Peripherin/rds co-distributes with putative binding partners in basal rod outer segment disks

Abstract

The retinal degeneration slow protein peripherin/rds, (a.k.a. RDS), encoded by the rds gene, is essential for the formation, organization and maintenance of outer segments (Arikawa et al., 1992; Connell et al., 1991; Connell and Molday, 1990; Kedzierski et al., 2001; Molday, 1998). In humans, any one of over 160 mutations within this gene results in a broad variety of late onset progressive retinal dystrophies characterized by abnormal photoreceptor structure (Dryja et al., 1997; Keen and Inglehearn, 1996; Kohl et al., 1998). The pathogenic mechanism(s) underlying peripherin/rds mediated retinal dystrophies are unknown, however new insight has been gained in our understanding of peripherin/rds function based upon recent structural studies identifying the C-terminal domain of this protein as homologous to structures called intrinsically disordered domains (IDD) (Dyson, 2005; Edrington, 2007b; Ritter, 2005). IDDs are unstructured domains that become structurally stabilized by interacting with one or with several binding partners (Uversky et al., 2008). Structural flexibility imparts multi-functionality to the protein and binding partners act as regulators of its function (Lakoucheva et al., 2002; Vucetic et al., 2007). In humans, numerous mutations in the rds C-terminus result in rod/cone or cone/rod dystrophies. In a murine model of retinitis pigmentosa, deletion of codon 307 in the rds gene results in severely dysmorphic outer segments (OSs) in mice (McNally et al., 2002). The rds 307 del mouse provides the first in vivo evidence for a correlation between intrinsic disorder and retinopathy. In these mice disruption of the peripherin/rds C-terminus results in a gene product with a more intrinsically ordered C-terminal domain characterized by an increase in α-helical content.