Proteome analysis of peroxisomes-Function of novel peroxisomal proteins and pathogenesis of peroxisome disorders

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To understand function of peroxisomes and pathogenesis of peroxisome disorders, we performed proteome analysis of rat liver peroxisomes. Further, we investigated function of novel peroxisomal proteins that we identified. Concerning peroxisome disorders, we analyzed fate of an ABC protein, ALDP that is responsible for adrenoleukodystrophy (ALD) in normal and human ALD fibroblasts. As a result, following new findings were obtained.1.We prepared rat liver peroxiomes by Nycodenz gradient centrifugation and further by immunoisolation using antibody against PMP70. We identified 65 peroxisomal proteins including 5 novel proteins in the peroxisomes by LC/MS/MS analysis after digestion of the protein bands subjected to SDS-PAGE. RAB2, VAP-A, B, which might be involved in peroxisome biogenesis were identified.2.As novel 5 peroxisomal proteins, peroxisomal isozyme of Ion protease, a bi-functional enzyme containing aminoglycoside transferase and acyl-CoA dehydrogenease domains, a homolog to endozepine-related protein, a tumor-related protein with ribonuclease domain, a homolog of CGI-135 which is required organelle fission were identified.3.We cloned the human lon protease cDNA and express Lon protease-His in E.coli. We purified the lon protease and found that the enzyme showed ATP-dependent protease activity against denatured proteins4.We identified 12 peroxin on rat liver peroxisomes. Pex3p was associated with Pex16p and Pex19p and suggested to be important for peroxisomes biogenesis.5.We found most ALDPs with missense mutations were deficient on peroxiomes of human ALD fibroblasts. In addition, the mutant proteins were found to be degraded rapidly after synthesis by proteasomes.Roles of novel peroxisomal proteins are now under investigation.