Abstract
The adapter protein Lamellipodin (Lpd) plays an important role in cell migration. In particular, Lpd mediates lamellipodia formation by regulating actin dynamics via interacting with Ena/VASP proteins. Its RA-PH tandem domain configuration suggests that like its paralog RIAM, Lpd may also mediate particular Ras GTPase signaling. We determined the crystal structures of the Lpd RA-PH domains alone and with an N-terminal coiled-coil region (cc-RA-PH). These structures reveal that apart from the anticipated coiled-coil interaction, Lpd may also oligomerize through a second intermolecular contact site. We then validated both oligomerization interfaces in solution by mutagenesis. A fluorescence-polarization study demonstrated that Lpd binds phosphoinositol with low affinity. Based on our crystallographic and biochemical data, we propose that Lpd and RIAM serve diverse functions: Lpd plays a predominant role in regulating actin polymerization, and its function in mediating Ras GTPase signaling is largely suppressed compared to RIAM.
Original language | English |
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Pages (from-to) | 211-219 |
Number of pages | 9 |
Journal | Protein and Cell |
Volume | 4 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2013 |
Keywords
- Actins/metabolism
- Amino Acid Sequence
- Binding Sites
- Carrier Proteins/chemistry
- Crystallography, X-Ray
- Humans
- Membrane Proteins/chemistry
- Molecular Sequence Data
- Mutagenesis
- Phosphatidylinositols/metabolism
- Polymerization
- Protein Binding
- Protein Structure, Tertiary
- Recombinant Proteins/biosynthesis
- Signal Transduction
- ras Proteins/metabolism