Vol. 13, Issue 2, 711-722, February 2002

Peroxisomes Are Formed from Complex Membrane Structures in PEX6-deficient CHO Cells upon Genetic Complementation

Noriyo Hashiguchi,^* Tomoko Kojidani,^* Tsuneo Imanaka, Tokuko Haraguchi, Yasushi Hiraoka, Eveline Baumgart,^§ Sadaki Yokota,^¶ Toshiro Tsukamoto,^*@ and Takashi Osumi^*

 ^*Department of Life Science, Faculty of Science, Himeji Institute of Technology, Kamigori, Hyogo 678-1297, Japan;  Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Toyama 930-0194, Japan;  Kansai Advanced Research Center, Communications Research Laboratory and CREST of Japan Science and Technology Corporation, Kobe 651-2492, Japan;  ^§Department of Anatomy and Cell Biology, Division of Medical Cell Biology, University of Heidelberg, Heidelberg, Germany; and  ^¶Yamanashi Medical University, Yamanshi, 409-3898, Japan

Pex6p belongs to the AAA family of ATPases. Its CHO mutant, ZP92, lacks normal peroxisomes but contains peroxisomal membrane remnants, so called peroxisomal ghosts, which are detected with anti-70-kDa peroxisomal membrane protein (PMP70) antibody. No peroxisomal matrix proteins were detected inside the ghosts, but exogenously expressed green fluorescent protein (GFP) fused to peroxisome targeting signal-1 (PTS-1) accumulated in the areas adjacent to the ghosts. Electron microscopic examination revealed that PMP70-positive ghosts in ZP92 were complex membrane structures, rather than peroxisomes with reduced matrix protein import ability. In a typical case, a set of one central spherical body and two layers of double-membraned loops were observed, with endoplasmic reticulum present alongside the outer loop. In the early stage of complementation by PEX6 cDNA, catalase and acyl-CoA oxidase accumulated in the lumen of the double-membraned loops. Biochemical analysis revealed that almost all the peroxisomal ghosts were converted into peroxisomes upon complementation. Our results indicate that 1) Peroxisomal ghosts are complex membrane structures; and 2) The complex membrane structures become import competent and are converted into peroxisomes upon complementation with PEX6.