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Green tea polyphenol sensing.

Tachibana H - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Bottom Line: Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion.There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis.However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan. tatibana@agr.kyushu-u.ac.jp

ABSTRACT
Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis. However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated. Recently we have identified a cell-surface EGCG receptor and the relating molecules that confer EGCG responsiveness to many cancer cells at physiological concentrations. Here, we review some of the reported mechanisms for the cancer chemopreventive action of EGCG and provide an overview of several molecules that sense and manage the physiological functions of EGCG.

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Related in: MedlinePlus

The signaling pathways that sense and respond to EGCG through 67LR are depicted. After EGCG binding to lipid raft-associated 67LR, through eEF1A, the phosphorylation of MYPT1 at Thr-696 but not Thr-853 is reduced, which leads to the activation of myosin phosphatase. The activated myosin phosphatase dephosphorylates its substrates (e.g. MRLC), and actin cytoskeleton rearrangement is induced. The alteration of actin cytoskeleton might lead to cell growth inhibition. EGCG also induces apoptosis in the 67LR-expressing cells derived from multiple myeloma and acute myeloid leukaemia patient samples.
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fig04: The signaling pathways that sense and respond to EGCG through 67LR are depicted. After EGCG binding to lipid raft-associated 67LR, through eEF1A, the phosphorylation of MYPT1 at Thr-696 but not Thr-853 is reduced, which leads to the activation of myosin phosphatase. The activated myosin phosphatase dephosphorylates its substrates (e.g. MRLC), and actin cytoskeleton rearrangement is induced. The alteration of actin cytoskeleton might lead to cell growth inhibition. EGCG also induces apoptosis in the 67LR-expressing cells derived from multiple myeloma and acute myeloid leukaemia patient samples.

Mentions: In both 67LR-ablated HeLa cells and eEF1A-ablated HeLa cells, the inhibitory effect of EGCG on both the phosphorylation of MYPT1 at Thr-696 and the phosphorylation of MRLC was attenuated. In addition, EGCG-induced actin cytoskeleton rearrangement was no longer observed in MYPT1-, eEF1A-, or 67LR-ablated HeLa cells. The involvement of MYPT1 in downstream EGCG-triggered signaling from both 67LR and eEF1A was further documented by confirming abrogation of 1 µM EGCG-induced reduction of the MYPT1 phosphorylation level at Thr-696 and the MRLC phosphorylation in 67LR- or eEF1A-ablated B16 cells. These results suggest that MYPT1 is involved in downstream EGCG signaling from both 67LR and eEF1A (Fig. 4). It has been reported that MYPT1 binds to eEF1A,92) and more than half of the total eEF1A (>60%) binds to the actin cytoskeleton.93) Characterizing the mechanisms by which EGCG induces reduction of the MYPT1 phosphorylation at Thr-696 and reorganization of actin cytoskeleton through eEF1A should help in more precise understanding of cytoskeleton organization.


Green tea polyphenol sensing.

Tachibana H - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

The signaling pathways that sense and respond to EGCG through 67LR are depicted. After EGCG binding to lipid raft-associated 67LR, through eEF1A, the phosphorylation of MYPT1 at Thr-696 but not Thr-853 is reduced, which leads to the activation of myosin phosphatase. The activated myosin phosphatase dephosphorylates its substrates (e.g. MRLC), and actin cytoskeleton rearrangement is induced. The alteration of actin cytoskeleton might lead to cell growth inhibition. EGCG also induces apoptosis in the 67LR-expressing cells derived from multiple myeloma and acute myeloid leukaemia patient samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3066547&req=5

fig04: The signaling pathways that sense and respond to EGCG through 67LR are depicted. After EGCG binding to lipid raft-associated 67LR, through eEF1A, the phosphorylation of MYPT1 at Thr-696 but not Thr-853 is reduced, which leads to the activation of myosin phosphatase. The activated myosin phosphatase dephosphorylates its substrates (e.g. MRLC), and actin cytoskeleton rearrangement is induced. The alteration of actin cytoskeleton might lead to cell growth inhibition. EGCG also induces apoptosis in the 67LR-expressing cells derived from multiple myeloma and acute myeloid leukaemia patient samples.
Mentions: In both 67LR-ablated HeLa cells and eEF1A-ablated HeLa cells, the inhibitory effect of EGCG on both the phosphorylation of MYPT1 at Thr-696 and the phosphorylation of MRLC was attenuated. In addition, EGCG-induced actin cytoskeleton rearrangement was no longer observed in MYPT1-, eEF1A-, or 67LR-ablated HeLa cells. The involvement of MYPT1 in downstream EGCG-triggered signaling from both 67LR and eEF1A was further documented by confirming abrogation of 1 µM EGCG-induced reduction of the MYPT1 phosphorylation level at Thr-696 and the MRLC phosphorylation in 67LR- or eEF1A-ablated B16 cells. These results suggest that MYPT1 is involved in downstream EGCG signaling from both 67LR and eEF1A (Fig. 4). It has been reported that MYPT1 binds to eEF1A,92) and more than half of the total eEF1A (>60%) binds to the actin cytoskeleton.93) Characterizing the mechanisms by which EGCG induces reduction of the MYPT1 phosphorylation at Thr-696 and reorganization of actin cytoskeleton through eEF1A should help in more precise understanding of cytoskeleton organization.

Bottom Line: Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion.There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis.However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan. tatibana@agr.kyushu-u.ac.jp

ABSTRACT
Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis. However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated. Recently we have identified a cell-surface EGCG receptor and the relating molecules that confer EGCG responsiveness to many cancer cells at physiological concentrations. Here, we review some of the reported mechanisms for the cancer chemopreventive action of EGCG and provide an overview of several molecules that sense and manage the physiological functions of EGCG.

Show MeSH
Related in: MedlinePlus