Eligible Student Poster 49th Lorne Conference on Protein Structure and Function 2024

Developing nanobodies as subtype-selective α1A adrenergic receptor tools  (#154)

Yiling Yu 1 , Saund Yadanar 1 , Feng-jie Wu 1 2 , Eddy Yang 1 , Lisa Williams 1 , Riley Cridge 1 , Daniel Scott 1 , Christopher Draper-Joyce 1
  1. The Florey, Parkville, Victoria, Australia
  2. Biozentrum, University of Basel, Basel, Switzerland

The α1-adrenergic receptors (α1-ARs) are a family of Class A G protein-coupled receptors (GPCRs) that play an essential role in mediating the physiological function of noradrenaline through the sympathetic nervous system. The lack of subtype-selective tools for the three subtypes of the α1-AR family (α1A, α1B and α1D) has long been a bottleneck to studying and understanding their specific roles and distribution. Consequently, this lack of selective tools has hindered the validation of the therapeutic potential of the α1-AR family. Further, the α1A- and α1B- subtypes are proposed to mediate opposing pathophysiological effects in cardiovascular and CNS indications. We have used combined structural biology and antibody discovery workflows to address this shortfall by identifying α1A-adrenoceptor subtype-selective heavy-chain antibody fragments (nanobodies).

Here, we report approaches to isolate a panel of subtype-selective α1A-adrenoceptor nanobodies that recognise therapeutically relevant epitopes on the extracellular solvent's accessible binding pocket. A representative nanobody (Nb#9) has been extensively pharmacologically characterised and demonstrates high-affinity and functional antagonism. Further, by solving the cryo-EM structure of Nb#9 bound to the α1A-AR we have shown it achieves this functional effect by CDR3 engaging with the drug binding pocket and the other CDRs making extensive contacts across the extracellular loops of the receptor. These nanobodies represent the first subtype selective antibodies for a Class A GPCR and will be valuable tools in studying the specific biology of α1A-AR.

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