title: Cofilin recruits F-actin to SPCA1 and promotes Ca2+-mediated secretory cargo sorting.
abstract: The actin filament severing protein cofilin-1 (CFL-1) is required for actin and P-type ATPase secretory pathway calcium ATPase (SPCA)-dependent sorting of secretory proteins at the trans-Golgi network (TGN). How these proteins interact and activate the pump to facilitate cargo sorting, however, is not known. We used purified proteins to assess interaction of the cytoplasmic domains of SPCA1 with actin and CFL-1. A 132-amino acid portion of the SPCA1 phosphorylation domain (P-domain) interacted with actin in a CFL-1-dependent manner. This domain, coupled to nickel nitrilotriacetic acid (Ni-NTA) agarose beads, specifically recruited F-actin in the presence of CFL-1 and, when expressed in HeLa cells, inhibited Ca(2+) entry into the TGN and secretory cargo sorting. Mutagenesis of four amino acids in SPCA1 that represent the CFL-1 binding site also affected Ca(2+) import into the TGN and secretory cargo sorting. Altogether, our findings reveal the mechanism of CFL-1-dependent recruitment of actin to SPCA1 and the significance of this interaction for Ca(2+) influx and secretory cargo sorting.
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Kienzle
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Nirakar
authors.initials: N
authors.lastname: Basnet
authors.affiliation: Physical Chemistry, Department of Chemistry and Biochemistry and Center for NanoScience (CeNS), Ludwig Maximilians University of Munich, 81377 Munich, Germany.
authors.forename: Alvaro H
authors.initials: AH
authors.lastname: Crevenna
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Gisela
authors.initials: G
authors.lastname: Beck
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Habermann
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
authors.forename: Naoko
authors.initials: N
authors.lastname: Mizuno
authors.affiliation: Max Planck Institute of Biochemistry, 82152 Martinsried, Germany vonblume@biochem.mpg.de.
authors.forename: Julia
authors.initials: J
authors.lastname: von Blume
mesh_terms: D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D051338:Cofilin 1 / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D017354:Point Mutation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D055571:Secretory Pathway
chemical_list: D000199:Actins; C495810:CFL1 protein, human; D051338:Cofilin 1; C403624:ATP2C1 protein, human; D000252:Calcium-Transporting ATPases; D002118:Calcium