uptake of $[^3H]2dGlc$ from both low $(100{\mu}M)$ and high (10 mM) extracellular concentrations was measured over periods ranging from 30 sec to30 min. The data obtained indicated that the uptake was linear for at least 2 min at both concentrations, suggesting that measurements made over a 1min time course would reflect initial rates of the jexpse uptake. To determine $K_m\;and\;V_{max}$ of the endogenous glucose transporter(s) in Sf21 cells, the uptake of 2dG1c was measured over a range of substrate concentrations $(50{\mu}M\~10mM)$ 2dG1c uptake by the Sf21 cells appeared to involve both saturable and non-saturable (or very low affinity) components. A saturable transport system for 2dG1c was relatively high, the $K_m$ value for uptake being < 0.45 mM. The $V_{max}$ value obtained for 2dG1c transport in the Sf21 cells was about 9.7-folds higher than that reported for Chinese hamster ovary cells, which contain a GLUT1 homologue. Thus, it appeared that the transport activity of the Sf21 cells was very high. In addition, the Sf21 glucose transporter was found to have very low affinity for cytochalasin B, a potent inhibitor of human erythrocyte glucose transporter

• Biomedical Science Letters
• /
• v.15 no.4
• /
• pp.343-347
• /
• 2009

Cytochalasin D (CD) is known as a disruptor of actin cytoskeleton architecture in chondrocytes. We have studied the role of CD in retinoic acid (RA) caused dedifferentiation and inflammation responses in rabbit articular chondrocytes. We have examined the effect of CD on RA induced dedifferentiation of chondrocytes. CD inhibited RA induced dedifferentiation determined by Western blot analysis and Alcian blue staining in rabbit articular chondrocytes. Also, CD additionally reduced inflammation response molecules such as cyclooxygenase-2 (COX-2) and prostaglandin $E_2$ ($PGE_2$) in RA treated cells. Treatment of CD reduced phosphorylation of p38 by treatment of RA. Inhibiton of p38kinase with SB203580 reduced expression of COX-2 and production of $PGE_2$ by treatment of CD in RA treated cells. But, Inhibiton of p38kinase with SB203580 did not any relationship with effect of CD on RA caused dedifferentiation. In summary, our results indicate that CD regulates RA reduced expression of COX-2 and production of PGE2 via p38kinase pathway.