Thermostable direct hemolysin diminishes tyrosine phosphorylation of epidermal growth factor receptor through protein kinase C dependent mechanism

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• 作者：Poulomee Karmakar ; Manoj K. Chakrabarti ; ^{mkc_niced@yahoo.co.in}
• 关键词：TDH ; thermostable direct hemolysin ; PKC ; protein kinase C ; EGFR ; epidermal growth factor receptor ; ERK ; extracellular signal-related kinase ; MEK ; mitogen activated protein kinase kinase/ERK kinase
• 刊名：Biochimica et Biophysica Acta (BBA)/General Subjects
• 出版年：2012
• 期刊代码：16_03044165
• 类别：bio
• 出版时间：July, 2012
• 卷：1820
• 期：7
• 页码：1073-1080
• 文件大小：828 K

摘要

Background

Adequate evidence mounts to the fact that several bacteria and their toxins have protective or curative roles in colorectal cancers. Thermostable direct hemolysin (TDH), produced by Vibrio parahaemolyticus, down regulates cell proliferation in colon carcinoma cell lines. TDH induces Ca²⁺ influx from an extracellular environment accompanied by protein kinase C phosphorylation. Activated protein kinase C inhibits the tyrosine kinase activity of epidermal growth factor receptor (EGFR), the rational target of anti-colorectal cancer therapy.

Methods

Immunoblotting analyses were performed to ascertain protein kinase C activation, EGFR status, EGFR phosphorylation and mitogen activated protein kinase (MAPK) activity. Flow cytometry analysis and ELISA reconfirmed tyrosine phosphorylation of EGFR and ERK activations, respectively. PKC-伪 siRNA knockdown was done to corroborate the involvement of PKC-伪 in the undertaken study.

Results

Our study showed the translocation of PKC-伪 from cytosol to the membrane fraction in colon carcinoma cell lines on incubation with TDH. The EGFR tyrosine kinase activity exhibited a down regulation on TDH treatment which involved PKC-伪, as confirmed by siRNA knockdown. Also ERK phosphorylation occurred on PKC-伪 activation. Conclusion: TDH activated PKC鈥愇?down regulates EGFR tyrosine kinase activity by MEK dependent mechanism involving MAPK.

General significance

In this study we have seen that TDH has an implication in EGFR based therapeutic approach in colorectal cancer via PKC mediated mechanism.