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Syndecan-4-PKCα complex interacted and induced phosphorylation of α-actinin
Oh, Eok-Soo 이화여자대학교 세포신호전달연구센터 2001 고사리 세포신호전달 심포지움 Vol. No.3
Syndecan-4, one of cell surface heparan sulfate proteoglycans, is known to regulate the organization of cytoskeleton and/or actin microfilaments. Upon plating on fibronectin, syndecan-4 functions as co-receptor for integrin, and these two receptors cooperatively regulate focal adhesion and stress fiber formations. Previously, we have shown that syndecan-4 cytoplasmic domain interacts with PIP2 and potentiate protein kinase Cα(PKCα) activity to regulate this events. However, it is not much known about the detail mechanism. Therefore, we further investigated the activation mechanism and downstream substrate of syndecan-4 and PKCα complex. We first investigated several cytoskeletal proteins which might interact with syndecan4 cytoplasmic domain by (1) GST-pull down assay using recombinant GST-syndecan-4 mutants and (2) syndecan-4 peptide-conjugated column chromatography. Among them, α-actinin is the only one that interacted with syndecan-4 cytoplasmic domain. Consistently, over-expression of syndecan-4 caused localization of α-actinin into 1% Triton-X100 insoluble fraction of Rat Embryo Fibroblasts(REFs). This interaction was dependent on oligomeric status of syndecan-4 cytoplasmic domain, and occurred through interaction with PIP2. Both gel filtration and NMR studies confirmed that syndecan-4 cytoplasmic domain itself forms a dimer and further stabilized by PIP2. In vitro kinase assay showed that sydnecan-4 cytoplasmic domain activated specifically PKCα, but not others, in the presence of PIP-2, implying specific activation of PKCαby syndecan-4 cytoplasmic domain. Phosphorylation of α-actinin in vivo was also confirmed using phospho-enrichment column chromatography. In addition, syndecan-4-PIP-2-PKCα complex phosphorylated purified recombinant α-actinin in vitro. Therefore, we believe that syndecan-4-PKCα complex interacts and induces phosphorylation of α-actinin to regulate focal adhesion and stress fiber formations.
Syndecans-2 and -4; close cousins, but not identical twins.
Oh, Eok-Soo,Couchman, John R Korean Society for Molecular Biology 2004 Molecules and cells Vol.17 No.2
<P>The vertebrate syndecans, which make up a four-member family of small type I transmembrane heparan sulfate proteoglycans, constitute evolutionarily conserved family proteins. In particular, sequences in the transmembrane and cytoplasmic domains are a unifying feature within the family. However, the extracellular domain sequences are molecule-specific, implying that different syndecans have evolved to carry out similar, but non-identical, functions. While all four syndecans have been implicated in regulation of the cytoskeleton, their roles are clearly complex. Recent developments indicate that the closely related syndecan-2 and -4 have separable functions, though both bind a number of ligands through their heparan sulfate chains. The specification of these activities is probably core protein related, but is it due to a distinct expression pattern or molecule-specific regulatory mechanisms? Although there is not yet enough data to provide unambiguous answers, here we shall review the known functions and regulatory mechanisms of syndecan-2 and -4.</P>
Regulation of early events in integrin signaling by the protein-tyrosine phosphatase SHP-2
Oh, Eok-soo 이화여자대학교 세포신호전달연구센터 1999 고사리 세포신호전달 심포지움 Vol. No.1
The non-transmembrane protein-tyrosine phosphatase SHP-2 plays a critical role in growth factor/cytokine signaling pathways. Previous studies revealed that a fraction of SHP-2 moves to focal contacts upon integrin engagement, and SHP-2 binds to SHPS-1/SIRP-1a, a transmembrane glycoprotein with adhesion molecule characteristics. Therefore, we asked whether SHP-2/SHPS-1 complexes participate in integrin signaling. SHPS-1 tyrosyl phosphorylation increased upon plating of murine fibroblasts onto specific extracellular matrices. Both in vitro and in vivo studies indicate that SHPS-1 tyrosyl phosphorylation is catalyzed by Src family PTKs. Overexpression of SHPS-1 in 293 cells protentiated integrin-mediated MAPK activation and potentiation required functional SHP-2. To further explore the role of SHP-2 in integrin signaling, we analyzed the response of SHP-2 exon 3(-/-) and wild type cell lines to plating on fibronectin. Integrin-induced activation of Src family PTKs, tyrosyl phosphorylation of several focal adhesion proteins, MAPK activation, and spreading on fibronectin were defective in SHP-2 mutant fibroblasts, but were restored upon SHP-2 expression. Our data suggest that, upon integrin engagement, basal level of cSrc activity catalyze the tyrosyl phosphorvlation of SHPS-1, theredy recruiting SHP-2 to the plasma membrane, where, prehaps by further activiating Src PTKs, SHP-2 transduce positive signals for downstream events such as MAP kinase activation and cell shape changes.
Oh, Eok-Soo 이화여자대학교 세포신호전달연구센터 2003 고사리 세포신호전달 심포지움 Vol. No.5
Syndecan-4, one of cell surface heparan sulphate proteoglycans, play a role in a variety of cellular functions, including cell proliferation and cell-matrix and cell-cell adhesion. In general, the main function of the syndecan-4 core protein is to target the heparan sulfate chains to the appropriate plasma-membrane compartment and to interact with components of the actin-based cytoskeleton, which is dependent on interaction with phosphatidylinositol4,5-bisphosphate. These include syndecan-4 oligomerization, interactions with Protein kinase Cα and α-actinin. Syndecan-4 also regulates the function of PIP2 through regulation of its stability. In addition, their interactions are regulated by either ways; syndecan-4 phosphorylation and PIP2 metabolism. All these data suggest that there are mutual regrulatory mechanisms in the plasma membrane where syndecan-4 and PIP2 cooperatively regulates their own functions.
Syndecan-2, a key mediator of tumorigenesis and metastasis in cancer cells
Oh, Eok-Soo 이화여자대학교 세포신호전달연구센터 2009 고사리 세포신호전달 심포지움 Vol. No.11
The syndecans, a major family of transmembrane cell surface heparan sulfate proteoglycans, regulate ECM-mediated signal transduction including cell adhesion and migration. While syndecan-1 and syndecan-4 are known to inhibit cell migration, several reports indicate that syndecan-2 may have the opposite effect as the gene is highly expressed in cells under migratory conditions. Consistently, the expression of syndecan-1 and -4 is decreased in several cancer cell lines, while that of syndecan-2 was increased in several cancer cell lines compared with normal epithelial cell lines, consistent with their migratory/tumorigenic characteristics. Syndecan-2 expression was critical for cancer cell adhesion and proliferation as well as other tumorigenic behaviors such as anchorage-independent growth and increased metastasis. Therefore, increased syndecan-2 expression appears to be crucial for cancer cell carcinogenesis. However, the underlying molecular mechanism is still unclear. Since syndecan in general acts a multi-potent cell surface receptor, it is highly possible that syndecan-2 may be involved in the regulation of tumorigenic activity in many different ways. Current state of knowledge of syndecan-2 mediated tumorigenesis and metastasis of cancer cells will be presented including interactions with several prominent regulatory signal pathways implicated in cancer development.
pH가 Bacillus Cereus의 Enterotoxin 생산에 미치는 영향
김을수,이시억,이언탁,이명수,오양효 인제대학교 1988 仁濟醫學 Vol.9 No.3
Bacillus cereus에 의한 식중독의 진단에는 원인균의 분리 동정은 물론 신속한 enterotoxin의 검출이 필수적인데 enterotoxin의 생산은 배지나 배양 조건에 영향을 많이 받는다. 본 실험에서는 CAYE-2배지에서 pH 8.5에서 가장 많은 양의 enterotoxin이 생산되었다. Cell-free culture filtrates of enterotoxin producing strain of Bacillus cereus biotype I were detected by RPLA test for the production of enterotoxin. The media used were CAYE-2, Biken No. 2 and BHI medium. The results obtained were as follows : 1) Among CAYE-2, Biken No. 2 and BHI medium, enterotoxin production was the highest in CAYE-2 medium. Enterotoxin production was appreciably diminished at or below pH 6.0 and at above pH 9.0 of the various test media. 2) B. cereus produced high levels of enterotoxin when grown in CAYE-2 medium pH initial pH at 85 and the 512-1014ng quantity of enterotoxin per ml can be detected by the RPLA method.