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Fig 19.6  PKC and migration of astrocytes.

(a) A scratch in a near-confluent culture of astrocytes provokes reorientation and migration of the adjacent cells to fill the gap. This is guided by the accumulation of the scaffold protein Scrib, bound to PIX (RhoGEF). Ensuing activation of the Par-6 polarity complex causes protrusion formation, involving the GTPase Rac1, and reorientation of the microtubule cytoskeleton. In order to achieve this, atypical PKC phosphorylates and inactivates GSK3 , causing clustering of APC at the microtubule plus ends. It also phosphorylates and activates Dlg, which is now recruited to the membrane. Binding of Dlg and APC assures anchorage of the microtubules to the protruding membrane to provide directionality to the migration process. (b) Immunocytochemical staining

of the Golgi apparatus (green), the centrosome (red) and the nucleus (blue) reveals the orientation of the astrocytes perpendicular to the scratch line.

(c) Immunocytochemical staining of APC (red and indicated by an asterisk) at the plus end of the microtubules (green). Locations of the centromeres are indicated by blue crosses and the nuclei are red.

Images b and c courtesy of Dr Etienne-Manneville, Institut Pasteur, Paris, France.

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Fig 19.7  Domain architecture of proteins involved in astrocyte migration and axonal outgrowth. See also Figure 14, page 434.

Regulation of atypical PKC by Dishevelled and its role in axon outgrowth

Neurons transmit their signal via axons. These are typically long, thin processes of uniform width. Each cell produces a single axon, although near to its end the axon may branch to form one or more presynaptic terminals. Neurons receive inputs via other processes called dendrites which also extend from the cell body. They are relatively short, but close to the cell body they are thick and with increasing distance they become thinner, forming numerous Y-shaped branches. (Figure 19.8). These two cellular structures, with the synaptic contacts they make with other cells, are the basic means by which nerve cells receive, process, and transmit signals. Axon formation has been extensively studied in cultured hippocampal neurons. These cells initially form multiple projections called neurites which extend and retract, until, at a moment,

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Fig 19.8  Axon outgrowth.

(a)Morphology of hippocampal neurons in culture. Note the numerous short dendrites and the single long axon.

(b)Loss of expression of Dvl, by siRNA knockdown, leads to loss of polarity and numerous short axons are produced.

(c)Injection of PKCinto Dvl-depleted neurons restores polarity with the formation of a single long axon. Adapted from Arimura and Kaibuchi.61

just one of them stretches a little beyond the others to become the unique axon. Its formation then prevents the extension of other neurites, most likely through depletion of Cdc42. In consequence, the remaining neurites become dendrites.

The tip of the growing axon accumulates dishevelled (Dvl is the human orthologue of Drosophila Dsh), associated with Frizzled (Fz), a receptor for the family of Wnt ligands (see page 421). Both Dsh/Dvl and Fz were discovered in Drosophila mutants in which the epithelial cells had lost the polarized positioning of the wing hairs (see Figure 14.2, page 422). Dvl binds the aPKC– Par-6–Par-3 polarity complex and this leads to stabilization and activation.

Although Cdc42 also accumulates in the growing axon,62 its precise role in the activation of Dvl-associated PKC remains to be determined.

An important substrate of the atypical PKC is the serine/threonine kinase MARK2 (Figure 19.9) which, on phosphorylation is inactivated and detaches from the membrane.63 This removes an inhibitory constraint for a number of components that normally interact with microtubules. Among these are Tau and MAP1B. The other substrate is GSK3 which also becomes inactivated, so enabling the association of APC and CRMP2 with microtubules. These proteins stabilize microtubules and also facilitate their attachment to the plasma membrane. In so doing, they provide important support for the growing axon. The domain architecture of proteins involved in axon outgrowth is summarized in Figure 19.7.

The Rac1 guanine exchange protein Tiam1/STEF lies downstream of the aPKC–Par-6–Par-3 polarity complex. It therefore activates Rac1 which leads to cytoskeletal reorganization which also contributes to neuronal polarity.64

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Fig 19.9  Dv1, PKC , Par-6, and polarity of axonal outgrowth.

(a) Hippocampal neurons form multiple neurites of which only one becomes an axon. (b) Axon outgrowth, stimulated by Wnt at the Fz receptor is initiated by the binding of a PKC –Par-3–Par-6 polarity complex to Dvl. Activated PKC phosphorylates and inactivates both MARK2 and GSK3 . Loss of kinase activity leads to a dephosphorylation of the microtubule binding proteins CRMP2, MAP1B, Tau, and APC. These now bind to microtubules, preventing depolymerization and allowing their interaction with the plasma membrane.

List of abbreviations

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References

 1. Berenblum I. Cocarcinogenic action of croton resin. Cancer Res. 1941;1:48.

 2. Sivak A, Van Duuren BL. Phenotypic expression of transformation: induction in cell culture by a phorbol ester. Science. 1967;157:1443–1444.

 3. Cook J, Hewett C, Hieger I. The isolation of a cancer-producing hydrocarbon from coal tar. J Chem Soc. 1933:395–405.

 4. Ling H, Sayer JM, Plosky BS, et al. Crystal structure of a benzo[a]pyrene diol epoxide adduct in a ternary complex with a DNA polymerase. Proc Natl Acad Sci U S A. 2004;101:2269.

 5. Pfeifer GP, Denissenko MF, Olivier M, Tretyakova N, Hecht SS, Hainaut

P.Tobacco smoke carcinogens, DNA damage and p53 mutations in smoking-associated cancers. Oncogene. 2002;21:7435–7451.

 6. Imbra RJ, Karin M. Phorbol ester induces the transcriptional stimulatory activity of the SV40 enhancer. Nature. 1986;323:555–558.

 7. Housey GM, Johnson MD, Hsiao WL, et al. Overproduction of protein kinase

Ccauses disordered growth control in rat fibroblasts. Cell. 1998;52:343–345.

 8. Angel P, Imagawa M, Chiu R, et al. Phorbol ester-inducible genes contain a common cis element recognized by a TPA-modulated trans-acting factor. Cell. 1987;49:729–739.

 9. Shaulian E, Karin M. AP-1 in cell proliferation and survival. Oncogene. 2001;20:2390–2400.

10.Sassone-Corsi P, Ransone LJ, Lamph WW, Verma IM. Direct interaction between fos and jun nuclear oncoproteins: role of the ‘leucine zipper’ domain. Nature. 1988;336:692–695.

11.Karin M, Liu Z, Zandi E. AP-1 function and regulation. Cell. 1997;9:240–246.

12.Bohmann D, Tjian R. Biochemical analysis of transcriptional activation by Jun: differential activity of c- and v-Jun. Cell. 1989;59:709–717.

13.Kramer IM, Koornneef I, de Laat SW, van den Eijnden-van Raaij AJ. TGF- 1 induces phosphorylation of the cyclic AMP responsive element binding protein in ML-CCl64 cells. EMBO J. 1991;10:1083–1089.

594

Protein Kinase C Revisited

14.Masquilier D, Sassone CP. Transcriptional cross-talk: nuclear factors CREM and CREB bind to AP-1 sites and inhibit activation by Jun. J Biol Chem. 1992;267:22460–22466.

15.Vogt PK. Jun, the oncoprotein. Oncogene. 2001;20:2365–2377.

16.Eferl R, Wagner EF. AP-1: a double-edged sword in tumorigenesis. Nat Rev Cancer. 2003;3:859–868.

17.Boyle WJ, Smeal T, Defize LH, et al. Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity. Cell. 1991;64:573–584.

18.Goode N, Hughes K, Woodgett JR, Parker PJ. Differential regulation of glycogen synthase kinase-3 by protein kinase C isotypes. J Biol Chem. 1992;267:16878–16882.

19.Smeal T, Binetruy B, Mercola DA, Birrer M, Karin M. Oncogenic and transcriptional cooperation with Ha-Ras requires phosphorylation of c-Jun on serines 63 and 73. Nature. 2000;354:494–496.

20.Behrens A, Jochum W, Sibilia M, Wagner EF. Oncogenic transformation by ras and fos is mediated by c-Jun N-terminal phosphorylation. Oncogene. 2000;19:2657–2663.

21.Derijard B, Hibi M, Wu IH, et al. JNK1: a protein kinase stimulated by UV light and Ha-Ras that binds and phosphorylates the c-Jun activation domain. Cell. 1994;76:1025–1037.

22.Kallunki T, Deng T, Hibi M, Karin M. c-Jun can recruit JNK to phosphorylate dimerization partners via specific docking interactions. Cell. 1996;87: 929–939.

23.Kolch W, Heidecker G, Kochs G, et al. Protein kinase C activates RAF-1 by direct phosphorylation. Nature. 1993;364:249–252.

24.Cacace AM, Ueffing M, Philipp A, et al. PKC functions as an oncogene by enhancing activation of the Raf kinase. Oncogene. 1996;13:2517–2526.

25.Yeung K, Seitz T, Li S, et al. Suppression of Raf-1 kinase activity and MAP kinase signalling by RKIP. Nature. 1999;401:173–177.

26.Corbit KC, Trakul N, Eves EM, Diaz B, Marshall M, Rosner MR. Activation of Raf-1 signaling by protein kinase C through a mechanism involving Raf kinase inhibitory protein. J Biol Chem. 2003;278:13061–13068.

27.Schonwasser DC, Marais RM, Marshall CJ, Parker PJ. Activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway by conventional, novel, and atypical protein kinase C isotypes. Mol Cell Biol. 1998;18:790–798.

28.Whitmarsh AJ, Shore P, Sharrocks AD, Davis RJ. Integration of MAP kinase signal transduction pathways at the serum response element. Science. 1995;269:403–407.

29.Gille H, Downward J. Multiple ras effector pathways contribute to G(1) cell cycle progression. J Biol Chem. 1999;274:22033–22040.

30.Lopez-Bergami P, Huang C, Goydos JS, et al. Rewired ERK-JNK signaling pathways in melanoma. Cancer Cell. 2007;11:447–460.

595

Signal Transduction

31.Weston CR, Davis RJ. The JNK signal transduction pathway. Curr Opin Genet Dev. 2002;12:14–21.

32.Lopez-Bergami P, Habelhah H, Bhoumik A, Zhang W, Wang LH, Ronai Z. RACK1 mediates activation of JNK by protein kinase C. Mol Cell 2005;19:309–320.

33.Berns H, Humar R, Hengerer B, Kiefer FN, Battegay EJ. RACK1 is up-regulated in angiogenesis and human carcinomas. FASEB J. 2000;14:2549–2558.

34.Heo YS, Kim SK, Seo CI, et al. Structural basis for the selective inhibition of JNK1 by the scaffolding protein JIP1 and SP600125. EMBO J. 2004;23:2185–2195.

35.Borner C, Ueffing M, Jaken S, Parker PJ, Weinstein IB. Two closely related isoforms of protein kinase C produce reciprocal effects on the growth of rat fibroblasts Possible molecular mechanisms. J Biol Chem. 1995;270:78–86.

36.Hsiao WL, Housey GM, Johnson MD, Weinstein IB. Cells that overproduce protein kinase C are more susceptible to transformation by an activated H-ras oncogene. Mol Cell Biol. 1989;9:2641–2647.

37.Besson A, Yong VW. Involvement of p21(Waf1/Cip1) in protein kinase C-induced cell cycle progression. Mol Cell Biol. 2000;20:4580–4590.

38.Kieser A, Sietz T, Adler HS, et al. Protein kinase C reverts v-raf transformation of NIH-3T3 cells. Genes Dev. 1966;10:1455–1466.

39.Fukumoto S, Nishizawa Y, Hosoi M, et al. Protein kinase Cδ inhibits the proliferation of vascular smooth muscle cells by suppressing G1 cyclin expression. J Biol Chem. 1997;272:13816–13822.

40.Jackson DN, Foster DA. The enigmatic protein kinase Cδ: complex roles in cell proliferation and survival. FASEB J. 2004;18:627–636.

41.Griner EM, Kazanietz MG. Protein kinase C and other diacylglycerol effectors in cancer. Nat Rev Cancer. 2007;7:281–294.

42.Ruegg C. Leukocytes, inflammation, and angiogenesis in cancer: fatal attractions. J Leukoc Biol. 2006;80:682–684.

43.Prevostel C, Martin A, Alvaro V, Jaffiol C, Joubert D. Protein kinase C and tumorigenesis of the endocrine gland. Horm Res. 1997;47:140–144.

44.Prevostel C, Alvaro V, Vallentin A, Martin A, Jaken S, Joubert D. Selective loss of substrate recognition induced by the tumour-associated D294G point mutation in protein kinase C . Biochem J. 1998;334:393–397.

45.Tognon CE, Kirk HE, Passmore LA, Whitehead IP, Der CJ, Kay RJ. Regulation of RasGRP via a phorbol ester-responsive C1 domain. Mol Cell Biol. 1998;18:6995–7008.

46.Kemphues KJ, Priess JR, Morton DG, Cheng NS. Identification of genes required for cytoplasmic localization in early C. elegans embryos. Cell. 1988;52:311–320.

47.Henrique D, Schweisguth F. Cell polarity: the ups and downs of the Par6/ aPKC complex. Curr Opin Genet Dev. 2003;13:341–350.

48.Munro E, Nance J, Priess JR. Cortical flows powered by asymmetrical contraction transport PAR proteins to establish and maintain anteriorposterior polarity in the early C. elegans embryo. Dev Cell. 2004;7:413–424.

596