The Calcineurin-TFEB-p62 Pathway Mediates the Activation of Cardiac Macroautophagy by Proteasomal Malfunction

• Published in: Circulation research Vol. 127; no. 4; pp. 502 - 518
• Main Authors: Pan, Bo, Li, Jie, Parajuli, Nirmal, Tian, Zongwen, Wu, Penglong, Lewno, Megan T, Zou, Jianqiu, Wang, Wenjuan, Bedford, Lynn, Mayer, R John, Fang, Jing, Liu, Jinbao, Cui, Taixing, Su, Huabo, Wang, Xuejun
• Format: Journal Article
• Language: English
• Published: United States American Heart Association, Inc 31.07.2020
• Subjects: cardiotoxicity; autophagy; proteasome inhibitor; sequestosome-1; calcineurin; TFEB protein, rat; ubiquitin
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/CIRCRESAHA.119.316007

RATIONALE:The ubiquitin-proteasome system (UPS) and the autophagic-lysosomal pathway are pivotal to proteostasis. Targeting these pathways is emerging as an attractive strategy for treating cancer. However, a significant proportion of patients who receive a proteasome inhibitor-containing regime show cardiotoxicity. Moreover, UPS and autophagic-lysosomal pathway defects are implicated in cardiac pathogenesis. Hence, a better understanding of the cross-talk between the 2 catabolic pathways will help advance cardiac pathophysiology and medicine. OBJECTIVE:Systemic proteasome inhibition (PSMI) was shown to increase p62/SQSTM1 expression and induce myocardial macroautophagy. Here we investigate how proteasome malfunction activates cardiac autophagic-lysosomal pathway. METHODS AND RESULTS:Myocardial macroautophagy, TFEB (transcription factor EB) expression and activity, and p62 expression were markedly increased in mice with either cardiomyocyte-restricted ablation of Psmc1 (an essential proteasome subunit gene) or pharmacological PSMI. In cultured cardiomyocytes, PSMI-induced increases in TFEB activation and p62 expression were blunted by pharmacological and genetic calcineurin inhibition and by siRNA-mediated Molcn1 silencing. PSMI induced remarkable increases in myocardial autophagic flux in wild type mice but not p62 null (p62-KO) mice. Bortezomib-induced left ventricular wall thickening and diastolic malfunction was exacerbated by p62 deficiency. In cultured cardiomyocytes from wild type mice but not p62-KO mice, PSMI induced increases in LC3-II flux and the lysosomal removal of ubiquitinated proteins. Myocardial TFEB activation by PSMI as reflected by TFEB nuclear localization and target gene expression was strikingly less in p62-KO mice compared with wild type mice. CONCLUSIONS:(1) The activation of cardiac macroautophagy by proteasomal malfunction is mediated by the Mocln1-calcineurin-TFEB-p62 pathway; (2) p62 unexpectedly exerts a feed-forward effect on TFEB activation by proteasome malfunction; and (3) targeting the Mcoln1 (mucolipin1)-calcineurin-TFEB-p62 pathway may provide new means to intervene cardiac autophagic-lysosomal pathway activation during proteasome malfunction.