Biology subjects

Cahill, E.

Publications and source records attributed to Cahill, E..

3 recordsLinked to original sources

bioRxiv2026

The novel viper FETUA-3 protein evolved a unique mode of inhibiting snake venom metalloproteinases

Molecular innovation and coevolution play major roles in the evolution of biological diversity, yet we have relatively few instances in which we understand the biological and molecular bases of coevolution. Rattlesnakes and other vipers have evolved resistance to their own novel venom metalloproteinase (MP) toxins through the invention and coevolution of serum-borne inhibitors (FETUAs) derived from the ancestral, non-inhibitory, serum glycoprotein Fetuin-A. However, how FETUAs acquired their function and their mechanism of action are unknown. Here, we use a combination of structure prediction, site-directed mutagenesis, functional analyses, and molecular dynamics to elucidate how the rattlesnake FETUA-3 protein evolved to inhibit three classes of venom MP toxins. We show that FETUA-3 uses a combination of structural motifs to bind multiple MPs with high-affinity and acts as a potent noncompetitive inhibitor by inserting its N-terminus into MP active sites and directly disrupting substrate cleavage. We also find strong selective constraints on key N-terminal residues that maintain FETUA-3 specificity for multiple MP targets. These results reveal that FETUA-3 evolved a unique mechanism of action distinct from other vertebrate metalloproteinase inhibitors and how a small number of FETUA proteins controls the activities of a large family of venom toxins.

evolutionary biology↗

bioRxiv2025

Loss of a major venom toxin gene in a Western Diamondback rattlesnake population

The biochemical complexity and evolutionary diversity of snake venom composition reflects adaptation to the diversity of prey in their diets. However, the genetic mechanisms underlying the evolutionary diversity of venoms are not well understood. Here, we explored the potential extent of and genetic basis for venom protein variation in the widely-distributed Western Diamondback rattlesnake (Crotalus atrox). As in many rattlesnake venoms, metalloproteinases (SVMPs) are the major component of C. atrox venom, with three proteins belonging to three distinct major structural SVMP classes, MDC4, MAD3a, and MPO1, constituting the most abundant SVMPs. We found that while most venom proteins, including MDC4 and MAD3a, vary little among individuals, the MPO1 protein is completely absent from some animals, most commonly those from the western part of the species geographic range. This distribution correlates with the previous finding of two distinct lineages within C. atrox and indicates that different ecological factors have shaped venom composition across the species range. We further show that the loss of MPO1 expression is not due to transcriptional down-regulation, but to several independent inactivating mutations at the locus, including whole gene deletion. The recurrent inactivation of a major toxin gene within a C. atrox population may reflect relaxed selection on the maintenance of MPO1 function, but we also raise the possibility that the loss of venom components may be favored if there is a cost to producing a less effective toxin in protein-rich venoms.

evolutionary biology↗

bioRxiv2021

Proteolysis of fibrillin-2 microfibrils is essential for normal skeletal development

The embryonic extracellular matrix (ECM) undergoes transition to mature ECM as development progresses, yet specific transition mechanisms ensuring ECM proteostasis and their regulatory impact are poorly defined. Fibrillin microfibrils are macromolecular ECM complexes serving structural and regulatory roles. In mice, Fbn1 and Fbn2, encoding major microfibrillar components, are strongly expressed during embryogenesis, but fibrillin-1 is the major component observed in adult tissue microfibrils. Here, analysis of mouse Adamts6 and Adamts10 mutant embryos, lacking these homologous secreted metalloproteases individually and in combination, along with in vitro analysis of microfibrils, measurement of ADAMTS6-fibrillin affinities and N-terminomics identification of ADAMTS6-cleaved sites, demonstrates a transcriptionally adapted system for fibrillin-2 proteolysis that contributes to postnatal fibrillin-1 dominance. The lack of ADAMTS6, alone and in combination with ADAMTS10 led to excess fibrillin-2 in perichondrium, with impaired skeletal development resulting from a drastic reduction of aggrecan, cartilage link protein and impaired BMP, but not TGF{beta} signaling in cartilage. Although ADAMTS6 cleaves fibrillin-1 and fibrillin-2 as well as fibronectin, which provides the initial scaffold for microfibril assembly, primacy of the protease-substrate relationship between ADAMTS6 and fibrillin-2 was unequivocally established by reversal of these defects in Adamts6-/- embryos by genetic reduction of Fbn2, but not Fbn1.

developmental biology↗