The dynamic behavior of the APC-binding protein EB1 on the distal ends of microtubules.
Adenomatous polyposis coli protein (APC) is a well-characterized tumor suppressor protein [1] [2] [3]. We previously showed that APC tagged with green fluorescent protein (GFP) in Xenopus A6 epithelial cells moves along a subset of microtubules and accumulates at their growing plus ends in cell extensions [4]. EB1, which was identified as an APC-binding protein by yeast two-hybrid analysis [5], was also reported to be associated with microtubules [6] [7] [8]. To examine the interaction between APC and EB1 within cells, we compared the dynamic behavior of EB1-GFP with that of APC-GFP in A6 transfectants. Time-lapse microscopy of live cells at interphase revealed that EB1-GFP was concentrated at all of the growing microtubule ends throughout the cytoplasm and abruptly disappeared from the ends when microtubules began to shorten. Therefore, EB1 appeared to be co-localized and interact with APC on the growing ends of a subset of microtubules. When APC-GFP was overexpressed, endogenous EB1 was recruited to APC-GFP, which accumulated in large amounts on microtubules. On the other hand, when microtubules were disassembled by nocodazole, EB1 was not co-localized with APC-GFP, which was concentrated along the basal plasma membrane. During mitosis, APC appeared to be dissociated from microtubules, whereas EB1-GFP continued to concentrate at microtubule growing ends. These findings showed that the APC-EB1 interaction is regulated within cells and is allowed near the ends of microtubules only under restricted conditions.
Mimori-Kiyosue
Y
Y
Tsukita Cell Axis Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Shimogyo-ku, 600-8813, Japan.
Shiina
N
N
Tsukita
S
S
D025601:Adenomatous Polyposis Coli Protein; D000818:Animals; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D017491:Genes, APC; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014981:Xenopus
D025601:Adenomatous Polyposis Coli Protein; D003598:Cytoskeletal Proteins; C405804:EB1 microtubule binding proteins; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins