• Molecules and Cells
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• v.21 no.3
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• pp.428-435
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• 2006

Specific interaction of the epsin N-terminal homology(ENTH) domain with the plasma membrane appears to bridge other related proteins to the specific regions of the membrane that are invaginated to form endocytic vesicles. An additional $\alpha$-helix, referred to as helix 0 (H0), is formed in the presence of the soluble ligand inositol-1,4,5-trisphosphate [$Ins(1,4,5)P_3$] at the N terminus of the ENTH domain (amino acid residues 3-15). The ENTH domain alone and full-length epsin cause tubulation of liposomes made of brain lipids. Thus, it is believed that H0 is membrane-inserted when it is coordinated with the phospholipid phosphatidylinositol-4,5-bisphosphate [$PtdIns(4,5)P_2$], resulting in membrane deformation as well as recruitment of accessory factors to the membrane. However, formation of H0 in a real biological membrane has not been demonstrated. In the present study, the membrane structure of H0 was determined by measurement of electron paramagnetic resonance (EPR) nitroxide accessibility. H0 was located at the phosphate head-group region of the membrane. Moreover, EPR line-shape analysis indicated that no pre-formed H0-like structure were present on normal acidic membranes. $PtdIns(4,5)P_2$ was necessary and sufficient for interaction of the H0 region with the membrane. H0 was stable only in the membrane. In conclusion, the H0 region of the ENTH domain has an intrinsic ability to form H0 in a $PtdIns(4,5)P_2$-containing membrane, perhaps functioning as a sensor of membrane patches enriched with $PtdIns(4,5)P_2$ that will initiate curvature to form endocytic vesicles.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.10a
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• pp.175-176
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• 2000

PtdIns(4)P와 PtdIns(4,5)P$_2$등과 같은 폴리포스이노시타이드(Polyphosph-oinositide)는 여러 가지 호르몬 및 성장인자들에 의한 세포의 신호전달기작에 있어서 중요한 역할을 한다. 이들은 세포내 여러효소 및 단백질의 활성을 조절하기도 하고, cofilin(1), destrin(2), $\alpha$-actinin(3), gCap39(4) 및 CapZ등과 같은 여러 actin binding protein들의 성질을 변화시키기도 한다. (중략)

• Journal of Life Science
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• v.24 no.1
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• pp.14-19
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• 2014

Kinesin-1 consists of two heavy chains (KHCs), also called KIF5s, and two light chains (KLCs) that form a heterotetrameric complex. Here, we demonstrate the binding of a neuronal KHC, KIF5A, to the carboxyl (C)-terminal tail region of Fig4 (also known as Sac3), a phosphatase that removes the 5-phosphate from phosphatidylinositol-3,5-bisphosphate ($PtdIns(3,5)P_2$). Fig4 bound to the C-terminal region of KIF5A but not to other KHCs (KIF5B and KIF5C) and KLC1 in yeast two-hybrid assays. The interaction was further confirmed in a glutathione S-transferase pull-down assay and by co-immunoprecipitation. Anti-KIF5A antibody co-immunoprecipitated Fig4 with KIF5A from mouse brain extracts. These results suggest that kinesin-1 could transport the Fig4-associated protein complex or cargo in cells.

• Journal of Microbiology and Biotechnology
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• v.28 no.8
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• pp.1401-1411
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• 2018

The serine-threonine kinase AKT plays a pivotal role in tumor progression and is frequently overactivated in cancer cells; this protein is therefore a critical therapeutic target for cancer intervention. We aimed to identify small molecule inhibitors of the pleckstrin homology (PH) domain of AKT to disrupt binding of phosphatidylinositol-3,4,5-trisphosphate (PIP3), thereby downregulating AKT activity. Liposome pulldown assays coupled with fluorescence spectrometry were used to screen flavonoids for inhibition of the AKT PH-PIP3 interaction. Western blotting was used to determine the effects of the inhibitors on AKT activation in cancer cells, and in silico docking was used for structural analysis and optimization of inhibitor structure. Several flavonoids showing up to 50% inhibition of the AKT PH-PIP3 interaction decreased the level of AKT activation at the cellular level. In addition, the modified flavonoid showed increased inhibitory effects and the approach would be applied to develop anticancer drug candidates. In this study, we provide a rationale for targeting the lipid-binding domain of AKT, rather than the catalytic kinase domain, in anticancer drug development.