Structural effects of fibulin 5 missense mutations associated with age-related macular degeneration and cutis laxa.

Abstract

PURPOSE:

AMD has a complex etiology with environmental and genetic risk factors. Ten fibulin 5 sequence variants have been associated with AMD and two other fibulin 5 mutations cause autosomal-recessive cutis laxa. Fibulin 5 is a 52-kDa calcium-binding epidermal growth factor (cbEGF)-rich extracellular matrix protein that is essential for the formation of elastic tissues. Biophysical techniques were used to detect structural changes in the fibulin 5 mutants and to determine whether changes are predictive of pathogenicity.

METHODS:

Native PAGE, nonreduced SDS-PAGE, size-exclusion column multiangle laser light scattering, sedimentation velocity, and circular dichroism (CD) were used to investigate the mobility, hydrodynamic radii, folding, and oligomeric states of the fibulin 5 mutants in the absence and presence of Ca(2+).

RESULTS:

CD showed that all mutants are folded, although perturbations to secondary structure contents were detected. Both cutis laxa mutants increased dimerization. Most other mutants slightly increased self-association in the absence of Ca(2+) but this was also demonstrated by G202R, a polymorphism detected in a control individual. The AMD-associated mutant G412E showed lower-than-expected mobility during native-PAGE, the largest hydrodynamic radius for the monomer form and the highest levels of aggregation in both the absence and presence of Ca(2+).

CONCLUSIONS:

The results identified structural differences for the disease-causing cutis laxa mutants and for one AMD variant (G412E), suggesting that this may also be pathogenic. Although the other AMD-associated mutants showed no gross structural differences, they cannot be excluded as pathogenic by differences outside the scope of this study-for example, disruption of heterointeractions.

• Authors: Richard P O Jones, Caroline Ridley, Thomas A Jowitt, Ming-Chuan Wang, Marjorie Howard, Nicoletta Bobola, Tao Wang, Paul N Bishop, Cay M Kielty, Clair Baldock, Andrew J Lotery, Dorothy Trump
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 51 Issue 5 Pg. 2356-62 (May 2010) ISSN: 1552-5783 [Electronic] United States
• PMID: 20007835 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Extracellular Matrix Proteins
• FBLN5 protein, human
• Calcium

Topics

• Calcium (pharmacology)
• Chromatography, Gel
• Circular Dichroism
• Cutis Laxa (genetics)
• Electrophoresis, Polyacrylamide Gel
• Extracellular Matrix Proteins (chemistry, genetics)
• Humans
• Macular Degeneration (genetics)
• Molecular Structure
• Mutagenesis, Site-Directed
• Mutation, Missense
• Protein Folding