Hetero-oligomeric interactions of an ELOVL4 mutant protein: implications in the molecular mechanism of Stargardt-3 macular dystrophy

摘要

Purpose: Stargardt disease 3 (STGD3) isa juvenile macular dystrophy caused by mutations in the elongase ofvery long-chain fatty acids-like 4 (ELOVL4) gene, which encodesan elongase involved in the production of extremely long-chain fattyacids. The STGD3-related mutations cause production of C-terminallytruncated proteins (ELOVL4ΔC). STGD3 is transmitted in an autosomaldominant manner. To date, molecular mechanisms of this pathology havebeen proposed based solely on the interaction between wild-type ELOVL4and ELOVL4ΔC. However, analyses of Elovl4ΔC knockin micerevealed reduced levels of not only ELOVL4 substrates, but also offatty acids with a broad spectrum of chain lengths. Therefore, weinvestigated the molecular mechanisms responsible for ELOVL4ΔCaffecting the entire very long-chain fatty acid (VLCFA) elongationpathway. Methods: The ELOVL4ΔC protein wasexpressed in HEK 293T cells, and its effect on elongase activitiestoward several acyl-CoAs were examined. We also investigated the homo-and hetero-oligomerization of ELOVL4ΔC with other elongases (ELOVL1–7)or with other enzymes involved in VLCFA elongation usingcoimmunoprecipitation experiments. Results: We found that ELOVL4ΔC forms ahomo-oligomer more strongly than wild-type ELOVL4. ELOVL4ΔC alsointeracts strongly with other elongases, although similar interactionsfor wild-type ELOVL4 were observed as only weak. In addition, ELOVL4ΔCis able to form an elongase complex by interacting with othercomponents of the VLCFA elongation machinery, similar to wild-typeELOVL4. Conclusions: We propose that not onlythe ELOVL4-ELOVL4ΔC homo-oligomeric interaction, but also severalhetero-oligomeric interactions, may contribute to the pathology ofSTGD3.