Nanobody-boosted human ASIC1a endocytosis alleviates chronic pain and anxiety-like behaviours.

Chronic pain is frequently accompanied by affective disturbances, yet existing analgesics provide limited efficacy and raise substantial safety concerns. The proton-gated ion channel ASIC1a contributes to nociceptive sensitisation and affective pain processing, but the lack of tools that selectively target human ASIC1a has hindered translational progress. Here, we identify a nanobody that selectively recognises human ASIC1a and enhances its endocytosis, thereby reducing surface channel availability and suppressing proton-evoked currents. Using a humanised ASIC1a knock-in mouse model, we combine molecular, electrophysiological, and behavioural approaches to dissect the functional consequences of human ASIC1a modulation in vivo. We show that human ASIC1a expressed in both the anterior cingulate cortex and peripheral nociceptors contributes to inflammatory hypersensitivity and anxiety-like behaviours in chronic pain. Targeted adeno-associated virus-mediated expression of the nanobody in the anterior cingulate cortex, as well as local peripheral delivery of purified nanobody protein, produces analgesic effects accompanied by improvements in affective behaviour. These findings define a trafficking-based mode of human ASIC1a regulation that can be selectively engaged by nanobody binding, supporting nanobody-mediated modulation of human ASIC1a as a translationally tractable strategy for rebalancing the sensory and emotional dimensions of chronic pain.