Highlights d Structure-guided design of PARP inhibitors d Identification of a potent and selective PARP11 inhibitor (ITK7) d ITK7 inhibits PARP11 auto-MARylation in cells d ITK7 causes PARP11 to dissociate from the nuclear envelope

The three Drosophila atypical soluble guanylyl cyclases, Gyc-89Da, Gyc-89Db, and Gyc-88E, have been proposed to act as oxygen detectors mediating behavioral responses to hypoxia. Drosophila larvae mutant in any of these subunits were defective in their hypoxia escape response-a rapid cessation of feeding and withdrawal from their food. This response required cGMP and the cyclic nucleotide-gated ion channel, cng, but did not appear to be dependent on either of the cGMP-dependent protein kinases, dg1 and dg2. Specific activation of the Gyc-89Da neurons using channel rhodopsin showed that activation of these neurons was sufficient to trigger the escape behavior. The hypoxia escape response was restored by reintroducing either Gyc-89Da or Gyc-89Db into either Gyc-89Da or Gyc-89Db neurons in either mutation. This suggests that neurons that co-express both Gyc-89Da and Gyc-89Db subunits are primarily responsible for activating this behavior. These include sensory neurons that innervate the terminal sensory cones. Although the roles of Gyc-89Da and Gyc-89Db in the hypoxia escape behavior appeared to be identical, we also showed that changes in larval crawling behavior in response to either hypoxia or hyperoxia differed in their requirements for these two atypical sGCs, with responses to 15% oxygen requiring Gyc-89Da and responses to 19 and 25% requiring Gyc-89Db. For this behavior, the identity of the neurons appeared to be critical in determining the ability to respond appropriately.

Many chronic trigeminal pain conditions, such as migraine or temporo-mandibular disorders, are associated with inflammation within peripheral endings of trigeminal ganglion (TG) sensory neurons. A critical role in mechanisms of neuroinflammation is attributed to proinflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α (TNFα) that also contribute to mechanisms of persistent neuropathic pain resulting from nerve injury. However, the mechanisms of cytokine-mediated synaptic plasticity and nociceptor sensitization are not completely understood. In the present study, we examined the effects of TNFα on neuronal expression of brain-derived neurotrophic factor (BDNF), whose role in synaptic plasticity and sensitization of nociceptive pathways is well documented. We show that 4-and 24-hr treatment with TNFα increases BDNF mRNA and protein, respectively, in neuron-enriched dissociated cultures of rat TG. TNFα increases the phosphorylated form of the cyclic adenosine monophosphate-responsive element binding protein (CREB), a transcription factor involved in regulation of BDNF expression in neurons, and activates transcription of BDNF exon IV (former exon III) and, to a lesser extent, exon VI (former exon IV), but not exon I. TNFα-mediated increase in BDNF expression was accompanied by increase in calcitonin gene-related peptide (CGRP), which is consistent with © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.Corresponding author: Dr. Agnieszka Balkowiec, Department of Integrative Biosciences, Oregon Health and Science University School of Dentistry, 611 S.W. Campus Drive, Portland, OR 97239; Phone: (503) 418-0190; Fax: (503) 494-8554; balkowie@ohsu.edu. All experimental protocols are available in a detailed, step-by-step format upon request from Dr. Ewa Bałkowiec-Iskra (ebalkowiec@wum.edu.pl).. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Research Highlights:1. BDNF mRNA and protein are upregulated in trigeminal ganglion neurons by TNF-α 2. TNF-α upregulates BDNF expression in a promoter-selective manner 3. TNF-α upregulation of BDNF expression is potentiated by neuronal activity and cAMP 4. TNF-α upregulation of BDNF expression depends on sodium channels and p38-MAPK 5. These data have implications for BDNF-dependent sensory plasticity NIH Public Access Vitkovic et al., 2000;Boulanger, 2009;Carpentier and Palmer, 2009). Thus, identifying the mechanisms that underlie neuro-immune interactions could become fundamental to understanding how the nervous system functions under physiological conditions and what goes awry in the disorders whose pa...

Poly(ADP-ribose) polymerase 14 (PARP14) is a member of the PARP family of enzymes that transfer ADP-ribose from NAD + to nucleophilic amino acids on target proteins, a process known as mono-ADP-ribosylation (MARylation). PARP14 is involved in normal immune function through the IL-4 signaling pathway and is a prosurvival factor in multiple myeloma and hepatocellular carcinoma. A mechanistic understanding of the physiological and pathophysiological roles of PARP14 has been limited by the dearth of PARP14-specific MARylation targets. Herein we engineered a PARP14 variant that uses an NAD + analog that is orthogonal to wild-type PARPs for identifying PARP14specific MARylation targets. Combining this chemical genetics approach with a BioID approach for proximity-dependent labeling of PARP14 interactors, we identified 114 PARP14-specific protein substrates, several of which are RNA regulatory proteins. One of these targets is PARP13, a protein known to play a role in regulating RNA stability. PARP14 MARylates PARP13 on several acidic amino acids. This study not only reveals crosstalk among PARP family members but also highlights the advantage of using disparate approaches for identifying the direct targets of individual PARP family members.

Mono-ADP-ribosylation (MARylation) of mammalian proteins was first described as a post-translational modification catalyzed by bacterial toxins. It is now known that endogenous MARylation occurs in mammalian cells and is catalyzed by 11 members of the poly-ADP-ribose polymerase (PARP) family of proteins (17 in humans). The physiological roles of these PARPs remain largely unknown. Here we demonstrate that PARP6, a neuronally enriched PARP that catalyzes MARylation, regulates hippocampal dendrite morphogenesis, a process that is critical for proper neural circuit formation during development. Knockdown of PARP6 significantly decreased dendritic complexity in embryonic rat hippocampal neurons in culture and in vivo. Expression of wild-type PARP6 increased dendritic complexity; conversely, expression of a catalytically inactive PARP6 mutant, or a cysteine-rich domain deletion mutant that has significantly reduced catalytic activity, decreased dendritic complexity. The identification of PARP6 as a regulator of dendrite morphogenesis supports a role for MARylation in neurons during development.