Regulation of actin dynamics by annexin 2.
Annexin 2 is a ubiquitous Ca(2+)-binding protein that is essential for actin-dependent vesicle transport. Here, we show that in spontaneously motile cells annexin 2 is concentrated in dynamic actin-rich protrusions, and that depletion of annexin 2 using siRNA leads to the accumulation of stress fibres and loss of protrusive and retractile activity. Cells co-expressing annexin 2-CFP and actin-YFP exhibit Ca(2+)-dependent fluorescense resonance energy transfer throughout the cytoplasm and in membrane ruffles and protrusions, suggesting that annexin 2 may directly interact with actin. This notion was supported by biochemical studies, in which we show that annexin 2 reduces the polymerisation rate of actin monomers in a dose-dependent manner. By measuring actin polymerisation rates in the presence of barbed-end and pointed-end cappers, we further demonstrate that annexin 2 specifically inhibits filament elongation at the barbed ends. These results show that annexin 2 has an essential role in maintaining the plasticity of the dynamic membrane-associated actin cytoskeleton, and that its activity in this context may be at least partly explained through direct interactions with polymerised and monomeric actin.
Hayes
Matthew J
MJ
Division of Cell Biology, Institute of Ophthalmology, University College London, UK.
Shao
Dongmin
D
Bailly
Maryse
M
Moss
Stephen E
SE
D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000199:Actins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017306:Annexin A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008164:Luminescent Proteins / Q000032:analysis; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D011817:Rabbits
D000199:Actins; D017306:Annexin A2; D008164:Luminescent Proteins; D034741:RNA, Small Interfering