Mycobacterium ulcerans, the etiological agent of Buruli ulcer, causes extensive skin lesions, which despite their severity are not accompanied by pain. It was previously thought that this remarkable analgesia is ensured by direct nerve cell destruction. We demonstrate here that M. ulcerans-induced hypoesthesia is instead achieved through a specific neurological pathway triggered by the secreted mycobacterial polyketide mycolactone. We decipher this pathway at the molecular level, showing that mycolactone elicits signaling through type 2 angiotensin II receptors (AT2Rs), leading to potassium-dependent hyperpolarization of neurons. We further validate the physiological relevance of this mechanism with in vivo studies of pain sensitivity in mice infected with M. ulcerans, following the disruption of the identified pathway. Our findings shed new light on molecular mechanisms evolved by natural systems for the induction of very effective analgesia, opening up the prospect of new families of analgesics derived from such systems.

Mechanosensitive K ؉ channels TREK1 and TREK2 form a subclass of two P-domain K ؉ channels. They are potently activated by polyunsaturated fatty acids and are involved in neuroprotection, anesthesia, and pain perception. Here, we show that acidification of the extracellular medium strongly inhibits TREK1 with an apparent pK near to 7.4 corresponding to the physiological pH. The all-ornone effect of pH variation is steep and is observed within one pH unit. TREK2 is not inhibited but activated by acidification within the same range of pH, despite its close homology with TREK1. A single conserved residue, H126 in TREK1 and H151 in TREK2, is involved in proton sensing. This histidine is located in the M1P1 extracellular loop preceding the first P domain. The differential effect of acidification, that is, activation for TREK2 and inhibition for TREK1, involves other residues located in the P2M4 loop, linking the second P domain and the fourth membrane-spanning segment. Structural modeling of TREK1 and TREK2 and site-directed mutagenesis strongly suggest that attraction or repulsion between the protonated side chain of histidine and closely located negatively or positively charged residues in P2M4 control outer gating of these channels. The differential sensitivity of TREK1 and TREK2 to external pH variations discriminates between these two K ؉ channels that otherwise share the same regulations by physical and chemical stimuli, and by hormones and neurotransmitters.ion channel ͉ mutagenesis ͉ structural modeling T REK1 and TREK2 are two pore-domain K ϩ (K 2P ) channels sharing 78% of sequence homology (1-3). They are expressed in large amount in the nervous system (1, 3). In mouse brain, they display both overlapping and distinct distributions (4). TREK1 is highly expressed in the striatum and the cortex and TREK2 in the cerebellar granule cell layer. The two channels are detected in the hippocampus. Unlike other K 2P channels like the TASK channels, TREK1 and TREK2 are not very active at room temperature, but can be stimulated by a wide range of stimuli, including mechanical stretch (5), cell swelling (5), intracellular acidification (6, 7), heat (8, 9), lysophospholipids (10), and polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA) (5), and by pharmacological agents such as volatile anesthetics (1, 11) and riluzole (12), a drug used to protect motoneurons in amyotrophic lateral sclerosis. Both TREK1 and TREK2 are inhibited by neurotransmitters and hormones that activate protein kinase A and C pathways resulting in phosphorylation of conserved residues in their cytoplasmic C-ter (5, 13, 14). TREK1 and TREK2 also share interacting partners in the brain (15,16). A kinase anchoring protein (AKAP) 150 is one of them. By binding to a major regulatory site of the TREK channels, AKAP150 transforms low activity outwardly rectifying channels into robust leak channels that become largely insensitive to AA, stretch, and internal acidification. Inhibition by Gs-coupled receptors is conserved but inhibition by Gq-co...