Reptin regulates insulin-stimulated Akt phosphorylation in hepatocellular carcinoma via the regulation of SHP-1/PTPN6

Cell Biochem Funct. 2017 Aug;35(6):289-295. doi: 10.1002/cbf.3274. Epub 2017 Aug 22.

Abstract

Hepatocellular carcinoma (HCC) is the main primary cancer of the liver. Many studies have shown that insulin resistance is a risk factor for HCC. We previously discovered the overexpression and oncogenic role of the Reptin/RUVBL2 ATPase in HCC. Here, we found that Reptin silencing enhanced insulin sensitivity in 2 HCC cell lines, as shown by a large potentiation of insulin-induced AKT phosphorylation on Ser473 and Thr308, and of downstream signalling. Reptin silencing did not affect the tyrosine phosphorylation of the insulin receptor nor of IRS1, but it enhanced the tyrosine phosphorylation of the p85 subunit of PI3K. The expression of the SHP-1/PTPN6 phosphatase, which dephosphorylates p85, was reduced after Reptin depletion. Forced expression of SHP-1 restored a normal AKT phosphorylation after insulin treatment in cells where Reptin was silenced, demonstrating that the downregulation of SHP1 is mechanistically linked to increased Akt phosphorylation. In conclusion, we have uncovered a new function for Reptin in regulating insulin signalling in HCC cells via the regulation of SHP-1 expression. We suggest that the regulation of insulin sensitivity by Reptin contributes to its oncogenic action in the liver.

Keywords: RUVBL2; TIP49; insulin; mTOR; phosphatase.

MeSH terms

  • ATPases Associated with Diverse Cellular Activities
  • Carcinoma, Hepatocellular / metabolism
  • Carcinoma, Hepatocellular / pathology
  • Carrier Proteins / antagonists & inhibitors
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line, Tumor
  • DNA Helicases / antagonists & inhibitors
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • Doxycycline / pharmacology
  • Humans
  • Insulin / pharmacology
  • Liver Neoplasms / metabolism
  • Liver Neoplasms / pathology
  • Phosphorylation / drug effects
  • Protein Tyrosine Phosphatase, Non-Receptor Type 6 / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Signal Transduction / drug effects

Substances

  • Carrier Proteins
  • Insulin
  • RNA, Small Interfering
  • Proto-Oncogene Proteins c-akt
  • PTPN6 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 6
  • ATPases Associated with Diverse Cellular Activities
  • DNA Helicases
  • RUVBL2 protein, human
  • Doxycycline