RESUMO
TRPM3 channels play important roles in the detection of noxious heat and in inflammatory thermal hyperalgesia. The activity of these ion channels in somatosensory neurons is tightly regulated by µ-opioid receptors through the signaling of Gßγ proteins, thereby reducing TRPM3-mediated pain. We show here that Gßγ directly binds to a domain of 10 amino acids in TRPM3 and solve a cocrystal structure of this domain together with Gßγ. Using these data and mutational analysis of full-length proteins, we pinpoint three amino acids in TRPM3 and their interacting partners in Gß1 that are individually necessary for TRPM3 inhibition by Gßγ. The 10-amino-acid Gßγ-interacting domain in TRPM3 is subject to alternative splicing. Its inclusion in or exclusion from TRPM3 channel proteins therefore provides a mechanism for switching on or off the inhibitory action that Gßγ proteins exert on TRPM3 channels.
Assuntos
Subunidades beta da Proteína de Ligação ao GTP/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/farmacologia , Subunidades gama da Proteína de Ligação ao GTP/metabolismo , Subunidades gama da Proteína de Ligação ao GTP/farmacologia , Canais de Cátion TRPM/química , Canais de Cátion TRPM/efeitos dos fármacos , Canais de Cátion TRPM/metabolismo , Sítios de Ligação , Cálcio/metabolismo , Subunidades beta da Proteína de Ligação ao GTP/química , Subunidades gama da Proteína de Ligação ao GTP/química , Células HEK293 , Humanos , Hiperalgesia/metabolismo , Modelos Moleculares , Mutação , Neurônios/metabolismo , Dor/metabolismo , Receptores Opioides/metabolismo , Canais de Cátion TRPM/genéticaRESUMO
Opioids, agonists of µ-opioid receptors (µORs), are the strongest pain killers clinically available. Their action includes a strong central component, which also causes important adverse effects. However, µORs are also found on the peripheral endings of nociceptors and their activation there produces meaningful analgesia. The cellular mechanisms downstream of peripheral µORs are not well understood. Here, we show in neurons of murine dorsal root ganglia that pro-nociceptive TRPM3 channels, present in the peripheral parts of nociceptors, are strongly inhibited by µOR activation, much more than other TRP channels in the same compartment, like TRPV1 and TRPA1. Inhibition of TRPM3 channels occurs via a short signaling cascade involving Gßγ proteins, which form a complex with TRPM3. Accordingly, activation of peripheral µORs in vivo strongly attenuates TRPM3-dependent pain. Our data establish TRPM3 inhibition as important consequence of peripheral µOR activation indicating that pharmacologically antagonizing TRPM3 may be a useful analgesic strategy.
