Integral membrane proteins are important drug targets, and monoclonal antibodies (mAbs) against them are highly sought for therapeutic and diagnostic purposes. However, the complex structure of multipass membrane proteins makes discovery of these mAbs particularly challenging. By employing strategies such as sequential immunization with DNA (prime) and virus-like particles (boost), and using divergent species (chickens) as immunization hosts, we routinely isolate diverse panels of mAbs against structurally complex and highly conserved membrane protein targets. Here, we report the isolation and characterization of mAbs recognizing two distinct metabolically relevant targets: the 12-transmembrane insulin-responsive glucose transporter GLUT4 and the 7-transmembrane GPCR cannabinoid receptor-1 (CB1).
In both cases, we isolated diverse panels of mAbs against native conformational epitopes. Affinities ranged from 2.6 nM (anti-CB1 IM-102) to 1 pM (anti-GLUT4 LM048). Two anti-GLUT4 mAbs discriminated between inward-open and outward-open conformational states, including one mAb (LM048) that inhibited transporter function. Similarly, we isolated several anti-CB1 mAbs that antagonized CB1-mediated calcium flux. Lead mAbs were confirmed to be specific for their target proteins, based on reactivity profiling in the Membrane Proteome Array of >5,600 human membrane proteins. Identified mAbs represent novel and valuable molecular tools for understanding and potentially treating common metabolic diseases, such as type 2 diabetes mellitus and nonalcoholic steatohepatitis/fatty liver disease (NASH/NAFLD). Furthermore, the technologies underpinning their discovery can be rapidly and routinely employed to facilitate discovery of mAbs against other therapeutically relevant membrane protein targets.
D. Tucker: None. T. Charpentier: None. N. Molino: None. E. Rosenberg: None. B. Screnci: None. L.J. Stafford: None. C. Sulli: None. R. Chambers: None. B.J. Doranz: None. J.B. Rucker: None.
National Institutes of Health