Targeted wild-type and jerker espins reveal a novel, WH2-domain-dependent way to make actin bundles in cells.
The espin actin-bundling proteins, which are the target of deafness mutations, are present in the parallel actin bundles of stereocilia and microvilli and appear to increase their steady-state length. Here, we report a new activity of the espins, one that depends on their enigmatic WH2 domain: the ability to assemble a large actin bundle when targeted to a specific subcellular location. This activity was observed for wild-type espins targeted to the centrosome in transfected neuronal cells and for jerker espins targeted to the nucleolus in a wide variety of transfected cells as a result of the frameshifted peptide introduced into the espin C-terminus by the jerker deafness mutation. This activity, which appears specific to espins, requires two espin F-actin-binding sites and the actin-monomer-binding activity of the espin WH2 domain, but can be mimicked by adding a WH2 domain to an unrelated actin-bundling protein, villin. Espins do not activate the Arp2/3 complex in vitro, and bundle assembly is not indicative of in-vitro nucleation activity. Our results suggest a novel way to build actin bundles at specific sites in cells.
Loomis
Patricia A
PA
Department of Cell and Molecular Biology, Feinberg School of Medicine, and Institute for Neuroscience, Northwestern University, Chicago, IL 60611, USA.
Kelly
Alexander E
AE
Zheng
Lili
L
Changyaleket
Benjarat
B
Sekerková
Gabriella
G
Mugnaini
Enrico
E
Ferreira
Adriana
A
Mullins
R Dyche
RD
Bartles
James R
JR
D051376:Actin-Related Protein 2-3 Complex / Q000502:physiology; D000199:Actins / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002503:Centromere / Q000378:metabolism*; D018374:LLC-PK1 Cells; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D020033:Protein Isoforms / Q000235:genetics*; D051381:Rats; D013552:Swine; D014162:Transfection
D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; C493274:ESPN protein, human; D008840:Microfilament Proteins; D020033:Protein Isoforms