TY - JOUR
T1 - Genetic deletion of ABP-120 alters the three-dimensional organization of actin filaments in Dictyostelium pseudopods
AU - Cox, Dianne
AU - Ridsdale, J. Andrew
AU - Condeelis, John
AU - Hartwig, John
PY - 1995/3
Y1 - 1995/3
N2 - 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.
AB - 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.
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U2 - 10.1083/jcb.128.5.819
DO - 10.1083/jcb.128.5.819
M3 - Article
C2 - 7876307
AN - SCOPUS:0028919541
SN - 0021-9525
VL - 128
SP - 819
EP - 835
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 5
ER -