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Peripherin/rds influences membrane vesicle morphology. Implications for retinopathies
J D Wrigley1, T Ahmed, C L Nevett
1School of Biochemistry, University of Leeds, Leeds LS2 9JT, United Kingdom.
Abstract:
Peripherin/rds is an integral membrane glycoprotein found in the rim regions of vertebrate photoreceptor cell discs. Natural mutations of the encoding gene result in degenerative retinal disorders, such as retinitis pigmentosa. The retinal degeneration slow (rds) phenotype, observed in mice, is considered to be an appropriate model for peripherin/rds-mediated retinitis pigmentosa. Associated abnormalities in the outer segment of photoreceptor cells have implicated peripherin/rds in some aspect of disc morphology, yet it remains unclear whether such morphological effects are the cause or the result of this condition. Here we present the first direct evidence to support a role for peripherin/rds in maintaining the flattened vesicle morphology characteristic of photoreceptor outer segments. In vitro expression yields a 36-kDa immunoreactive species, which is inserted into membranes and undergoes N-glycosylation, inter- and intramolecular disulfide bonding, and dimerization. Electron microscopy reveals that peripherin/rds flattens microsomal vesicles. This effect appears to be dependent on disulfide bond formation but not N-glycosylation. The inability of two pathogenic peripherin/rds mutants (P216L and C165Y) to flatten membrane vesicles implicates such mutations as the primary cause of the retinal degeneration observed in retinitis pigmentosa.
Insights
Peripherin/rds protein is crucial for maintaining photoreceptor cell disc shape. Mutations in this protein cause retinitis pigmentosa by preventing proper vesicle morphology.
Area of Science:
- Ophthalmology
- Cell Biology
- Biochemistry
Background:
- Peripherin/rds is a photoreceptor glycoprotein implicated in retinal degenerative disorders.
- Its precise role in photoreceptor outer segment disc morphology remains unclear.
- The retinal degeneration slow (rds) mouse model mimics human retinitis pigmentosa.
Purpose of the Study:
- To provide direct evidence for peripherin/rds's role in maintaining photoreceptor outer segment vesicle morphology.
- To investigate the molecular mechanisms underlying peripherin/rds's function.
- To link specific mutations to the pathogenesis of retinitis pigmentosa.
Main Methods:
- In vitro expression and characterization of peripherin/rds.
- Biochemical analysis including N-glycosylation and disulfide bonding.
- Electron microscopy of microsomal vesicles treated with peripherin/rds.
- Analysis of pathogenic mutants (P216L and C165Y).
Main Results:
- Expressed peripherin/rds is a 36-kDa membrane glycoprotein undergoing N-glycosylation, disulfide bonding, and dimerization.
- Peripherin/rds directly flattens microsomal vesicles in vitro.
- This flattening effect depends on disulfide bond formation but not N-glycosylation.
- Pathogenic mutants P216L and C165Y fail to flatten vesicles.
Conclusions:
- Peripherin/rds plays a direct, essential role in maintaining the flattened morphology of photoreceptor outer segment discs.
- Disulfide bond formation is critical for this function.
- Mutations impairing vesicle flattening are a primary cause of peripherin/rds-mediated retinitis pigmentosa.