Mackessy, Stephen P.
For decades, snakes and snake venoms have been utilized in numerous
aspects of biological and biomedical research. Behaviorally, snakes have been
examined for their extraordinary chemosensory capabilities, providing a detailed
understanding of their foraging ecology and predatory responses. The presence of
a highly complex vomeronasal organ has enabled snakes to not only respond to,
but also discriminate between a high-range of heterospecific, conspecific,
predatory, and prey-derived chemical odors.
Snake venom has allowed for a transition in predatory behaviors, and this
often complex mixture of proteins and peptides has provided researchers with an
ever growing catalog of natural compounds that may be applicable as novel
therapeutics or as biomedical reagents. Research into venomous systems also
provides a detailed understanding of the biological roles of venom compounds, as
well as providing critical information necessary for the proper assessment and
treatment of snakebite.
The current work addresses several aspects of snake behavior and snake
venom toxinology and has four major objectives: i) to examine the chemosensory
responses of neonate, subadult and adult Prairie Rattlesnake (Crotalus viridis
viridis) to various prey chemical stimuli, ii) to identify the chemical component(s) of
venom which allows for prey recovery during viperid predatory episodes, iii) to examine
the anti-cancer effects of a novel snake venom disintegrin towards various human derived
cancer cell lines and iv) to complete in-depth proteomic analyses of the neonate and adult
C. v. viridis and examine the efficacy of the current anti-venom treatment CroFab®
against this species’ venom.
Chapter I presents the objectives and aims of my dissertation work, and provides
background on chemosensory systems in squamates, and the numerous studies examining
prey relocation in viperid snakes. Further, this chapter addresses the importance of
examining the potential medicinal values of disintegrins as anti-cancer therapeutics, and
the utilization of proteomics to develop a better understanding of venom composition and
anti-venom efficacy. Chapters II focuses on the chemosensory responses of wild-caught
neonate, subadult, and adult C. v. viridis to natural and non-natural prey-derived chemical
odors. Results indicate that responses to chemical stimuli shift with snake age, correlating
with ontogenetic changes in snake diet. Chapter III examines this phenomenon in more
detail with a group of “stunted” C. v. viridis which had been in captivity since birth and
had only consumed neonate lab mice (Mus musculus). Further, these snakes were the age
of adults yet only the size of large juveniles, therefore they could not consume larger prey
normally taken by adult snakes. Results suggest that ontogenetic shifts in responsiveness
to natural prey chemical cues are innately programmed and are not based on body size or
feeding experience. Chapter IV identifies the venom component, disintegrins, which are
responsible for prey recovery during strike-induced chemosensory searching in Western
Diamondback Rattlesnakes (Crotalus atrox). In Chapter V, a novel disintegrin protein
(named tzabcanin) was isolated from the venom of the Middle American Rattlesnake
(Crotalus simus tzabcan) and the cytotoxic and anti-adhesion properties of this protein
toward Colo-205 and MCF-7 cell lines was examined. Chapter VI also examines the anticancer
effects of tzabcanin towards A-375 and A-549 cell lines, and by specifically
binding integrin αvβ3, tzabcanin inhibits cell migration and cell adhesion to vitronectin.
In Chapter VII, a detailed proteomic analysis of the venoms of four individual C. v.
viridis is presented, showing a novel trend in ontogenetic changes in venom composition,
as well as identifying which compounds are, and which are not, effectively
immunocaptured by the current anti-venom therapy used in the United States, CroFab®.
Snakes; Cancer; Venom; Proteomics
Copyright is held by author.
Saviola, Anthony J., "Proteomic Analyses of Snake Venoms with an Examination of the Biological Roles and Anti-cancer Effects of Venom Disintegrins" (2015). Dissertations. 48.