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

• Published in: Biochimica et biophysica acta Vol. 1820; no. 7; pp. 1073 - 1080
• Main Authors: Karmakar, Poulomee, Chakrabarti, Manoj K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2012
• Subjects: bacteria; Bacterial Toxins - pharmacology; Blotting, Western; calcium; cell proliferation; Cell Proliferation - drug effects; Colonic Neoplasms - drug therapy; Colonic Neoplasms - metabolism; Colorectal cancer; colorectal neoplasms; cytosol; EGFR; Enterotoxins - pharmacology; Enzyme-Linked Immunosorbent Assay; epidermal growth factor receptors; Flow Cytometry; gene expression regulation; Hemolysin Proteins - pharmacology; hemolysins; Humans; immunoblotting; Immunoprecipitation; mitogen-activated protein kinase; Mitogen-Activated Protein Kinases - metabolism; neoplasm cells; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; PKC-α; protein kinase C; Protein Kinase C-alpha - antagonists & inhibitors; Protein Kinase C-alpha - genetics; Protein Kinase C-alpha - metabolism; Receptor, Epidermal Growth Factor - metabolism; RNA, Small Interfering - genetics; Signal Transduction - drug effects; small interfering RNA; therapeutics; thermal stability; Thermostable direct hemolysin; toxins; tyrosine; Tyrosine - metabolism; Vibrio parahaemolyticus; Thermostable direct hemolysin; MEK; PKC-α; Colorectal cancer; TDH; PKC; EGFR; ERK
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2012.04.011

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. 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-α siRNA knockdown was done to corroborate the involvement of PKC-α in the undertaken study. Our study showed the translocation of PKC-α 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-α, as confirmed by siRNA knockdown. Also ERK phosphorylation occurred on PKC-α activation. Conclusion: TDH activated PKC‐α down regulates EGFR tyrosine kinase activity by MEK dependent mechanism involving MAPK. In this study we have seen that TDH has an implication in EGFR based therapeutic approach in colorectal cancer via PKC mediated mechanism. ► TDH phosphorylates PKC-α in colon carcinoma cell line and causes its activation. ► Activated PKC-α downregulates tyrosine phosphorylation of EGFR. ► PKC-α exerts its effect on EGFR through MAPK activation.