Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies.

Toxic cardiotonic steroids (CTSs) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na,K-ATPase (NKA). Although most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication.

Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies.

Toxic cardiotonic steroids (CTS) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na,K-ATPase (NKA). While most fireflies produce these toxins internally, species of the genus acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication.

Impact of Updating Pharmacogenetic Results: Lessons Learned from the PREDICT Program.

Pharmacogenomic (PGx) evidence for selective serotonin reuptake inhibitors (SSRIs) continues to evolve. For sites offering testing, maintaining up-to-date interpretations and implementing new clinical decision support (CDS) driven by existing results creates practical and technical challenges. Vanderbilt University Medical Center initiated panel testing in 2010, added testing in 2017, and released CDS for SSRIs in 2020.

Exofacial membrane composition and lipid metabolism regulates plasma membrane P4-ATPase substrate specificity.

The plasma membrane of a cell is characterized by an asymmetric distribution of lipid species across the exofacial and cytofacial aspects of the bilayer. Regulation of membrane asymmetry is a fundamental characteristic of membrane biology and is crucial for signal transduction, vesicle transport, and cell division. The type IV family of P-ATPases, or P4-ATPases, establishes membrane asymmetry by selection and transfer of a subset of membrane lipids from the lumenal or exofacial leaflet to the cytofacial aspect of the bilayer.

A Tutorial for Pharmacogenomics Implementation Through End-to-End Clinical Decision Support Based on Ten Years of Experience from PREDICT.

Vanderbilt University Medical Center implemented pharmacogenomics (PGx) testing with the Pharmacogenomic Resource for Enhanced Decisions in Care and Treatment (PREDICT) initiative in 2010. This tutorial reviews the laboratory considerations, technical infrastructure, and programmatic support required to deliver panel-based PGx testing across a large health system with examples and experiences from the first decade of the PREDICT initiative. From the time of inception, automated clinical decision support (CDS) has been a critical capability for delivering PGx results to the point-of-care.

Adaptive substitutions underlying cardiac glycoside insensitivity in insects exhibit epistasis in vivo.

Predicting how species will respond to selection pressures requires understanding the factors that constrain their evolution. We use genome engineering of to investigate constraints on the repeated evolution of unrelated herbivorous insects to toxic cardiac glycosides, which primarily occurs via a small subset of possible functionally-relevant substitutions to Na,K-ATPase. Surprisingly, we find that frequently observed adaptive substitutions at two sites, 111 and 122, are lethal when homozygous and adult heterozygotes exhibit dominant neural dysfunction.

Missense variant in TPI1 (Arg189Gln) causes neurologic deficits through structural changes in the triosephosphate isomerase catalytic site and reduced enzyme levels in vivo.

Mutations in the gene triosephosphate isomerase (TPI) lead to a severe multisystem condition that is characterized by hemolytic anemia, a weakened immune system, and significant neurologic symptoms such as seizures, distal neuropathy, and intellectual disability. No effective therapy is available. Here we report a compound heterozygous patient with a novel TPI pathogenic variant (NM_000365.

Yeast and human P4-ATPases transport glycosphingolipids using conserved structural motifs.

Lipid transport is an essential process with manifest importance to human health and disease. Phospholipid flippases (P4-ATPases) transport lipids across the membrane bilayer and are involved in signal transduction, cell division, and vesicular transport. Mutations in flippase genes cause or contribute to a host of diseases, such as cholestasis, neurological deficits, immunological dysfunction, and metabolic disorders.

Decoding P4-ATPase substrate interactions.

Cellular membranes display a diversity of functions that are conferred by the unique composition and organization of their proteins and lipids. One important aspect of lipid organization is the asymmetric distribution of phospholipids (PLs) across the plasma membrane. The unequal distribution of key PLs between the cytofacial and exofacial leaflets of the bilayer creates physical surface tension that can be used to bend the membrane; and like Ca, a chemical gradient that can be used to transduce biochemical signals.

Directed evolution of a sphingomyelin flippase reveals mechanism of substrate backbone discrimination by a P4-ATPase.

Phospholipid flippases in the type IV P-type ATPase (P4-ATPases) family establish membrane asymmetry and play critical roles in vesicular transport, cell polarity, signal transduction, and neurologic development. All characterized P4-ATPases flip glycerophospholipids across the bilayer to the cytosolic leaflet of the membrane, but how these enzymes distinguish glycerophospholipids from sphingolipids is not known. We used a directed evolution approach to examine the molecular mechanisms through which P4-ATPases discriminate substrate backbone.

Structural and Genetic Studies Demonstrate Neurologic Dysfunction in Triosephosphate Isomerase Deficiency Is Associated with Impaired Synaptic Vesicle Dynamics.

Triosephosphate isomerase (TPI) deficiency is a poorly understood disease characterized by hemolytic anemia, cardiomyopathy, neurologic dysfunction, and early death. TPI deficiency is one of a group of diseases known as glycolytic enzymopathies, but is unique for its severe patient neuropathology and early mortality. The disease is caused by missense mutations and dysfunction in the glycolytic enzyme, TPI.

Triosephosphate isomerase I170V alters catalytic site, enhances stability and induces pathology in a Drosophila model of TPI deficiency.

Triosephosphate isomerase (TPI) is a glycolytic enzyme which homodimerizes for full catalytic activity. Mutations of the TPI gene elicit a disease known as TPI Deficiency, a glycolytic enzymopathy noted for its unique severity of neurological symptoms. Evidence suggests that TPI Deficiency pathogenesis may be due to conformational changes of the protein, likely affecting dimerization and protein stability.

A serendipitous survey of prediction algorithms for amyloidogenicity.

The 17- amino acid N-terminal segment of the Huntingtin protein, htt(NT), grows into stable α-helix rich oligomeric aggregates when incubated under physiological conditions. We examined 15 scrambled sequence versions of an htt(NT) peptide for their stabilities against aggregation in aqueous solution at low micromolar concentration and physiological conditions. Surprisingly, given their derivation from a sequence that readily assembles into highly stable α-helical aggregates that fail to convert into β-structure, we found that three of these scrambled peptides rapidly grow into amyloid-like fibrils, while two others also develop amyloid somewhat more slowly.

Evidence of a triosephosphate isomerase non-catalytic function crucial to behavior and longevity.

Triosephosphate isomerase (TPI) is a glycolytic enzyme that converts dihydroxyacetone phosphate (DHAP) into glyceraldehyde 3-phosphate (GAP). Glycolytic enzyme dysfunction leads to metabolic diseases collectively known as glycolytic enzymopathies. Of these enzymopathies, TPI deficiency is unique in the severity of neurological symptoms.

Inhibiting the nucleation of amyloid structure in a huntingtin fragment by targeting α-helix-rich oligomeric intermediates.

Although oligomeric intermediates are transiently formed in almost all known amyloid assembly reactions, their mechanistic roles are poorly understood. Recently, we demonstrated a critical role for the 17-amino-acid N-terminus (htt(NT) segment) of huntingtin (htt) in the oligomer-mediated amyloid assembly of htt N-terminal fragments. In this mechanism, the htt(NT) segment forms the α-helix-rich core of the oligomers, leaving much of the polyglutamine (polyQ) segment disordered and solvent-exposed.

Genetically engineered mesenchymal stem cells reduce behavioral deficits in the YAC 128 mouse model of Huntington's disease.

The purpose of this study was to evaluate the therapeutic effects of the transplantation of bone-marrow mesenchymal stem cells (MSCs), genetically engineered to over-express brain-derived neurotrophic factor (BDNF) or nerve growth factor (NGF) on motor deficits and neurodegeneration in YAC 128 transgenic mice. MSCs, harvested from mouse femurs, were genetically engineered to over-express BDNF and/or NGF and these cells, or the vehicle solution, were injected into the striata of four-month old YAC 128 transgenic and wild-type mice. Assessments of motor ability on the rotarod and the severity of clasping were made one day prior to transplantation and once monthly, thereafter, to determine the effects of the transplanted cells on motor function.