title: The Calcium-Dependent Switch Helix of L-Plastin Regulates Actin Bundling.
abstract: L-plastin is a calcium-regulated actin-bundling protein that is expressed in cells of hematopoietic origin and in most metastatic cancer cells. These cell types are mobile and require the constant remodeling of their actin cytoskeleton, where L-plastin bundles filamentous actin. The calcium-dependent regulation of the actin-bundling activity of L-plastin is not well understood. We have used NMR spectroscopy to determine the solution structure of the EF-hand calcium-sensor headpiece domain. Unexpectedly, this domain does not bind directly to the four CH-domains of L-plastin. A novel switch helix is present immediately after the calcium-binding region and it binds tightly to the EF-hand motifs in the presence of calcium. We demonstrate that this switch helix plays a major role during actin-bundling. Moreover a peptide that competitively inhibits the association between the EF-hand motifs and the switch helix was shown to deregulate the actin-bundling activity of L-plastin. Overall, these findings may help to develop new drugs that target the L-plastin headpiece and interfere in the metastatic activity of cancer cells.
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ishida
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Katharine V
authors.initials: KV
authors.lastname: Jensen
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Woodman
authors.affiliation: Prostate Cancer Centre, Southern Alberta Institute of Urology, Rockyview General Hospital, Calgary, Alberta, T2V 1P9, Canada.
authors.forename: M Eric
authors.initials: ME
authors.lastname: Hyndman
authors.affiliation: Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002151:Calorimetry; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
chemical_list: D000199:Actins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C026742:plastin; D002118:Calcium