Biomedical subjects

Sung Dae Kim

Publications and source records attributed to Sung Dae Kim.

5 recordsLinked to original sources

PubMed2006

Molecular characterization of miniature porcine RANTES and its chemotactic effect on human mononuclear cells.

To elucidate the potential role of porcine RANTES (Regulated upon Activation Normal T cells Expressed and Secreted) in xenograft rejection, we investigated its chemotactic activity for human mononuclear cells, as well as the effect of human cytokines on its expression in porcine endothelial cells. Porcine RANTES cDNA was successfully cloned from aortic endothelial cells of miniature pigs, and its protein expression was induced by transfection. Its deduced amino acid sequence was 83.5% identical to that of human RANTES. Porcine RANTES triggered transmigration of human mononuclear cells across the species barrier, and this chemotactic effect was suppressed by anti-RANTES neutralizing antibodies. The chemotactic effect of porcine RANTES was most prominent on human monocytes. Human tumor necrosis factor-alpha induced significant expression of porcine RANTES messenger RNA in endothelial cells; however both human interferon-gamma and interleukin-1beta failed. These results suggest that porcine RANTES can play an important role in xenotransplant rejection, through participating in the interaction between porcine endothelial cells and human monocytes.

Amino Acid Sequence↗

PubMed2006

Mechanism of isoproterenol-induced RGS2 up-regulation in astrocytes.

Regulators of G protein signaling (RGSs) are inducibly expressed in response to various stimuli and the up-regulation of RGSs leads to significant decreases in GPCR responsiveness. Isoproterenol, an adrenergic receptor agonist, stimulated RGS2 mRNA in C6 rat astrocytoma cells. The up-regulation of RGS2 mRNA was abrogated by genistein, a protein tyrosine kinase inhibitor (PTK), and by broad-spectrum protein kinase C (PKC) inhibitors (staurosporine and GF109203X). alpha-Adrenergic antagonist (prazocin), beta-adrenergic antagonist (prazocin), and pertussis toxin only partially blocked the RGS2 up-regulation, suggesting that the RGS2 up-regulation is concomitantly mediated by Galphai, Galphas, and Galphaq. It is interesting to note that SB203580, a potent p38 mitogen-activated protein kinase (MAPK) inhibitor, completely inhibited the isoproterenol-mediated RGS2 expression. In addition, isoproterenol also markedly stimulated RGS2 mRNA in rat primary astrocytes, which were sensitive to SB203580 and staurosporine. Therefore, our data suggest that adrenergic receptor-mediated signaling (induced by isoproterenol) may be involved in the regulation of RGS2 expression in astrocytes via activating PTK, PKC, and p38 MAPK.

Animals↗

PubMed2006

The expression patterns of RGS transcripts in platelets.

Regulators of G protein signalling (RGS) are involved in the negative regulation of cell activation processes and are involved in the pathophysiology of cardiovascular diseases. To get some further evidence for a role of RGS proteins in platelets, we determined the expression profile of RGS-specific mRNA in rat platelets using reverse transcription-polymerase chain reaction (RT-PCR) with a poly dT18 primer and transcript-specific primers. We found that RGS2, RGS3, RGS5, RGS6, RGS10, RGS14, RGS16 and RGS18, Leukemia-associated Rho-GEF factor (LARG), and Galpha interacting protein (GAIP) were differentially expressed in platelets. The highest expression rate was found for RGS18 (about 1.3 fold when compared to GAPDH), followed by LARG, RGS6, RGS10 and RGS16 (0.7 to 0.95), whereas expression rates for RGS2, RGS3, RGS5, RGS14, and GAIP were in a range of 0.1 to 0.3. Our results suggest that G-protein-coupled receptor-mediated signalling in platelet may be regulated mainly by RGS 18, 16, 10, 6, and LARG.

Animals↗

PubMed2006

Surfactin C inhibits platelet aggregation.

This study was designed to investigate the effect of surfactin C, which is derived from Bacillus subtilis, on platelet aggregation and homotypic leucocyte aggregation. Surfactin C strongly and dose-dependently inhibited platelet aggregation, which was stimulated both by thrombin (0.1 U mL(-1)), a potent agonist that activates the G protein-coupled protease receptor, and by collagen (5 microg mL(-1)), a potent ligand that activates alpha(IIb)beta(3) with IC50 values (concentration inhibiting platelet aggregation by 50%) of 10.9 and 17.0 microM, respectively. Moreover, surfactin C significantly suppressed the intracellular Ca(2+) mobilization in thrombin-activated platelets. Surfactin C, however, did not affect various integrin-mediated U937 cell aggregation, implying that the anti-platelet activity of surfactin C was not due to its detergent effect but by its action on the downstream signalling pathway. Therefore, the results suggest that surfactin C may have a beneficial therapeutic effect on aberrant platelet aggregation-mediated cardiovascular diseases.

Animals↗

PubMed2005

Molecular cloning, expression and functional characterization of miniature swine CD86.

CD86 is one of the key molecules involved in the co-stimulation of T cells. The complete cDNA encoding CD86 molecule of miniature swine was cloned and analyzed. A comparison of two CD86 amino acid sequences of miniature swine and domestic swine showed only three amino acid differences suggesting that it is unlikely to affect the major structural features of the miniature swine CD86 (msCD86). In the expression study, constitutive expression of CD86 mRNA was detected in various tissues, and the aberrant expression of the transcriptional variant (putative soluble form) was noted. The cDNA and amino acid sequences for this variant were determined and compared with those for the human soluble CD86, which was previously reported to co-stimulate the T cells. Interestingly, an alignment of the two sequences revealed that 51 amino acids corresponding to the sequence for the boundary of the extracellular and intracellular domains including the transmembrane domain are deleted at almost an identical location within the full form of CD86 from both species. This suggests the possibility of a co-stimulatory function of the putative soluble msCD86. In order to determine if the cloned msCD86 molecules has co-stimulatory activity, the proliferative responses of the human CD4(+) T cells to the msCD86-transfected COS cells were measured in the presence of Con A. The results revealed that CD86/COS, but not the mock/COS, efficiently co-stimulated the proliferation of the Con A-stimulated CD4(+) T cells and this co-stimulatory effect was blocked by CTLA4-Ig. The structural and functional information on the miniature swine CD86 from this study will enable a further genetic manipulation of CD86 as a therapeutic strategy for controlling the xenogeneic T cell immune responses mediated by the CD86-CD28 signal pathway.

Amino Acid Sequence↗