title: Rapid actin monomer-insensitive depolymerization of Listeria actin comet tails by cofilin, coronin, and Aip1.
abstract: Actin filaments in cells depolymerize rapidly despite the presence of high concentrations of polymerizable G actin. Cofilin is recognized as a key regulator that promotes actin depolymerization. In this study, we show that although pure cofilin can disassemble Listeria monocytogenes actin comet tails, it cannot efficiently disassemble comet tails in the presence of polymerizable actin. Thymus extracts also rapidly disassemble comet tails, and this reaction is more efficient than pure cofilin when normalized to cofilin concentration. By biochemical fractionation, we identify Aip1 and coronin as two proteins present in thymus extract that facilitate the cofilin-mediated disassembly of Listeria comet tails. Together, coronin and Aip1 lower the amount of cofilin required to disassemble the comet tail and permit even low concentrations of cofilin to depolymerize actin in the presence of polymerizable G actin. The cooperative activities of cofilin, coronin, and Aip1 should provide a biochemical basis for understanding how actin filaments can grow in some places in the cell while shrinking in others.
authors.affiliation: Department of Systems Biology and 2Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. bill_brieher@hms.harvard.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Brieher
authors.forename: Hao Yuan
authors.initials: HY
authors.lastname: Kueh
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Ballif
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Mitchison
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins; D002417:Cattle; D051528:Guanylate Kinases; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D008089:Listeria monocytogenes / Q000472:pathogenicity / Q000502:physiology*; D013058:Mass Spectrometry; D008840:Microfilament Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D051304:Profilins / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011817:Rabbits; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism
chemical_list: D051339:Actin Depolymerizing Factors; D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D008840:Microfilament Proteins; D051304:Profilins; D011506:Proteins; C072061:coronin proteins; D051528:Guanylate Kinases; C485777:MAGI2 protein, human