Espin cross-links cause the elongation of microvillus-type parallel actin bundles in vivo

Patricia A. Loomis, Lili Zheng, Gabriella Sekerková, Benjarat Changyaleket, Enrico Mugnaini, James R. Bartles*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

153 Scopus citations


The espin actin-bundling proteins, which are the target of the jerker deafness mutation, caused a dramatic, concentration-dependent lengthening of LLC-PK1-CL4 cell microvilli and their parallel actin bundles. Espin level was also positively correlated with stereocilium length in hair cells. Villin, but not fascin or fimbrin, also produced noticeable lengthening. The espin COOH-terminal peptide, which contains the actin-bundling module, was necessary and sufficient for lengthening. Lengthening was blocked by 100 nM cytochalasin D. Espin cross-links slowed actin depolymerization in vitro less than twofold. Elimination of an actin monomer-binding WASP homology 2 domain and a profilin-binding proline-rich domain from espin did not decrease lengthening, but made it possible to demonstrate that actin incorporation was restricted to the microvillar tip and that bundles continued to undergo actin treadmilling at ∼1.5 s-1 during and after lengthening. Thus, through relatively subtle effects on actin polymerization/depolymerization reactions in a treadmilling parallel actin bundle, espin crosslinks cause pronounced barbed-end elongation and, thereby, make a longer bundle without joining shorter modules.

Original languageEnglish (US)
Pages (from-to)1045-1055
Number of pages11
JournalJournal of Cell Biology
Issue number5
StatePublished - Dec 8 2003


  • Deafness
  • Hair cell
  • Jerker
  • Microvilli
  • Stereocilia

ASJC Scopus subject areas

  • Cell Biology


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