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Vol. 18, Issue 11, 4669-4680, November 2007

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Amphiphysin 1 Is Important for Actin Polymerization during Phagocytosis

Hiroshi Yamada^*, Emiko Ohashi^*, Tadashi Abe^*, Norihiro Kusumi, Shun-AI Li^*, Yumi Yoshida^*, Masami Watanabe, Kazuhito Tomizawa, Yuji Kashiwakura, Hiromi Kumon, Hideki Matsui, and Kohji Takei^*

Departments of *Neuroscience, Urology and Cell Physiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan; and Innovation Center Okayama for Nanobio-Targeted Therapy, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8558, Japan

Submitted April 2, 2007; Revised August 21, 2007; Accepted August 30, 2007
Monitoring Editor: David Drubin

Amphiphysin 1 is involved in clathrin-mediated endocytosis. In this study, we demonstrate that amphiphysin 1 is essential for cellular phagocytosis and that it is critical for actin polymerization. Phagocytosis in Sertoli cells was induced by stimulating phosphatidylserine receptors. This stimulation led to the formation of actin-rich structures, including ruffles, phagocytic cups, and phagosomes, all of which showed an accumulation of amphiphysin 1. Knocking out amphiphysin 1 by RNA interference in the cells resulted in the reduction of ruffle formation, actin polymerization, and phagocytosis. Phagocytosis was also drastically decreased in amph 1 (–/–) Sertoli cells. In addition, phosphatidylinositol-4,5-bisphosphate–induced actin polymerization was decreased in the knockout testis cytosol. The addition of recombinant amphiphysin 1 to the cytosol restored the polymerization process. Ruffle formation in small interfering RNA-treated cells was recovered by the expression of constitutively active Rac1, suggesting that amphiphysin 1 functions upstream of the protein. These findings support that amphiphysin 1 is important in the regulation of actin dynamics and that it is required for phagocytosis.

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

Address correspondence to: Kohji Takei (kohji{at}md.okayama-u.ac.jp)

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