OBJECTIVETo study the effect of protein tyrosine phosphatase non-receptor type 12 (PTPN12) in regulating cardiac HERG channel currents.

METHODSThe plasmids pcDNA3.1-PTPN12-RFP and herg mutant constructed by PCR technique were transfected into HEK293 cells via Lipofectamine 2000, and the cells stably expressing PTPN12 selected with G418 were identified by Western blotting with anti-PTPN12 antibody. HERG channel current in cells expressing HERG alone (HEK293/HERG cells), cells overexpressing PTPN12 (HEK293/HERG cells transfected with pCDNA3.1-PTPN12-RFP), PAO-treated cells (PTPN12/HERG cells treated with PAO), and herg mutant cells (HEK293/HERGY327A-Y700A-Y845A cells transfected with pcDNA3.1-PTPN12-RFP) were recorded by patch-clamp technique.

RESULTSThe plasmids pcDNA3.1-PTPN12-RFP and herg mutant were successfully constructed, and the stable expressing cell lines were established. Red fluorescence was obversed in HEK293/HERG cells transfected with pcDNA3.1-PTPN12-RFP, and the protein expression of PTPN12 was detected. Overexpression of PTPN12 significantly decreased HERG current density in HEK293/HERG cells, and this change was significantly weakened in the inhibitor group and herg mutant group.

CONCLUSIONPTPN12 negatively regulates cardiac HERG channel cerrent possibly by decreasing the phosphorylation level of HERG tyrosine residues. This finding provides further insight into the regulatory mechanism of HERG channel and the pathogenesis of long QT syndrome.

Ether-A-Go-Go Potassium Channels ; physiology ; HEK293 Cells ; Heart ; Humans ; Long QT Syndrome ; Patch-Clamp Techniques ; Protein Tyrosine Phosphatase, Non-Receptor Type 12 ; physiology ; Transfection

Protein tyrosine phosphatase (PTP)-proline-, glutamate-, serine-, and threonine-rich sequence (PEST) is ubiquitously expressed and is a critical regulator of cell adhesion and migration. PTP-PEST activity can be regulated transcriptionally via gene deletion or mutation in several types of human cancers or via post-translational modifications, including phosphorylation, oxidation, and caspase-dependent cleavage. PTP-PEST interacts with and dephosphorylates cytoskeletal and focal adhesion-associated proteins. Dephosphorylation of PTP-PEST substrates regulates their enzymatic activities and/or their interaction with other proteins and plays an essential role in the tumor cell migration process.
Cell Adhesion ; Cell Movement ; Focal Adhesion Protein-Tyrosine Kinases ; metabolism ; Humans ; Neoplasms ; metabolism ; pathology ; Oxidation-Reduction ; Phosphorylation ; Protein Processing, Post-Translational ; Protein Tyrosine Phosphatase, Non-Receptor Type 12 ; metabolism ; Shc Signaling Adaptor Proteins ; metabolism ; rho GTP-Binding Proteins ; metabolism ; src-Family Kinases ; metabolism