Fusion between Retinal Rod Outer Segment Membranes and Model Membranes:  A Role for Photoreceptor Peripherin/rds

• Published in: Biochemistry (Easton) Vol. 37; no. 26; pp. 9477 - 9487
• Main Authors: Boesze-Battaglia, Kathleen, Lamba, Om P, Napoli, Andrew A, Sinha, Santosh, Guo, Yuqing
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 30.06.1998
• Subjects: Amino Acid Sequence; Animals; Binding Sites, Antibody; Cattle; Cell Membrane - metabolism; Cell Membrane - physiology; Cell-Free System; Eye Proteins - physiology; Hydrolysis; Intermediate Filament Proteins - immunology; Intermediate Filament Proteins - metabolism; Intermediate Filament Proteins - physiology; Liposomes; Membrane Fusion; Membrane Glycoproteins; Models, Biological; Molecular Sequence Data; Nerve Tissue Proteins - immunology; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Peptide Fragments - chemical synthesis; Peptide Fragments - chemistry; Peptide Fragments - physiology; Peripherins; Rod Cell Outer Segment - metabolism; Rod Cell Outer Segment - physiology; Spectroscopy, Fourier Transform Infrared; Trypsin
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi980173p

Peripherin/rds plays an essential role in the maintenance of photoreceptor rod cell disk membrane structure. The purification of this protein to homogeneity [Boesze-Battaglia, K., et al. (1997) Biochemistry 36, 6835−6846] has allowed us to characterize the functional role of peripherin/rds in the maintenance of rod outer segment (ROS) membrane fusion processes. Utilizing a cell-free fusion assay system, we report that the fusion of R18-labeled ROS plasma membrane (R18-PM) with disk membranes or peripherin/rds-enriched large unilammellar vesicles (LUVs) is inhibited upon trypsinolysis of peripherin/rds. To understand this phenomenon, we tested the ability of a series of overlapping synthetic C-terminal peripherin/rds peptides to mediate model membrane fusion. Within the 63 amino acid long region of the C-terminus, we identified a minimal 15 residue long amino acid sequence (PP-5), which is necessary to promote membrane fusion. PP-5 was able to inhibit R18-PM disk membrane fusion and promoted ANTS/DPX contents mixing in a pure vesicle system. This peptide (PP-5) promoted calcium-induced vesicle aggregation of phosphatidylethanolamine:phosphatidylserine LUVs. FTIR analysis confirmed the structural prediction of this peptide as α-helical. When modeled as an α-helix, this peptide is amphiphilic with a hydrophobicity index of 0.75 and a hydrophobic moment of 0.59. PP-5 has substantial biochemical and functional homology with other well-characterized membrane fusion proteins. These results demonstrate the necessity for peripherin/rds in ROS membrane fusion, specifically the requirement for an intact C-terminal region of this protein.