Abstract
Purpose :
CFAP418 is a causative gene for several inherited retinal degenerative diseases. Cfap418 knockout in mice leads to photoreceptor cell death by disrupting the membrane disk alignment and reducing the membrane proteins in the outer segment (OS). In this report, we investigated the moculuar mechanism that underlies the retinal phenotypes in Cfap418 knockout mice.
Methods :
We systematically examined the protein expression and phosphorylation profiles as well as membrane lipid composition in Cfap418-/- retinas using various quantitative mass spectrometry at the onset and during the robust progress of the phenotypes. Semi-quantitative immunoblotting analysis and standard immunofluorescence were conducted to verify the omics findings. Affinity purifications coupled with mass spectrometry and proten lipid overlay assays were performed to identify CFAP418-binding partners.
Results :
We observed differentially expressed proteins that are involved in membrane remodeling and mitochondrial function. In Cfap418-/- photoreceptors, the expression and localization of endosomal sorting complex proteins, mitochondrial morphology, and OS targeting were affected. The phosphorylation of lipid-binding and -activated protein kinase Ca was significantly increased. In addition, a broad range of membrane lipids were altered in abundance. Affinity purifications failed to identify stable CFAP418-interacting proteins, but revealed an indirect associated protein RAB28, which is encoded by another retinal degeneration gene. However, CFAP418 protein binds to lipid metabolism precursor phosphatidic acid and mitochondrial-specific cardiolipin.
Conclusions :
Our findings indicate that CFAP418 is a lipid-binding protein and functions in membrane lipid homeostasis, membrane remodeling, and mitochondrial function during photoreceptor OS development.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.