Journal of Biochemistry Advance Access originally published online on February 14, 2008
Journal of Biochemistry 2008 143(5):649-660; doi:10.1093/jb/mvn020
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© 2008 The Japanese Biochemical Society.
Contribution of Peroxisome-specific Isoform of Lon Protease in Sorting PTS1 Proteins to Peroxisomes
Institute for Enzyme Research, The University of Tokushima, Tokushima 770-8503, Japan
*To whom correspondence should be addressed. Tel: +81 88 633 7427, Fax: +81 88 633 7428, E-mail: konishi{at}ier.tokushima-u.ac.jp
Received January 15, 2008; Accepted January 31, 2008
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Abstract |
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Using an organelle proteomics approach, we previously studied the rat peroxisome in order to characterize the proteins participating in its biogenesis. A peroxisome-specific isoform of Lon (pLon) protein was accordingly identified. However, the precise role of pLon in peroxisomes remains to be elucidated. Here, we demonstrate that pLon plays a role in processing and activating a specific regulatory protein belonging to the peroxisome targeting signal (PTS) 1-containing proteins. Proteomic analysis of proteins co-immunoprecipitated with Lon suggested that Lon interacts with PMP70 and several enzymes involved in β-oxidation, including acyl-CoA oxidase (AOX). The processing of AOX for its activation in peroxisomes was strongly inhibited in cells expressing a dominant negative form of pLon. Furthermore, a catalase possessing a modified PTS1 sequence was misdistributed in this cell line. pLon exhibits little, if any, in vitro AOX processing activity, and does not process PTS2-containing 3-ketoacyl-coenzyme A thiolase (PTL). Therefore, pLon may specifically control, sort and process PTS1 proteins. Based on the relationship between pLon and the β-oxidation enzymes that regulate peroxisomal morphology, the observation of enlarged peroxisomes in cells expressing recombinant pLon suggests that pLon is a critical factor determining peroxisome morphology.
Key Words: peroxisome, β-oxidation, PTS1, protease, proteomics
Abbreviations: CBB, Coomassie brilliant blue; HEK, human embryonic kidney; RT–PCR, reverse transcriptase–PCR; siRNA, small interference RNA
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