Project 06

VLGR1 signaling at focal adhesions and ICD release as a non-canonical signaling pathway of aGPCRs 

Uwe Wolfrum, University of Mainz

Team members
Barbara Knapp
Farina Eich
Jens Rödig
Heiko Rödig

Project Description
VLGR1 (very large G protein-coupled receptor-1), also known as ADGRV1, GPR98 and MASS is by far the largest adhesion GPCR (aGPCR). Although VLGR1 expression is almost ubiquitous, it is highly concentrated in the nervous system. Mutations in the human VLGR1 gene cause the human Usher syndrome (USH), the most common form of hereditary deaf-blindness. In addition, there is growing evidence that defects in VLGR1 are also associated with epilepsy. So far, little is known about its dual function in membrane-membrane adhesion and signaling. In the current funding period, we identified interaction partners and protein clusters related to VLGR1, and to several other aGPCRs by applying affinity proteomics (tandem affinity purifications (TAPs) in combination with mass spec). Bioinformatics analyses of the interactomes of these aGPCRs have defined Gene Ontology (GO) terms and cell modules related to putative aGPCR function.

For the second grant period, we have selected specific functional modules for further evaluation and in-depth characterization of their signaling function for VLGR1 and for aGPCRs. (1) We will elucidate the role of VLGR1 in focal adhesions (FAs) which act as signaling hubs between the ECM and the actin cytoskeleton essential for cell outgrowth and migration. We will test VLGR1´s contribution to the spatial and temporal control of FA turnover, the regulation of cell migration and the modulation of the cytoskeleton using divers VLGR1 deficient cellular models including different types of neural cell.
(2) We will decipher the interaction of VLGR1 and other aGPCRs with the gamma-secretase complex as a common non-canonical aGPCR signaling pathway. For this, we will test whether aGPCRs are substrates of the gamma-secretase and how their intracellular domains (ICDs) are released into the cytoplasm. Furthermore, we will evaluate nuclear functions of aGPCRs.
We are certain that our results will help to understand how aGPCRs work. We also hope to gain new insights into the pathomechanisms of diseases associated with the dysfunction of aGPCRs and see opportunities to identify new therapeutic targets for the treatment of these diseases.