title: c-Jun N-terminal kinase 1 (JNK1) is required for coordination of netrin signaling in axon guidance.
abstract: The JNK family of MAPKs is involved in a large variety of physiological and pathological processes in brain development, such as neural survival, migration, and polarity as well as axon regeneration. However, whether JNK activation is involved in axon guidance remains unknown. Here, we provide evidence indicating the JNK pathway is required for Netrin signaling in the developing nervous system. Netrin-1 increased JNK1, not JNK2 or JNK3, activity in the presence of deleted in colorectal cancer (DCC) or Down syndrome cell adhesion molecule (DSCAM), and expression of both of them further enhanced Netrin-1-induced JNK1 activity in vitro. Inhibition of JNK signaling either by a JNK inhibitor, SP600125, or expression of a dominant negative form of MKK4, a JNK upstream activator, blocked Netrin-1-induced JNK1 activation in HEK293 cells. Netrin-1 increased endogenous JNK activity in primary neurons. Netrin-1-induced JNK activation was inhibited either by the JNK inhibitor or an anti-DCC function-blocking antibody. Combination of the anti-DCC function-blocking antibody with expression of DSCAM shRNA in primary neurons totally abolished Netrin-1-induced JNK activation, whereas knockdown of DSCAM partially inhibited the Netrin-1 effect. In the developing spinal cord, phospho-JNK was strongly expressed in commissural axons before and as they crossed the floor plate, and Netrin-1 stimulation dramatically increased the level of endogenous phospho-JNK in commissural axon growth cones. Inhibition of JNK signaling either by JNK1 RNA interference (RNAi) or the JNK inhibitor suppressed Netrin-1-induced neurite outgrowth and axon attraction. Knockdown of JNK1 in ovo caused defects in spinal cord commissural axon projection and pathfinding. Our study reveals that JNK1 is important in the coordination of DCC and DSCAM in Netrin-mediated attractive signaling.
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio 43606, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Qu
authors.forename: Weiquan
authors.initials: W
authors.lastname: Li
authors.forename: Qiangqiang
authors.initials: Q
authors.lastname: Shao
authors.forename: Trisha
authors.initials: T
authors.lastname: Dwyer
authors.forename: Huai
authors.initials: H
authors.lastname: Huang
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.forename: Guofa
authors.initials: G
authors.lastname: Liu
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002642:Chick Embryo; D000075389:DCC Receptor; D004622:Embryo, Mammalian; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D048055:Mitogen-Activated Protein Kinase 8 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000075388:Netrin-1; D061251:Primary Cell Culture; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000873:Anthracenes; D015815:Cell Adhesion Molecules; D000075389:DCC Receptor; C501910:Dcc protein, mouse; C491735:Dscam protein, mouse; D007527:Isoenzymes; C000617351:NTN1 protein, human; D009414:Nerve Growth Factors; C000617353:Ntn1 protein, mouse; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; C432165:pyrazolanthrone; D048055:Mitogen-Activated Protein Kinase 8; D048670:MAP Kinase Kinase 4