title: The RhoGDI-alpha/JNK signaling pathway plays a significant role in mycophenolic acid-induced apoptosis in an insulin-secreting cell line.
abstract: Mycophenolic acid (MPA)-induced beta-cell toxicity is an important factor for islet graft function. The signal transduction mechanisms underlying this process have not been fully explored. Using a proteomics approach, we examined protein expression patterns in MPA-treated RIN-5 cells and found that RhoGDI-alpha expression is altered by MPA-treatment. We examined the relationship between RhoGDI-alpha expression and activated JNK during MPA-induced apoptosis. Cells were treated with N-acetyl-cysteine (NAC), caspase inhibitor, JNK inhibitor, guanosine or GTP for 1 h before being treated with MPA. To investigate the regulatory effects of RhoGDI-alpha on JNK activity, we examined cells showing either elevated or reduced expression of RhoGDI-alpha as a result of transfection with cDNA or siRNA constructs, respectively. MPA significantly increased cell death, caspase-3 expression and JNK activation, but it decreased the expression of a protein spot 25 observed by two-dimensional electrophoresis. This protein 25 was identified as RhoGDI-alpha by mass spectrometry. MPA-induced cell death and down-regulation of RhoGDI-alpha were prevented by guanosine, GTP or a JNK inhibitor. However, MPA-induced cell death was partially restored by treatment with a caspase inhibitor, but not by NAC treatment. RhoGDI-alpha expression was not affected by treatment with NAC or caspase inhibitor. Over-expression of RhoGDI-alpha increased cell viability and decreased activated JNK expression following exposure to MPA, whereas knockdown of RhoGDI-alpha enhanced MPA-induced cell death and increased the activation of JNK. In conclusion, MPA induces significant apoptosis in insulin-secreting cells via down-regulation of RhoGDI-alpha linked with increased JNK expression. This RhoGDI-alpha/JNK pathway might be the focus of therapeutic target for the prevention of MPA-induced islet apoptosis.
authors.affiliation: The Research Institute for Transplantation, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Yun-Jong
authors.initials: YJ
authors.lastname: Park
authors.forename: Hyung Joon
authors.initials: HJ
authors.lastname: Ahn
authors.forename: Hye Kyung
authors.initials: HK
authors.lastname: Chang
authors.forename: Joon Ye
authors.initials: JY
authors.lastname: Kim
authors.forename: Kyu Ha
authors.initials: KH
authors.lastname: Huh
authors.forename: Myoung Soo
authors.initials: MS
authors.lastname: Kim
authors.forename: Yu Seun
authors.initials: YS
authors.lastname: Kim
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D015180:Electrophoresis, Gel, Two-Dimensional; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009173:Mycophenolic Acid / Q000494:pharmacology*; D040901:Proteomics; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3; D009173:Mycophenolic Acid