Altered Rhodopsin and Its Link to Retinitis Pigmentosa

How does P23H mutated rhodopsin result in the disease Retinitis Pigmentosa?

In figure 7, healthy amounts of rhodopsin are seen within the endoplasmic reticulum of the cell. In contrast, misfolded rhodopsin builds up within the endoplasmic reticulum as it cannot be trafficked properly to the outer segment, which overloads the protein degrading system of rod cells, as seen in figure 8.(1) Build-up of misfolded rhodopsin causes the release of molecules which inhibit the protein degrading system, continuing the progressive build-up of rhodopsin.(2) The protein degrading system is important for healthy protein cycling in cells. Dysfunction of the protein degradation system leads to death of rod cells, which can progress in cone cells as well.(3) Retinal cell death reduces the thickness of the retina, resulting in progressive loss of vision.(3) Patients lose peripheral vision, and their visual field is continuously reduced to the point of tunnel vision and in some cases, complete blindness.