Unnexins: Homologs of innexin proteins in Trypanosomatidae parasites

Abstract

Large-pore channels, including those formed by connexin, pannexin, innexin proteins, are part of a broad family of plasma membrane channels found in vertebrates and invertebrates, which share topology features. Despite their relevance in parasitic diseases such as Chagas and malaria, it was unknown whether these large-pore channels are present in unicellular organisms. We identified 14 putative proteins in Trypanosomatidae parasites as presumptive homologs of innexin proteins. All proteins possess the canonical motif of the innexin family, a pentapeptide YYQWV, and 10 of them share a classical membrane topology of large-pore channels. A sequence similarity network analysis confirmed their closeness to innexin proteins. A bioinformatic model showed that a homolog of Trypanosoma cruzi (T. cruzi) could presumptively form a stable octamer channel with a highly positive electrostatic potential in the internal cavities and extracellular entrance due to the notable predominance of residues such as Arg or Lys. In vitro dye uptake assays showed that divalent cations-free solution increases YO-PRO-1 uptake and hyperosmotic stress increases DAPI uptake in epimastigotes of T. cruzi. Those effects were sensitive to probenecid. Furthermore, probenecid reduced the proliferation and transformation of T. cruzi. Moreover, probenecid or carbenoxolone increased the parasite sensitivity to antiparasitic drugs commonly used in therapy against Chagas. Our study suggests the existence of innexin homologs in unicellular organisms, which could be protein subunits of new large-pore channels in unicellular organisms.

TriTrypDB: An integrated functional genomics resource for kinetoplastida

“…Below are a few recent examples of how TriTrypDB data and tools have been utilized by the research community to conduct their own research. TriTrypDB genomes and annotations have been used to characterize individual genes [ 69 – 73 ] or gene families [ 74 , 75 ], identify orthologs across species [ 55 , 70 , 76 ], conduct genome-wide analyses to study genetic variations such as SNPs, CNVs and hybridization events [ 77 – 79 ], perform comparative genomic [ 80 – 82 ] and phylogenetic/ phylogenomic [ 82 , 83 ] analyses, and as reference genomes for the assembly and/or annotation of newly generated genomes [ 16 , 84 ]. Similarly, the genome assemblies and annotations have also been utilized for the analysis of differential gene expression [ 19 , 72 , 85 ], protein expression [ 85 – 87 ], the identification of post-translational modifications [ 72 ] and potential new genes missing in the official gene sets [ 88 ].…”

Prophages carrying Zot toxins on different Vibrio genomes: A comprehensive assessment using multilayer networks

“…The representative protein sequence for each cluster was chosen based on the following hierarchy: (a) If a cluster has a Zot protein sequence from the Vibrio genus, and (b) If a cluster includes at least one Zot protein originating from Vibrio genomes. This approach aimed to construct a representative network where each node corresponds to a group of proteins with at least 90% sequence identity, following methodologies similar to those employed in previous research (Arias‐Darraz et al, 2015; González, 2021; Güiza et al, 2022).…”

Contribution of large-pore channels to inflammation induced by microorganisms

“…In parasite infections, T. cruzi or T. cruzi -virulence factors have been described to activate Panx1 hemichannels in cardiac cells, causing an outflow of ATP, and increasing the concentration of cytosolic Ca 2+ through the activation of P2Y 1 receptors, which is necessary for parasite invasion ( Barria et al, 2018 ) ( Figure 1C ). Recent evidence suggests the presence of members of large-pore channels in T. cruzi, which could be a route for ATP release, and could be considered for future research ( Güiza et al, 2022 ).…”

“…Plasma membrane ionic channels selectively permeate ions (i.e., K + , Na + , Cl − , or Ca 2+ ); However, large-pore channels are also permeable to small molecules, such as ATP, ADP, and NAD + , and glutamate, which contribute to physiological and pathophysiological responses ( Kang et al, 2008 ; Cisterna et al, 2020 ; Syrjanen et al, 2021 ). Large-pore channels are structures formed by several protein families with no evolutionary linkages, including Cxs, Panxs, Inxs, Unxs, CALHMs, and LRRC8 proteins ( Guiza et al, 2022 ). Despite little sequence homology, the large-pore channel members have similar transmembrane topologies with four transmembrane helices ( Syrjanen et al, 2021 ).…”

“…The VRACs are composed of LRRC8 proteins and are responsible for regulatory volume decreases after hypotonic cell swelling ( Concepcion et al, 2022 ). Recent evidence suggests that kinetoplastid parasites have large-pore channel members formed by homologs of innexins, named unnexins, which seem to have a membrane topology similar to that of large-pore channels, and might play a critical role in infections ( Guiza et al, 2022 ).…”