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Vol. 18, Issue 10, 3741-3751, October 2007

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p180 Is Involved in the Interaction between the Endoplasmic Reticulum and Microtubules through a Novel Microtubule-binding and Bundling Domain

Kiyoko Ogawa-Goto^*,,, Keiko Tanaka^*, Tomonori Ueno, Keisuke Tanaka, Takeshi Kurata^*, Tetsutaro Sata^*, and Shinkichi Irie^,

*Department of Pathology, National Institute of Infectious Diseases, Shinjuku, Tokyo 162-8640, Japan; Nippi Research Institute of Biomatrix, Toride, Ibaraki 302-0017, Japan; and Japan Institute of Leather Research, Adachi, Tokyo 120-8601, Japan

Submitted December 19, 2006; Revised June 27, 2007; Accepted July 6, 2007
Monitoring Editor: Sean Munro

p180 was originally reported as a ribosome-binding protein on the rough endoplasmic reticulum membrane, although its precise role in animal cells has not yet been elucidated. Here, we characterized a new function of human p180 as a microtubule-binding and -modulating protein. Overexpression of p180 in mammalian cells induced an elongated morphology and enhanced acetylated microtubules. Consistently, electron microscopic analysis clearly revealed microtubule bundles in p180-overexpressing cells. Targeted depletion of endogenous p180 by small interfering RNAs led to aberrant patterns of microtubules and endoplasmic reticulum in mammalian cells, suggesting a specific interaction between p180 and microtubules. In vitro sedimentation assays using recombinant polypeptides revealed that p180 bound to microtubules directly and possessed a novel microtubule-binding domain (designated MTB-1). MTB-1 consists of a predicted coiled-coil region and repeat domain, and strongly promoted bundle formation both in vitro and in vivo when expressed alone. Overexpression of p180 induced acetylated microtubules in cultured cells in an MTB-1-dependent manner. Thus, our data suggest that p180 mediates interactions between the endoplasmic reticulum and microtubules mainly through the novel microtubule-binding and -bundling domain MTB-1.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Kiyoko Ogawa-Goto (kgoto{at}nippi-inc.co.jp)

Abbreviations used: Cnx, calnexin; Crt, calreticulin; CLIMP-63, cytoskeleton-linking membrane protein of 63-kDa; CLIP, cytoskeleton-linking protein; DMP, dimethyl pimelimidate; ER, endoplasmic reticulum; HCMV, human cytomegalovirus; HEL, human embryonic lung; MAP, microtubule-associated protein; MT, microtubule; PDI, protein disulfide isomerase; TEM, transmission electron microscopy; WT, wild type.