title: Heterodimeric capping protein from Arabidopsis is a membrane-associated, actin-binding protein.
abstract: The actin cytoskeleton is a major regulator of cell morphogenesis and responses to biotic and abiotic stimuli. The organization and activities of the cytoskeleton are choreographed by hundreds of accessory proteins. Many actin-binding proteins are thought to be stimulus-response regulators that bind to signaling phospholipids and change their activity upon lipid binding. Whether these proteins associate with and/or are regulated by signaling lipids in plant cells remains poorly understood. Heterodimeric capping protein (CP) is a conserved and ubiquitous regulator of actin dynamics. It binds to the barbed end of filaments with high affinity and modulates filament assembly and disassembly reactions in vitro. Direct interaction of CP with phospholipids, including phosphatidic acid, results in uncapping of filament ends in vitro. Live-cell imaging and reverse-genetic analyses of cp mutants in Arabidopsis (Arabidopsis thaliana) recently provided compelling support for a model in which CP activity is negatively regulated by phosphatidic acid in vivo. Here, we used complementary biochemical, subcellular fractionation, and immunofluorescence microscopy approaches to elucidate CP-membrane association. We found that CP is moderately abundant in Arabidopsis tissues and present in a microsomal membrane fraction. Sucrose density gradient separation and immunoblotting with known compartment markers were used to demonstrate that CP is enriched on membrane-bound organelles such as the endoplasmic reticulum and Golgi. This association could facilitate cross talk between the actin cytoskeleton and a wide spectrum of essential cellular functions such as organelle motility and signal transduction.
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907.
authors.forename: Jose C
authors.identifier: http://orcid.org/0000-0002-1470-360X
authors.initials: JC
authors.lastname: Jimenez-Lopez
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907.
authors.forename: Xia
authors.initials: X
authors.lastname: Wang
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907.
authors.forename: Simeon O
authors.initials: SO
authors.lastname: Kotchoni
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907.
authors.forename: Shanjin
authors.initials: S
authors.lastname: Huang
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Szymanski
authors.affiliation: Departments of Biological Sciences (J.C.J.-L., X.W., S.H., C.J.S.) and Agronomy (S.O.K., D.B.S.), Bindley Bioscience Center (C.J.S.), Purdue University, West Lafayette, Indiana 47907 staiger@purdue.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Staiger
mesh_terms: D051344:Actin Capping Proteins / Q000235:genetics / Q000378:metabolism*; D008841:Actin Cytoskeleton / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D036226:Seedlings / Q000235:genetics / Q000378:metabolism
chemical_list: D051344:Actin Capping Proteins; D029681:Arabidopsis Proteins