Background. The poor survival rates of transplanted mesenchymal stem cells (MSCs) in harsh microenvironments impair the efficacy of MSCs transplantation in myocardial infarction (MI). Extrinsic apoptosis pathways play an important role in the apoptosis of transplanted MSCs, and Fas apoptosis inhibitory molecule (FAIM) is involved in regulation of the extrinsic apoptosis pathway. Thus, we aimed to explore whether FAIM augmentation protects MSCs against stress-induced apoptosis and thereby improves the therapeutic efficacy of MSCs. Methods. We ligated the left anterior descending coronary artery (LAD) in the mouse heart to generate an MI model and then injected FAIM-overexpressing MSCs (MSCsFAIM) into the peri-infarction area in vivo. Moreover, FAIM-overexpressing MSCs were challenged with oxygen, serum, and glucose deprivation (OGD) in vitro, which mimicked the harsh microenvironment that occurs in cardiac infarction. Results. FAIM was markedly downregulated under OGD conditions, and FAIM overexpression protected MSCs against OGD-induced apoptosis. MSCsFAIM transplantation improved cell retention, strengthened angiogenesis, and ameliorated heart function. The antiapoptotic effect of FAIM was mediated by cellular-FLICE inhibitory protein (c-FLIP), and FAIM augmentation improved the protein expression of c-FLIP by reducing ubiquitin–proteasome-dependent c-FLIP degradation. Furthermore, FAIM inhibited the activation of JNK, and treatment with the JNK inhibitor SP600125 abrogated the reduction in c-FLIP protein expression caused by FAIM silencing. Conclusions. Overall, these results indicated that FAIM curbed the JNK-mediated, ubiquitination–proteasome-dependent degradation of c-FLIP, thereby improving the survival of transplanted MSCs and enhancing their efficacy in MI. This study may provide a novel approach to strengthen the therapeutic effect of MSC-based therapy.
Li Yuan,Liu Wenna,Fan Xushen,Wu Xinyi,Cao Mingbo,Li Xiuling,Wurita Amin,Sun Suofeng
Background Hepatocellular carcinoma (HCC), characterized by its aggressive trait and rapid progression, stands as one of the leading causes of cancer-related death worldwide. Fas apoptotic inhibitory molecule (FAIM), a death receptor antagonist, impedes cell apoptosis by reinforcing protein phosphorylation and stability. High mobility group A1 (HMGA1) is reported to be subject to multiple posttranslational modification, and plays a crucial role in HCC development. However, whether FAIM facilitates tumorigenesis through modulating HMGA1 phosphorylation remains unclear.Methods We applied Huh7 and SNU387 cells to investigate the regulatory role of FAIM in cell proliferation and apoptosis. Next, we constructed a male BALB/C mouse model with HCC to explore the biological function of FAIM in tumor growth. Subsequently, anti-FAIM proteomic and phosphorylation proteomic profiles were performed to screen HMGA1 as the FAIM-modulated downstream phosphorylated protein. Eventually, a series of immunoprecipitation (IP) tests and in vitro kinase assay revealed the crosstalk of FAIM, cyclin-dependent kinase7 (CDK7) and HMGA1, and unveiled the vital value of FAIM in HCC pathogenesis.Results In vitro and in vivo experiments validated that FAIM overexpression was advantageous for HCC progression. Thereafter, anti-FAIM proteomic profile identified that FAIM interacted with CDK7 and HMGA1. Phosphorylation proteomic profile revealed that the Ser36 of HMGA1 was a downstream phosphorylation site of FAIM. Consistently, Co-IP and cycloheximide assays verified that FAIM enhanced HMGA1 phosphorylation and stability. More importantly, recovery experiments identified that silencing HMGA1 altered the regulatory role of overexpressed FAIM in Huh7 cells. Furthermore, we transduced Flag-HMGA1WT or Flag-HMGA1S36A plasmids into overexpressed FAIM cells and demonstrated that Ser36 phosphorylation influenced HMGA1 stability.Conclusion sSummarily, we elucidated that FAIM modulated HCC progression through facilitating the interaction of CDK7 and HMGA1 as well as elevating HMGA1 phosphorylation and stability.Graphical abstract
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