Lipoprotein receptor‐related protein 6 is required to maintain intercalated disk integrity

Abstract

The intercalated disk (ID), a highly organized adhesion structure connecting neighboring cardiomyocytes, fulfills mechanical and electrical signaling communication to ensure normal heart function. Lipoprotein receptor‐related protein 6 (LRP6) is a co‐receptor inducing canonical Wnt/β‐catenin signaling. It was recently reported that LRP6 deficiency in cardiomyocytes predisposes to arrhythmia independent of Wnt signaling. However, whether LRP6 directly regulates the structure of IDs requires further investigation. The aim of the present study was to explore the role of LRP6 in IDs and the potential underlying mechanisms by inducible cardiac‐specific LRP6 knockout mice. The results revealed that LRP6 was predominately expressed in the cell membrane, including the IDs of cardiomyocytes. Tamoxifen‐inducible cardiac‐specific LRP6 knockout mice displayed overt cardiac dysfunction and disruption of ID structure. Further analysis revealed that cardiac LRP6 deficiency induced the imbalance of ID component proteins, characterized by the sharply decreased expression of connexin 43 (Cx43) and the significantly increased expression of N‐cadherin, desmoplakin and γ‐catenin in tissue lysates or membrane fraction from the left ventricle. STRING database analysis indicated that β‐catenin, but no other ID‐associated proteins, interacted with LRP6. Our immunoprecipitation analysis demonstrated that LRP6 strongly interacted with Cx43, N‐cadherin and γ‐catenin, and weakly interacted with β‐catenin, whereas there was no association with desmoplakin. In response to LRP6 deficiency, the recruitment of β‐ or γ‐catenin to N‐cadherin was increased, but they displayed little interaction with Cx43. In conclusion, LRP6 is required to maintain the integrity of ID structure and the balance of ID proteins, and the interaction between LRP6 and Cx43, N‐cadherin and γ‐catenin may be involved in this process.

Low density lipoprotein receptor related protein 6 (LRP6) protects heart against oxidative stress by the crosstalk of HSF1 and GSK3β

“…Mutations in LRP6 relate to early onset hypercholesterolemia, atherosclerosis, and osteoporosis in human [ 8 , 9 ]. We also observed LRP6 is a critical protein in intercalated disc (ID) and regulates the components of IDs [ 10 ]. In Li J’s work that LRP6 acts as a scaffold protein in cardiac gap junction assembly [ 11 ].…”

LRP6 Polymorphisms Is Associated With Sudden Cardiac Death in Patients With Chronic Heart Failure in the Chinese Han Population

“…On the other hand, many studies demonstrated that Wnt signaling was linked to cardiac fibrosis which could impede electrical wave propagation and potentially cause arrhythmias (38)(39)(40). Furthermore, a recent study reported that LRP6 played an important role in keeping the integrity of the intercalated disk, on which the coordinated excitation and contractile performance of the myocardium were dependent, and the interaction between LRP6 and connexin43 might be involved in this process (41). Therefore, LRP6 variants might cause malignant arrhythmias and SCD via disturbing Wnt signaling pathways, as well as disrupting the function of gap junction and the intercalated disk of the myocardium.…”