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Merlin phosphorylation by p21-activated kinase 2 and effects of phosphorylation on merlin localization
Joseph L Kissil1, Kristen C Johnson, Matthew S Eckman
1Department of Biology and Center for Cancer Research and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Abstract:
The Nf2 tumor suppressor gene product merlin is related to the membrane-cytoskeleton linker proteins of the band 4.1 superfamily, including ezrin, radixin, and moesin (ERMs). Merlin is regulated by phosphorylation in a Rac/cdc42-dependent fashion. We report that the phosphorylation of merlin at serine 518 is induced by the p21-activated kinase PAK2. This is demonstrated by biochemical fractionation, use of active and dominant-negative mutants of PAK2, and immunodepletion. By using wild-type and mutated forms of merlin and phospho-directed antibodies, we show that phosphorylation of merlin at serine 518 leads to dramatic protein relocalization.
Insights
The Nf2 tumor suppressor merlin protein
Area of Science:
- Cell biology
- Molecular biology
- Biochemistry
Background:
- Merlin (the Nf2 tumor suppressor gene product) is linked to membrane-cytoskeleton proteins like ezrin, radixin, and moesin (ERMs).
- Merlin's activity is controlled by phosphorylation, influenced by Rac/cdc42 signaling pathways.
Purpose of the Study:
- To investigate the specific kinase responsible for merlin phosphorylation at serine 518.
- To determine the functional consequences of merlin phosphorylation at serine 518.
Main Methods:
- Biochemical fractionation
- Utilizing active and dominant-negative mutants of p21-activated kinase 2 (PAK2)
- Immunodepletion assays
- Employing wild-type and mutated merlin forms
- Using phospho-specific antibodies
Main Results:
- p21-activated kinase 2 (PAK2) was identified as the kinase that induces merlin phosphorylation at serine 518.
- Phosphorylation of merlin at serine 518 results in significant changes in its cellular localization.
- These findings were validated through various biochemical and genetic approaches.
Conclusions:
- PAK2-mediated phosphorylation of merlin at serine 518 is a key regulatory event.
- This phosphorylation event triggers merlin's relocalization within the cell, impacting its function.
- Understanding this mechanism is crucial for comprehending Nf2-related tumor suppression and cell signaling.