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J. Biol. Chem., Vol. 280, Issue 52, 42801-42808, December 30, 2005

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Polyamine Transport by Mammalian Cells and Mitochondria

ROLE OF ANTIZYME AND GLYCOSAMINOGLYCANS^*

From the Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan

The role of antizyme (AZ) and glycosaminoglycans in polyamine uptake by mammalian cells and mitochondria was examined using NIH3T3 and FM3A cells and rat liver mitochondria. AZ is synthesized as two isoforms (29 and 24.5 kDa) due to the existence of two initiation codon AUGs in the AZ mRNA. Most AZ existed as the 24.5-kDa form translatable from the second AUG, but a portion of the 29-kDa AZ from the first AUG was associated with mitochondria because of the presence of a mitochondrial targeting signal between the first and the second methionine. The predominance of the 24.5-kDa isoform was mainly due to the presence of spermidine and a favorable sequence context (Kozak sequence) at the second initiation codon AUG. Spermine uptake by NIH3T3 cells was inhibited by both 29- and 24.5-kDa AZs, but uptake by rat liver mitochondria was not influenced by either form of AZ. Because spermine uptake by mitochondria caused a release of cytochrome c, an enhancer of apoptosis, we looked for inhibitors of mitochondrial spermine uptake other than AZ. Cations such as Na⁺, K⁺, and Mg²⁺ were inhibitors of the mitochondrial uptake. It has been reported that heparan sulfate on glypican-1 plays important roles in spermine uptake by human embryonic lung fibroblasts. Heparin, but not heparan sulfate, slightly inhibited spermine uptake by FM3A cells in the absence of Mg²⁺ and Ca²⁺ but had no effect under physiological conditions in the presence of Mg²⁺ and Ca²⁺.

Received for publication, May 18, 2005 , and in revised form, October 31, 2005.

^* This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan and by the Tokyo Biochemical Research Foundation, Japan. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ Both authors contributed equally to this work.

² Present address: Faculty of Pharmaceutical Sciences, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba 288-0025, Japan.

³ To whom correspondence should be addressed. Tel.: 81-43-226-2871; Fax: 81-43-226-2873; E-mail: iga16077{at}p.chiba-u.ac.jp.

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