1
|
Esapa CT, McIlhinney RAJ, Waite AJ, Benson MA, Mirzayan J, Piko H, Herczegfalvi Á, Horvath R, Karcagi V, Walter MC, Lochmüller H, Rizkallah PJ, Lu QL, Blake DJ. Misfolding of fukutin-related protein (FKRP) variants in congenital and limb girdle muscular dystrophies. Front Mol Biosci 2023; 10:1279700. [PMID: 38161385 PMCID: PMC10755465 DOI: 10.3389/fmolb.2023.1279700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 11/16/2023] [Indexed: 01/03/2024] Open
Abstract
Fukutin-related protein (FKRP, MIM ID 606596) variants cause a range of muscular dystrophies associated with hypo-glycosylation of the matrix receptor, α-dystroglycan. These disorders are almost exclusively caused by homozygous or compound heterozygous missense variants in the FKRP gene that encodes a ribitol phosphotransferase. To understand how seemingly diverse FKRP missense mutations may contribute to disease, we examined the synthesis, intracellular dynamics, and structural consequences of a panel of missense mutations that encompass the disease spectrum. Under non-reducing electrophoresis conditions, wild type FKRP appears to be monomeric whereas disease-causing FKRP mutants migrate as high molecular weight, disulfide-bonded aggregates. These results were recapitulated using cysteine-scanning mutagenesis suggesting that abnormal disulfide bonding may perturb FKRP folding. Using fluorescence recovery after photobleaching, we found that the intracellular mobility of most FKRP mutants in ATP-depleted cells is dramatically reduced but can, in most cases, be rescued with reducing agents. Mass spectrometry showed that wild type and mutant FKRP differentially associate with several endoplasmic reticulum (ER)-resident chaperones. Finally, structural modelling revealed that disease-associated FKRP missense variants affected the local environment of the protein in small but significant ways. These data demonstrate that protein misfolding contributes to the molecular pathophysiology of FKRP-deficient muscular dystrophies and suggest that molecules that rescue this folding defect could be used to treat these disorders.
Collapse
Affiliation(s)
| | | | - Adrian J. Waite
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | | | - Jasmin Mirzayan
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Henriett Piko
- Department of Internal Medicine and Oncology, Semmelweis University, Budapest, Hungary
| | - Ágnes Herczegfalvi
- Semmelweis University Pediatric Center Tűzoltó Street Unit, Budapest, Hungary
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Veronika Karcagi
- National Institute of Environmental Health, Department of Molecular Genetics and Diagnostics, Istenhegyi Genetic Diagnostic Centre, Budapest, Hungary
| | - Maggie C. Walter
- Friedrich-Baur-Institute at the Department of Neurology, University Hospital, Munich, Germany
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Division of Neurology, Department of Medicine, The Ottawa Hospital, and Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
| | - Pierre J. Rizkallah
- Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Qi L. Lu
- McColl-Lockwood Laboratory for Muscular Dystrophy Research, Carolinas Medical Center, Charlotte, United States
| | - Derek J. Blake
- Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| |
Collapse
|