Pathway maps

Neurophysiological process_Receptor-mediated axon growth repulsion
Neurophysiological process_Receptor-mediated axon growth repulsion

Object List (links open in MetaCore):

ROCK, Rac1, B-Raf, Ephrin-A, Tubulin (in microtubules), Tau, EGFR, RAP-1A, Cortactin, Neuropilin-1, Fer, Ephrin-A receptor 2, Tiam 1, Plexin A2, Arp2/3, Pleiotrophin (OSF1), Fyn, PDZ-RhoGEF, Semaphorin 3A, c-Fes, VAV-2, HB-EGF, ROCK2, Ephexin, GRB7, LARG, c-Raf-1, LIMK1, Syndecan-3, CDK5, Destrin, CDC42, Plexin A1, Ephrin-A receptors, Cofilin, c-Src, RHO6, glycosylphosphatidylinositol, PAK1, RhoA, CRMP2, LIMK2, Semaphorin 4D, Actin cytoskeletal, Plexin B1


Receptor-mediated axon growth repulsion

Ephrin-A proteins which are anchored in the plasma membrane through attachment of glycosylphosphatidylinositol ( GPI ) [1], are the ligands for Ephrin-A receptors, which belong to the membrane family of receptor tyrosine kinases [2].

In the absence of Ephrin-A stimulation, Ephrin-A receptors are shown to target Ephexin exchange factor to the plasma membrane. Ephrin-A stimulation of Ephrin-A receptors activates exchange factors Ephexin [3], VAV-2 [3] and Tiam 1 [4]. Src-family tyrosine kinases c-Src and Fyn are recruited to Ephrin-A receptors after Ephrin-A stimulation [5]. In response to Ephrin-A signaling Ephexin becomes phosphorylated by c-Src [5] and this phosphorylation enhances its activity toward Ras homolog gene family, member A ( RhoA ) [6]. VAV-2 is rapidly phosphorylated by c-Src upon stimulation by Ephrin-A [3] and activates RhoA [7].

Ephrin-A receptors have also been shown to signal through the Ras-related C3 botulinum toxin substrate 1 ( Rac1 ) exchange factors Tiam1 [4] and VAV-2 [8] to promote neurite outgrowth.

In response to Ephrin-A1 stimulation, Ras-related protein Rap-1A is activated [9] and can regulate MAPK signaling cascade by reducing c-Raf-1 activation [10] or by stimulation of B-Raf kinase [11], [9].

When Ephrin-A receptors are activated, phosphorylation of Ephexin promotes its GTPase activity toward RhoA. RhoA downstream effector Rho-associated kinase ROCK directly phosphorylates LIM-kinases LIMK1 and LIMK2, which in turn phosphorylates actin-depolymerizing factor destrin and actin-associated protein cofilin. Activity of LIMK1 is also regulated by p21-activated kinase 1 ( PAK1 ) [12]. Cofilin and destrin both exhibit actin -depolymerizing activity followed by reorganization of the actin cytoskeleton [13], [14].

The F-actin-binding protein cortactin is an important regulator of cytoskeletal dynamics, and a prominent target of various tyrosine kinases ( c-Src, Fyn, Fer ) [5], [15]. Tyrosine phosphorylation of cortactin has been suggested to reduce its F-actin cross-linking capability [15].

The semaphorins family of secreted or membrane-bound proteins was identified originally as axonal guidance factors functioning during neuronal development. The class 4 semaphorin Semaphorin 4D utilizes Plexin B1 (transmembrane protein) as receptor. [16] Plexin B1 directly interacts with exchange factors PDZ-RhoGEF and LARG to regulate RhoA and the growth cone morphology [17].

Rho6 is a member of Rho family GTPases. It is activated by adaptor protein Grb7 and directly interacts with the cytoplasmic domain of Plexin B1 in response to Semaphorin 4D. Rho6 promotes the interaction between Plexin B1 and PDZ-RhoGEF and thereby potentiates the PDZ-RhoGEF -induced RhoA activation [18].

PAK1 promotes activation of actin polymerization by phosphorylation of Arp2/3 (complex of actin-related proteins) [19]. c-Raf-1 kinase, a member of the MAPK pathway, is also phosphorylated and activated by PAK1 [20]. Inhibition of Pak1 by Plexin B1 is believed to cause suppression of membrane protrusions, thus supporting the cell repulsion response. Furthermore, active Rac1 was shown to promote cell surface localization of Plexin B1 thus enhancing Semaphorin 4D binding to the receptor. Thus, Rac1 and Plexin B1 signaling appears to be bidirectional: Rac-1 modulates Plexin B1 activity, and Plexin B1 modulates Rac-1 function [21].

Another semaphorin, Semaphorin 3A, binds to Neuropilin-1/ Plexin A1 complex and induces repulsive responses [22]. The active form of Rac1 directly binds to Plexin-A1. A ctivated Rac1 mediates endocytosis of the growth cone plasma membranes and reorganization of F-actin in neurons [23]. Endocytosis of plasma membranes is supposed to be an important step for growth cone collapse.

c-Fes tyrosine kinase also is implicated in Semaphorin 3A -induced collapse [24]. c-Fes directly binds to the cytoplasmic region of Plexin A1. In the resting state, neuropilin-1 associates with Plexin-A1 and blocks the binding of c-Fes to Plexin A1. Semaphorin 3A binding to Neuropilin-1 permits c-Fes to associate with and phosphorylate Plexin A1. This tyrosine phosphorylation stimulates repulsive action in the receptor.

c-Fes also phosphorylates collapsin response mediator protein CRMP2 [25].

Fyn, a member of src-family of tyrosine kinases, associates with Plexin A2 in response to Semaphorin 3A and phosphorylates serine/threonine kinase CDK5. [26] Activated CDK5 phosphorylates CRMP2 [27]. ROCK2 kinase also has been shown to phosphorylate CRMP2 [28]. CRMP2 binds to tubulin heterodimers to promote microtubule assembly that is important for axonal growth and branching [29]. Phosphorylation of CRMP2 reduces its tubulin-heterodimer binding and the promotion of microtubule assembly.

CDK5 also phosphorylates the microtubule-associated protein Tau, thereby reduces its ability to induce tubulin microtubule formation [30].


  1. Poliakov A, Cotrina M, Wilkinson DG
    Diverse roles of eph receptors and ephrins in the regulation of cell migration and tissue assembly. Developmental cell 2004 Oct;7(4):465-80
  2. Murai KK, Pasquale EB
    New exchanges in eph-dependent growth cone dynamics. Neuron 2005 Apr 21;46(2):161-3
  3. Cowan CW, Shao YR, Sahin M, Shamah SM, Lin MZ, Greer PL, Gao S, Griffith EC, Brugge JS, Greenberg ME
    Vav family GEFs link activated Ephs to endocytosis and axon guidance. Neuron 2005 Apr 21;46(2):205-17
  4. Tanaka M, Ohashi R, Nakamura R, Shinmura K, Kamo T, Sakai R, Sugimura H
    Tiam1 mediates neurite outgrowth induced by ephrin-B1 and EphA2. The EMBO journal 2004 Mar 10;23(5):1075-88
  5. Knoll B, Drescher U
    Src family kinases are involved in EphA receptor-mediated retinal axon guidance. The Journal of neuroscience : the official journal of the Society for Neuroscience 2004 Jul 14;24(28):6248-57
  6. Sahin M, Greer PL, Lin MZ, Poucher H, Eberhart J, Schmidt S, Wright TM, Shamah SM, O'connell S, Cowan CW, Hu L, Goldberg JL, Debant A, Corfas G, Krull CE, Greenberg ME
    Eph-dependent tyrosine phosphorylation of ephexin1 modulates growth cone collapse. Neuron 2005 Apr 21;46(2):191-204
  7. Schmidt A, Hall A
    Guanine nucleotide exchange factors for Rho GTPases: turning on the switch. Genes & development 2002 Jul 1;16(13):1587-609
  8. Bustelo XR
    Regulatory and signaling properties of the Vav family. Molecular and cellular biology 2000 Mar;20(5):1461-77
  9. Aoki M, Yamashita T, Tohyama M
    EphA receptors direct the differentiation of mammalian neural precursor cells through a mitogen-activated protein kinase-dependent pathway. The Journal of biological chemistry 2004 Jul 30;279(31):32643-50
  10. Hu CD, Kariya K, Kotani G, Shirouzu M, Yokoyama S, Kataoka T
    Coassociation of Rap1A and Ha-Ras with Raf-1 N-terminal region interferes with ras-dependent activation of Raf-1. The Journal of biological chemistry 1997 May 2;272(18):11702-5
  11. Bos JL, de Bruyn K, Enserink J, Kuiperij B, Rangarajan S, Rehmann H, Riedl J, de Rooij J, van Mansfeld F, Zwartkruis F
    The role of Rap1 in integrin-mediated cell adhesion. Biochemical Society transactions 2003 Feb;31(Pt 1):83-6
  12. Sumi T, Matsumoto K, Nakamura T
    Specific activation of LIM kinase 2 via phosphorylation of threonine 505 by ROCK, a Rho-dependent protein kinase. The Journal of biological chemistry 2001 Jan 5;276(1):670-6
  13. Wilson JG
    Reproduction and teratogenesis: current methods and suggested improvements. Journal - Association of Official Analytical Chemists. 1975 Jul;58(4):657-67
  14. Maekawa M, Ishizaki T, Boku S, Watanabe N, Fujita A, Iwamatsu A, Obinata T, Ohashi K, Mizuno K, Narumiya S
    Signaling from Rho to the actin cytoskeleton through protein kinases ROCK and LIM-kinase. Science 1999 Aug 6;285(5429):895-8
  15. Fan L, Di Ciano-Oliveira C, Weed SA, Craig AW, Greer PA, Rotstein OD, Kapus A
    Actin depolymerization-induced tyrosine phosphorylation of cortactin: the role of Fer kinase. The Biochemical journal 2004 Jun 1;380(Pt 2):581-91
  16. Kumanogoh A, Kikutani H
    Biological functions and signaling of a transmembrane semaphorin, CD100/Sema4D. Cellular and molecular life sciences : CMLS 2004 Feb;61(3):292-300
  17. Swiercz JM, Kuner R, Behrens J, Offermanns S
    Plexin-B1 directly interacts with PDZ-RhoGEF/LARG to regulate RhoA and growth cone morphology. Neuron 2002 Jul 3;35(1):51-63
  18. Oinuma I, Katoh H, Harada A, Negishi M
    Direct interaction of Rnd1 with Plexin-B1 regulates PDZ-RhoGEF-mediated Rho activation by Plexin-B1 and induces cell contraction in COS-7 cells. The Journal of biological chemistry 2003 Jul 11;278(28):25671-7
  19. Cowan CA, Henkemeyer M
    The SH2/SH3 adaptor Grb4 transduces B-ephrin reverse signals. Nature 2001 Sep 13;413(6852):174-9
  20. Coles LC, Shaw PE
    PAK1 primes MEK1 for phosphorylation by Raf-1 kinase during cross-cascade activation of the ERK pathway. Oncogene 2002 Mar 28;21(14):2236-44
  21. Negishi M, Oinuma I, Katoh H
    Plexins: axon guidance and signal transduction. Cellular and molecular life sciences : CMLS 2005 Jun;62(12):1363-71
  22. Bagri A, Cheng HJ, Yaron A, Pleasure SJ, Tessier-Lavigne M
    Stereotyped pruning of long hippocampal axon branches triggered by retraction inducers of the semaphorin family. Cell 2003 May 2;113(3):285-99
  23. Jurney WM, Gallo G, Letourneau PC, McLoon SC
    Rac1-mediated endocytosis during ephrin-A2- and semaphorin 3A-induced growth cone collapse. The Journal of neuroscience : the official journal of the Society for Neuroscience 2002 Jul 15;22(14):6019-28
  24. Mitsui N, Inatome R, Takahashi S, Goshima Y, Yamamura H, Yanagi S
    Involvement of Fes/Fps tyrosine kinase in semaphorin3A signaling. The EMBO journal 2002 Jul 1;21(13):3274-85
  25. Goshima Y, Nakamura F, Strittmatter P, Strittmatter SM
    Collapsin-induced growth cone collapse mediated by an intracellular protein related to UNC-33. Nature 1995 Aug 10;376(6540):509-14
  26. Sasaki Y, Cheng C, Uchida Y, Nakajima O, Ohshima T, Yagi T, Taniguchi M, Nakayama T, Kishida R, Kudo Y, Ohno S, Nakamura F, Goshima Y
    Fyn and Cdk5 mediate semaphorin-3A signaling, which is involved in regulation of dendrite orientation in cerebral cortex. Neuron 2002 Aug 29;35(5):907-20
  27. Uchida Y, Ohshima T, Sasaki Y, Suzuki H, Yanai S, Yamashita N, Nakamura F, Takei K, Ihara Y, Mikoshiba K, Kolattukudy P, Honnorat J, Goshima Y
    Semaphorin3A signalling is mediated via sequential Cdk5 and GSK3beta phosphorylation of CRMP2: implication of common phosphorylating mechanism underlying axon guidance and Alzheimer's disease. Genes to cells : devoted to molecular & cellular mechanisms 2005 Feb;10(2):165-79
  28. Arimura N, Inagaki N, Chihara K, Menager C, Nakamura N, Amano M, Iwamatsu A, Goshima Y, Kaibuchi K
    Phosphorylation of collapsin response mediator protein-2 by Rho-kinase. Evidence for two separate signaling pathways for growth cone collapse. The Journal of biological chemistry 2000 Aug 4;275(31):23973-80
  29. Fukata Y, Itoh TJ, Kimura T, Menager C, Nishimura T, Shiromizu T, Watanabe H, Inagaki N, Iwamatsu A, Hotani H, Kaibuchi K
    CRMP-2 binds to tubulin heterodimers to promote microtubule assembly. Nature cell biology 2002 Aug;4(8):583-91
  30. Hashiguchi M, Saito T, Hisanaga S, Hashiguchi T
    Truncation of CDK5 activator p35 induces intensive phosphorylation of Ser202/Thr205 of human tau. The Journal of biological chemistry 2002 Nov 15;277(46):44525-30