The retinal pigment epithelium (RPE) is a tissue, which lines the back of the eye. Aging, environmental insults and genetic predispositions contribute to blindness diseases causing RPE degeneration, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP).
The findings, published online October 24 in The Journal of Biological Chemistry (Patil, H et al, (2014) J. Biol. Chem. 289 (43) 29767-29789) and supported by grants from the National Institutes of Health, provide a tantalizing genetic link between a multifunctional protein, called Ranbp2, and RPE degeneration and Parkinson's diseases.
The team led by Dr. Paulo A Ferreira at Duke University Medical Center, Durham, North Carolina, found that removal of Ranbp2 from the RPE in mice led to RPE degeneration with features that resemble a severe form of AMD, wet AMD.
They also pinpointed that impairment of a signaling activity of Ranbp2 that controls the flow of signaling proteins between the nuclear and cytoplasmic compartments, suffices by itself to trigger RPE degeneration. Strikingly, and like in wet AMD, such impairment of Ranbp2 caused also severe damage to neighboring blood vessels and bleeding.
Another surprising discovery was that a subset of mice without Ranbp2 in the RPE developed Parkinsonism tremors. This outcome results likely from the unexpected removal of Ranbp2 from selective brain regions controlling voluntary motor activity, an issue the authors are currently investigating.
These findings are exciting because they support that Parkinsonism and RPE degeneration share multifunctional players and they open new venues toward the development of therapeutic approaches to prevent or slow aging-related disorders, such as AMD and Parkinson's diseases.