Impact of LCA-Associated E14L LRAT Mutation on Protein Stability and Retinoid Homeostasis.
Sylwia ChelstowskaMade Airanthi K Widjaja-AdhiJosie A SilvaroliMarcin GolczakPublished in: Biochemistry (2017)
Vitamin A (all-trans-retinol) is metabolized to the visual chromophore (11-cis-retinal) in the eyes and to all-trans-retinoic acid, a hormone like compound, in most tissues. A key enzyme in retinoid metabolism is lecithin:retinol acyltransferase (LRAT), which catalyzes the esterification of vitamin A. The importance of LRAT is indicated by pathogenic missense and nonsense mutations, which cause devastating blinding diseases. Retinoid-based chromophore replacement therapy has been proposed as treatment for these types of blindness based on studies in LRAT null mice. Here, we analyzed the structural and biochemical basis for retinal pathology caused by mutations in the human LRAT gene. Most LRAT missense mutations associated with retinal degeneration are localized within the catalytic domain, whereas E14L substitution is localized in an N-terminal α-helix, which has been implicated in interaction with the phospholipid bilayer. To elucidate the biochemical consequences of this mutation, we determined LRAT(E14L)'s enzymatic properties, protein stability, and impact on ocular retinoid metabolism. Bicistronic expression of LRAT(E14L) and enhanced green fluorescence protein revealed instability and accelerated proteosomal degradation of this mutant isoform. Surprisingly, instability of LRAT(E14L) did not abrogate the production of the visual chromophore in a cell-based assay. Instead, expression of LRAT(E14L) led to a rapid increase in cellular levels of retinoic acid upon retinoid supplementation. Thus, our study unveils the potential role of retinoic acid in the pathology of a degenerative retinal disease with important implications for the use of retinoid-based therapeutics in affected patients.
Keyphrases
- optical coherence tomography
- replacement therapy
- diabetic retinopathy
- poor prognosis
- optic nerve
- binding protein
- gene expression
- endothelial cells
- small molecule
- protein protein
- end stage renal disease
- single cell
- type diabetes
- intellectual disability
- ejection fraction
- amino acid
- newly diagnosed
- dna methylation
- chronic kidney disease
- autism spectrum disorder
- bone marrow
- adipose tissue
- combination therapy
- nitric oxide
- high throughput
- smoking cessation
- climate change
- transcription factor
- fatty acid
- patient reported
- insulin resistance