Mitochondrial cereblon functions as a Lon-type protease.

Kosuke Kataoka,Toru Asahi,China Nakamura,Naoya Sawamura

doi:10.1038/srep29986

Abstract

Lon protease plays a major role in the protein quality control system in mammalian cell mitochondria. It is present in the mitochondrial matrix, and degrades oxidized and misfolded proteins, thereby protecting the cell from various extracellular stresses, including oxidative stress. The intellectual disability-associated and thalidomide-binding protein cereblon (CRBN) contains a large, highly conserved Lon domain. However, whether CRBN has Lon protease-like function remains unknown. Here, we determined if CRBN has a protective function against oxidative stress, similar to Lon protease. We report that CRBN partially distributes in mitochondria, suggesting it has a mitochondrial function. To specify the mitochondrial role of CRBN, we mitochondrially expressed CRBN in human neuroblastoma SH-SY5Y cells. The resulting stable SH-SY5Y cell line showed no apparent effect on the mitochondrial functions of fusion, fission, and membrane potential. However, mitochondrially expressed CRBN exhibited protease activity, and was induced by oxidative stress. In addition, stably expressed cells exhibited suppressed neuronal cell death induced by hydrogen peroxide. These results suggest that CRBN functions specifically as a Lon-type protease in mitochondria.

Highlights

CRBN contains a 237-residue Lon domain: a conserved N-terminal domain found in the Lon protease, an ATP-dependent protease within the mitochondrial matrix[1], suggesting that CRBN may have a mitochondrial function
CRBN contains a highly conserved, large Lon domain, which is found in the N-terminus of the ATP-dependent Lon protease that localizes to the mitochondrial matrix, and raises the possibility that CRBN might have a mitochondrial function
The Lon protease is reported to be induced by oxidative stress and have protective effects against extracellular stress, including oxidative stress induced by hydorgen peroxide[25,28]

Summary

Introduction

CRBN contains a 237-residue Lon domain: a conserved N-terminal domain found in the Lon protease, an ATP-dependent protease within the mitochondrial matrix[1], suggesting that CRBN may have a mitochondrial function. Lon protease is a highly conserved ATP-dependent serine peptidase in both prokaryotes and eukaryotes, and is required for maintenance of mitochondrial homeostasis[24] It plays a pivotal role in mitochondrial protein quality control by degrading oxidized and misfolded proteins generated within the mitochondrial matrix[25,26,27]. By contrast, reduced levels and activities of Lon protease are associated with the aging process In such conditions, oxidized proteins accumulate in an age-related manner and cause mitochondrial dysfunction, which leads to cell death[26,31]. CRBN contains a large, highly conserved Lon domain, the function of CRBN as a Lon protease in mitochondrial protein quality control remains unclear. We show that similar to Lon protease, CRBN functions in protection against oxidative stress

Methods

Results

Conclusion