CARD9 protein SUMOylation regulates HOXB5 nuclear translocation and Parkin-mediated mitophagy in myocardial I/R injury

Myocardial injury induced by ischemia–reperfusion (I/R) remains a difficult clinical problem. However, the exact mechanisms underlying I/R-induced have yet to be clarified. CARD9 is an important cytoplasmic-binding protein. In this study, an immunocoprecipitation assay showed that SUMOylation of the CARD9 protein promoted the binding of CARD9 to HOXB5, but hindered the O-GlcNAc glycosylation of HOXB5, a predicted transcription factor of Parkin and a key factor in mitophagy. O-GlcNAc glycosylation is an important signal for translocation of proteins from the cytoplasm to the nucleus. CARD9 protein SUMOylation is regulated by PIAS3, which is related to I/R-induced myocardial injury. Therefore, we propose that knockdown of PIAS3 inhibits SUMOylation of the CARD9 protein, facilitates the dissociation of CARD9 and HOXB5, which increases the O-GlcNAc-mediated glycosylation of HOXB5, while the resulting HOXB5 nuclear translocation promotes Parkin-induced mitophagy and alleviates myocardial I/R injury.