title: Involvement of ubiquitin-proteasome system in icariin-induced cardiomyocyte differentiation of embryonic stem cells using two-dimensional gel electrophoresis.
abstract: Icariin has been shown to significantly facilitate the differentiation of embryonic stem (ES) cells into cardiomyocytes in vitro. However, the mechanism underlying the icariin-induced cardiomyocyte differentiation is still not fully understood. In the present study, 52 differentially displayed proteins selected from two-dimensional electrophoresis gels were identified by MALDI-TOF mass spectrometry analysis. More than half of proteins could be assigned to six main categories: (1) protein synthesis, metabolism, processing and degradation, (2) stress response, (3) cytoskeleton proteins, (4) energy metabolism, (5) carbohydrate metabolism/transport, and (6) RNA/other nucleic acids metabolisms and transport, nuclear proteins. MALDI-TOF/MS showed that icariin treatment resulted in the induction of five ubiquitin-proteasome system (UPS)-related proteins, such as ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), ubiquitin-conjugating enzyme E2N, proteasome 26S, proteasome subunit-alpha type 6, and proteasome subunit-alpha type 2 in the differentiated cardiomyocytes. These results implied that UPS might play an important role in the control of cardiomyocyte differentiation. Epoxomicin (a proteasome inhibitor) significantly reduced the cardiomyocyte differentiation rate of ES cells and proteasome activities, as well as inhibited NF-κB translocation into the nucleus, which were evidently reversed by presence of icariin. Meanwhile, icariin could significantly reverse the reduction of four proteins (proteasome subunit-alpha type 6, proteasome subunit-alpha type 2, UCH-L1, and ubiquitin-conjugating enzyme E2N) expressions owing to application of epoxomicin. These suggest UPS could be a means by which icariin may regulate expressions of key proteins that control cardiomyocyte differentiation. Taken together, these results indicated that UPS played an important role in ES cell differentiate into cardiomyocytes induced by icariin.
authors.affiliation: Institute of Pharmacology, Toxicology, and Biochemical Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China. zdyzxb@zju.edu.cn
authors.forename: Dan-Yan
authors.initials: DY
authors.lastname: Zhu
authors.forename: Rong
authors.initials: R
authors.lastname: Cui
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Zhang
authors.forename: Huan
authors.initials: H
authors.lastname: Li
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Zhou
authors.forename: Yi-Jia
authors.initials: YJ
authors.lastname: Lou
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D017931:DNA Primers; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods*; D053595:Embryonic Stem Cells / Q000166:cytology*; D005419:Flavonoids / Q000494:pharmacology*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D005419:Flavonoids; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; C056599:icariin