Critical role for the EB1 and APC interaction in the regulation of microtubule polymerization

• Published in: Current biology 2001-07, Vol.11 (13), p.1062-1067
• Main Authors: Nakamura, Masafumi, Zhou, Xiao Zhen, Lu, Kun Ping
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Adenomatous Polyposis Coli Protein; Amino Acid Sequence; Animals; APC gene; Biological Evolution; Cytoskeletal Proteins - chemistry; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - physiology; EB1 protein; Fungal Proteins - physiology; Humans; Mice; Microtubule-Associated Proteins - physiology; Microtubules - metabolism; Molecular Sequence Data; Mutation; Phosphorylation; Polymers - metabolism; Protein Structure, Tertiary
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/S0960-9822(01)00297-4

Human EB1 was originally cloned as a protein that interacts with the COOH terminus of adenomatous polyposis coli (APC) [1]. Interestingly, this interaction is often disrupted in colon cancer, due to mutations in APC. EB1 also interacts with the plus-ends of microtubules and targets APC to microtubule tips [2–6]. Since APC is detected on the kinetochores of chromosomes, it has been hypothesized that the EB1-APC interaction connects microtubule spindles to the kinetochores and regulates microtubule stability [7–9]. In yeast, EB1 regulates microtubule dynamics [6, 10, 11], and its binding domain in APC may be conserved in Kar9, an EB1 binding protein involved in the microtubule-capturing mechanism [12–14]. These results suggest that the interaction of EB1 and APC is important and may be conserved. However, it is largely unknown whether the EB1-APC interaction affects microtubule dynamics. Here, we show that EB1 potently promotes microtubule polymerization in vitro and in permeabilized cells, but, surprisingly, only in the presence of the COOH-terminal EB1 binding domain of APC (C-APC). Significantly, this C-APC activity is abolished by phosphorylation, which also disrupts its ability to bind to EB1. Furthermore, yeast EB1 protein effectively substitutes for the human protein but also requires C-APC in promoting microtubule polymerization. Finally, C-APC is able to promote microtubule polymerization when stably expressed in APC mutant cells, demonstrating the ability of C-APC to promote microtubule assembly in vivo. Thus, the interaction between EB1 and APC plays an essential role in the regulation of microtubule polymerization, and a similar mechanism may be conserved in yeast.