Limits...
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.

Show MeSH

Related in: MedlinePlus

Integrins are not required for ILK localization at muscle attachment sites. Lateral view of the embryonic muscles at stage 16 in wild-type (a) and βPS integrin mutant myospheroid (mys) (b) embryos. The actin filaments have been labeled with rhodamine-phalloidin (red) and ILK is visualized by GFP fluorescence (green). The plain arrows indicate localization of ILK-GFP at the corresponding muscle-attachment site. The dashed arrow shows a detached muscle in the mys embryo. Normal ILK localization to the ends of muscles (a) is not blocked by the absence of integrins (b). Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2198807&req=5

Figure 4: Integrins are not required for ILK localization at muscle attachment sites. Lateral view of the embryonic muscles at stage 16 in wild-type (a) and βPS integrin mutant myospheroid (mys) (b) embryos. The actin filaments have been labeled with rhodamine-phalloidin (red) and ILK is visualized by GFP fluorescence (green). The plain arrows indicate localization of ILK-GFP at the corresponding muscle-attachment site. The dashed arrow shows a detached muscle in the mys embryo. Normal ILK localization to the ends of muscles (a) is not blocked by the absence of integrins (b). Bar, 10 μm.

Mentions: The colocalization of ILK-GFP with integrins raises the question as to whether this is due to the binding of ILK to the cytoplasmic tail of the βPS subunit. We examined the distribution of ILK-GFP in embryos mutant for the βPS subunit and found that ILK-GFP is still concentrated at the muscle attachments (Fig. 4, a and b). In addition, we could not detect any interaction between Drosophila ILK and the βPS subunit cytoplasmic domain by two-hybrid analysis, although we were able to reproduce the interaction between human ILK and human β1 integrin (Table ; Hannigan et al. 1996). We see weak interaction between Drosophila ILK and the β1 integrin cytoplasmic tail, but not between human ILK and βPS, indicating that the differences between the cytoplasmic tails (11 of 47 amino acids) have caused the loss of this interaction. Thus, we have not been able to provide evidence for a direct interaction between Drosophila ILK and the PS integrins, either in yeast or in the Drosophila embryonic muscles.


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)

Integrins are not required for ILK localization at muscle attachment sites. Lateral view of the embryonic muscles at stage 16 in wild-type (a) and βPS integrin mutant myospheroid (mys) (b) embryos. The actin filaments have been labeled with rhodamine-phalloidin (red) and ILK is visualized by GFP fluorescence (green). The plain arrows indicate localization of ILK-GFP at the corresponding muscle-attachment site. The dashed arrow shows a detached muscle in the mys embryo. Normal ILK localization to the ends of muscles (a) is not blocked by the absence of integrins (b). Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2198807&req=5

Figure 4: Integrins are not required for ILK localization at muscle attachment sites. Lateral view of the embryonic muscles at stage 16 in wild-type (a) and βPS integrin mutant myospheroid (mys) (b) embryos. The actin filaments have been labeled with rhodamine-phalloidin (red) and ILK is visualized by GFP fluorescence (green). The plain arrows indicate localization of ILK-GFP at the corresponding muscle-attachment site. The dashed arrow shows a detached muscle in the mys embryo. Normal ILK localization to the ends of muscles (a) is not blocked by the absence of integrins (b). Bar, 10 μm.
Mentions: The colocalization of ILK-GFP with integrins raises the question as to whether this is due to the binding of ILK to the cytoplasmic tail of the βPS subunit. We examined the distribution of ILK-GFP in embryos mutant for the βPS subunit and found that ILK-GFP is still concentrated at the muscle attachments (Fig. 4, a and b). In addition, we could not detect any interaction between Drosophila ILK and the βPS subunit cytoplasmic domain by two-hybrid analysis, although we were able to reproduce the interaction between human ILK and human β1 integrin (Table ; Hannigan et al. 1996). We see weak interaction between Drosophila ILK and the β1 integrin cytoplasmic tail, but not between human ILK and βPS, indicating that the differences between the cytoplasmic tails (11 of 47 amino acids) have caused the loss of this interaction. Thus, we have not been able to provide evidence for a direct interaction between Drosophila ILK and the PS integrins, either in yeast or in the Drosophila embryonic muscles.

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