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  3. Hsp70/CHIP E3 ligase complex triggers K149-linked ubiquitination and degradation of BEST1 mutants p.P233L and p.P346H, impairing chloride channel function and retinal integrity

Hsp70/CHIP E3 ligase complex triggers K149-linked ubiquitination and degradation of BEST1 mutants p.P233L and p.P346H, impairing chloride channel function and retinal integrity

  • Cell Signal. 2025 Dec 26:139:112343. doi: 10.1016/j.cellsig.2025.112343.
Zhongxue Zhou 1,  Hongxia Tian 2,  Ning Ma 3,  Wen Fang 4,  Qingxia Lu 5,  Huiyang 6,  HaiyingTian 7,  Yu Tang 8,  Ling Tian 8,  Xu Jia 9,  Yuanju Zhang 2,  Yuqian Li 2,  Xiaoyan Zhu 10,  Qiao Yu 10,  Ding'an Zhou 11
Affiliations

Affiliations

  • 1 Department of Clinical Biochemistry, the Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, PR China; Clinical laboratory department, Hospital of Qianxinan Prefecture, Xingyi, Guizhou 562400, PR China; Clinical Research Center, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 55004, PR China.
  • 2 Department of Clinical Biochemistry, the Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, PR China; Clinical Research Center, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 55004, PR China.
  • 3 Department of Vascular and Thyroid Surgery, Guizhou Provincial People's Hospital, Guiyang 550002, PR China.
  • 4 School of Clinical Laboratory Science, Guizhou Medical University, Guiyang, Guizhou 550004, PR China.
  • 5 Department of Clinical Biochemistry, the Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, PR China.
  • 6 Clinical Research Center, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 55004, PR China.
  • 7 Department of Ultrasound Medicine, Guizhou Provincial People's Hospital, Guiyang, Guiyang, Guizhou 550002, PR China.
  • 8 Key Laboratory of Thermoregulation and Inflammation of Sichuan Higher Education Institutes, Department of Physiology, Chengdu Medical College, Chengdu, Sichuan 610500, PR China.
  • 9 Key Laboratory of Non-coding RNA and Drug Discovery at Chengdu Medical College of Sichuan Province, School of Basic Medical Sciences, Chengdu Medical College, Chengdu 610500, Sichuan, China.
  • 10 Department of Ophthalmology, Guizhou Provincial People's Hospital, Guiyang, 550002, Guizhou, China.
  • 11 Department of Clinical Biochemistry, the Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 550004, PR China; Clinical Research Center, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou 55004, PR China; Key Laboratory of Endemic and Ethnic Diseases, Ministry of Education & Key Laboratory of Medical Molecular Biology of Guizhou Province, Guizhou Medical University, Guiyang 550004, Guizhou, China. Electronic address: [email protected].
PMID: 41456629 DOI: 10.1016/j.cellsig.2025.112343
Abstract

The mechanisms underlying ubiquitination-mediated degradation of bestrophinopathy-causing mutants and their in vivo effects on retinal pigment epithelium (RPE) localization and retinal structure remain poorly understood. Furthermore, the upstream signaling cascade that induces degradation of these mutants and the detailed ubiquitination mechanism are unknown. Here, we report a c.1037C > A (p.P346H) mutation and a c.698C > T (p.P233L) mutation that co-segregate with the phenotypes of pedigrees affected by RP50 and Best vitelliform macular dystrophy (BVMD), respectively. The BEST1 mutants p.P233L and p.P346H reduced Chloride Channel activity and induced mislocalization of bestrophin-1 in polarized MDCK II cells, significantly affecting the channel activity of wild-type bestrophin-1. Lys149 was identified as the site responsible for ubiquitination of p.P346H- and p.P233L-bestrophin-1, mediated by HSP70 and the C-terminal Hsp70-interacting protein (CHIP). Mutant bestrophin-1 proteins p.P346H and p.P233L undergo ubiquitination and degradation, preventing their localization to the cell membrane of MDCK II cells and the RPE of zebrafish, thereby reducing Chloride Channel activity. Mislocalization of mutant bestrophin-1 to the RPE impaired the multicellular layered structure of the retina. Our study reveals a ubiquitination signaling pathway mediated by HSP70 and CHIP that depends on Lys149 of bestrophin-1. Aberrant activation of this pathway leads to loss of function in the p.P233L and p.P346H mutants and triggers retinopathy.

Keywords

BEST1; Bestrophinopathies; CHIP; Hsp70; Protein mislocalization; Ubiquitination modification.

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