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Drosophila Kelch functions with Cullin-3 to organize the ring canal actin cytoskeleton.

Hudson AM, Cooley L - J. Cell Biol. (2010)

Bottom Line: Drosophila melanogaster Kelch (KEL) is the founding member of a diverse protein family defined by a repeated sequence motif known as the KEL repeat (KREP).In this study, we demonstrate that association of Drosophila KEL with Cullin-3, likely in a cullin-RING ligase, is essential for the growth of Drosophila female germline ring canals.These results suggest a role for protein ubiquitylation in the remodeling of a complex F-actin cytoskeletal structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, Yale University, New Haven, CT 06520, USA.

ABSTRACT
Drosophila melanogaster Kelch (KEL) is the founding member of a diverse protein family defined by a repeated sequence motif known as the KEL repeat (KREP). Several KREP proteins, including Drosophila KEL, bind filamentous actin (F-actin) and contribute to its organization. Recently, a subset of KREP proteins has been shown to function as substrate adaptor proteins for cullin-RING (really interesting new gene) ubiquitin E3 ligases. In this study, we demonstrate that association of Drosophila KEL with Cullin-3, likely in a cullin-RING ligase, is essential for the growth of Drosophila female germline ring canals. These results suggest a role for protein ubiquitylation in the remodeling of a complex F-actin cytoskeletal structure.

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kel mutant ring canals accumulate high levels of F-actin. (A and B) Comparison of the actin content of wild-type (WT; A) and kel (B) mutant egg chambers fixed, prepared, and imaged under identical conditions. (C) Representative ring canals from wild-type and kel mutant egg chambers from the indicated stages of egg chamber development labeled with fluorescent phalloidin. Bars: (A and B) 20 µm; (C) 5 µm.
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fig1: kel mutant ring canals accumulate high levels of F-actin. (A and B) Comparison of the actin content of wild-type (WT; A) and kel (B) mutant egg chambers fixed, prepared, and imaged under identical conditions. (C) Representative ring canals from wild-type and kel mutant egg chambers from the indicated stages of egg chamber development labeled with fluorescent phalloidin. Bars: (A and B) 20 µm; (C) 5 µm.

Mentions: The F-actin cross-linking activity of KEL can explain the disorganization of ring canal F-actin in kel mutant egg chambers. However, we also observed an increase in the quantity of F-actin (Fig. 1, A and B), as well as the ovarian hu-li tai shao–ring canal protein (Ovhts-RC) and filamin ring canal proteins (Robinson et al., 1994; Sokol and Cooley, 1999) in kel egg chambers. These observations are not fully explained by the loss of an F-actin cross-linking protein. A potential cause of the increase in ring canal proteins was suggested by comparing the development of kel mutant ring canals with wild type over the course of oogenesis (Fig. 1 C). Consistent with previous studies (Xue and Cooley, 1993; Tilney et al., 1996), the kel ring canal phenotype first appeared at approximately stage 6 of oogenesis (for an explanation of developmental staging of oogenesis, see Spradling, 1993). From stage 6 until the end of oogenesis, the growth of the outer diameters of kel ring canals was similar to wild type; however, the inner diameter failed to expand, leaving a small lumen similar in size to ring canals of very young egg chambers. These observations suggested that KEL might function to disassemble the innermost ring canal cytoskeleton as the outer diameter grows.


Drosophila Kelch functions with Cullin-3 to organize the ring canal actin cytoskeleton.

Hudson AM, Cooley L - J. Cell Biol. (2010)

kel mutant ring canals accumulate high levels of F-actin. (A and B) Comparison of the actin content of wild-type (WT; A) and kel (B) mutant egg chambers fixed, prepared, and imaged under identical conditions. (C) Representative ring canals from wild-type and kel mutant egg chambers from the indicated stages of egg chamber development labeled with fluorescent phalloidin. Bars: (A and B) 20 µm; (C) 5 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2812842&req=5

fig1: kel mutant ring canals accumulate high levels of F-actin. (A and B) Comparison of the actin content of wild-type (WT; A) and kel (B) mutant egg chambers fixed, prepared, and imaged under identical conditions. (C) Representative ring canals from wild-type and kel mutant egg chambers from the indicated stages of egg chamber development labeled with fluorescent phalloidin. Bars: (A and B) 20 µm; (C) 5 µm.
Mentions: The F-actin cross-linking activity of KEL can explain the disorganization of ring canal F-actin in kel mutant egg chambers. However, we also observed an increase in the quantity of F-actin (Fig. 1, A and B), as well as the ovarian hu-li tai shao–ring canal protein (Ovhts-RC) and filamin ring canal proteins (Robinson et al., 1994; Sokol and Cooley, 1999) in kel egg chambers. These observations are not fully explained by the loss of an F-actin cross-linking protein. A potential cause of the increase in ring canal proteins was suggested by comparing the development of kel mutant ring canals with wild type over the course of oogenesis (Fig. 1 C). Consistent with previous studies (Xue and Cooley, 1993; Tilney et al., 1996), the kel ring canal phenotype first appeared at approximately stage 6 of oogenesis (for an explanation of developmental staging of oogenesis, see Spradling, 1993). From stage 6 until the end of oogenesis, the growth of the outer diameters of kel ring canals was similar to wild type; however, the inner diameter failed to expand, leaving a small lumen similar in size to ring canals of very young egg chambers. These observations suggested that KEL might function to disassemble the innermost ring canal cytoskeleton as the outer diameter grows.

Bottom Line: Drosophila melanogaster Kelch (KEL) is the founding member of a diverse protein family defined by a repeated sequence motif known as the KEL repeat (KREP).In this study, we demonstrate that association of Drosophila KEL with Cullin-3, likely in a cullin-RING ligase, is essential for the growth of Drosophila female germline ring canals.These results suggest a role for protein ubiquitylation in the remodeling of a complex F-actin cytoskeletal structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, Yale University, New Haven, CT 06520, USA.

ABSTRACT
Drosophila melanogaster Kelch (KEL) is the founding member of a diverse protein family defined by a repeated sequence motif known as the KEL repeat (KREP). Several KREP proteins, including Drosophila KEL, bind filamentous actin (F-actin) and contribute to its organization. Recently, a subset of KREP proteins has been shown to function as substrate adaptor proteins for cullin-RING (really interesting new gene) ubiquitin E3 ligases. In this study, we demonstrate that association of Drosophila KEL with Cullin-3, likely in a cullin-RING ligase, is essential for the growth of Drosophila female germline ring canals. These results suggest a role for protein ubiquitylation in the remodeling of a complex F-actin cytoskeletal structure.

Show MeSH