title: Formin DAAM1 Organizes Actin Filaments in the Cytoplasmic Nodal Actin Network.
abstract: A nodal cytoplasmic actin network underlies actin cytoplasm cohesion in the absence of stress fibers. We previously described such a network that forms upon Latrunculin A (LatA) treatment, in which formin DAAM1 was localized at these nodes. Knock down of DAAM1 reduced the mobility of actin nodes but the nodes remained. Here we have investigated DAAM1 containing nodes after LatA washout. DAAM1 was found to be distributed between the cytoplasm and the plasma membrane. The membrane binding likely occurs through an interaction with lipid rafts, but is not required for F-actin assembly. Interesting the forced interaction of DAAM1 with plasma membrane through a rapamycin-dependent linkage, enhanced F-actin assembly at the cell membrane (compared to the cytoplasm) after the LatA washout. However, immediately after addition of both rapamycin and LatA, the cytoplasmic actin nodes formed transiently, before DAAM1 moved to the membrane. This was consistent with the idea that DAAM1 was initially anchored to cytoplasmic actin nodes. Further, photoactivatable tracking of DAAM1 showed DAAM1 was immobilized at these actin nodes. Thus, we suggest that DAAM1 organizes actin filaments into a nodal complex, and such nodal complexes seed actin network recovery after actin depolymerization.
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore, 117411, Singapore.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Luo
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore, 117411, Singapore.
authors.forename: Zi Zhao
authors.initials: ZZ
authors.lastname: Lieu
authors.affiliation: sGSK Group, Institute of Molecular and Cell Biology, Agency for Science Technology and Research, Proteos Building, 61 Biopolis Drive, Singapore, 138673, Singapore.
authors.forename: Ed
authors.initials: E
authors.lastname: Manser
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore, 117411, Singapore.|Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, 76100, Israel.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Bershadsky
authors.affiliation: Mechanobiology Institute, National University of Singapore, Singapore, 117411, Singapore.|Department of Biological Sciences, Columbia University, New York, New York, 10027, United States of America.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Sheetz
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000737:chemistry / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021381:Protein Transport; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C499094:DAAM1 protein, human; D008840:Microfilament Proteins; C500365:Daam1 protein, mouse; D020741:rho GTP-Binding Proteins