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Hereditary spastic paraplegia‐linked REEP1 modulates endoplasmic reticulum/mitochondria contacts
Author(s) -
Lim Youngshin,
Cho IlTaeg,
Schoel Leah J.,
Cho Ginam,
Golden Jeffrey A.
Publication year - 2015
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.24488
Subject(s) - endoplasmic reticulum , mitochondrion , hereditary spastic paraplegia , biology , microbiology and biotechnology , mutation , unfolded protein response , mutant , gene knockdown , genetics , phenotype , cell culture , gene
Objective Mutations in receptor expression enhancing protein 1 (REEP1) are associated with hereditary spastic paraplegias (HSPs). Although axonal degeneration is thought to be a predominant feature in HSP, the role of REEP1 mutations in degeneration is largely unknown. Previous studies have implicated a role for REEP1 in the endoplasmic reticulum (ER), whereas others localized REEP1 with mitochondria. We sought to resolve the cellular localization of REEP1 and further elucidate the pathobiology underlying REEP1 mutations in patients. Methods A combination of cellular imaging and biochemical approaches was used to refine the cellular localization of REEP1. Next, Reep1 mutations associated with HSP were functionally tested in neuritic growth and degeneration assays using mouse cortical culture. Finally, a novel assay was developed and used with wild‐type and mutant Reep1s to measure the interactions between the ER and mitochondria. Results We found that REEP1 is present at the ER‐mitochondria interface, and it contains subdomains for mitochondrial as well as ER localization. Knockdown of Reep1 and expression of pathological Reep1 mutations resulted in neuritic growth defects and degeneration. Finally, using our novel split‐ R Luc8 assay, we show that REEP1 facilitates ER‐mitochondria interactions, a function diminished by disease‐associated mutations. Interpretation Our data potentially reconcile the current conflicting reports regarding REEP1 being either an ER or a mitochondrial protein. Furthermore, our results connect, for the first time, the disrupted ER‐mitochondria interactions to a failure in maintaining health of long axons in HSPs. Finally, the split‐ R Luc8 assay offers a new tool to identify potential drugs for multiple neurodegenerative diseases with ER‐mitochondria interaction defects. Ann Neurol 2015;78:Ann Neurol 2015;78:679–696