Project Details
Projekt
Particle–Based Modulation, Signaling Properties and Function of GPR133 (ADGRD1) in Glioblastoma Cells
Applicant
Gabriele Stephan
Subject Area
Pharmacology
Term
from 2019 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 422420339
As a member of the family of adhesion G protein-coupled receptors (aGPCRs), GPR133 is involved in numerous physiological processes. To date, it is known that GPR133 is not present in normal brain tissue but is de novo expressed in glioblastoma (GBM), an aggressive and treatment-resistant brain malignancy, where it promotes tumor growth. This underlines the importance of understanding the receptor’s mode of action. A few studies have produced initial insights to GPR133 canonical signaling, which suggests the coupling to Gs or Gi proteins leading to activation or inhibition of adenylate cyclase and subsequent increase or decrease of cAMP levels, respectively. The extracellular domain of GPR133 harbors a tethered agonist sequence referred to as the Stachel sequence. Peptides derived from this sequence were shown to modulate GPR133 activity. However, the hydrophobic nature, promiscuity and low potency limit their use. Hence, new tools are necessary for specific modulation of GPR133 activity and detailed characterization of GPR133 signaling.There is preliminary data suggesting mechanical stimuli modulate GPR133 function. The overall aim of this project is to test this hypothesis by pharmacological as well as biochemical approaches. Therefore, mechanical modulation of GPR133 activity by antibody-conjugated particles and magnetic forces will be characterized in a heterologous overexpression system and subsequently tested in GBM cells. This includes further elucidation of receptor coupling to Gs or Gi proteins under different conditions by analyzing the accumulation of the respective second messengers. Taking GPR133-mediated cAMP modulation into consideration, putative cAMP effectors will be identified by FRET-based approches in GBM cells. This would give further insights into downstream signaling cascades after receptor activation. The effects of GPR133 modulation by antibody-conjugated beads or the Stachel peptide on tumor-associated processes, such as proliferation, migration and colony formation will be analyzed in GBM cells. Future tasks include the testing of GPR133’s effectiveness, as informed by the proposed in vitro experiments, in an in vivo tumor xenograft model.Taken together, this project will elucidate GPR133 signaling mechanisms in relation to GBM growth. Insights from the proposed experiments will be applicable not only to GBM, but also to other biological systems. Furthermore, elucidation of GPR133 signaling is also likely to generate novel therapeutic approaches in GBM, and possibly other malignancies where GPR133 is relevant.
DFG Programme
Research Fellowships
International Connection
USA
