title: Mammalian CARMIL inhibits actin filament capping by capping protein.
abstract: Actin polymerization in cells occurs via filament elongation at the barbed end. Proteins that cap the barbed end terminate this elongation. Heterodimeric capping protein (CP) is an abundant and ubiquitous protein that caps the barbed end. We find that the mouse homolog of the adaptor protein CARMIL (mCARMIL) binds CP with high affinity and decreases its affinity for the barbed end. Addition of mCARMIL to cell extracts increases the rate and extent of Arp2/3 or spectrin-actin seed-induced polymerization. In cells, GFP-mCARMIL concentrates in lamellipodia and increases the fraction of cells with large lamellipodia. Decreasing mCARMIL levels by siRNA transfection lowers the F-actin level and slows cell migration through a mechanism that includes decreased lamellipodia protrusion. This phenotype is reversed by full-length mCARMIL but not mCARMIL lacking the domain that binds CP. Thus, mCARMIL is a key regulator of CP and has profound effects on cell behavior.
authors.affiliation: Biology Department, University of Pennsylvania, Philadelphia, PA 19104, USA. yangc@sas.upenn.edu
authors.forename: Changsong
authors.initials: C
authors.lastname: Yang
authors.forename: Martin
authors.initials: M
authors.lastname: Pring
authors.forename: Martin A
authors.initials: MA
authors.lastname: Wear
authors.forename: Minzhou
authors.initials: M
authors.lastname: Huang
authors.forename: John A
authors.initials: JA
authors.lastname: Cooper
authors.forename: Tatyana M
authors.initials: TM
authors.lastname: Svitkina
authors.forename: Sally H
authors.initials: SH
authors.lastname: Zigmond
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002457:Cell Extracts; D045744:Cell Line, Tumor; D002465:Cell Movement; D051345:Destrin; D005909:Glioblastoma; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011554:Pseudopodia / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; C504800:Carmil1 protein, mouse; D002352:Carrier Proteins; D002457:Cell Extracts; D051345:Destrin; D008840:Microfilament Proteins; D034741:RNA, Small Interfering; D011994:Recombinant Proteins