QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Vol. 17, Issue 4, 1971-1984, April 2006

This Article Full Text Full Text (PDF) Supplemental Material All Versions of this Article: E05-10-0956v1 17/4/1971    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Clark, M. G. Articles by Amberg, D. C. Search for Related Content PubMed PubMed Citation Articles by Clark, M. G. Articles by Amberg, D. C.

A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities

Michael G. Clark ^*, Joseph Teply , Brian K. Haarer ^*, Susan C. Viggiano ^*, David Sept , and David C. Amberg ^*

^* Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210; Department of Biomedical Engineering and Center for Computational Biology, Washington University, St. Louis, MO 63130

Submitted October 14, 2005; Revised December 27, 2005; Accepted January 6, 2006
Monitoring Editor: Thomas Pollard

Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal -propeller and a secondary actin binding site lies in a comparable location on its C-terminal -propeller. Random mutagenesis followed by screening for separation of function mutants led to the identification of several mutants specifically defective for interacting with cofilin but still able to interact with actin. These mutants suggested that cofilin binds across the cleft between the two propeller domains, leaving the actin binding sites exposed and flanking the cofilin binding site. Biochemical, genetic, and cell biological analyses confirmed that the actin binding- and cofilin binding-specific mutants are functionally defective, whereas the genetic analyses further suggested a role for Aip1p in an early, internalization step of endocytosis. A complementary, unbiased molecular modeling approach was used to derive putative structures for the Aip1p-cofilin complex, the most stable of which is completely consistent with the mutagenesis data. We theorize that Aip1p-severing activity may involve simultaneous binding to two actin subunits with cofilin wedged between the two actin binding sites of the N- and C-terminal propeller domains.

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

Address correspondence to: David C. Amberg (ambergd{at}upstate.edu).

This article has been cited by other articles:

				N. T. Ahmed, C. Gao, B. F. Lucker, D. G. Cole, and D. R. Mitchell ODA16 aids axonemal outer row dynein assembly through an interaction with the intraflagellar transport machinery J. Cell Biol., October 20, 2008; 183(2): 313 - 322. [Abstract] [Full Text] [PDF]

				N. Ren, J. Charlton, and P. N. Adler The flare Gene, Which Encodes the AIP1 Protein of Drosophila, Functions to Regulate F-Actin Disassembly in Pupal Epidermal Cells Genetics, August 1, 2007; 176(4): 2223 - 2234. [Abstract] [Full Text] [PDF]

				M. G. Clark and D. C. Amberg Biochemical and Genetic Analyses Provide Insight Into the Structural and Mechanistic Properties of Actin Filament Disassembly by the Aip1p Cofilin Complex in Saccharomyces cerevisiae Genetics, July 1, 2007; 176(3): 1527 - 1539. [Abstract] [Full Text] [PDF]

				J. B. Moseley and B. L. Goode The Yeast Actin Cytoskeleton: from Cellular Function to Biochemical Mechanism Microbiol. Mol. Biol. Rev., September 1, 2006; 70(3): 605 - 645. [Abstract] [Full Text] [PDF]

				K. Okada, H. Ravi, E. M. Smith, and B. L. Goode Aip1 and Cofilin Promote Rapid Turnover of Yeast Actin Patches and Cables: A Coordinated Mechanism for Severing and Capping Filaments Mol. Biol. Cell, July 1, 2006; 17(7): 2855 - 2868. [Abstract] [Full Text] [PDF]

				K. Mohri, K. Ono, R. Yu, S. Yamashiro, and S. Ono Enhancement of Actin-depolymerizing Factor/Cofilin-dependent Actin Disassembly by Actin-interacting Protein 1 Is Required for Organized Actin Filament Assembly in the Caenorhabditis elegans Body Wall Muscle Mol. Biol. Cell, May 1, 2006; 17(5): 2190 - 2199. [Abstract] [Full Text] [PDF]