Genetic deletion of ABP-120 alters the three-dimensional organization of actin filaments in Dictyostelium pseudopods

Dianne Cox, J. Andrew Ridsdale, John Condeelis, John Hartwig

Research output: Contribution to journalArticle

63 Scopus citations

Abstract

This study extends the observations on the defects in pseudopod formation of ABP-120+ and ABP-120- cells by a detailed morphological and biochemical analysis of the actin based cytoskeleton. Both ABP-120+ and ABP-120- cells polymerize the same amount of F-actin in response to stimulation with cAMP. However, unlike ABP-120+ cells, ABP-120- cells do not incorporate actin into the Triton X-100-insoluble cytoskeleton at 30-50 s, the time when ABP- 120 is incorporated into the cytoskeleton and when pseudopods are extended after cAMP stimulation in wild-type cells. By confocal and electron microscopy, pseudopods extended by ABP-120- cells are not as large or thick as those produced by ABP-120+ cells and in the electron microscope, an altered filament network is found in pseudopods of ABP-120- cells when compared to pseudopods of ABP-120+ cells. The actin filaments found in areas of pseudo-pods in ABP-120+ cells either before or after stimulation were long, straight, and arranged into space filling orthogonal networks. Protrusions of ABP-120- cells are less three-dimensional, denser, and filled with multiple loci of aggregated filaments consistent with collapse of the filament network due to the absence of ABP-120-mediated cross-linking activity. The different organization of actin filaments may account for the diminished size of protrusions observed in living and fixed ABP- 120- cells compared to ABP-120+ cells and is consistent with the role of ABP-120 in regulating pseudopod extension through its cross-linking of actin filaments.

Original languageEnglish (US)
Pages (from-to)819-835
Number of pages17
JournalJournal of Cell Biology
Volume128
Issue number5
DOIs
StatePublished - Mar 1 1995

ASJC Scopus subject areas

  • Cell Biology

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