A missense allele of PEX5 is responsible for the defective import of PTS2 cargo proteins into peroxisomes.

Abstract

Peroxisomes, single-membrane intracellular organelles, play an important role in various metabolic pathways. The translocation of proteins from the cytosol to peroxisomes depends on peroxisome import receptor proteins and defects in peroxisome transport result in a wide spectrum of peroxisomal disorders. Here, we report a large consanguineous family with autosomal recessive congenital cataracts and developmental defects. Genome-wide linkage analysis localized the critical interval to chromosome 12p with a maximum two-point LOD score of 4.2 (θ = 0). Next-generation exome sequencing identified a novel homozygous missense variant (c.653 T > C; p.F218S) in peroxisomal biogenesis factor 5 (PEX5), a peroxisome import receptor protein. This missense mutation was confirmed by bidirectional Sanger sequencing. It segregated with the disease phenotype in the family and was absent in ethnically matched control chromosomes. The lens-specific knockout mice of Pex5 recapitulated the cataractous phenotype. In vitro import assays revealed a normal capacity of the mutant PEX5 to enter the peroxisomal Docking/Translocation Module (DTM) in the presence of peroxisome targeting signal 1 (PTS1) cargo protein, be monoubiquitinated and exported back into the cytosol. Importantly, the mutant PEX5 protein was unable to form a stable trimeric complex with peroxisomal biogenesis factor 7 (PEX7) and a peroxisome targeting signal 2 (PTS2) cargo protein and, therefore, failed to promote the import of PTS2 cargo proteins into peroxisomes. In conclusion, we report a novel missense mutation in PEX5 responsible for the defective import of PTS2 cargo proteins into peroxisomes resulting in congenital cataracts and developmental defects.

• Authors: Muhammad Ali, Shahid Y Khan, Tony A Rodrigues, Tânia Francisco, Xiaodong Jiao, Hang Qi, Firoz Kabir, Bushra Irum, Bushra Rauf, Asma A Khan, Azra Mehmood, Muhammad Asif Naeem, Muhammad Zaman Assir, Muhammad Hassaan Ali, Mohsin Shahzad, Khaled K Abu-Amero, Shehla Javed Akram, Javed Akram, Sheikh Riazuddin, Saima Riazuddin, Michael L Robinson, Myriam Baes, Jorge E Azevedo, J Fielding Hejtmancik, S Amer Riazuddin
• Journal: Human genetics (Hum Genet) Vol. 140 Issue 4 Pg. 649-666 (Apr 2021) ISSN: 1432-1203 [Electronic] Germany
• PMID: 33389129 (Publication Type: Journal Article)

Chemical References

• ABCD3 protein, human
• ATP-Binding Cassette Transporters
• PEX5 protein, human
• Peroxisomal Targeting Signals
• Peroxisome-Targeting Signal 1 Receptor
• SQSTM1 protein, human
• Sequestosome-1 Protein

Topics

• ATP-Binding Cassette Transporters (metabolism)
• Animals
• Biological Transport, Active
• Cataract (congenital, genetics, metabolism)
• Chromosomes, Human, Pair 12
• Consanguinity
• Female
• Genetic Linkage
• Humans
• Lens, Crystalline (metabolism)
• Male
• Mice
• Mice, Knockout
• Mutation, Missense
• Peroxisomal Targeting Signals
• Peroxisome-Targeting Signal 1 Receptor (genetics, metabolism)
• Peroxisomes (metabolism)
• Sequestosome-1 Protein (metabolism)
• Exome Sequencing