RESUMO
ATP-sensitive potassium channels (K) are energy sensors on the plasma membrane. By sensing the intracellular ADP/ATP ratio of β-cells, pancreatic K channels control insulin release and regulate metabolism at the whole body level. They are implicated in many metabolic disorders and diseases and are therefore important drug targets. Here, we present three structures of pancreatic K channels solved by cryo-electron microscopy (cryo-EM), at resolutions ranging from 4.1 to 4.5 Å. These structures depict the binding site of the antidiabetic drug glibenclamide, indicate how Kir6.2 (inward-rectifying potassium channel 6.2) N-terminus participates in the coupling between the peripheral SUR1 (sulfonylurea receptor 1) subunit and the central Kir6.2 channel, reveal the binding mode of activating nucleotides, and suggest the mechanism of how Mg-ADP binding on nucleotide binding domains (NBDs) drives a conformational change of the SUR1 subunit.
Assuntos
Animais , Camundongos , Trifosfato de Adenosina , Metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Microscopia Crioeletrônica , Ligantes , Mesocricetus , Modelos Moleculares , Nucleotídeos , Metabolismo , Pâncreas , Metabolismo , Canais de Potássio Corretores do Fluxo de Internalização , Química , Metabolismo , Ligação Proteica , Multimerização Proteica , Estrutura Quaternária de Proteína , Subunidades Proteicas , Química , Metabolismo , Células Sf9 , Spodoptera , Receptores de Sulfonilureias , Química , MetabolismoRESUMO
Objective: To observe the immunoreactive changes of P2X, receptor and examine P2X3 receptor mRNA level in the dorsal root ganglia (DRG) in a rat model of bone cancer pain. Methods: Sixty fernale Wistar rats, weighing 150-200 g, were randomly allocated to three groups (n=20 each): group CP (cancer pain) received intra-tibial injection of Syngeneic Walker 256 mammary gland carcinoma cells (2 × 105), group S received intra-tibial injection of equal volume 0.9% sodium chloride, and group C received blank control. Mechanical allodynia and thermal hyperalgesia tests were taken on 4, 7, 10, 14, 17, and 21 days after inoculation. On day 14 and 21, ten rats of each group were chosen for either immunohistochemistry or real-time RT-PCR to examine the changes of P2X2 receptor and mRNA. Results: The rats in group CP began to display hyperalgesia on day 10 and the pain became most obvious between day 14 and 21. Immunohistochemistry showed that the proportion of DRG neurons positive of P2X3 receptor in group CP was significantly increased on 14 and 21 d(P<0.05), and RT-PCR showed that the expression of P2X3 receptor mRNA was also significantly increased. Conclusion: These results suggest that our rat model of bone cancer pain has hyperalgesia, which might be related to the increase of P2X3 receptor expression.