1. Targeted wild-type and jerker espins reveal a novel, WH2-domain-dependent way to make actin bundles in cells
- Author
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R. Dyche Mullins, Patricia A. Loomis, Benjarat Changyaleket, Adriana Ferreira, Gabriella Sekerková, Lili Zheng, Alexander E. Kelly, Enrico Mugnaini, and James R. Bartles
- Subjects
Swine ,Nucleolus ,Centromere ,Molecular Sequence Data ,macromolecular substances ,Biology ,Transfection ,medicine.disease_cause ,PC12 Cells ,Actin-Related Protein 2-3 Complex ,Article ,Microtubule ,otorhinolaryngologic diseases ,medicine ,Animals ,Protein Isoforms ,Amino Acid Sequence ,Actin ,Neurons ,Mutation ,Microfilament Proteins ,Stereocilia ,Cell Biology ,Actins ,Rats ,Cell biology ,Centrosome ,biology.protein ,LLC-PK1 Cells ,sense organs ,Villin ,Cell Nucleolus - Abstract
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.
- Published
- 2006