Date: Sunday, June 2, 2019
Session Time: 4:30pm-6:00pm
Presentation Time: 4:54pm-5:06pm
Location: Room 309
*Purpose: Endothelin-1 type A receptor (ETAR) exhibits multiligand binding abilities and may signal upon natural ligand Endothelin-1 (ET-1) and non-HLA ETAR-agonistic IgG (ETAR-IgG)-mediated stimulation similar to AT1R-IgG. Development of high-resolution methods allows for structural-functional relationship studies of specific receptor modules involved in the receptor activation. Elucidation of ETAR activation mechanisms could have broad clinical relevance for vascular transplant pathologies across whole spectrum of solid organ Transplantation.
*Methods: To distinguish the activation mediated by the natural ligand or the agonistic antibodies, we developed a GPCR activation assay relying on solely expressed human ETAR in yeasts and signalling reporter assays for down-stream effectors in mammalian cells. ETAR activation was induced by either by natural ligand, ET-1 or by ETAR-IgG isolated from patients with vascular pathology.
*Results: Both, ET-1 and ETAR-IgG triggered a dose-dependent activation. ETAR-IgG induced a stronger activation of the receptor than ET-1, implicating their high biologic potency. ETAR antagonist blocked completely ETAR activation induced by ET-1, but only partially ETAR activation mediated by the IgG isolated from patients. Intact first (ECL1) or second extracellular loop (ECL2) were instrumental for G12/13 signalling. ECL3 mutation led to a constitutive activation of the receptor. Deletion of the N-terminal part of the receptor showed that this domain is involved in the receptor activation mediated by ETAR-IgG. We successfully created models allowing for structural and functional studies of molecular architecture modules appreciating ETAR receptor plasticity, which helped us to define the role of the specific extracellular domains.
*Conclusions: ETAR exhibit unique mode of GPCR targeting that differs from the similar AT1R-IgG. Better understanding of the molecular mechanisms responsible for ETAR activation holds great potential for refining mechanisms of rejection and more precise diagnostic and therapeutic developments.
To cite this abstract in AMA style:Philippe A, Catar R, Scheerer P, Szczepek M, Dragun D. Solving Target Recognition and Activation Mediated by Non-HLA Agonistic Antibodies Targeting ETAR [abstract]. Am J Transplant. 2019; 19 (suppl 3). https://atcmeetingabstracts.com/abstract/solving-target-recognition-and-activation-mediated-by-non-hla-agonistic-antibodies-targeting-etar/. Accessed September 19, 2020.
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