Insertion-trigger residues differentially modulate endosomal escape by cytotoxic necrotizing factor toxins

Abstract

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Hierarchical determinants in cytotoxic necrotizing factor (CNF) toxins driving Rho G-protein deamidation versus transglutamination

“…2B . These two positions were previously shown to be productive joining sites among the CNF1, CNF2, CNF3, and CNFy proteins ( 28 , 29 ). As shown in Fig.…”

“…Because CNF1 action results in constitutive activation of Rho GTPases and their downstream signaling pathways, the potential role of CNF1 in cancer progression has been noted ( 17 – 22 ). On the other hand, CNF1 has been explored as a Rho-protein modulator or biologic cargo-delivery system for a number of diverse applications ( 1 , 23 ), including serving as a vaccine adjuvant ( 24 – 26 ), a bacterial toxin-inspired drug delivery (BTIDD) platform ( 27 – 29 ), a therapeutic tool for pain control ( 30 ), and an antineoplastic agent for brain tumors ( 31 – 34 ). CNF1 has also been tested for use in neurodegenerative therapy ( 35 – 38 ) and in learning and memory enhancement ( 36 , 39 , 40 ).…”

“…The modular interchangeability of the Gln-deamidase cargo and cargo-delivery domains of the CNF1, CNF2, CNF3, and CNFy variants has been demonstrated and exploited to gain insights regarding the protein determinants that define both the efficacy of cytosolic delivery of cargo and the subsequent intracellular activity ( 29 ). In previous studies, comparative analysis of a series of chimeras and selected point mutations between CNF3 and CNFy identified two residues within the putative translocation domain of the delivery vehicles that differentially modulate endosomal escape by the toxins ( 28 ).…”

C910 chemical compound inhibits the traffiking of several bacterial AB toxins with cross-protection against influenza virus

“…Notably, these different compounds have been used as tools to discern the different physicochemical requirements of AB toxins. For example, CNFy and CNF3 showed distinctive sensitivity to EGA but similar dose-response profiles to ABMA, indicating differential endosomal escape of the two highly homologous toxins ( Haywood et al., 2021 ). Similarly, tamoxifen was identified in a drug repurposing screen to block the fusion of late endosomes with lysosomes with consequences on the dynamics of retromer cycling on early endosomes, leading to the impaired sorting of Stx1 and Stx2 toxins from early endosomes to the Golgi network ( Selyunin et al., 2019 , 2021 ).…”

Prospects of Using Protein Engineering for Selective Drug Delivery into a Specific Compartment of Target Cells

“…Another option for delivery to the cytosol is to use fragments of a number of bacterial toxins that are specialized for this process ( Figure 5 ). They include Corynebacterium diphtheriae toxin [ 201 ], anthrax toxins [ 202 ], Clostridium botulinum C2 toxin [ 203 ], binary toxin (CDT), toxin A (TcdA) and B (TcdB) from Clostridium difficile [ 204 , 205 ], and others [ 206 , 207 , 208 ]. An essential feature of these toxins is their ability to undergo conformational rearrangements in a weakly acidic environment.…”