PT  - JOURNAL ARTICLE
AU  - Loomis, Patricia A.
AU  - Kelly, Alexander E.
AU  - Zheng, Lili
AU  - Changyaleket, Benjarat
AU  - Sekerková, Gabriella
AU  - Mugnaini, Enrico
AU  - Ferreira, Adriana
AU  - Mullins, R. Dyche
AU  - Bartles, James R.
TI  - Targeted wild-type and jerker espins reveal a novel, WH2-domain-dependent way to make actin bundles in cells
AID  - 10.1242/jcs.02869
DP  - 2006 Apr 15
TA  - Journal of Cell Science
PG  - 1655--1665
VI  - 119
IP  - 8
4099  - http://jcs.biologists.org/content/119/8/1655.short
4100  - http://jcs.biologists.org/content/119/8/1655.full
SO  - J. Cell Sci.2006 Apr 15; 119
AB  - 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.