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Structure and function of disease-causing missense mutations in the PHEX gene
Yves Sabbagh1, Guy Boileau, Marcelo Campos
1Department of Biology, McGill University, and The McGill University-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada H3Z 2Z3.
Summary
Missense mutations in the PHEX gene disrupt protein trafficking and activity, causing X-linked hypophosphatemia (XLH). This study investigates how specific PHEX mutations impact protein function and cellular localization in XLH patients.
Area of Science:
- Biochemistry
- Genetics
- Molecular Biology
Background:
- X-linked hypophosphatemia (XLH) is a genetic disorder caused by mutations in the PHEX gene.
- The PHEX gene encodes a metallopeptidase crucial for phosphate homeostasis.
Purpose of the Study:
- To investigate the functional consequences of nine PHEX missense mutations found in XLH patients.
- To determine the impact of these mutations on PHEX protein trafficking, enzymatic activity, and conformation.
Main Methods:
- Utilized PCR mutagenesis to generate wild-type and mutant PHEX proteins.
- Assessed protein secretion and cellular localization via cell culture and transfection.
- Measured endopeptidase activity using a fluorogenic peptide substrate.
- Analyzed protein conformation using limited proteolysis.
Main Results:
- Mutations C85R, G579R, G579V, S711R, and A720T resulted in intracellular retention of PHEX protein.
- Mutations E581V and S711R abolished endopeptidase activity; D237G and Y317F reduced activity by 50-60%.
- Mutations A720T and F731Y retained full catalytic activity, while F731Y and D237G showed altered protein conformation.
Conclusions:
- Missense mutations in PHEX lead to XLH through impaired protein trafficking, reduced endopeptidase activity, or altered protein conformation.
- Understanding these molecular defects is crucial for developing targeted therapies for XLH.