Tumor susceptibility gene 101 ameliorates endotoxin-induced cardiac dysfunction by enhancing Parkin-mediated mitophagy

Abstract

Edited by Phyllis I. Hanson Cardiac mitochondrial damage and subsequent inflammation are hallmarks of endotoxin-induced myocardial depression. Activation of the Parkin/PTEN-induced kinase 1 (PINK1) pathway has been shown to promote autophagy of damaged mitochondria (mitophagy) and to protect from endotoxin-induced cardiac dysfunction. Tumor susceptibility gene 101 (TSG101) is a key member of the endosomal recycling complexes required for transport, which may affect autophagic flux. In this study, we investigated whether TSG101 regulates mitophagy and influences the outcomes of endotoxin-induced myocardial dysfunction. TSG101 transgenic and knockdown mice underwent endotoxin/lipopolysaccharide treatment (10 g/g) and were assessed for survival, cardiac function, systemic/local inflammation, and activity of mitophagy mediators in the heart. Upon endotoxin challenge and compared with WT mice, TSG101 transgenic mice exhibited increased survival, preserved cardiac contractile function, reduced inflammation, and enhanced mitophagy activation in the heart. By contrast, TSG101 knockdown mice displayed opposite phenotypes during endotoxemia. Mechanistically, both coimmunoprecipitation assays and coimmunofluorescence staining revealed that TSG101 directly binds to Parkin in the cytosol of myocytes and facilitates translocation of Parkin from the cytosol to the mitochondria. Our results indicate that TSG101 elevation could protect against endotoxin-triggered myocardial injury by promoting Parkin-induced mitophagy.

Tsg101 Is Involved in the Sorting and Re-Distribution of Glucose Transporter-4 to the Sarcolemma Membrane of Cardiac Myocytes

“…To investigate the possible role of Tsg101 in Glut-4 translocation during ischemia, we generated a mouse model with heart-specific overexpression of Tsg101. Such transgenic (TG) mice have been phenotypically characterized in our previous publications [ 24 , 25 , 26 ] and validated here that Tsg101 was overexpressed by ~4-fold in TG hearts, compared to WT-hearts ( Figure 2 A,B). Interestingly, total levels of Glut-4 were also significantly higher in TG hearts than WT hearts ( Figure 2 A,C).…”

“…Hence, overexpression of Tsg101 in mouse hearts and cardiomyocytes may alleviate the deleterious effects during ischemia and hypoxia, thereby rendering protection from tissue damage and cardiomyocyte death after reperfusion. In the same light, we cannot exclude the effects of Tsg101 on other signaling pathways (i.e., Nrf2, Parkin-mediated mitophagy) [ 25 , 26 ] that may have contribution to the protective effects of Tsg101 in this study. Finally, we cannot exclude the contributions of AMPK-dependent pathway to the increased membrane levels of Glut-4 in the ischemic myocardium, as ischemic conditions can activate AMPK-mediated Glut-4 translocation to the sarcolemma [ 41 , 42 ].…”

“…The mouse model with heart-specific overexpression of Tsg101 is of FVB/N background and was generated by the Transgenic Animal and Genome Editing Core at Cincinnati Children’s Hospital Center (Cincinnati, OH, USA) as described previously [ 26 ]. Inducible cardiac-specific Tsg101-knockdown (KD) mouse model was generated by mating female mice harboring the Tsg101 floxed allele (Tsg101fl/fl,129/SvJ background) with male mice expressing the inducible Cre recombinase transgene under the control of the αMHC promoter (αMHC-Mer-Cre-Mer, C57BL/6 background).…”

“…Inducible cardiac-specific Tsg101-knockdown (KD) mouse model was generated by mating female mice harboring the Tsg101 floxed allele (Tsg101fl/fl,129/SvJ background) with male mice expressing the inducible Cre recombinase transgene under the control of the αMHC promoter (αMHC-Mer-Cre-Mer, C57BL/6 background). Male hetero-zygotes (MerCreMer-Tsg101fl/+) offspring from this cross were injected with tamoxifen (Sigma, St. Louis, MO, USA, 30 μg/g) at eight-weeks-old for three consecutive days to obtain knockdown of Tsg101 in the heart [ 26 ]. Previous work had indicated that complete knockout of Tsg101 in mice was lethal [ 27 ].…”

The Multifaceted Roles of the Tumor Susceptibility Gene 101 (TSG101) in Normal Development and Disease

“…In contrast, animals with a 50% knockdown of TSG101 through the expression of an shRNA construct were able to survive, but they exhibited defects in exercise-induced cardiac hypertrophy. This suggests that optimal expression of TSG101 is required for heart muscle growth under specific physiological conditions, and interestingly, reduced levels of TSG101 can still be lethal when the mice are being challenged with endotoxin-triggered myocardial injury [50]. On the mechanistic level, exercise-induced cardiac growth is being mediated by IGF-1R signaling through AKT, and a knockdown of TSG101 caused a defect in the recycling of the IGF1 receptor, possibly due to the downregulation of RAB11a and FIP3.…”