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Drosophila integrin-linked kinase is required at sites of integrin adhesion to link the cytoskeleton to the plasma membrane.

Zervas CG, Gregory SL, Brown NH - J. Cell Biol. (2001)

Bottom Line: Integrin-linked kinase (ILK) was identified by its interaction with the cytoplasmic tail of human beta1 integrin and previous data suggest that ILK is a component of diverse signaling pathways, including integrin, Wnt, and protein kinase B.ILK mutations cause embryonic lethality and defects in muscle attachment, and clones of cells lacking ILK in the adult wing fail to adhere, forming wing blisters.Surprisingly, mutations in the kinase domain shown to inactivate the kinase activity of human ILK do not show any phenotype in Drosophila, suggesting a kinase-independent function for ILK.

View Article: PubMed Central - PubMed

Affiliation: Wellcome/CRC Institute and Department of Anatomy, University of Cambridge, Cambridge CB2 1QR, United Kingdom.

ABSTRACT
Integrin-linked kinase (ILK) was identified by its interaction with the cytoplasmic tail of human beta1 integrin and previous data suggest that ILK is a component of diverse signaling pathways, including integrin, Wnt, and protein kinase B. Here we show that the absence of ILK function in Drosophila causes defects similar to loss of integrin adhesion, but not similar to loss of these signaling pathways. ILK mutations cause embryonic lethality and defects in muscle attachment, and clones of cells lacking ILK in the adult wing fail to adhere, forming wing blisters. Consistent with this, an ILK-green fluorescent protein fusion protein colocalizes with the position-specific integrins at sites of integrin function: muscle attachment sites and the basal junctions of the wing epithelium. Surprisingly, mutations in the kinase domain shown to inactivate the kinase activity of human ILK do not show any phenotype in Drosophila, suggesting a kinase-independent function for ILK. The muscle detachment in ILK mutants is associated with detachment of the actin filaments from the muscle ends, unlike integrin mutants, in which the primary defect is detachment of the plasma membrane from the extracellular matrix. Our data suggest that ILK is a component of the structure linking the cytoskeleton and the plasma membrane at sites of integrin-mediated adhesion.

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ILK maintains cell adhesion in the adult wing. (a) Blister caused by a clone of cells lacking ILK on one surface of the wing. The position of the clone was identified by the mwh marker and is marked by the dashed line. (b) ILK-GFP is localized basally in the pupal wing epithelium. This image is a stack of confocal sections from a live pupal wing. Bar, 10 μm. (c) Expression of UAS::ILK in the mesoderm by 24B::Gal4 rescues the lethality of ilk1/Df(3L)Pc-14d, but the adult flies have blistered wings.
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Figure 7: ILK maintains cell adhesion in the adult wing. (a) Blister caused by a clone of cells lacking ILK on one surface of the wing. The position of the clone was identified by the mwh marker and is marked by the dashed line. (b) ILK-GFP is localized basally in the pupal wing epithelium. This image is a stack of confocal sections from a live pupal wing. Bar, 10 μm. (c) Expression of UAS::ILK in the mesoderm by 24B::Gal4 rescues the lethality of ilk1/Df(3L)Pc-14d, but the adult flies have blistered wings.

Mentions: The phenotype of ilk1 in the embryo is consistent with a role for ILK in integrin-mediated adhesion, and we wished to assess whether this is also true during adult development. Although ILK activity is required for viability, it is possible to assay the role of ilk after embryogenesis by making mosaic mutant animals by mitotic recombination. Clones of cells within the wing that are homozygous for the ilk1 allele cause a wing blister (Fig. 7 a). This phenotype appears identical to that caused by clones mutant for the integrin subunits βPS, αPS1, and αPS2, as well as a number of other loci (see Brown et al. 2000). The marked ilk1 clones allowed us to determine that wing blisters are associated with clones on either side of the wing blade, indicating either that ILK is essential for both PS1 and PS2 integrin-mediated adhesion, whose functions are primarily restricted to the dorsal and ventral sides, respectively (Brabant and Brower 1993; Brower et al. 1995), or that ILK is required for a parallel pathway required for wing adhesion. We examined the localization of ILK-GFP within the pupal wing and found that it is concentrated in a series of discs corresponding to the sites of adhesion between the dorsal and ventral surfaces (Fig. 7 b), as the integrins are (Fristrom et al. 1993). Clones within the wing mutant for β-catenin, or GSK3, cause a clear phenotype (loss/gain of wing margin; Couso et al. 1994), which were not seen in any of the ilk mutant wings (Fig. 7, a and c, and data not shown), providing additional evidence that ILK is not required for the function of this pathway in Drosophila.


Drosophila integrin-linked kinase is required at sites of integrin adhesion to link the cytoskeleton to the plasma membrane.

Zervas CG, Gregory SL, Brown NH - J. Cell Biol. (2001)

ILK maintains cell adhesion in the adult wing. (a) Blister caused by a clone of cells lacking ILK on one surface of the wing. The position of the clone was identified by the mwh marker and is marked by the dashed line. (b) ILK-GFP is localized basally in the pupal wing epithelium. This image is a stack of confocal sections from a live pupal wing. Bar, 10 μm. (c) Expression of UAS::ILK in the mesoderm by 24B::Gal4 rescues the lethality of ilk1/Df(3L)Pc-14d, but the adult flies have blistered wings.
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Related In: Results  -  Collection

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Figure 7: ILK maintains cell adhesion in the adult wing. (a) Blister caused by a clone of cells lacking ILK on one surface of the wing. The position of the clone was identified by the mwh marker and is marked by the dashed line. (b) ILK-GFP is localized basally in the pupal wing epithelium. This image is a stack of confocal sections from a live pupal wing. Bar, 10 μm. (c) Expression of UAS::ILK in the mesoderm by 24B::Gal4 rescues the lethality of ilk1/Df(3L)Pc-14d, but the adult flies have blistered wings.
Mentions: The phenotype of ilk1 in the embryo is consistent with a role for ILK in integrin-mediated adhesion, and we wished to assess whether this is also true during adult development. Although ILK activity is required for viability, it is possible to assay the role of ilk after embryogenesis by making mosaic mutant animals by mitotic recombination. Clones of cells within the wing that are homozygous for the ilk1 allele cause a wing blister (Fig. 7 a). This phenotype appears identical to that caused by clones mutant for the integrin subunits βPS, αPS1, and αPS2, as well as a number of other loci (see Brown et al. 2000). The marked ilk1 clones allowed us to determine that wing blisters are associated with clones on either side of the wing blade, indicating either that ILK is essential for both PS1 and PS2 integrin-mediated adhesion, whose functions are primarily restricted to the dorsal and ventral sides, respectively (Brabant and Brower 1993; Brower et al. 1995), or that ILK is required for a parallel pathway required for wing adhesion. We examined the localization of ILK-GFP within the pupal wing and found that it is concentrated in a series of discs corresponding to the sites of adhesion between the dorsal and ventral surfaces (Fig. 7 b), as the integrins are (Fristrom et al. 1993). Clones within the wing mutant for β-catenin, or GSK3, cause a clear phenotype (loss/gain of wing margin; Couso et al. 1994), which were not seen in any of the ilk mutant wings (Fig. 7, a and c, and data not shown), providing additional evidence that ILK is not required for the function of this pathway in Drosophila.

Bottom Line: Integrin-linked kinase (ILK) was identified by its interaction with the cytoplasmic tail of human beta1 integrin and previous data suggest that ILK is a component of diverse signaling pathways, including integrin, Wnt, and protein kinase B.ILK mutations cause embryonic lethality and defects in muscle attachment, and clones of cells lacking ILK in the adult wing fail to adhere, forming wing blisters.Surprisingly, mutations in the kinase domain shown to inactivate the kinase activity of human ILK do not show any phenotype in Drosophila, suggesting a kinase-independent function for ILK.

View Article: PubMed Central - PubMed

Affiliation: Wellcome/CRC Institute and Department of Anatomy, University of Cambridge, Cambridge CB2 1QR, United Kingdom.

ABSTRACT
Integrin-linked kinase (ILK) was identified by its interaction with the cytoplasmic tail of human beta1 integrin and previous data suggest that ILK is a component of diverse signaling pathways, including integrin, Wnt, and protein kinase B. Here we show that the absence of ILK function in Drosophila causes defects similar to loss of integrin adhesion, but not similar to loss of these signaling pathways. ILK mutations cause embryonic lethality and defects in muscle attachment, and clones of cells lacking ILK in the adult wing fail to adhere, forming wing blisters. Consistent with this, an ILK-green fluorescent protein fusion protein colocalizes with the position-specific integrins at sites of integrin function: muscle attachment sites and the basal junctions of the wing epithelium. Surprisingly, mutations in the kinase domain shown to inactivate the kinase activity of human ILK do not show any phenotype in Drosophila, suggesting a kinase-independent function for ILK. The muscle detachment in ILK mutants is associated with detachment of the actin filaments from the muscle ends, unlike integrin mutants, in which the primary defect is detachment of the plasma membrane from the extracellular matrix. Our data suggest that ILK is a component of the structure linking the cytoskeleton and the plasma membrane at sites of integrin-mediated adhesion.

Show MeSH
Related in: MedlinePlus