• Brain endothelial cell trpa1 channels initiate neurovascular coupling

      Thakore, P.; Alvarado, M.G.; Ali, S.; Mughal, A.; Pires, P.W.; Yamasaki, E.; Pritchard, H.A.T.; Isakson, B.E.; Tran, C.H.T.; Earley, S.; et al. (eLife Sciences Publications Ltd, 2021)
      Cerebral blood flow is dynamically regulated by neurovascular coupling to meet the dynamic metabolic demands of the brain. We hypothesized that TRPA1 channels in capillary endothelial cells are stimulated by neuronal activity and instigate a propagating retrograde signal that dilates upstream parenchymal arterioles to initiate functional hyperemia. We find that activation of TRPA1 in capillary beds and post-arteriole transitional segments with mural cell coverage initiates retrograde signals that dilate upstream arterioles. These signals exhibit a unique mode of biphasic propagation. Slow, short-range intercellular Ca2+ signals in the capillary network are converted to rapid electrical signals in transitional segments that propagate to and dilate upstream arterioles. We further demonstrate that TRPA1 is necessary for functional hyperemia and neurovascular coupling within the somatosensory cortex of mice in vivo. These data establish endothelial cell TRPA1 channels as neuronal activity sensors that initiate microvascular vasodilatory responses to redirect blood to regions of metabolic demand. © 2021, eLife Sciences Publications Ltd. All rights reserved.
    • Injection with toxoplasma gondii protein affects neuron health and survival

      Mendez, O.A.; Machado, E.F.; Lu, J.; Koshy, A.A.; Graduate Interdisciplinary Program in Neuroscience, University of Arizona; BIO5 Institute, University of Arizona; College of Nursing, University of Arizona; Department of Immunobiology, University of Arizona; Department of Neurology, University of Arizona (eLife Sciences Publications Ltd, 2021)
      Toxoplasma gondii is an intracellular parasite that causes a long-term latent infection of neurons. Using a custom MATLAB-based mapping program in combination with a mouse model that allows us to permanently mark neurons injected with parasite proteins, we found that Toxoplasma-injected neurons (TINs) are heterogeneously distributed in the brain, primarily localizing to the cortex followed by the striatum. In addition, we determined that cortical TINs are commonly (>50%) excitatory neurons (FoxP2+) and that striatal TINs are often (>65%) medium spiny neurons (MSNs) (FoxP2+). By performing single neuron patch-clamping on striatal TINs and neighboring uninfected MSNs, we discovered that TINs have highly aberrant electrophysiology. As approximately 90% of TINs will die by 8 weeks post-infection, this abnormal physiology suggests that injection with Toxoplasma protein— either directly or indirectly— affects neuronal health and survival. Collectively, these data offer the first insights into which neurons interact with Toxoplasma and how these interactions alter neuron physiology in vivo. © 2021, eLife Sciences Publications Ltd. All rights reserved.
    • Molecular basis for functional connectivity between the voltage sensor and the selectivity filter gate in shaker k+ channels

      Bassetto, C.A.Z., Jr; Carvalho-De-souza, J.L.; Bezanilla, F.; Department of Anesthesiology, University of Arizona (eLife Sciences Publications Ltd, 2021)
      In Shaker K+ channels, the S4-S5 linker couples the voltage sensor (VSD) and pore domain (PD). Another coupling mechanism is revealed using two W434F-containing channels: L361R:W434F and L366H:W434F. In L361R:W434F, W434F affects the L361R VSD seen as a shallower Q-V curve that crosses the G-V. In L366H:W434F, L366H relieves the W434F effect converting a non-conductive channel in a conductive one. We report a chain of residues connecting the VSD (S4) to the selectivity filter (SF) in the PD of an adjacent subunit as the molecular basis for voltage-sensor selectivity filter gate (VS-SF) coupling. Single alanine substitutions in this region (L409A, S411A, S412A or F433A) are enough to disrupt the VS-SF coupling, shown by the absence of Q-V and G-V crossing in L361R:W434F mutant and by the lack of ionic conduction in the L366H:W434F mutant. This residue chain defines a new coupling between the VSD and the PD in voltage-gated channels. © 2021, eLife Sciences Publications Ltd. All rights reserved.
    • Shore crabs reveal novel evolutionary attributes of the mushroom body

      Strausfeld, N.; Sayre, M.E.; Department of Neuroscience, University of Arizona (eLife Sciences Publications Ltd, 2021)
      Neural organization of mushroom bodies is largely consistent across insects, whereas the ancestral ground pattern diverges broadly across crustacean lineages resulting in successive loss of columns and the acquisition of domed centers retaining ancestral Hebbian-like networks and aminergic connections. We demonstrate here a major departure from this evolutionary trend in Brachyura, the most recent malacostracan lineage. In the shore crab Hemigrapsus nudus, instead of occupying the rostral surface of the lateral protocerebrum, mushroom body calyces are buried deep within it with their columns extending outwards to an expansive system of gyri on the brain’s surface. The organization amongst mushroom body neurons reaches extreme elaboration throughout its constituent neuropils. The calyces, columns, and especially the gyri show DC0 immunoreactivity, an indicator of extensive circuits involved in learning and memory. © Strausfeld and Sayre.
    • Targeting a cell surface vitamin D receptor on tumor-associated macrophages in triple-negative breast cancer

      Staquicini, F.I.; Hajitou, A.; Driessen, W.H.; Proneth, B.; Cardó-Vila, M.; Staquicini, D.I.; Markosian, C.; Hoh, M.; Cortez, M.; Hooda-Nehra, A.; et al. (eLife Sciences Publications Ltd, 2021)
      Triple-negative breast cancer (TNBC) is an aggressive tumor with limited treatment options and poor prognosis. We applied the in vivo phage display technology to isolate peptides homing to the immunosuppressive cellular microenvironment of TNBC as a strategy for non-malignant target discovery. We identified a cyclic peptide (CSSTRESAC) that specifically binds to a vitamin D receptor, protein disulfide-isomerase A3 (PDIA3) expressed on the cell surface of tumor-associated macrophages (TAM), and targets breast cancer in syngeneic TNBC, non-TNBC xenograft, and transgenic mouse models. Systemic administration of CSSTRESAC to TNBC-bearing mice shifted the cytokine profile toward an antitumor immune response and delayed tumor growth. Moreover, CSSTRESAC enabled ligand-directed theranostic delivery to tumors and a mathematical model confirmed our experimental findings. Finally, in silico analysis showed PDIA3-expressing TAM in TNBC patients. This work uncovers a functional interplay between a cell surface vitamin D receptor in TAM and antitumor immune response that could be therapeutically exploited. © 2021, Staquicini et al.
    • Traumatic injury compromises nucleocytoplasmic transport and leads to TDP-43 pathology

      Anderson, E.N.; Morera, A.A.; Kour, S.; Cherry, J.D.; Ramesh, N.; Gleixner, A.; Schwartz, J.C.; Ebmeier, C.; Old, W.; Donnelly, C.J.; et al. (eLife Sciences Publications Ltd, 2021)
      Traumatic brain injury (TBI) is a predisposing factor for many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and chronic traumatic encephalopathy (CTE). Although defects in nucleocytoplasmic transport (NCT) is reported ALS and other neurodegenerative diseases, whether defects in NCT occur in TBI remains unknown. We performed proteomic analysis on Drosophila exposed to repeated TBI and identified resultant alterations in several novel molecular pathways. TBI upregulated nuclear pore complex (NPC) and nucleocytoplasmic transport (NCT) proteins as well as alter nucleoporin stability. Traumatic injury disrupted RanGAP1 and NPC protein distribution in flies and a rat model and led to coaggregation of NPC components and TDP-43. In addition, trauma-mediated NCT defects and lethality are rescued by nuclear export inhibitors. Importantly, genetic upregulation of nucleoporins in vivo and in vitro triggered TDP-43 cytoplasmic mislocalization, aggregation, and altered solubility and reduced motor function and lifespan of animals. We also found NUP62 pathology and elevated NUP62 concentrations in postmortem brain tissues of patients with mild or severe CTE as well as co-localization of NUP62 and TDP-43 in CTE. These findings indicate that TBI leads to NCT defects, which potentially mediate the TDP-43 pathology in CTE. © 2021, Anderson et al.
    • Universal and taxon-specific trends in protein sequences as a function of age

      James, Jennifer E; Willis, Sara M; Nelson, Paul G; Weibel, Catherine; Kosinski, Luke J; Masel, Joanna; Department of Ecology and Evolutionary Biology, University of Arizona; Department of Physics, University of Arizona; Department of Mathematics, University of Arizona; Department of Molecular and Cellular Biology, University of Arizona (eLife Sciences Publications Ltd, 2021-01-08)
      Extant protein-coding sequences span a huge range of ages, from those that emerged only recently to those present in the last universal common ancestor. Because evolution has had less time to act on young sequences, there might be ‘phylostratigraphy’ trends in any properties that evolve slowly with age. A long-term reduction in hydrophobicity and hydrophobic clustering was found in previous, taxonomically restricted studies. Here we perform integrated phylostratigraphy across 435 fully sequenced species, using sensitive HMM methods to detect protein domain homology. We find that the reduction in hydrophobic clustering is universal across lineages. However, only young animal domains have a tendency to have higher structural disorder. Among ancient domains, trends in amino acid composition reflect the order of recruitment into the genetic code, suggesting that the composition of the contemporary descendants of ancient sequences reflects amino acid availability during the earliest stages of life, when these sequences first emerged. © James et al.