Rhodopsin T17M Mutant Inhibits Complement C3 Secretion in Retinal Pigment Epithelium via ROS Induced Downregulation of TWIST1

Abstract

Rhodopsin mutations cause autosomal dominant form of retinitis pigmentosa (RP). T17M rhodopsin predisposes cells to endoplasmic reticulum stress induced apoptosis. However, the pathogenic role of T17M rhodopsin in RP is not completely understood. Complement C3 has a protective role in RP pathogenesis. This study aimed to investigate whether T17M rhodopsin regulates C3 secretion in retinal pigment epithelium. The human retinal pigment epithelial cell line (ARPE-19) was engineered to overexpress wide-type (WT) and T17M rhodopsin. Gene expression was detected by RT-PCR and Western blot analysis. C3 secretion was detected by ELISA. The overexpression of T17M rhodopsin significantly induced ROS and reduced C3 secretion and transcription in ARPE-19 cells, but ROS scavengers could partially rescue reduced C3 secretion and transcription. Mechanistically, we found that ROS suppressed transcription factor TWIST1 which is responsible for activated transcription of C3. In conclusion, our data provide the first evidence that T17M rhodopsin mutant disrupts C3 secretion via the induction of ROS and the suppression of TWIST1. These findings reveal novel insight into the pathogenic role of mutant rhodopsin in RP.

Properdin Modulates Complement Component Production in Stressed Human Primary Retinal Pigment Epithelium Cells

“…(ii) Autocrine regulation of complement transcripts/secretion by complement complexes or cleavage products, which are only produced if the SNP is present, could be imaginable. Complement components or complement cleavage products can activate cellular signaling pathways via specific receptors [ 63 , 64 , 65 ], which can result in increased or reduced transcription of complement components by associated transcription factors [ 66 , 67 , 68 ]. As we showed the secretion of complement components and presents of complement activation products as well as of receptors in hpRPE cells an autocrine regulation of complement is speculatively possible.…”

Modulation of three key innate immune pathways for the most common retinal degenerative diseases

“…However, earlier studies reported reduced C3 and C4 levels and increased immune complexes in the sera from RP patients, and this reduced systemic complement activity appears to be related to poor disease prognosis (Heredia et al, ). The rhodopsin T17M mutation also reduces C3 secretion in RPE cells (Xiong et al, ), suggesting that some RP‐related genes may regulate complement expression/secretion by RPE cells. Humphries et al showed that C1q, the primary component of the classical pathway of the complement system, is a survival factor for cone cells, and C1q deficiency promoted photoreceptor death in Rho −/− mice, a mouse model of Leber's congenital amaurosis (LCA; Humphries et al, ).…”