Overview of protein posttranslational modifications in Arthropoda venoms

Abstract

Accidents with venomous animals are a public health issue worldwide. Among the species involved in these accidents are scorpions, spiders, bees, wasps, and other members of the phylum Arthropoda. The knowledge of the function of proteins present in these venoms is important to guide diagnosis, therapeutics, besides being a source of a large variety of biotechnological active molecules. Although our understanding about the characteristics and function of arthropod venoms has been evolving in the last decades, a major aspect crucial for the function of these proteins remains poorly studied, the posttranslational modifications (PTMs). Comprehension of such modifications can contribute to better understanding the basis of envenomation, leading to improvements in the specificities of potential therapeutic toxins. Therefore, in this review, we bring to light protein/toxin PTMs in arthropod venoms by accessing the information present in the UniProtKB/Swiss-Prot database, including experimental and putative inferences. Then, we concentrate our discussion on the current knowledge on protein phosphorylation and glycosylation, highlighting the potential functionality of these modifications in arthropod venom. We also briefly describe general approaches to study "PTM-functional-venomics", herein referred to the integration of PTM-venomics with a functional investigation of PTM impact on venom biology. Furthermore, we discuss the bottlenecks in toxinology studies covering PTM investigation. In conclusion, through the mining of PTMs in arthropod venoms, we observed a large gap in this field that limits our understanding on the biology of these venoms, affecting the diagnosis and therapeutics development. Hence, we encourage community efforts to draw attention to a better understanding of PTM in arthropod venom toxins.

Keywords: Arthropod venom; Glycosylation; Mass spectrometry-based proteomics; PTM-functional-venomics; PTM-venomics; Phosphorylation; Posttranslational modification; UniProtKB/Swiss-Prot database.

Figure 1.. Arthropod venom proteins containing posttranslational modification (PTM) information in the keyword subsection of UniProtKB/Swiss-Prot Protein Database. (A) Phylogenetic tree of arthropods species, with PTMs information in the database (experimental plus putative), grouped by Order. Purple corresponds to Araneae, green to Scorpiones, pink to Hymenoptera, blue to Diptera, yellow to Scolopendromorpha and orange to Scutigeromorpha. (B) Gene ontology classification of arthropod venom proteins containing PTMs information based on their molecular function from 2481 entries and (C) biological process from 1664 entries. Phylogenetic figure was created in the interactive Tree of Life web server (http://itol.embl.de) [14].

Figure 2.. Protein posttranslational modifications (PTMs) in arthropod venom included in the UniProtKB/Swiss-Prot Protein Database. Circos table viewer representation of 14 PTM types identified in all the arthropod venom proteins from UniProtKB/Swiss-Prot Protein and their dual interaction when multiple PTMs were identified in one entry. The circle represents the entries with specific modification, taking into consideration different PTM combinations. This data set includes experimental and putative PTMs. The image was created in http://mkweb.bcgsc.ca/tableviewer/ [15]. PCA: pyrrolidone carboxylic acid; CPBR: cleavage on pair of basic residues.

Figure 3.. Arthropod venom proteins glycosylation and phosphorylation from UniProtKB/Swiss-Prot Protein Database. (A) Phylogenetic tree of arthropods species that contains phosphorylation and glycosylation information in the database. The species are grouped in colored range by Family taxonomy and the outer circle shows the Order they belong to. 🞴 Species containing proteins with both glycosylation and phosphorylation information. #Species with proteins presenting only phosphorylation information. (Family and species with experimental glycosylation and/or phosphorylation. (B) The database contains different evidence of 118 protein entries containing glycosylation information. (C) Distribution of 111 glycoproteins (experimental and putative) among different protein families provided by Uniprot based on the InterPro database [67].

Figure 4.. PTM-functional venomics. General strategies based on venomics studies on protein phosphorylation and glycosylation and the integration with functional assays and structural proteomics to investigate PTM biological/functional impact on venom activities. Target proteomics and site mutation can be performed to validate PTM assignment and PTM function, respectively. HDX: hydrogen/deuterium exchange; CPP: covalent protein painting; SRM: selected reaction monitoring; MRM: multiple reaction monitoring; PRM: parallel reaction monitoring. Figure created with elements from BioRender.com and Servier Medical Art.