Wnt Signaling from the Plasma Membrane

The Wnt-dependent, b-catenin-independent pathway modulates cell movement and behavior. A downstream regulator of this signaling pathway is Dishevelled (Dvl), which among other multiple interactions, binds to the Frizzled receptor and the plasma membrane via phosphatidic acid (PA) in a mechanism proposed to be pH dependent. While the Dvl DEP domain is central to the b-catenin-independent Wnt signaling function, the mechanism underlying its physical interaction with the membrane remains elusive. Dvl proteins are modular, having DIX, PDZ, and DEP domains. The DEP domain has previously been reported to facilitate plasma membrane interaction of Dvl, which occurs by binding to acidic phospholipids with a preference for phosphatidic acid (PA). We defined the structural and functional basis of PA recognition by the Dvl2 DEP domain. By obtaining the backbone resonance assignments of the NMR spectrum of the Dvl2 DEP domain, we were able to identify chemical shift perturbations induced by the phospholipid. Combining these data with tryptophan fluorescence, molecular dynamics simulations, circular dichroism, and site-directed mutagenesis, we were able to identify the PA-interacting region as well as other regions of the proteins that underwent local conformational changes upon PA binding. We also established that PA binding by the Dvl2 DEP domain was pH-dependent and resembled the mechanism of PA deprotonation. We propose that an incremental change in the local pH at the membrane would not only favor PA deprotonation but also the presence of positive charges in the PA-binding region of the Dvl2 DEP domain. This project is in collaboration with Drs. Carla Finkielstein and Dave Bevan (Virginia Tech).

 

 

 

 

Daniel G. S. Capelluto
Associate Professor
Biological Sciences Department
Virginia Bioinformatics Institute 263C
1015 Life Science Circle
Blacksburg, VA 24061-0477
E-mail: capellut@vt.edu
Phone: (540) 231-0974

College of Science

 

 

Department of Biological Sciences
2125 Derring Hall
Mail Code 0406
Virginia Tech
Blacksburg, VA 24061-0406
Phone: (540) 231-8930
Fax: (540) 231-9307

Last update 31 May 2017