ABSTRACT
Objective Cardiac HERG potassium channel currents can cause long QT syndrome .The function of the cardiac HERG potassium channel is regulated by tyrosine kinase and phosphatase , and protein tyrosine phosphatase non-receptor type 11 ( PTPN11) negatively regulates the HERG potassium channel .This study aimed to investigate the effect of PTPN 11 on the electrophysio-logical characteristics of the HERG channel . Methods The plasmids of pcDNA3.1-PTPN11-EGFP were constructed by PCR technique and transfected or cotransfected with the pcDNA 3.1-PTPN11-EGFP plasmid into HEK293 cells using Lipofectamine 2000.The patch clamp technique was employed to record the HERG channel currents in the control group ( HEK293 cells transfected with pcDNA3.0-HERG-EGFP), PTPN11 overexpression group (pcDNA3.0-HERG and pcDNA3.1-PTPN6-EGFP cotransfected HEK293 cells), and PTPN11 overexpression with PAO group . Results The pcDNA3.1-PTPN11-EGFP plasmid was successfully constructed .Green fluorescence was observed in the HEK293 cells transfected with pcDNA3.0-HERG-EG-FP or cotransfected with pcDNA3.0-HERG and pcDNA3.1-PTPN11.The maximum densities of pulse and tail currents were significantly decreased in the PTPN11 overexpression group as compared with the control ([31.85 ±5.54] vs [45.92 ±3.18] pApF, P<0.05;[73.82 ±11.31] vs [108.43 ±7.98] pApF, P<0.05) but markedly in-creased in the PTPN11 overexpression with PAO group ([48.08 ±4.32] pApF;[120.06 ±8.02] pApF) (P<0.05).The time con-stant of deactivation was significantly higher in the PTPN 11 overexpression group than in the control ([622.16 ±46.49] vs [440.70 ± 49.49] ms, P<0.05). Conclusion The overexpression of PTPN11 decreases HERG potassium channel currents , which can be re-versed by PAO.This finding provides a theoretical basis for the application of certain regulatory enzymes in the HERG channel as a treat -ment of long QT syndrome .
ABSTRACT
<p><b>OBJECTIVE</b>To study the effect of protein tyrosine phosphatase non-receptor type 12 (PTPN12) in regulating cardiac HERG channel currents.</p><p><b>METHODS</b>The 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.</p><p><b>RESULTS</b>The 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.</p><p><b>CONCLUSION</b>PTPN12 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.</p>
Subject(s)
Humans , Ether-A-Go-Go Potassium Channels , Physiology , HEK293 Cells , Heart , Long QT Syndrome , Patch-Clamp Techniques , Protein Tyrosine Phosphatase, Non-Receptor Type 12 , Physiology , TransfectionABSTRACT
OBJECTIVE: To introduce the sorts of biomedical fibers, collagenous fibers, chitin fibers polyactic acid(PLA) fibers, etc. , and their preparation,properties and application respectively, and suggest China to pay attention to the research and development of biomedical fiber.DATA SOURCES: Literatures from January 1993 to December 2001 were computer-searched in http://www.sciencedirect.com, http://worldscinet.lib.tsinghua.edu.cn, with the key words of "biomedical and polymer,fibre" and the language was limited to English.: Literatures from January 1999 to December 2004 were computer-searched in http://www.wanfangdata.com.cn,with the key words of "Biological, medical, polymer and Chitin Fibers" and the language was limited to Chinese.STUDY SELECTION: Inclusion criteria: ①Chitin fibers②Collagenous fibers and PLA fibers③Alginic acid fibers④Polyglycolide fibers⑤β-hy droxybutanoic acid ester (PHB)⑥Polycaprolactone fiber. Exclusion criteria:① Obsolete literatures. ② Repeated study. DATA EXTRACTION: Totally 60 tests on biomedical fiber were collected, but only 15 literatures met the inclusion criteria. Altogether 45 literatures were excluded due to older and repeated study.DATA SYNTHESIS: ①The sorts of biomedical fibers: Classified according to the sources, biomedical fibers include metal ones (e.g. stainless steel wire), inorganic and nonmetal ones (e.g. alumina fibers) and macromolecular ones. Classified according to the interaction between living tissues and materials, they include bioinert fibers, bioactive fibers and bioabsobable fibers. Classified according to biomedical use, they include biomedical fibers compatible with hard tissues, biomedical fibers compatible with parenchyma, biomedical fibers compatible with blood and biomedical fibers used as medicine or for regulating the release of medicine ②The main biodegradable fibers include chitin fibers, collagenous fibers, PLA fibers and their copolymer fibers.CONCLUSION: As one of the important functional fibers, the biomedical fibers attract wide attention both at home and abroad. The research and development about them are still on the way and has shown hopeful prospective of application. Much attention should be paid on the research and development of biomechanical fibres.