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Angiomotin binding-induced activation of Merlin/NF2 in the Hippo pathway.

Li Y, Zhou H, Li F, Chan SW, Lin Z, Wei Z, Yang Z, Guo F, Lim CJ, Xing W, Shen Y, Hong W, Long J, Zhang M - Cell Res. (2015)

Bottom Line: Phosphorylation of Ser518 outside the Merlin's auto-inhibitory tail does not obviously alter Merlin's conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation.Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation.Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong, China.

ABSTRACT
The tumor suppressor Merlin/NF2 functions upstream of the core Hippo pathway kinases Lats1/2 and Mst1/2, as well as the nuclear E3 ubiquitin ligase CRL4(DCAF1). Numerous mutations of Merlin have been identified in Neurofibromatosis type 2 and other cancer patients. Despite more than two decades of research, the upstream regulator of Merlin in the Hippo pathway remains unknown. Here we show by high-resolution crystal structures that the Lats1/2-binding site on the Merlin FERM domain is physically blocked by Merlin's auto-inhibitory tail. Angiomotin binding releases the auto-inhibition and promotes Merlin's binding to Lats1/2. Phosphorylation of Ser518 outside the Merlin's auto-inhibitory tail does not obviously alter Merlin's conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation. Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation. Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.

No MeSH data available.


Related in: MedlinePlus

Lats1/2 bind to the F2 lobe of Merlin-FERM. (A) Domain organizations of Lats1/2 and Merlin. The Merlin-FERM/Lats1/2 interaction is indicated by a two-way arrow. (B, C) ITC-based measurements show the binding of Lats1-FBD to Merlin-FERM (B) or A585W-Merlin (C). (D) A table summarizing the binding affinities between Merlin-FERM and various forms of Lats1, and between Lats1-FBD and various forms of full-length Merlin. (E) The crystal structures of Merlin-FERM in complex with Lats1- and Lats2-FBD drawn in ribbon diagram representation. (F) Sequence alignment of Lats1/2-FBD across different species and human Merlin-α1CTD fragment. The hydrophobic residues of Lats1/2-FBD and Merlin-α1CTD responsible for their respective binding to the Merlin-FERM F2 lobe are highlighted in green. (G) Surface representations showing the comparison of Merlin-FERM/Lats1-FBD (G1) and Merlin-FERM/Merlin-CTD (G2). Residues in Merlin-FERM that are hydrophobic, positively charged and negatively charged are colored in yellow, blue, and red, respectively.
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fig3: Lats1/2 bind to the F2 lobe of Merlin-FERM. (A) Domain organizations of Lats1/2 and Merlin. The Merlin-FERM/Lats1/2 interaction is indicated by a two-way arrow. (B, C) ITC-based measurements show the binding of Lats1-FBD to Merlin-FERM (B) or A585W-Merlin (C). (D) A table summarizing the binding affinities between Merlin-FERM and various forms of Lats1, and between Lats1-FBD and various forms of full-length Merlin. (E) The crystal structures of Merlin-FERM in complex with Lats1- and Lats2-FBD drawn in ribbon diagram representation. (F) Sequence alignment of Lats1/2-FBD across different species and human Merlin-α1CTD fragment. The hydrophobic residues of Lats1/2-FBD and Merlin-α1CTD responsible for their respective binding to the Merlin-FERM F2 lobe are highlighted in green. (G) Surface representations showing the comparison of Merlin-FERM/Lats1-FBD (G1) and Merlin-FERM/Merlin-CTD (G2). Residues in Merlin-FERM that are hydrophobic, positively charged and negatively charged are colored in yellow, blue, and red, respectively.

Mentions: The auto-inhibited structure of Merlin is also valuable for us to understand the mechanisms governing many human disease-related mutations identified in Merlin (39 and http://www.hgmd.org). All, except one (“Q178del”), of the 12 mutations found in the F2 and F3 lobes are expected to cause folding defects of the FERM domain (Figure 2E and 2F, labeled in red), and thus impair Merlin's function (see40 for detailed discussions of this category of Merlin mutations). Gln178 is located in the so-called “blue box” (BB) region, and mutation or deletion of the BB region is known to result in an over-proliferation phenotype in Drosophila41. In the closed Merlin structure, the BB region (residues176-183) directly contacts the loop between α1CTD and α2CTD (Figure 2D and 2E, and Supplementary information, Figure S3B). A shortened BB region resulted from the deletion of Gln178 may perturb a series of interactions between the α1CTD/α2CTD loop and the BB region (Supplementary information, Figure S3B), thus weakening the auto-inhibited conformation of Merlin. Counterintuitively, the BB mutant of Drosophila Merlin is known to be inactive in suppressing cell proliferation41, yet our structure-based analysis indicates that the mutant Merlin should adopt a more open conformation and thus more active in suppressing cell growth. This apparent contradiction can be nicely explained by the structure of Merlin-FERM in complex with Lats1/2 presented in the next section. The BB region of Merlin-FERM forms a large part of the Lats1/2-binding surface (Figure 3G). The deletion of the BB region is expected to weaken or disrupt Lats1/2 (or Wts in fly) binding capacity of Merlin, thus preventing Lats1/2 from phosphorylating YAP13.


Angiomotin binding-induced activation of Merlin/NF2 in the Hippo pathway.

Li Y, Zhou H, Li F, Chan SW, Lin Z, Wei Z, Yang Z, Guo F, Lim CJ, Xing W, Shen Y, Hong W, Long J, Zhang M - Cell Res. (2015)

Lats1/2 bind to the F2 lobe of Merlin-FERM. (A) Domain organizations of Lats1/2 and Merlin. The Merlin-FERM/Lats1/2 interaction is indicated by a two-way arrow. (B, C) ITC-based measurements show the binding of Lats1-FBD to Merlin-FERM (B) or A585W-Merlin (C). (D) A table summarizing the binding affinities between Merlin-FERM and various forms of Lats1, and between Lats1-FBD and various forms of full-length Merlin. (E) The crystal structures of Merlin-FERM in complex with Lats1- and Lats2-FBD drawn in ribbon diagram representation. (F) Sequence alignment of Lats1/2-FBD across different species and human Merlin-α1CTD fragment. The hydrophobic residues of Lats1/2-FBD and Merlin-α1CTD responsible for their respective binding to the Merlin-FERM F2 lobe are highlighted in green. (G) Surface representations showing the comparison of Merlin-FERM/Lats1-FBD (G1) and Merlin-FERM/Merlin-CTD (G2). Residues in Merlin-FERM that are hydrophobic, positively charged and negatively charged are colored in yellow, blue, and red, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4493278&req=5

fig3: Lats1/2 bind to the F2 lobe of Merlin-FERM. (A) Domain organizations of Lats1/2 and Merlin. The Merlin-FERM/Lats1/2 interaction is indicated by a two-way arrow. (B, C) ITC-based measurements show the binding of Lats1-FBD to Merlin-FERM (B) or A585W-Merlin (C). (D) A table summarizing the binding affinities between Merlin-FERM and various forms of Lats1, and between Lats1-FBD and various forms of full-length Merlin. (E) The crystal structures of Merlin-FERM in complex with Lats1- and Lats2-FBD drawn in ribbon diagram representation. (F) Sequence alignment of Lats1/2-FBD across different species and human Merlin-α1CTD fragment. The hydrophobic residues of Lats1/2-FBD and Merlin-α1CTD responsible for their respective binding to the Merlin-FERM F2 lobe are highlighted in green. (G) Surface representations showing the comparison of Merlin-FERM/Lats1-FBD (G1) and Merlin-FERM/Merlin-CTD (G2). Residues in Merlin-FERM that are hydrophobic, positively charged and negatively charged are colored in yellow, blue, and red, respectively.
Mentions: The auto-inhibited structure of Merlin is also valuable for us to understand the mechanisms governing many human disease-related mutations identified in Merlin (39 and http://www.hgmd.org). All, except one (“Q178del”), of the 12 mutations found in the F2 and F3 lobes are expected to cause folding defects of the FERM domain (Figure 2E and 2F, labeled in red), and thus impair Merlin's function (see40 for detailed discussions of this category of Merlin mutations). Gln178 is located in the so-called “blue box” (BB) region, and mutation or deletion of the BB region is known to result in an over-proliferation phenotype in Drosophila41. In the closed Merlin structure, the BB region (residues176-183) directly contacts the loop between α1CTD and α2CTD (Figure 2D and 2E, and Supplementary information, Figure S3B). A shortened BB region resulted from the deletion of Gln178 may perturb a series of interactions between the α1CTD/α2CTD loop and the BB region (Supplementary information, Figure S3B), thus weakening the auto-inhibited conformation of Merlin. Counterintuitively, the BB mutant of Drosophila Merlin is known to be inactive in suppressing cell proliferation41, yet our structure-based analysis indicates that the mutant Merlin should adopt a more open conformation and thus more active in suppressing cell growth. This apparent contradiction can be nicely explained by the structure of Merlin-FERM in complex with Lats1/2 presented in the next section. The BB region of Merlin-FERM forms a large part of the Lats1/2-binding surface (Figure 3G). The deletion of the BB region is expected to weaken or disrupt Lats1/2 (or Wts in fly) binding capacity of Merlin, thus preventing Lats1/2 from phosphorylating YAP13.

Bottom Line: Phosphorylation of Ser518 outside the Merlin's auto-inhibitory tail does not obviously alter Merlin's conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation.Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation.Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong, China.

ABSTRACT
The tumor suppressor Merlin/NF2 functions upstream of the core Hippo pathway kinases Lats1/2 and Mst1/2, as well as the nuclear E3 ubiquitin ligase CRL4(DCAF1). Numerous mutations of Merlin have been identified in Neurofibromatosis type 2 and other cancer patients. Despite more than two decades of research, the upstream regulator of Merlin in the Hippo pathway remains unknown. Here we show by high-resolution crystal structures that the Lats1/2-binding site on the Merlin FERM domain is physically blocked by Merlin's auto-inhibitory tail. Angiomotin binding releases the auto-inhibition and promotes Merlin's binding to Lats1/2. Phosphorylation of Ser518 outside the Merlin's auto-inhibitory tail does not obviously alter Merlin's conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation. Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation. Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.

No MeSH data available.


Related in: MedlinePlus