Phosphatidylinositol 3-kinase/Akt pathway is involved in transforming growth factor-beta1-induced phenotypic modulation of 10T1/2 cells to smooth muscle cells.
Transforming growth factor-beta1 (TGF-beta1) is known to induce phenotypic modulation of mesenchymal cells to SMCs. However, the intracellular signals regulating induction of the SMC phenotype of mesenchymal cells have not been fully clarified. In the present study, we examined the role of the mitogen-activated protein kinase (MAPK) superfamily and phosphatidylinositol 3-kinase (PI3K)/Akt in the TGF-beta1-mediated phenotypic modulation of 10T1/2 mesenchymal cells to SMCs characterized by the expression of SMC-specific markers, including smooth muscle alpha-actin (SMalpha-actin), myosin heavy chain (SM-MHC), and protein 22-alpha (SM22alpha). The results showed the following: (1) TGF-beta1 induced SMalpha-actin and SM-MHC expressions in 10T1/2 cells in a time-dependent manner. (2) TGF-beta1 induced biphasic increases in extracellular signal-regulated kinase (ERK), p38 MAPK, c-Jun-NH2-terminal kinase (JNK), and Akt phosphorylation. (3) The inhibitor for PI3K/Akt (i.e., LY294002), but not those for MAPKs (i.e., SB203580, PD98059, and SP600125), attenuated the TGF-beta1-induced SMalpha-actin and SM-MHC expressions in 10T1/2 cells; in addition, transfection of 10T1/2 cells with the Akt-specific small interfering RNA (siRNA) significantly reduced their SMalpha-actin and SM-MHC expressions. (4) LY294002 and the Akt-specific siRNA inhibited the TGF-beta1-induced SM22alpha gene expression and promoter activity, suggesting that the TGF-beta1-induced gene expression was mediated by PI3K/Akt at the transcriptional level. (5) LY294002 inhibited the TGF-beta1-induced gene expression and DNA binding activity of serum response factor (SRF). These results indicate that TGF-beta1 is capable of inducing the SMC phenotype of 10T1/2 cells and that this induction is mediated through the PI3K/Akt signaling pathway.
Lien
Sheng-Chieh
SC
Division of Medical Engineering Research, National Health Research Institutes, Miaoli 350, Taiwan, ROC.
Usami
Shunichi
S
Chien
Shu
S
Chiu
Jeng-Jiann
JJ
D000199:Actins / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000187:drug effects*; D018995:Myosin Heavy Chains / Q000235:genetics; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D026362:Serum Response Factor / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D000199:Actins; D008840:Microfilament Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D026362:Serum Response Factor; C058992:Tagln protein, mouse; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D018995:Myosin Heavy Chains