9huo
A01 mAbs bound to cobratoxin at pH 5.5
Structural highlights
Function3L21_NAJKA Monomer: binds with high affinity to muscular (alpha-1-beta-1-gamma-delta/CHRNA1-CHRNB1-CHRNG-CHRND) nAChR (tested on Torpedo californica, Kd=0.2-4.5 nM) and neuronal alpha-7/CHRNA7 nicotinic acetylcholine receptors (Kd=13-105 nM) (PubMed:18381281, PubMed:22223648, PubMed:9305882). Also inhibits GABA(A) channels (PubMed:26221036). Heteropentamer targets studied are composed of alpha-1-beta-3-gamma-2 (GABRA1-GABRB3-GABRG2) subunits (IC(50)=236 nM), alpha-1-beta-2-gamma-2 (GABRA1-GABRB2-GABRG2) subunits (IC(50)=469 nM), alpha-2-beta-2-gamma-2 (GABRA2-GABRB2-GABRG2) subunits (IC(50)=485 nM), alpha-5-beta-3-gamma-2 (GABRA5-GABRB3-GABRG2) subunits (IC(50)=635 nM), and alpha-2-beta-3-gamma-2 (GABRA2-GABRB3-GABRG2) subunits (IC(50)=1099 nM) (activated by 10 uM GABA) (PubMed:26221036).[1] [2] [3] [4] Homodimer: binds with high affinity (but lower than the monomeric form) to muscular (IC(50)=9.7 nM) and with low affinity to neuronal alpha-7/CHRNA7 nAChRs (IC(50)=1370 nM) (PubMed:22223648). However, it acquires (compared to the monomeric form) the capacity to block alpha-3/beta-2 (CHRNA3/CHRNB2) nAChRs (PubMed:18381281).[5] [6] Heterodimer with cytotoxin 3 (AC P01446): is slightly more active than the homodimer in inhibiting alpha-7/CHRNA7 nAChR and is considerably more active in blocking the alpha-3-beta-2/CHRNA3-CHRNB2 nAChR.[7] Publication Abstract from PubMedAntibodies that bind in a pH-dependent manner to their antigens show promise for enhanced neutralization potency and blocking capacity against extracellular targets. However, because the mechanisms governing pH-dependent antigen binding remain poorly understood, engineering approaches are often limited to incorporating histidine residues in the antibody complementarity-determining regions. Here, we use a panel of human monoclonal antibodies with neutralizing activity to long-chain alpha-neurotoxins (LNTxs) to investigate pH-dependent antigen binding. The antibodies vary in their light chains but have conserved histidine residues in their variable domains, allowing us to explore how other residues may affect pH dependence. Comparative structural and molecular dynamics studies between two antibodies with and without pH-dependent antigen-binding properties reveal that both antibodies neutralize LNTxs by mimicking LNTx-receptor interactions through their heavy chains. We hypothesize that part of the pH-dependency can be controlled by the light chain through modulation of water access to residues at the heavy-light-chain interface. We show that pH-dependent antigen-binding properties can be introduced into monoclonal antibodies through the substitution of selected residues at the heavy-light-chain interface. Specifically, we replaced tyrosine residues in the light chain with small polar and apolar amino acid residues in a structurally related anti-LNTx antibody with limited inherent pH-dependent antigen-binding properties, and found that these smaller substitutions enhanced pH-dependence more effectively than histidine substitutions alone. Our findings suggest a strategy for engineering pH-dependent antigen binding in antibodies that goes beyond the exclusive use of histidine doping. Rational design of antibodies with pH-dependent antigen-binding properties using structural insights from broadly neutralizing antibodies against alpha-neurotoxins.,Wade J, Strancar N, Fernandez-Quintero ML, Siebenhaar S, Jansen T, Meier EPW, Jenkins TP, Bjorn SP, Nguyen GTT, Lomonte B, Gutierrez JM, Sorensen CV, Loeffler JR, Paul A, Tulika T, Arnsdorf J, Schoffelen S, Lundquist EVS, Sorensen J, Ward AB, Voldborg BG, Bohn MF, Rivera-de-Torre E, Morth JP, Laustsen AH MAbs. 2025 Dec;17(1):2553624. doi: 10.1080/19420862.2025.2553624. Epub 2025 Sep , 11. PMID:40936197[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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