Membrane localization of transporter associated with antigen processing (TAP)-like (ABCB9) visualized in vivo with a fluorescence protein-fusion technique.
Transporter associated with antigen processing (TAP)-like (TAPL, ABCB9) is a half-type ATP binding cassette (ABC) protein belonging to subfamily B highly homologous to the TAP, a hetero-dimeric complex consisting of a TAP1 and a TAP2 subunit. Human TAPL, to which was tagged with green fluorescence protein (GFP) at its carboxyl terminus (TAPL-GFP), showed fluorescence on intracellular membranes similar to TAP1-GFP. A truncated form of TAPL-L-GFP (M1-S275 was followed by GFP) showed a similar cellular fluorescence pattern to TAPL-GFP. However, the fluorescence of TAPL-S-GFP (M1-G75) was distributed over all the cellular membranes including plasma membrane, indicating that the amino terminal region of TAPL (M1-S275) is essential for its localization to the intracellular membranes. A co-expression study demonstrated that TAPL-S-GFP was co-localized with TAPL-DR (DsRed-tagged TAPL) or TAP1-DR, suggesting that TAPL is able to interact with not only itself but also with TAP1 through the M1-G75 region of TAPL. It is also proposed that a further downstream sequence of TAPL would confine the distribution of TAPL-S-GFP to the intracellular membranes. Similarly, the distribution of TAP2-S-GFP (M1-R88) was restricted to the intracellular membranes by TAPL-DR or TAP1-DR, indicating that the M1-R88 region of TAP2 is able to interact with TAPL as well as TAP1. Therefore, TAPL would form a homo-dimer with itself, and a hetero-dimer with TAP1 and TAP2. TAPL-GFP was co-localized with the fluorescence endoplasmic reticulum (ER) marker, suggesting that TAPL is mainly localized to the ER in the intracellular membranes.
Kobayashi
Ayako
A
Laboratory of Biochemistry and Molecular Biology, Graduate School of Pharmaceutical Sciences, Osaka University, Japan.
Maeda
Tatsuo
T
Maeda
Masatomo
M
D018528:ATP-Binding Cassette Transporters / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017951:Antigen Presentation / Q000502:physiology*; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D002522:Chlorocebus aethiops; D049452:Green Fluorescent Proteins / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods
C412573:ABCB9 protein, human; D018528:ATP-Binding Cassette Transporters; D049452:Green Fluorescent Proteins