Mutation in human CLPX elevates levels of δ-aminolevulinate synthase and protoporphyrin IX to promote erythropoietic protoporphyria
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Author(s)
Yien, Yvette Y.
Ducamp, Sarah
van der Vorm, Lisa N.
Manceau, Hana
Kannengiesser, Caroline
Bergonia, Hector A.
Kafina, Martin D.
Karim, Zoubida
Gouya, Laurent
Puy, Hervé
Date Issued
September 2017
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences (U.S.)
Citation
Yien, Yvette Y. et al. “Mutation in humanCLPXelevates Levels ofδ-Aminolevulinate Synthase and Protoporphyrin IX to Promote Erythropoietic Protoporphyria.” Proceedings of the National Academy of Sciences 114, 38 (September 2017): E8045–E8052 © 2017 National Academy of Sciences
Version
Final published version
Abstract
Loss-of-function mutations in genes for heme biosynthetic enzymes can give rise to congenital porphyrias, eight forms of which have been described. The genetic penetrance of the porphyrias is clinically variable, underscoring the role of additional causative, contributing, and modifier genes. We previously discovered that the mitochondrial AAA+ unfoldase ClpX promotes heme biosynthesis by activation of δ-aminolevulinate synthase (ALAS), which catalyzes the first step of heme synthesis. CLPX has also been reported to mediate heme-induced turnover of ALAS. Here we report a dominant mutation in the ATPase active site of human CLPX, p.Gly298Asp, that results in pathological accumulation of the heme biosynthesis intermediate protoporphyrin IX (PPIX). Amassing of PPIX in erythroid cells promotes erythropoietic protoporphyria (EPP) in the affected family. The mutation in CLPX inactivates its ATPase activity, resulting in coassembly of mutant and WT protomers to form an enzyme with reduced activity. The presence of low-activity CLPX increases the posttranslational stability of ALAS, causing increased ALAS protein and ALA levels, leading to abnormal accumulation of PPIX. Our results thus identify an additional molecular mechanism underlying the development of EPP and further our understanding of the multiple mechanisms by which CLPX controls heme metabolism. Keywords: heme biosynthesis; porphyria; ALAS; protein unfoldases; AAA+ ATPase
MIT Department
Massachusetts Institute of Technology. Department of Biology
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DOI of Published Version
https://doi.org/10.1073/PNAS.1700632114
