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Differential actin isoform reorganization in the contracting A7r5 cell
Author(s) -
Brown Dawn Leah,
Dykes Ava,
Black Jason,
Thatcher Sean,
Fultz Mike,
Wright Gary
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.lb14-c
Subject(s) - podosome , actin , phalloidin , stress fiber , microbiology and biotechnology , staurosporine , cytoskeleton , actin cytoskeleton , protein kinase c , actin remodeling , chemistry , actin remodeling of neurons , microfilament , biophysics , cell , biology , kinase , biochemistry
In the present study, we investigated the reorganization of α‐ and β‐actin in the contracting A7r5 smooth muscle cell. The remodeling of these actin variants was markedly different in response to increasing concentrations of phorbol‐12, 13‐dibutyrate (PDBu). At the lowest concentrations (≤10 −7 M), cells showed an approximate 70% loss in α‐actin stress fibers with robust transport of this isoform to podosomes. By comparison, β‐actin remained in stress fibers in cells stimulated at low concentrations (≤10 −7 M) of PDBu. However, at high concentrations (≥ 10 −6 M) approximately 50% of cells showed transport of β‐actin to podosomes. Consistent with these findings, staining with phalloidin indicated a significant decrease in the whole cell content of F‐actin with PDBu treatment. However, staining with DNase I indicated no change in the cellular content of G‐actin, suggesting reduced access of phalloidin to tightly packed actin in the podosome core. Inhibition of protein kinase C (PKC) (staurosporine, bisindolymaleimide) blocked PDBu‐induced (5 X 10 −8 M) loss in α‐actin stress fibers or reversed podosome formation with re‐establishment of α‐actin stress fibers. By comparison, these inhibitors caused partial loss of β‐actin stress fibers. The results support our earlier conclusion of independent remodeling of α‐ and β‐actin cytoskeletal structure (Fultz et al., 2000) and suggest that the regulation of these structures is different.