Structure and analysis of nanobody binding to the human ASIC1a ion channel

ASIC1a is a proton-gated sodium channel involved in modulation of pain, fear, addiction, and ischemia-induced neuronal injury. We report isolation and characterization of alpaca-derived nanobodies (Nbs) that specifically target human ASIC1a. Cryo-electron microscopy of the human ASIC1a channel at pH 7.4 in complex with one of these, Nb.C1, yielded a structure at 2.9 Å resolution. It is revealed that Nb.C1 binds to a site overlapping with that of the Texas coral snake toxin (MitTx1) and the black mamba venom Mambalgin-1; however, the Nb.C1-binding site does not overlap with that of the inhibitory tarantula toxin psalmotoxin-1 (PcTx1). Fusion of Nb.C1 with PcTx1 in a single polypeptide markedly enhances the potency of PcTx1, whereas competition of Nb.C1 and MitTx1 for binding reduces channel activation by the toxin. Thus, Nb.C1 is a molecular tool for biochemical and structural studies of hASIC1a; a potential antidote to the pain-inducing component of coral snake bite; and a candidate to potentiate PcTx1-mediated inhibition of hASIC1a in vivo for therapeutic applications.

Structural insights into human acid-sensing ion channel 1a inhibition by snake toxin mambalgin1

Acid-sensing ion channels (ASICs) are proton-gated cation channels that are involved in diverse neuronal processes including pain sensing. The peptide toxin Mambalgin1 (Mamba1) from black mamba snake venom can reversibly inhibit the conductance of ASICs, causing an analgesic effect. However, the detailed mechanism by which Mamba1 inhibits ASIC1s, especially how Mamba1 binding to the extracellular domain affects the conformational changes of the transmembrane domain of ASICs remains elusive. Here, we present single-particle cryo-EM structures of human ASIC1a (hASIC1a) and the hASIC1a-Mamba1 complex at resolutions of 3.56 and 3.90 Å, respectively. The structures revealed the inhibited conformation of hASIC1a upon Mamba1 binding. The combination of the structural and physiological data indicates that Mamba1 preferentially binds hASIC1a in a closed state and reduces the proton sensitivity of the channel, representing a closed-state trapping mechanism.

Effect of Snake Venom Metalloprotease Desintegrin in Hepatocarcinoma Tumor Cells

Hepatocellular carcinoma is the third leading cause of cancer-related death in the world. This cancer is associated with cirrhosis following the hepatitis B or C virus infection, alcohol addiction, metabolic liver disease and exposure to dietary toxins such as aflatoxins and aristolochic acid. Studies demonstrate the integration of the HBV genome into liver cell DNA, including cases of patients with HBV-negative serology. Despite advances in prevention techniques, screening, and technology in cancer diagnosis and treatments, the incidence and mortality remain worrisome. Therefore, this research is significant due to the contribution of the development of new biological agents that can be used as monotherapy or adjuvant chemotherapy. Jararhagin, a snake toxin isolated from Bothrops jararaca venom, has been the subject of many studies seeking alternatives for the treatment of cancer. This protein contains the cysteine-rich disintegrin-like metalloproteinase domains and desirable functions to combat tumor cells, such as promoting acute inflammation, damaging the vascular endothelium through the zinc-dependent catalytic domain (responsible for hemorrhagic function) and enzymatically degrading the constituents of the endothelial basement membrane. Due to the antitumor effects of jararhagin presented in previous research, this study aimed to describe the possible antitumor effects of this snake metalloprotease in the murine liver tumor, intending to propose a new therapeutic option in the human liver tumor.