Poulsen, M. H.; Ritter, N.; Maurya, S.; Xue, F.; Haider, S. S.; Usher, S. G.; Heusser, S. A.; Chua, H. C.; Fisker-Andersen, J.; Kickinger, S.; Schramek, D.; Wellendorph, P.; Lundby, A.; Pless, S. A.

Proton-mediated activation of acid-sensing ion channel 1a (ASIC1a) leads to influx of sodium and, to a lesser extent, calcium, followed by rapid and complete desensitization. However, various ASIC1a-expressing cell types display atypical proton-induced currents characterized by altered proton sensitivity and slow and incomplete desensitization. The origin of this functional diversity and its physiological relevance remain unclear. Here, we show that the monocarboxylate transporter 1 (MCT1) interacts with ASIC1a, leading to subtype-specific modulation of proton sensitivity and desensitization. We delineate the molecular mechanism of the ASIC1a-MCT1 coupling and find that the presence of MCT1 is required for the distinct ASIC1a-mediated currents observed in glioblastoma cells, the most lethal brain cancer in adults. Strikingly, presence of ASIC1a together with MCT1 significantly prolongs the lifespan of mice intracranially injected with glioblastoma cells. We thus uncover the basis for altered ASIC1a function in glioblastoma and highlight the importance of deciphering the cell-type specific ASIC1a interactome.