Mycophenolic acid (MPA)-induced beta cell toxicity limits islet graft survival. However, the signal transduction mechanisms underlying MPA-induced β-cell toxicity have not been fully elucidated. Previously, we showed that MPA-induced pancreatic β-cell apoptosis proceeds via RhoGDI-α down-regulation linked to Rac1 activation. In the present study, we investigated factors affecting RhoGDI-α during MPA-induced β-cell apoptosis. The presence of RhoGDI-α-related protein was determined with the use of yeast 2-hybrid (Y2H) analysis. Y2H screening of RhoGDI-α was performed in yeast PBN204 strain containing 3 reporters (URA3, lacZ, and ADE2) under the control of different GAL promoters. INS-1E cells (an insulin-secreting pancreatic β-cell line) were treated with MPA for 12, 24, and 36 hours. Eighty-three real positives were obtained by Y2H analysis, and of these, arginine N-methyltransferase 3 (PRMT3) protein interacted with RhoGDI-α in INS-1E cells. PRMT3 gene expressions and its protein levels were significantly decreased during MPA-induced apoptosis. In summary, PRMT3 and RhoGDI-α were found to interact in INS-1E cells. Furthermore, MPA was found to regulate this interaction in INS-1E cells by down-regulating the gene expression of PRMT3. These findings suggest that control of the interaction between PRMT3 and RhoGDI-α could be used to prevent MPA-induced β-cell death.
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