CUL4-DDB1-CRBN E3 Ubiquitin Ligase Regulates Proteostasis of ClC-2 Chloride Channels: Implication for Aldosteronism and Leukodystrophy

• Published in: Cells (Basel, Switzerland) Switzerland), 2020-05, Vol.9 (6), p.1332
• Main Authors: Fu, Ssu-Ju, Hu, Meng-Chun, Peng, Yi-Jheng, Fang, Hsin-Yu, Hsiao, Cheng-Tsung, Chen, Tsung-Yu, Jeng, Chung-Jiuan, Tang, Chih-Yung
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Animals; Brain Diseases - metabolism; Brain Diseases - pathology; channelopathy; Chloride Channels - metabolism; cullin E3 ubiquitin ligase; Cullin Proteins - metabolism; DNA-Binding Proteins - metabolism; HEK293 Cells; Humans; Hyperaldosteronism - metabolism; Hyperaldosteronism - pathology; MG132; Mice, Inbred C57BL; MLN4924; Models, Biological; Polyubiquitin - metabolism; polyubiquitination; proteasomal degradation; Proteolysis; Proteostasis; Rats, Wistar; Substrate Specificity; Ubiquitin-Protein Ligases - metabolism; Ubiquitination
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells9061332

Voltage-gated ClC-2 channels are essential for chloride homeostasis. Complete knockout of mouse ClC-2 leads to testicular degeneration and neuronal myelin vacuolation. Gain-of-function and loss-of-function mutations in the ClC-2-encoding human gene are linked to the genetic diseases aldosteronism and leukodystrophy, respectively. The protein homeostasis (proteostasis) mechanism of ClC-2 is currently unclear. Here, we aimed to identify the molecular mechanism of endoplasmic reticulum-associated degradation of ClC-2, and to explore the pathophysiological significance of disease-associated anomalous ClC-2 proteostasis. In both heterologous expression system and native neuronal and testicular cells, ClC-2 is subject to significant regulation by cullin-RING E3 ligase-mediated polyubiquitination and proteasomal degradation. The cullin 4 (CUL4)-damage-specific DNA binding protein 1 (DDB1)-cereblon (CRBN) E3 ubiquitin ligase co-exists in the same complex with and promotes the degradation of ClC-2 channels. The CRBN-targeting immunomodulatory drug lenalidomide and the cullin E3 ligase inhibitor MLN4924 promotes and attenuates, respectively, proteasomal degradation of ClC-2. Analyses of disease-related ClC-2 mutants reveal that aldosteronism and leukodystrophy are associated with opposite alterations in ClC-2 proteostasis. Modifying CUL4 E3 ligase activity with lenalidomide and MLN4924 ameliorates disease-associated ClC-2 proteostasis abnormality. Our results highlight the significant role and therapeutic potential of CUL4 E3 ubiquitin ligase in regulating ClC-2 proteostasis.