scholarly journals Compromised mutant EFEMP1 secretion associated with macular dystrophy remedied by proteostasis network alteration

2011 ◽  
Vol 22 (24) ◽  
pp. 4765-4775 ◽  
Author(s):  
John D. Hulleman ◽  
Shalesh Kaushal ◽  
William E. Balch ◽  
Jeffery W. Kelly
Keyword(s):  
Matrix Protein ◽  
Retinal Dystrophy ◽  
Extracellular Matrix Protein ◽  
Macular Dystrophy ◽  
Gaussia Luciferase ◽  
Disulfide Bonding ◽  
Cellular Environment ◽  
Luminescence Assay ◽  
Epidermal Growth ◽  
Doyne Honeycomb Retinal Dystrophy

An Arg345Trp (R345W) mutation in epidermal growth factor–containing, fibulin-like extracellular matrix protein 1 (EFEMP1) causes its inefficient secretion and the macular dystrophy malattia leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD). To understand the influence of the protein homeostasis (or proteostasis) network in rescuing mutant EFEMP1 misfolding and inefficient secretion linked to ML/DHRD, we developed a convenient and sensitive cell-based luminescence assay to monitor secretion versus intracellular accumulation. Fusing EFEMP1 to Gaussia luciferase faithfully recapitulates mutant EFEMP1 secretion defects observed previously using more cumbersome methodology. To understand what governs mutant intracellular retention, we generated a series of R345 mutants. These mutants revealed that aromatic residue substitutions (i.e., Trp, Tyr, and Phe) at position 345 cause significant EFEMP1 secretion deficiencies. These secretion defects appear to be caused, in part, by reduced native disulfide bonding in domain 6 harboring the 345 position. Finally, we demonstrate that mutant EFEMP1 secretion and proper disulfide formation are enhanced by adaptation of the cellular environment by a reduced growth temperature and/or translational attenuation. This study highlights the mechanisms underlying the inefficient secretion of R345W EFEMP1 and demonstrates that alteration of the proteostasis network may provide a strategy to alleviate or delay the onset of this macular dystrophy.

scholarly journals Clinically-identified C-terminal mutations in fibulin-3 are prone to misfolding and destabilization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
DaNae R. Woodard ◽  
Emi Nakahara ◽  
John D. Hulleman
Keyword(s):  
Matrix Protein ◽  
Cultured Cells ◽  
Open Angle Glaucoma ◽  
Culture Conditions ◽  
Glycosylation Site ◽  
Age Related Macular Degeneration ◽  
Extracellular Matrix Protein ◽  
Macular Dystrophy ◽  
Alternative Mechanism ◽  
Age Related

AbstractDistinct mutations in the secreted extracellular matrix protein, fibulin-3 (F3), have been associated with a number of ocular diseases ranging from primary open angle glaucoma to cuticular age-related macular degeneration to a rare macular dystrophy, Malattia Leventinese (ML). The R345W F3 mutation that causes ML leads to F3 misfolding, inefficient secretion and accumulation at higher intracellular steady state levels in cultured cells. Herein, we determined whether fifteen other clinically-identified F3 mutations also led to similar levels of misfolding and secretion defects, which might provide insight into their potential pathogenicity. Surprisingly, we found that only a single F3 variant, L451F, presented with a significant secretion defect (69.5 ± 2.4% of wild-type (WT) F3 levels) and a corresponding increase in intracellular levels (226.8 ± 25.4% of WT F3 levels). Upon follow-up studies, when this conserved residue (L451) was mutated to a charged (Asp or Arg) or bulky (Pro, Trp, Tyr) residue, F3 secretion was also compromised, indicating the importance of small side chains (Leu, Ala, or Gly) at this residue. To uncover potential inherent F3 instability not easily observed under typical culture conditions, we genetically eliminated the sole stabilizing N-linked glycosylation site (N249) from select clinically-identified F3 mutants. This removal exacerbated R345W and L451F secretion defects (19.8 ± 3.0% and 12.4 ± 1.2% of WT F3 levels, respectively), but also revealed a previously undiscovered secretion defect in another C-terminal variant, Y397H (42.0 ± 10.1% of WT F3 levels). Yet, glycan removal did not change the relative secretion of the N-terminal mutants tested (D49A, R140W, I220F). These results highlight the uniqueness and molecular similarities between the R345W and L451F variants and also suggest that previously identified disease-associated mutations (e.g., R140W) are indistinguishable from WT with respect to secretion, hinting that they may lead to disease by an alternative mechanism.

Utility of pattern recognition and multimodal imaging in the diagnosis and management of doyne honeycomb retinal dystrophy complicated with type one choroidal neovascular membrane

2021 ◽  
Vol 14 (2) ◽  
pp. e237635
Author(s):  
Deepika Chennapura Parameswarappa ◽  
Padmaja Kumari Rani
Keyword(s):  
Pattern Recognition ◽  
Multimodal Imaging ◽  
Fundus Autofluorescence ◽  
Retinal Pigment ◽  
Retinal Dystrophy ◽  
Bilateral Symmetry ◽  
Macular Dystrophy ◽  
Choroidal Neovascular Membrane ◽  
Endothelial Growth Factor ◽  
Doyne Honeycomb Retinal Dystrophy

A 44-year-old woman presented with decreased vision in both eyes. The retina in both eyes had drusen distributed along vascular arcades, central macula and in peripapillary region. Macula had pigmented scarring and exudation. Fundus autofluorescence showed drusen. Optical coherence tomography showed drusen, subretinal and intraretinal fluid. Fundus fluorescein and indocyanine green angiography showed drusen, retinal pigment epithelial atrophy and vascular network. Younger age at presentation, bilateral symmetry, typical distribution of drusen along the arcades in a radiating pattern, peripapillary involvement, scarring and atrophy at macula were suggestive of doyne honeycomb retinal dystrophy. The reduced vision was due to macular atrophy and an active choroidal neovascular membrane. The patient was treated with antivascular endothelial growth factor injections for choroidal neovascular membrane. Our case highlights the importance of pattern recognition and multimodal imaging for diagnosing the type of macular dystrophy as doyne honeycomb retinal dystrophy, while simultaneously managing choroidal neovascular membrane.

scholarly journals The Pathophysiological Significance of Fibulin-3

Biomolecules ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1294
Author(s):  
Imogen Livingstone ◽  
Vladimir N. Uversky ◽  
Dominic Furniss ◽  
Akira Wiberg
Keyword(s):  
Extracellular Matrix ◽  
Matrix Protein ◽  
Structural Integrity ◽  
Association Studies ◽  
Retinal Dystrophy ◽  
Elastic Fibre ◽  
Tissue Inhibitor Of Metalloproteinase ◽  
Extracellular Matrix Protein ◽  
Genome Wide Association Studies ◽  
Research Fields

Fibulin-3 (also known as EGF-containing fibulin extracellular matrix protein 1 (EFEMP1)) is a secreted extracellular matrix glycoprotein, encoded by the EFEMP1 gene that belongs to the eight-membered fibulin protein family. It has emerged as a functionally unique member of this family, with a diverse array of pathophysiological associations predominantly centered on its role as a modulator of extracellular matrix (ECM) biology. Fibulin-3 is widely expressed in the human body, especially in elastic-fibre-rich tissues and ocular structures, and interacts with enzymatic ECM regulators, including tissue inhibitor of metalloproteinase-3 (TIMP-3). A point mutation in EFEMP1 causes an inherited early-onset form of macular degeneration called Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD). EFEMP1 genetic variants have also been associated in genome-wide association studies with numerous complex inherited phenotypes, both physiological (namely, developmental anthropometric traits) and pathological (many of which involve abnormalities of connective tissue function). Furthermore, EFEMP1 expression changes are implicated in the progression of numerous types of cancer, an area in which fibulin-3 has putative significance as a therapeutic target. Here we discuss the potential mechanistic roles of fibulin-3 in these pathologies and highlight how it may contribute to the development, structural integrity, and emergent functionality of the ECM and connective tissues across a range of anatomical locations. Its myriad of aetiological roles positions fibulin-3 as a molecule of interest across numerous research fields and may inform our future understanding and therapeutic approach to many human diseases in clinical settings.

Sign in / Sign up

Export Citation Format

Share Document