Defective Mitochondrial Protein Translocation Precludes Normal Caenorhabditis elegans Development

Sean P Curran,Edward P Leverich,Carla M Koehler,Pamela L Larsen

doi:10.1074/jbc.m409618200

Sean P Curran, Edward P Leverich + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m409618200

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Abstract

We demonstrate biochemically that the genes identified by sequence similarity as orthologs of the mitochondrial import machinery are functionally conserved in Caenorhabditis elegans. Specifically, tin-9.1 and tin-10 RNA interference (RNAi) treatment of nematodes impairs import of the ADP/ATP carrier into isolated mitochondria. Developmental phenotypes are associated with gene knock-down of the mitochondrial import components. RNAi of tomm-7 and ddp-1 resulted in mitochondria with an interconnected morphology in vivo, presumably due to defects in the assembly of outer membrane fission/fusion components. RNAi of the small Tim proteins TIN-9.1, TIN-9.2, and TIN-10 resulted in a small body size, reduced number of progeny produced, and partial embryonic lethality. An additional phenotype of the tin-9.2(RNAi) animals is defective formation of the somatic gonad. The biochemical demonstration that the protein import activity is reduced, under the same conditions that yield the defects in specific tissues and lethality in a later generation, suggests that the developmental abnormalities observed are a consequence of defects in mitochondrial inner membrane biogenesis.

Highlights

We demonstrate biochemically that the genes identified by sequence similarity as orthologs of the mitochondrial import machinery are functionally conserved in Caenorhabditis elegans
We performed a phylogenetic analysis of five predicted genes in the C. elegans genome with sequence similarity to the small Tim family of proteins and Tom7p with S. cerevisiae, Mus musculus, and Homo sapiens
We demonstrate that coupled mitochondria can be isolated from C. elegans adults for in organello import assays and that genes homologous to those identified in S. cerevisiae are involved in this process

Summary

Introduction

We demonstrate biochemically that the genes identified by sequence similarity as orthologs of the mitochondrial import machinery are functionally conserved in Caenorhabditis elegans. The biochemical demonstration that the protein import activity is reduced, under the same conditions that yield the defects in specific tissues and lethality in a later generation, suggests that the developmental abnormalities observed are a consequence of defects in mitochondrial inner membrane biogenesis. There is an elaborate set of proteins within each sub-compartment of the mitochondrion for protein import [5, 6] These translocons are specialized and recognize precursors that possess specific targeting and sorting information. Precursors destined for the matrix typically contain an amino-terminal targeting signal that is utilized by the translocase of the inner membrane (TIM) complex [11, 12]. The first disease MohrTranebjaerg syndrome associated with a defect in protein import is caused by mutations in the intermembrane space import component DDP-1 (deafness dystonia polypeptide) [24, 25]

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