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EPLIN regulates actin dynamics by cross-linking and stabilizing filaments.

Maul RS, Song Y, Amann KJ, Gerbin SC, Pollard TD, Chang DD - J. Cell Biol. (2003)

Bottom Line: EPLIN does not affect the kinetics of spontaneous actin polymerization or elongation at the barbed end, but inhibits branching nucleation of actin filaments by Arp2/3 complex.Side binding activity may stabilize filaments and account for the inhibition of nucleation mediated by Arp2/3 complex.We propose that EPLIN promotes the formation of stable actin filament structures such as stress fibers at the expense of more dynamic actin filament structures such as membrane ruffles.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.

ABSTRACT
Epithelial protein lost in neoplasm (EPLIN) is a cytoskeleton-associated protein encoded by a gene that is down-regulated in transformed cells. EPLIN increases the number and size of actin stress fibers and inhibits membrane ruffling induced by Rac. EPLIN has at least two actin binding sites. Purified recombinant EPLIN inhibits actin filament depolymerization and cross-links filaments in bundles. EPLIN does not affect the kinetics of spontaneous actin polymerization or elongation at the barbed end, but inhibits branching nucleation of actin filaments by Arp2/3 complex. Side binding activity may stabilize filaments and account for the inhibition of nucleation mediated by Arp2/3 complex. We propose that EPLIN promotes the formation of stable actin filament structures such as stress fibers at the expense of more dynamic actin filament structures such as membrane ruffles. Reduced expression of EPLIN may contribute to the motility of invasive tumor cells.

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EPLIN inhibits membrane ruffling induced by Rac1. Transfected HeLa cells were stained with anti-HA (A, C, E, and G), rhodamine-phalloidin (B, F, and H), or anti-EPLIN (D) to visualize the transfected HA-tagged Rac1G12V, actin filaments, or endogenous EPLIN, respectively. In A–D, HeLa cells were transfected with HA-tagged Rac1G12V alone. In E–H, HeLa cells were co-transfected with HA-tagged Rac1G12V and EPLIN-α (E and F) or EPLIN-β (G and H).
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fig2: EPLIN inhibits membrane ruffling induced by Rac1. Transfected HeLa cells were stained with anti-HA (A, C, E, and G), rhodamine-phalloidin (B, F, and H), or anti-EPLIN (D) to visualize the transfected HA-tagged Rac1G12V, actin filaments, or endogenous EPLIN, respectively. In A–D, HeLa cells were transfected with HA-tagged Rac1G12V alone. In E–H, HeLa cells were co-transfected with HA-tagged Rac1G12V and EPLIN-α (E and F) or EPLIN-β (G and H).

Mentions: Activated Rac1 recruits WAVE/Scar (a member of WASp family of proteins) from the cytoplasm to the plasma membrane to induce actin filament assembly (Miki et al., 1998). To test if EPLIN influences the formation of actin filaments in vivo, we examined the effect of EPLIN expression on Rac1-induced membrane ruffling. Expression of constitutively active Rac1 (HA-tagged Rac1G12V) in HeLa cells produced extensive membrane ruffles containing Rac1G12V, actin filaments, and endogenous EPLIN (Fig. 2, A–D). Co-transfection of either EPLIN-α or EPLIN-β with Rac1G12V strongly inhibited membrane ruffling, producing thick actin stress fibers instead (Fig. 2, E–H). When EPLIN was coexpressed, transfected Rac1G12V was diffusely distributed in the cells, rather than localizing to membrane ruffles.


EPLIN regulates actin dynamics by cross-linking and stabilizing filaments.

Maul RS, Song Y, Amann KJ, Gerbin SC, Pollard TD, Chang DD - J. Cell Biol. (2003)

EPLIN inhibits membrane ruffling induced by Rac1. Transfected HeLa cells were stained with anti-HA (A, C, E, and G), rhodamine-phalloidin (B, F, and H), or anti-EPLIN (D) to visualize the transfected HA-tagged Rac1G12V, actin filaments, or endogenous EPLIN, respectively. In A–D, HeLa cells were transfected with HA-tagged Rac1G12V alone. In E–H, HeLa cells were co-transfected with HA-tagged Rac1G12V and EPLIN-α (E and F) or EPLIN-β (G and H).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172667&req=5

fig2: EPLIN inhibits membrane ruffling induced by Rac1. Transfected HeLa cells were stained with anti-HA (A, C, E, and G), rhodamine-phalloidin (B, F, and H), or anti-EPLIN (D) to visualize the transfected HA-tagged Rac1G12V, actin filaments, or endogenous EPLIN, respectively. In A–D, HeLa cells were transfected with HA-tagged Rac1G12V alone. In E–H, HeLa cells were co-transfected with HA-tagged Rac1G12V and EPLIN-α (E and F) or EPLIN-β (G and H).
Mentions: Activated Rac1 recruits WAVE/Scar (a member of WASp family of proteins) from the cytoplasm to the plasma membrane to induce actin filament assembly (Miki et al., 1998). To test if EPLIN influences the formation of actin filaments in vivo, we examined the effect of EPLIN expression on Rac1-induced membrane ruffling. Expression of constitutively active Rac1 (HA-tagged Rac1G12V) in HeLa cells produced extensive membrane ruffles containing Rac1G12V, actin filaments, and endogenous EPLIN (Fig. 2, A–D). Co-transfection of either EPLIN-α or EPLIN-β with Rac1G12V strongly inhibited membrane ruffling, producing thick actin stress fibers instead (Fig. 2, E–H). When EPLIN was coexpressed, transfected Rac1G12V was diffusely distributed in the cells, rather than localizing to membrane ruffles.

Bottom Line: EPLIN does not affect the kinetics of spontaneous actin polymerization or elongation at the barbed end, but inhibits branching nucleation of actin filaments by Arp2/3 complex.Side binding activity may stabilize filaments and account for the inhibition of nucleation mediated by Arp2/3 complex.We propose that EPLIN promotes the formation of stable actin filament structures such as stress fibers at the expense of more dynamic actin filament structures such as membrane ruffles.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA.

ABSTRACT
Epithelial protein lost in neoplasm (EPLIN) is a cytoskeleton-associated protein encoded by a gene that is down-regulated in transformed cells. EPLIN increases the number and size of actin stress fibers and inhibits membrane ruffling induced by Rac. EPLIN has at least two actin binding sites. Purified recombinant EPLIN inhibits actin filament depolymerization and cross-links filaments in bundles. EPLIN does not affect the kinetics of spontaneous actin polymerization or elongation at the barbed end, but inhibits branching nucleation of actin filaments by Arp2/3 complex. Side binding activity may stabilize filaments and account for the inhibition of nucleation mediated by Arp2/3 complex. We propose that EPLIN promotes the formation of stable actin filament structures such as stress fibers at the expense of more dynamic actin filament structures such as membrane ruffles. Reduced expression of EPLIN may contribute to the motility of invasive tumor cells.

Show MeSH
Related in: MedlinePlus