Shp2 SUMOylation Promotes ERK Activation And Hepatocellular Carcinoma Development

Shp2?Src homology 2-containing phosphotyrosine phosphatase 2?,an ubiquitously expressed non-receptor protein tyrosine phosphatase encoded by PTPN11,is mainly composed of N-terminal Src homology 2?N-SH2?,C-terminal Src homology 2?C-SH2?,catalytic protein-tyrosine phosphatase?PTPase?domain and C-terminal tail.Shp2 is involved in the regulation of Ras/ERK signaling pathway and tumorigenesis,and recently it has been reported that Shp2 is closely related with liver cancer.SUMO?Small Ubiquitin-related Modifier?is an important post-translational modification?PTM?that belongs to a ubiquitin-like family of protein modifiers,and regulates a vast variety of proteins in many signaling pathways.SUMOylation is subject to reversible modification affecting target protein activity,localization,stability,and protein-protein interaction,which all regulate many physiological events such as transcriptional regulation,chromatin organization,DNA repair,signal transduction.An increasing evidences show that SUMOylation is closely related with human diseases.SUMO1 is over-expressed in HCC cell lines and clinical tumor samples as reported,indicating that SUMO1 is a potential target in diagnosis and therapy of HCC.Here we searched multiple microarray data in the Oncomine database,and demonstrated that there was no significant difference in Shp2 mRNA levels,while the levels of SAE1 and Ubc9,which are E1 and E2 in SUMOylation,respectively,were significantly upregulated in HCC,suggesting that SUMOylation was strongly correlated with HCC.We identified that Shp2 was modified by SUMO1 at lysine residue 590(K⁵⁹⁰)in its C-terminus.Analysis of wild-type Shp2 and SUMOylation-defective Shp2^K590R mutant revealed that SUMOylation of Shp2promoted EGF-stimulated ERK signaling pathway and increased anchorage-independent cell growth and xenografted tumor growth of hepatocellular carcinoma?HCC?cell lines.Furthermore,we found that mutant Shp2^K590R reduced its binding with the scaffolding protein Gab1.More surprisingly,we showed that human Shp2?hShp2?and mouse Shp2?mShp2?had differential effects on ERK activation as a result of different SUMOylation level,which was due to the event of K⁵⁹⁰ at hShp2substituted by R⁵⁹⁴ at mShp2.In summary,our data demonstrated that SUMOylation of Shp2 promoted ERK activation via facilitating the formation of Shp2-Gab1 complex and thereby accelerates HCC cell and tumor growth,which presented a novel regulatory mechanism underlying Shp2 in regulation of HCC development.