title: Interactions of disulfide-deficient selenocysteine analogs of μ-conotoxin BuIIIB with the α-subunit of the voltage-gated sodium channel subtype 1.3.
abstract: Inhibitors of the α-subunit of the voltage-gated sodium channel subtype 1.3 (NaV 1.3) are of interest as pharmacological tools for the study of neuropathic pain associated with spinal cord injury and have potential therapeutic applications. The recently described μ-conotoxin BuIIIB (μ-BuIIIB) from Conus bullatus was shown to block NaV 1.3 with submicromolar potency (Kd = 0.2 μm), making it one of the most potent peptidic inhibitors of this subtype described to date. However, oxidative folding of μ-BuIIIB results in numerous folding isoforms, making it difficult to obtain sufficient quantities of the active form of the peptide for detailed structure-activity studies. In the present study, we report the synthesis and characterization of μ-BuIIIB analogs incorporating a disulfide-deficient, diselenide-containing scaffold designed to simplify synthesis and facilitate structure-activity studies directed at identifying amino acid residues involved in NaV 1.3 blockade. Our results indicate that, similar to other μ-conotoxins, the C-terminal residues (Trp16, Arg18 and His20) are most crucial for NaV 1 blockade. At the N-terminus, replacement of Glu3 by Ala resulted in an analog with an increased potency for NaV 1.3 (Kd = 0.07 μm), implicating this position as a potential site for modification for increased potency and/or selectivity. Further examination of this position showed that increased negative charge, through γ-carboxyglutamate replacement, decreased potency (Kd = 0.33 μm), whereas replacement with positively-charged 2,4-diamonobutyric acid increased potency (Kd = 0.036 μm). These results provide a foundation for the design and synthesis of μ-BuIIIB-based analogs with increased potency against NaV 1.3.
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia; Department of Medicinal Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT, USA.
authors.forename: Brad R
authors.initials: BR
authors.lastname: Green
authors.forename: Min-Min
authors.initials: MM
authors.lastname: Zhang
authors.forename: Sandeep
authors.initials: S
authors.lastname: Chhabra
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Robinson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wilson
authors.forename: Addison
authors.initials: A
authors.lastname: Redding
authors.forename: Baldomero M
authors.initials: BM
authors.lastname: Olivera
authors.forename: Doju
authors.initials: D
authors.lastname: Yoshikami
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bulaj
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000700:Analgesics / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D020916:Conotoxins / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D003553:Cystine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D062552:NAV1.3 Voltage-Gated Sodium Channel / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017279:Selenocysteine / Q000737:chemistry*; D013329:Structure-Activity Relationship; D061567:Voltage-Gated Sodium Channel Blockers / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D000700:Analgesics; D020916:Conotoxins; D062552:NAV1.3 Voltage-Gated Sodium Channel; D061567:Voltage-Gated Sodium Channel Blockers; D017279:Selenocysteine; D003553:Cystine
keywords: conotoxin; disulfide; neuropathic pain; selenocysteine; voltage-gated sodium channel