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

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The tumor suppressor Merlin/NF2 is crucial in the Hippo pathway, regulating cell proliferation and organ size.
• Merlin's upstream regulation within the Hippo pathway has remained elusive despite extensive research.
• Merlin mutations are linked to Neurofibromatosis type 2 and various cancers.

Purpose of the Study:

• To elucidate the upstream regulatory mechanism of Merlin in the Hippo signaling pathway.
• To determine how angiomotin interacts with Merlin and influences Hippo pathway activation.
• To investigate the impact of cancer-associated Merlin mutations on its regulation.

Main Methods:

• High-resolution crystal structure analysis to visualize protein interactions.
• Biochemical assays to assess protein binding and kinase activation.
• Analysis of cancer-associated Merlin mutations in the context of angiomotin binding.

Main Results:

• The Lats1/2-binding site on Merlin is auto-inhibited by its tail.
• Angiomotin binding to Merlin releases this auto-inhibition, facilitating Merlin's interaction with Lats1/2.
• Phosphorylation at Ser518 inhibits angiomotin binding, thereby blocking Hippo pathway activation.
• Cancer mutations in the angiomotin-binding domain disrupt Merlin activation by angiomotin.

Conclusions:

• Angiomotin acts as a key upstream regulator, linking cortical actin to the core Hippo kinase cascade via Merlin.
• This study provides a mechanistic understanding of Merlin regulation and its role in Hippo signaling.
• The findings offer insights into cancer development driven by Merlin mutations and suggest potential therapeutic targets.