Globotriaosylceramide Induces Lysosomal Degradation of Endothelial KCa3.1 in Fabry Disease

Objective-Globotriaosylceramide (Gb3) induces K(Ca)3.1 downregulation in Fabry disease (FD). We investigated whether Gb3 induces K(Ca)3.1 endocytosis and degradation. Approach and Results-K(Ca)3.1, especially plasma membrane-localized K(Ca)3.1, was downregulated in both Gb3-treated mouse aortic endothelial cells (MAECs) and human umbilical vein endothelial cells. Gb3-induced K(Ca)3.1 downregulation was prevented by lysosomal inhibitors but not by a proteosomal inhibitor. Endoplasmic reticulum stress-inducing agents did not induce K(Ca)3.1 downregulation. Gb3 upregulated the protein levels of early endosome antigen 1 and lysosomal-associated membrane protein 2 in MAECs. Compared with MAECs from age-matched wild-type mice, those from aged alpha-galactosidase A (Gla)-knockout mice, an animal model of FD, showed downregulated K(Ca)3.1 expression and upregulated early endosome antigen 1 and lysosomal-associated membrane protein 2 expression. In contrast, no significant difference was found in early endosome antigen 1 and lysosomal-associated membrane protein 2 expression between young Gla-knockout and wild-type MAECs. In aged Gla-knockout MAECs, clathrin was translocated close to the cell border and clathrin knockdown recovered K(Ca)3.1 expression. Rab5, an effector of early endosome antigen 1, was upregulated, and Rab5 knockdown restored K(Ca)3.1 expression, the current, and endothelium-dependent relaxation. Conclusions-Gb3 accelerates the endocytosis and lysosomal degradation of endothelial K(Ca)3.1 via a clathrin-dependent process, leading to endothelial dysfunction in FD.