title: Identification and characterisation of a novel human isoform of Arp2/3 complex subunit p16-ARC/ARPC5.
abstract: The Arp2/3 complex is an actin filament nucleator that activates regulated actin assembly in response to extracellular signals. The mammalian complex is composed of seven subunits, the smallest of which is known as ARPC5 or p16-Arc. We have identified a human cDNA sequence with homology to ARPC5 and here provide evidence that this encodes a novel ARPC5 isoform. Specific antibodies were generated against the novel protein, which we have termed ARPC5B, as well as the previously characterised ARPC5 isoform, henceforth ARPC5A. The presence of both ARPC5 isoforms was detected in Arp2/3 complex affinity purified from human neutrophil extract. The tissue distribution of ARPC5A and B was analysed using the isoform-specific antibodies and it was found that the two isoforms exhibited significant differences; ARPC5A was found to be highly enriched in spleen and thymus, while ARPC5B exhibits a more regular expression, with levels in the brain being highest. Myc-tagged ARPC5A and B co-localised with the Arp2/3 complex when expressed in C2C12 cells and the cellular distribution of the two isoforms could not be distinguished. Our data show for the first time that mammalian cells contain multiple forms of the Arp2/3 complex.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Millard
authors.forename: Barbara
authors.initials: B
authors.lastname: Behrendt
authors.forename: Sophie
authors.initials: S
authors.lastname: Launay
authors.forename: Klaus
authors.initials: K
authors.lastname: Fütterer
authors.forename: Laura M
authors.initials: LM
authors.lastname: Machesky
mesh_terms: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002999:Clone Cells; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000235:genetics; D018076:DNA, Complementary; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D032446:Myoblasts / Q000166:cytology; D009504:Neutrophils / Q000737:chemistry / Q000166:cytology; D020033:Protein Isoforms; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; C495927:Actr2 protein, mouse; C495929:Actr3 protein, mouse; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D020033:Protein Isoforms