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We report the identification and characterization of two new members of a family of bilirubin-inducible fluorescent proteins (FPs) from marine chlopsid eels and demonstrate a key region of the sequence that serves as an evolutionary switch from non-fluorescent to fluorescent fatty acid-binding proteins (FABPs). Using transcriptomic analysis of two species of brightly fluorescent Kaupichthys eels (Kaupichthys hyoproroides and Kaupichthys n. sp.), two new FPs were identified, cloned and characterized (Chlopsid FP I and Chlopsid FP II). We then performed phylogenetic analysis on 210 FABPs, spanning 16 vertebrate orders, and including 163 vertebrate taxa. We show that the fluorescent FPs diverged as a protein family and are the sister group to brain FABPs. Our results indicate that the evolution of this family involved at least three gene duplication events. We show that fluorescent FABPs possess a unique, conserved tripeptide Gly-Pro-Pro sequence motif, which is not found in non-fluorescent fatty acid binding proteins. This motif arose from a duplication event of the FABP brain isoforms and was under strong purifying selection, leading to the classification of this new FP family. Residues adjacent to the motif are under strong positive selection, suggesting a further refinement of the eel protein's fluorescent properties. We present a phylogenetic reconstruction of this emerging FP family and describe additional fluorescent FABP members from groups of distantly related eels. The elucidation of this class of fish FPs with diverse properties provides new templates for the development of protein-based fluorescent tools. The evolutionary adaptation from fatty acid-binding proteins to fluorescent fatty acid-binding proteins raises intrigue as to the functional role of bright green fluorescence in this cryptic genus of reclusive eels that inhabit a blue, nearly monochromatic, marine environment.

Pyrosomes are tunicates in the phylum Chordata, which also contains vertebrates. Their gigantic blooms play important ecological and biogeochemical roles in oceans. Pyrosoma , meaning “fire-body”, derives from their brilliant bioluminescence. The biochemistry of this light production is unknown, but has been hypothesized to be bacterial in origin. We found that mixing coelenterazine—a eukaryote-specific luciferin—with Pyrosoma atlanticum homogenate produced light. To identify the bioluminescent machinery, we sequenced P. atlanticum transcriptomes and found a sequence match to a cnidarian luciferase (RLuc). We expressed this novel luciferase (PyroLuc) and, combined with coelenterazine, it produced light. A similar gene was recently predicted from a bioluminescent brittle star, indicating that RLuc-like luciferases may have evolved convergently from homologous dehalogenases across phyla (Cnidaria, Echinodermata, and Chordata). This report indicates that a widespread gene may be able to functionally converge, resulting in bioluminescence across animal phyla, and describes and characterizes the first putative chordate luciferase.

Biofluorescence has recently been found to be widespread in marine fishes, including sharks. Catsharks, such as the Swell Shark ( Cephaloscyllium ventriosum ) from the eastern Pacific and the Chain Catshark ( Scyliorhinus retifer) from the western Atlantic, are known to exhibit bright green fluorescence. We examined the spectral sensitivity and visual characteristics of these reclusive sharks, while also considering the fluorescent properties of their skin. Spectral absorbance of the photoreceptor cells in these sharks revealed the presence of a single visual pigment in each species. Cephaloscyllium ventriosum exhibited a maximum absorbance of 484 ± 3 nm and an absorbance range at half maximum (λ 1/2max ) of 440–540 nm, whereas for S. retifer maximum absorbance was 488 ± 3 nm with the same absorbance range. Using the photoreceptor properties derived here, a “shark eye” camera was designed and developed that yielded contrast information on areas where fluorescence is anatomically distributed on the shark, as seen from other sharks’ eyes of these two species. Phylogenetic investigations indicate that biofluorescence has evolved at least three times in cartilaginous fishes. The repeated evolution of biofluorescence in elasmobranchs, coupled with a visual adaptation to detect it; and evidence that biofluorescence creates greater luminosity contrast with the surrounding background, highlights the potential importance of biofluorescence in elasmobranch behavior and biology.

Matrix metalloproteases (MMPs) undergo post-translational modifications including pro-domain shedding. The activated forms of these enzymes are effective drug targets, but generating potent biological inhibitors against them remains challenging. We report the generation of anti-MMP-7 inhibitory monoclonal antibody (GSM-192), using an alternating immunization strategy with an active site mimicry antigen and the activated enzyme. Our protocol yielded highly selective anti-MMP-7 monoclonal antibody, which specifically inhibits MMP-7′s enzyme activity with high affinity (IC50 = 132 ± 10 nM). The atomic model of the MMP-7-GSM-192 Fab complex exhibited antibody binding to unique epitopes at the rim of the enzyme active site, sterically preventing entry of substrates into the catalytic cleft. In human PDAC biopsies, tissue staining with GSM-192 showed characteristic spatial distribution of activated MMP-7. Treatment with GSM-192 in vitro induced apoptosis via stabilization of cell surface Fas ligand and retarded cell migration. Co-treatment with GSM-192 and chemotherapeutics, gemcitabine and oxaliplatin elicited a synergistic effect. Our data illustrate the advantage of precisely targeting catalytic MMP-7 mediated disease specific activity.

Since the initial discovery of Aqueoria victoria ’s green fluorescence off the coast of Washington’s Puget Sound, biofluorescent marine organisms have been found across the globe. The variety of colors of biofluorescence as well as the variability in the organisms that exhibit this fluorescence is astounding. The mechanisms of biofluorescence in marine organisms are also variable. To fluoresce, some organisms use fluorescent proteins, while others use small molecules. In eels, green biofluorescence was first identified in Anguilla japonica . The green fluorescence in A. japonica was discovered to be caused by a fatty acid binding protein (UnaG) whose fluorescence is induced by the addition of bilirubin. Members of this class of proteins were later discovered in Kaupichthys eels (Chlopsid FP I and Chlopsid FP II). Here, we report the discovery and characterization of the first member of this class of green fluorescent fatty acid binding proteins from the moray eel Gymnothorax zonipectis . This protein, GymFP, is 15.6 kDa with a fluorescence excitation at 496 nm and an emission maximum at 532 nm upon addition of bilirubin. GymFP is 61% homologous to UnaG and 47% homologous to Chlopsid FP I. Here, we report de novo transcriptome assembly, protein expression, and fluorescence spectroscopic characterization of GymFP. These findings extend the fluorescent fatty acid binding proteins into a third family of true eels (Anguilliformes).

Bioluminescent copepods are often the most abundant marine zooplankton and play critical roles in oceanic food webs. Metridia copepods exhibit particularly bright bioluminescence, and the molecular basis of their light production has just recently begun to be explored. Here we add to this body of work by transcriptomically profiling Metridia lucens , a common species found in temperate, northern, and southern latitudes. In this previously molecularly-uncharacterized species, we find the typical luciferase paralog gene set found in Metridia . More surprisingly, we recover noteworthy putative luciferase sequences that had not been described from Metridia species, indicating that bioluminescence produced by these copepods may be more complex than previously known. This includes another copepod luciferase, as well as one from a shrimp. Furthermore, feeding experiments using mass spectrometry and 13 C labelled L-tyrosine and L-phenylalanine firmly establish that M. lucens produces its own coelenterazine luciferin rather than acquiring it through diet. This coelenterazine synthesis has only been directly confirmed in one other copepod species.

Biofluorescence has been found to be an increasingly widespread phenomenon in the ocean. The reclusive Caribbean chlopsid eel, Kaupichthys hyoproroides displays bright green fluorescence in its native marine environment. We have previously shown the fluorescence to be attributed to a fluorescent fatty acid-binding protein, Chlopsid FP, part of a larger family of fluorescent fatty acid-binding proteins, including the homologous UnaG. All require the addition of exogenous bilirubin for fluorescence. Here, we report the generation of a series of point mutants, and deletions that result in the quenching of fluorescence in Chlopsid FP. In addition, we report the binding constants of bilirubin to Chlopsid FP and mutants, measured by fluorescence titration. This study provides key insights into the potential mechanism of fluorescence in this class of fluorescent fatty acid-binding proteins.

Discussing recent advances in the field of matrix metalloproteinase (MMP) research from a multidisciplinary perspective, Matrix Metalloproteinase Biology is a collection of chapters written by leaders in the field of MMPs. The book focuses on the challenges of understanding the mechanisms substrate degradation by MMPs, as well as how these enzymes are able to degrade large, highly ordered substrates such as collagen. All topics addressed are considered in relation to disease progression including roles in cancer metastasis, rheumatoid arthritis and other inflammatory diseases. The text first provides an overview of MMPs, focusing on the history, the development and failures of small molecule inhibitors in clinical trials, and work with TIMPS, the endogenous inhibitors of MMPs. These introductory chapters establish the foundation for later discussion of the recent progress on the design of different types of inhibitors, including novel antibody based therapeutics. The following section emphasizes research using novel methods to further the study of the MMPs. The third and final section focuses on in vivo research, particularly with respect to cancer models, degradation of the extracellular matrix, and MMP involvement in other disease states. Written and edited by leaders in the field, Matrix Metalloproteinase Biology addresses the rapidly growth in MMP research, and will be an invaluable resource to advanced students and researchers studying cell and molecular biology.

Polar fishes have evolved antifreeze proteins (AFPs) that allow them to survive in subzero temperatures. We performed deep transcriptomic sequencing on a postlarval/juvenile variegated snailfish, Liparis gibbus (Actinopterygii: Scorpaeniformes: Cottoidei: Liparidae), living in an iceberg habitat (−2°C) in Eastern Greenland and report detection of highly expressed transcripts that code for putative AFPs from 2 gene families, Type I and LS-12-like proteins (putative Type IV AFPs). The transcripts encoding both proteins have expression levels among the top <1% of expressed genes in the fish. The Type I AFP sequence is different from a reported Type I AFP from the same species, possibly expressed from a different genetic locus. While prior findings from related adult sculpins suggest that LS-12-like/Type IV AFPs may not have a role in antifreeze protection, our finding of very high relative gene expression of the LS-12-like gene suggests that highly active transcription of the gene is important to the fish in the iceberg habitat and raises the possibility that weak or combinatorial antifreeze activity could be beneficial. These findings highlight the physiological importance of antifreeze proteins to the survival of fishes living in polar habitats.

We report the identification and characterization of two new members of a family of bilirubin-inducible fluorescent proteins (FPs) from marine chlopsid eels and demonstrate a key region of the sequence that serves as an evolutionary switch from non-fluorescent to fluorescent fatty acid-binding proteins (FABPs). Using transcriptomic analysis of two species of brightly fluorescent Kaupichthys eels (Kaupichthys hyoproroides and Kaupichthys n. sp.), two new FPs were identified, cloned and characterized (Chlopsid FP I and Chlopsid FP II). We then performed phylogenetic analysis on 210 FABPs, spanning 16 vertebrate orders, and including 163 vertebrate taxa. We show that the fluorescent FPs diverged as a protein family and are the sister group to brain FABPs. Our results indicate that the evolution of this family involved at least three gene duplication events. We show that fluorescent FABPs possess a unique, conserved tripeptide Gly-Pro-Pro sequence motif, which is not found in non-fluorescent fatty acid binding proteins. This motif arose from a duplication event of the FABP brain isoforms and was under strong purifying selection, leading to the classification of this new FP family. Residues adjacent to the motif are under strong positive selection, suggesting a further refinement of the eel protein's fluorescent properties. We present a phylogenetic reconstruction of this emerging FP family and describe additional fluorescent FABP members from groups of distantly related eels. The elucidation of this class of fish FPs with diverse properties provides new templates for the development of protein-based fluorescent tools. The evolutionary adaptation from fatty acid-binding proteins to fluorescent fatty acid-binding proteins raises intrigue as to the functional role of bright green fluorescence in this cryptic genus of reclusive eels that inhabit a blue, nearly monochromatic, marine environment.