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Umano A, Fang K, Qu Z, Scaglione JB, Altinok S, Treadway CJ, Wick ET, Paulakonis E, Karunanayake C, Chou S, Bardakjian TM, Gonzalez-Alegre P, Page RC, Schisler JC, Brown NG, Yan D, Scaglione KM. The molecular basis of spinocerebellar ataxia type 48 caused by a de novo mutation in the ubiquitin ligase CHIP. J Biol Chem 2022; 298:101899. [PMID: 35398354 PMCID: PMC9097460 DOI: 10.1016/j.jbc.2022.101899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/24/2022] [Accepted: 03/28/2022] [Indexed: 11/25/2022] Open
Abstract
The spinocerebellar ataxias (SCAs) are a class of incurable diseases characterized by degeneration of the cerebellum that results in movement disorder. Recently, a new heritable form of SCA, spinocerebellar ataxia type 48 (SCA48), was attributed to dominant mutations in STIP1 homology and U box-containing 1 (STUB1); however, little is known about how these mutations cause SCA48. STUB1 encodes for the protein C terminus of Hsc70 interacting protein (CHIP), an E3 ubiquitin ligase. CHIP is known to regulate proteostasis by recruiting chaperones via a N-terminal tetratricopeptide repeat domain and recruiting E2 ubiquitin-conjugating enzymes via a C-terminal U-box domain. These interactions allow CHIP to mediate the ubiquitination of chaperone-bound, misfolded proteins to promote their degradation via the proteasome. Here we have identified a novel, de novo mutation in STUB1 in a patient with SCA48 encoding for an A52G point mutation in the tetratricopeptide repeat domain of CHIP. Utilizing an array of biophysical, biochemical, and cellular assays, we demonstrate that the CHIPA52G point mutant retains E3-ligase activity but has decreased affinity for chaperones. We further show that this mutant decreases cellular fitness in response to certain cellular stressors and induces neurodegeneration in a transgenic Caenorhabditis elegans model of SCA48. Together, our data identify the A52G mutant as a cause of SCA48 and provide molecular insight into how mutations in STUB1 cause SCA48.
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Affiliation(s)
- A Umano
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - K Fang
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - Z Qu
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - J B Scaglione
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - S Altinok
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - C J Treadway
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - E T Wick
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - E Paulakonis
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - C Karunanayake
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - S Chou
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin, USA; Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - T M Bardakjian
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - P Gonzalez-Alegre
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - R C Page
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - J C Schisler
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - N G Brown
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - D Yan
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA
| | - K M Scaglione
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA; Department of Neurology, Duke University, Durham, North Carolina, USA; Duke Center for Neurodegeneration and Neurotherapeutics, Duke University, Durham, North Carolina, USA.
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