Human ABCB6 Localizes to Both the Outer Mitochondrial Membrane and the Plasma Membrane

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• 作者：Jill K. Paterson ; Suneet Shukla ; Chelsea M. Black ; Tokushi Tachiwada ; Susan Garfield ; Stephen Wincovitch ; David N. Ernst ; Anissa Agadir ; Xuelin Li ; Suresh V. Ambudkar ; Gergely Szakacs ; Shin-ichi Akiya
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：August 21, 2007
• 年：2007
• 卷：46
• 期：33
• 页码：9443 - 9452
• 全文大小：349K
• 年卷期：v.46,no.33(August 21, 2007)
• ISSN：1520-4995

文摘

Expression of the ATP-binding cassette transporter ABCB6 has been associated with multiplecellular functions, including resistance to several cytotoxic agents, iron homeostasis, and porphyrin transport.To further elucidate its physiological function and/or role in drug resistance, we determined the subcellularlocation of ABCB6. Using three novel ABCB6-specific antibodies, Western blot analysis of cells expressingcDNA-derived or endogenous ABCB6 revealed two distinct molecular weight forms. Confocal microscopyindicates that the protein localizes to both mitochondria and the plasma membrane. Differentialcentrifugation revealed that the lower molecular weight form predominantly resides in the mitochondria,while the larger protein form is more abundant in the plasma membrane. Preliminary studies indicate thatABCB6 is functionally relevant in the plasma membrane, where its expression prevents the accumulationof specific porphyrins in the cell. Digitonin solubilization of mitochondria demonstrated that ABCB6 ispresent in the outer mitochondrial membrane, while back-titration assays with the ABCB6-specificantibodies reveal that the nucleotide binding domain of ABCB6 is cytoplasmic. These studies are the firstto demonstrate that ABCB6 exists in two molecular weight forms, is localized to both the outermitochondrial membrane and the plasma membrane, and plays a functional role in the plasma membrane.