1. Department of Pharmacology (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang, P. R. China.
2. The Centre of Functional Experiment Teaching, School of Basic Medicine, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China.
3. Department of Pharmacy, Sunshine Union Hospital, Shandong Weifang, China.
4. Research Unit of Noninfectious Chronic Diseases in Frigid Zone (2019RU070), Chinese Academy of Medical Sciences, Harbin, 150081, China.
5. Shanghai Frontiers Science Research Center for Druggability of Cardiovascular Noncoding RNA, Institute for Frontier Medical Technology, Shanghai University of Engineering Science, Shanghai, 201620, China.
*These authors contributed equally to this work.
Cardiac fibrosis is one of the common pathological processes in many cardiovascular diseases characterized by excessive extracellular matrix deposition. SerpinE2 is a kind of protein that inhibits peptidase in extracellular matrix and up-regulated tremendously in mouse model of cardiac fibrosis induced by pressure-overloaded via transverse aortic constriction (TAC) surgery. However, its effect on cardiac fibroblasts (CFs), collagen secretion and the underlying mechanism remains unclear. In this study, DyLight® 488 green fluorescent dye or His-tagged proteins were used to label the exogenous serpinE2 protein. It was showed that extracellular serpinE2 translocated into CFs by low-density lipoprotein receptor-related protein 1 (LRP1) and urokinase plasminogen activator receptor (uPAR) of cell membrane through endocytosis. Knockdown of LRP1 or uPAR reduced the level of serpinE2 in CFs and down-regulated the collagen expression. Inhibition of the endocytosis of serpinE2 could inhibit ERK1/2 and β-catenin signaling pathways and subsequently attenuated collagen secretion. Knockdown of serpinE2 attenuates cardiac fibrosis in TAC mouse. We conclude that serpinE2 could be translocated into cardiac fibroblasts due to endocytosis through directly interact with the membrane protein LRP1 and uPAR, and this process activated the ERK1/2, β-catenin signaling pathways, consequently promoting collagen production.
Keywords: Cardiac Fibrosis, SerpinE2, Endocytosis, ERK1/2, β-catenin signaling