Abstract
Cephalopods, successful predators, can use a mixture of substances to subdue their prey, becoming interesting sources of bioactive compounds. In addition to neurotoxins and enzymes, the presence of antimicrobial compounds has been reported. Recently, the transcriptome and the whole proteome of the Octopus vulgaris salivary apparatus were released, but the role of some compounds—e.g., histones, antimicrobial peptides (AMPs), and toxins—remains unclear. Herein, we profiled the proteome of the posterior salivary glands (PSGs) of O. vulgaris using two sample preparation protocols combined with a shotgun-proteomics approach. Protein identification was performed against a composite database comprising data from the UniProtKB, all transcriptomes available from the cephalopods’ PSGs, and a comprehensive non-redundant AMPs database. Out of the 10,075 proteins clustered in 1868 protein groups, 90 clusters corresponded to venom protein toxin families. Additionally, we detected putative AMPs clustered with histones previously found as abundant proteins in the saliva of O. vulgaris. Some of these histones, such as H2A and H2B, are involved in systemic inflammatory responses and their antimicrobial effects have been demonstrated. These results not only confirm the production of enzymes and toxins by the O. vulgaris PSGs but also suggest their involvement in the first line of defense against microbes.
Highlights
Cephalopods are highly competitive and efficient predators, sharing such remarkable morphological and physiological innovations as their highly advanced visual and nervous systems, camouflage abilities, diversified body shapes, sizes, Antibiotics 2020, 9, 757; doi:10.3390/antibiotics9110757 www.mdpi.com/journal/antibioticsAntibiotics 2020, 9, 757 and metabolic rates [1,2]
As previously described [18,19,20,22], Overall, we found a total of 90 proteinGroups encompassing most of the known venom protein the venomous repertoire is composed by serine proteases, CAP, metalloproteases, serine proteases families reported for the posterior salivary glands (PSGs) from O. vulgaris (Tables S2 and S4)
Other antimicrobial peptides (AMPs) detected in several proteinGroups are ubiquitin-derived peptides; in particular, we have identified similarity with the ubiquitin-like AMP isolated from the Pacific oyster
Summary
Cephalopods (octopus, squid, cuttlefish, and Nautilus) are highly competitive and efficient predators, sharing such remarkable morphological and physiological innovations as their highly advanced visual and nervous systems, camouflage abilities, diversified body shapes, sizes, Antibiotics 2020, 9, 757; doi:10.3390/antibiotics9110757 www.mdpi.com/journal/antibioticsAntibiotics 2020, 9, 757 and metabolic rates [1,2]. Cephalopods (octopus, squid, cuttlefish, and Nautilus) are highly competitive and efficient predators, sharing such remarkable morphological and physiological innovations as their highly advanced visual and nervous systems, camouflage abilities, diversified body shapes, sizes, Antibiotics 2020, 9, 757; doi:10.3390/antibiotics9110757 www.mdpi.com/journal/antibiotics. The highest competitiveness associated to cephalopods relies mostly on their complex behavior combined with their capacity to produce venom and enzymes present in their salivary glands [10,11,12]. The absence of an external protective shell combined with the active predatory lifestyle of Coleoid cephalopods might be driving the venom evolution in those glands [13]. The posterior salivary glands (PSGs), known as venom glands, are actively used in feeding by cephalopods such as squids, octopuses, and cuttlefishes to subdue their preys through the inoculation of toxins [14,15,16,17]. Cutting-edge approaches such as shotgun proteomics and transcriptomics have substantially increased the knowledge about those gland metabolites [18,19,20,21,22,23,24,25,26]
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