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• W2023220022 abstract "The angiotensin II (Ang II) type 2 (AT2) receptor is an atypical seven-transmembrane domain receptor. Controversy surrounding this receptor concerns both the nature of the second messengers produced as well as its associated signaling mechanisms. Using the neuronal cell line NG108-15, we have reported previously that activation of the AT2 receptor induced morphological differentiation in a p21 ras -independent, but p42/p44 mapk -dependent mechanism. The activation of p42/p44 mapk was delayed, sustained, and had been shown to be essential for neurite elongation. In the present report, we demonstrate that activation of the AT2 receptor rapidly, but transiently, activated the Rap1/B-Raf complex of signaling proteins. In RapN17- and Rap1GAP-transfected cells, the effects induced by Ang II were abolished, demonstrating that activation of these proteins was responsible for the observed p42/p44 mapk phosphorylation and for morphological differentiation. To assess whether cAMP was involved in the activation of Rap1/B-Raf and neuronal differentiation induced by Ang II, NG108-15 cells were treated with stimulators or inhibitors of the cAMP pathway. We found that dibutyryl cAMP and forskolin did not stimulate Rap1 or p42/p44 mapk activity. Furthermore, adding H-89, an inhibitor of protein kinase A, or Rp-8-Br-cAMP-S, an inactive cAMP analog, failed to impair p42/p44 mapk activity and neurite outgrowth induced by Ang II. The present observations clearly indicate that cAMP, a well known stimulus of neuronal differentiation, did not participate in the AT2 receptor signaling pathways in the NG108-15 cells. Therefore, the AT2 receptor of Ang II activates the signaling modules of Rap1/B-Raf and p42/p44 mapk via a cAMP-independent pathway to induce morphological differentiation of NG108-15 cells. The angiotensin II (Ang II) type 2 (AT2) receptor is an atypical seven-transmembrane domain receptor. Controversy surrounding this receptor concerns both the nature of the second messengers produced as well as its associated signaling mechanisms. Using the neuronal cell line NG108-15, we have reported previously that activation of the AT2 receptor induced morphological differentiation in a p21 ras -independent, but p42/p44 mapk -dependent mechanism. The activation of p42/p44 mapk was delayed, sustained, and had been shown to be essential for neurite elongation. In the present report, we demonstrate that activation of the AT2 receptor rapidly, but transiently, activated the Rap1/B-Raf complex of signaling proteins. In RapN17- and Rap1GAP-transfected cells, the effects induced by Ang II were abolished, demonstrating that activation of these proteins was responsible for the observed p42/p44 mapk phosphorylation and for morphological differentiation. To assess whether cAMP was involved in the activation of Rap1/B-Raf and neuronal differentiation induced by Ang II, NG108-15 cells were treated with stimulators or inhibitors of the cAMP pathway. We found that dibutyryl cAMP and forskolin did not stimulate Rap1 or p42/p44 mapk activity. Furthermore, adding H-89, an inhibitor of protein kinase A, or Rp-8-Br-cAMP-S, an inactive cAMP analog, failed to impair p42/p44 mapk activity and neurite outgrowth induced by Ang II. The present observations clearly indicate that cAMP, a well known stimulus of neuronal differentiation, did not participate in the AT2 receptor signaling pathways in the NG108-15 cells. Therefore, the AT2 receptor of Ang II activates the signaling modules of Rap1/B-Raf and p42/p44 mapk via a cAMP-independent pathway to induce morphological differentiation of NG108-15 cells. angiotensin II type 1 and 2 Ang II receptors, respectively 8-bromo-adenosine cyclic 3′:5′-phosphorothioate 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid cytomegalovirus Dulbecco's modified Eagle's medium fetal bovine serum glutathione S-transferase mitogen-activated protein kinase gene mitogen-activated protein kinase kinase nerve growth factor protein kinase A The angiotensin II (Ang II)1 octapeptide hormone binds two major receptor subtypes, type 1 (AT1) and type 2 (AT2), both of which are expressed in several tissues. One of the most remarkable features of the AT2receptor is its high level of expression in most fetal tissues (1Tanaka M. Ohnishi J. Ozawa Y. Sugimoto M. Usuki S. Naruse M. Murakami K. Miyazaki H. Biochem. Biophys. Res. Commun. 1995; 207: 593-598Crossref PubMed Scopus (123) Google Scholar, 2Schütz S., Le Moullec J.M. Corvol P. Gasc J.M. Am. J. Pathol. 1996; 149: 2067-2079PubMed Google Scholar, 3Breault L. Lehoux J.-G. Gallo-Payet N. J. Clin. Endocrinol. Metab. 1996; 81: 3914-3922PubMed Google Scholar) including the brain (4Millan M.A. Jacobowitz D.M. Aguilera G. Catt K.J. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 11440-11444Crossref PubMed Scopus (182) Google Scholar, 5Tsutsumi K. Strömberg C. Viswanathan M. Saavedra J.M. Endocrinology. 1991; 129: 1075-1082Crossref PubMed Scopus (135) Google Scholar). Some neuronal cell lines such as NG108-15 (6Buisson B. Bottari S.P., De Gasparo M. Gallo-Payet N. Payet M.-D. FEBS Lett. 1992; 309: 161-164Crossref PubMed Scopus (126) Google Scholar, 7Speth R.C. Mei L. Yamamura H.I. Peptide Res. 1989; 2: 232-239PubMed Google Scholar, 8Tallant E.A. Diz D.I. Khosla M.C. Ferrario C.M. Hypertension. 1991; 17: 1135-1143Crossref PubMed Google Scholar), PC12W (9Meffert S. Stoll M. Steckelings U.M. Bottari S.P. Unger T. Mol. Cell. Endocrinol. 1996; 122: 59-67Crossref PubMed Scopus (208) Google Scholar, 10Ouali R. LeBreton M. Saez J. Endocrinology. 1993; 133: 2766-2772Crossref PubMed Scopus (34) Google Scholar), and N1E 115 cells (11Reagan L.P., Ye, X. Maretzski C.H. Fluharty S.J. J. Neurochem. 1993; 60: 24-31Crossref PubMed Scopus (29) Google Scholar, 12Nahmias C. Cazaubon S.M. Briend-Sutren M.N. Lazard D. Villageois P. Strosberg A.D. Biochem. J. 1995; 306: 87-92Crossref PubMed Scopus (56) Google Scholar) also express the AT2 receptor at high levels. The AT1:AT2 receptor ratio increases dramatically after birth (5Tsutsumi K. Strömberg C. Viswanathan M. Saavedra J.M. Endocrinology. 1991; 129: 1075-1082Crossref PubMed Scopus (135) Google Scholar, 13Grady E.F. Sechi L. Griffin C. Schambelan M. Kalinyak J. J. Clin. Invest. 1991; 88: 921-933Crossref PubMed Scopus (497) Google Scholar), suggesting an involvement of the AT2receptor in fetal development. In the adult, the AT2receptor expression is limited to some tissues, such as the adrenal gland and specific areas of the brain. Several recent studies have indicated that ligand-independent activation (14Miura S. Karnik S. EMBO J. 2000; 19: 4026-4035Crossref PubMed Scopus (116) Google Scholar) or Ang II stimulation of the AT2 receptor is associated with antiproliferative effects (15Stoll M. Steckelings M. Paul M. Bottari S.P. Metzger R. Unger T. J. Clin. Invest. 1995; 95: 651-657Crossref PubMed Google Scholar, 16Tsuzuki S. Eguchi S. Inagami T. Biochem. Biophys. Res. Commun. 1996; 228: 825-830Crossref PubMed Scopus (66) Google Scholar), apoptosis (17Horiuchi M. Akishita M. Dzau V.J. Endocr. Res. 1998; 24: 307-314Crossref PubMed Scopus (86) Google Scholar, 18Chamoux E. Breault L. Lehoux J.-G. Gallo-Payet N. J. Clin. Endocrinol. Metab. 1999; 84: 4722-4730Crossref PubMed Scopus (46) Google Scholar), and differentiation. Indeed, involvement of the AT2 receptor has been documented in different models of differentiation such as steroidogenesis in gonads or the adrenal gland (19Johnson M. Vega M. Vantman D. Troncoso J. Devoto L. Mol. Hum. Reprod. 1997; 3: 663-668Crossref PubMed Scopus (32) Google Scholar, 20Moritz K.M. Boon W.C. Wintour E.M. Mol. Cell. Endocrinol. 1999; 157: 153-160Crossref PubMed Scopus (14) Google Scholar, 21Yoshimura Y. Karube M. Aoki H. Oda T. Koyama N. Nagai A. Akimoto Y. Hirano H. Nakamura Y. Endocrinology. 1996; 137: 1204-1211Crossref PubMed Scopus (81) Google Scholar), contractility in smooth muscle cells (22Yamada H. Akishita M. Ito M. Tamura K. Daviet L. Lehtonen J. Dzau V. Horiuchi M. Hypertension. 1999; 33: 1414-1419Crossref PubMed Scopus (74) Google Scholar, 23Akishita M. Ito M. Lehtonen J. Daviet L. Dzau V. Horiuchi M. J. Clin. Invest. 1999; 103: 63-71Crossref PubMed Scopus (88) Google Scholar), or neurite outgrowth in neuronal cell types (9Meffert S. Stoll M. Steckelings U.M. Bottari S.P. Unger T. Mol. Cell. Endocrinol. 1996; 122: 59-67Crossref PubMed Scopus (208) Google Scholar, 24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar, 25Côté F., Do, T. Laflamme L. Gallo J. Gallo-Payet N. J. Biol. Chem. 1999; 274: 31686-31692Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar) (for review, see Refs. 26Allen A. MacGregor D. McKinley M. Mendelsohn F. Regul. Pept. 1999; 79: 1-7Crossref PubMed Scopus (59) Google Scholar, 27Horiuchi M. Akishita M. Dzau V.J. Hypertension. 1999; 33: 613-621Crossref PubMed Scopus (400) Google Scholar, 28Nouet S. Nahmias C. Trends Endocrinol. Metab. 2000; 11: 1-6Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar, 29Unger T. Am. Heart J. 2000; 139: S2-S8Crossref PubMed Scopus (57) Google Scholar).The precise nature of the signaling pathways activated by the AT2 receptor is still controversial (for review, see Refs.26Allen A. MacGregor D. McKinley M. Mendelsohn F. Regul. Pept. 1999; 79: 1-7Crossref PubMed Scopus (59) Google Scholar, 27Horiuchi M. Akishita M. Dzau V.J. Hypertension. 1999; 33: 613-621Crossref PubMed Scopus (400) Google Scholar, 28Nouet S. Nahmias C. Trends Endocrinol. Metab. 2000; 11: 1-6Abstract Full Text Full Text PDF PubMed Scopus (164) Google Scholar, 29Unger T. Am. Heart J. 2000; 139: S2-S8Crossref PubMed Scopus (57) Google Scholar). This seven-transmembrane domain receptor is not coupled to any of the classical, well established, second messengers, such as cAMP or inositol phosphates, and its coupling to a Gαiprotein, reported by several authors (30Kambayashi Y. Bardhan S. Takahashi K. Tsuzuki S. Inui H. Hamakubo T. Inagami T. J. Biol. Chem. 1993; 268: 24543-24546Abstract Full Text PDF PubMed Google Scholar, 31Kang J. Posner P. Sumners C. Am. J. Physiol. 1994; 267: C1389-C1397Crossref PubMed Google Scholar, 32Hansen J.L. Servant G. Baranski T.J. Fujita T. Iiri T. Sheikh S.P. Circ. Res. 2000; 87: 753-759Crossref PubMed Scopus (59) Google Scholar, 33Gendron L. Côté F. Payet M.D. Gallo-Payet N. Neuroendocrinology. 2002; 75: 70-81Crossref PubMed Scopus (53) Google Scholar, 34Zhang J. Pratt R. J. Biol. Chem. 1996; 271: 15026-15033Abstract Full Text Full Text PDF PubMed Scopus (124) Google Scholar), is not a consensus. However, various mediators, which could individually exert opposite effects, such as cGMP, tyrosine or serine/threonine phosphatases, and the extracellular signal-regulated kinases ERK1/ERK2 (p42/p44 mapk ) have been associated with activation of the AT2 receptor, depending on cell types and experimental conditions used. More precisely, AT2 receptor activation was shown to decrease p42/p44 mapk activities (35Elbaz N. Bedecs K. Masson M. Sutren M. Strosberg A.D. Nahmias C. Mol. Endocrinol. 2000; 14: 795-804Crossref PubMed Scopus (56) Google Scholar, 36Huang X. Richards E. Sumners C. J. Biol. Chem. 1996; 271: 15635-15641Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar), a process often associated with programmed cell death (36Huang X. Richards E. Sumners C. J. Biol. Chem. 1996; 271: 15635-15641Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar, 37Haywood G. Gullestad L. Katsuya T. Hutchinson H. Pratt R. Horiuchi M. Fowler M. Circulation. 1997; 95: 1201-1206Crossref PubMed Scopus (170) Google Scholar, 38Cui T. Nakagami H. Iwai M. Takeda Y. Shiuchi T. Daviet L. Nahmias C. Horiuchi M. Cardiovasc. Res. 2001; 49: 863-871Crossref PubMed Scopus (69) Google Scholar, 39Bedecs K. Elbaz N. Sutren M. Masson M. Susini C. Strosberg A.D. Nahmias C. Biochem. J. 1997; 325: 449-454Crossref PubMed Scopus (199) Google Scholar), or stimulate a sustained increase in p42/p44 mapk activity (32Hansen J.L. Servant G. Baranski T.J. Fujita T. Iiri T. Sheikh S.P. Circ. Res. 2000; 87: 753-759Crossref PubMed Scopus (59) Google Scholar), a process more often associated with cellular differentiation (40Stroth U. Blume A. Mielke K. Unger T. Brain Res. Mol. Brain Res. 2000; 78: 175-180Crossref PubMed Scopus (53) Google Scholar, 41Gendron L. Laflamme L. Rivard N. Asselin C. Payet M. Gallo-Payet N. Mol. Endocrinol. 1999; 13: 1615-1626Crossref PubMed Google Scholar).To study the effects of Ang II on differentiation, we have used NG108-15 cells. In their undifferentiated state, neuroblastoma × glioma hybrid NG108-15 cells have a rounded shape and divide actively. It is now well documented that chronic exposure to dibutyryl cAMP induces a process resulting in both morphological and functional differentiation (42Beaman-Hall C.M. Vallano M.L. J. Neurobiol. 1993; 24: 1500-1516Crossref PubMed Scopus (13) Google Scholar, 43Hamprecht B. Glaser T. Reiser G. Bayer E. Propst F. Methods Enzymol. 1985; 109: 316-341Crossref PubMed Scopus (144) Google Scholar). We have shown previously that these cells express only the AT2 receptor of Ang II (6Buisson B. Bottari S.P., De Gasparo M. Gallo-Payet N. Payet M.-D. FEBS Lett. 1992; 309: 161-164Crossref PubMed Scopus (126) Google Scholar, 24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar) and that a 3-day treatment with Ang II or CGP42112 induced neurite outgrowth (24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar), through a mechanism involving p21 ras inhibition, and a sustained increase in p42/p44 mapk activity (41Gendron L. Laflamme L. Rivard N. Asselin C. Payet M. Gallo-Payet N. Mol. Endocrinol. 1999; 13: 1615-1626Crossref PubMed Google Scholar). Because inhibition of p21 ras using the dominant negative mutant RasN17 failed to impair the ability of Ang II to stimulate p42/p44 mapk activity, an alternative pathway for the activation of the p42/p44 mapk cascade must be considered. We have demonstrated recently that nitric oxide and cGMP are involved in the AT2 receptor effects on neurite outgrowth. However, this pathway appeared to be a parallel, complementary, rather than an intermediary step of the AT2 signaling cascade directed to p42/p44 mapk activation (33Gendron L. Côté F. Payet M.D. Gallo-Payet N. Neuroendocrinology. 2002; 75: 70-81Crossref PubMed Scopus (53) Google Scholar).In PC12 cells stimulated with NGF, initiation of neurite outgrowth was accompanied by a sustained increase in p42/p44 mapk activities (44Cowley S. Paterson H. Kemp P. Marshall C.J. Cell. 1994; 77: 841-852Abstract Full Text PDF PubMed Scopus (1845) Google Scholar, 45Pang L. Sawada T. Decker S. Saltiel A. J. Biol. Chem. 1995; 270: 13585-13588Abstract Full Text Full Text PDF PubMed Scopus (895) Google Scholar), mediated by Rap1, a small guanine nucleotide-binding protein of the Ras family, and B-Raf, a neuron-specific member of the Raf family of kinases (46Bos J.L. EMBO J. 1998; 17: 6776-6782Crossref PubMed Scopus (286) Google Scholar, 47York R. Yao H. Dillon T. Ellig C. Eckert S. McCleskey E. Stork P. Nature. 1998; 392: 622-626Crossref PubMed Scopus (757) Google Scholar, 48Zwartkruis F. Wolthuis R. Nabben N. Franke B. Bos J. EMBO J. 1998; 17: 5905-5912Crossref PubMed Scopus (191) Google Scholar). The active GTP-bound form of Rap1 is known to bind, in vitro, to most p21 ras effectors of the Raf family of kinases, in particular B-Raf and the Ral guanine nucleotide exchange factors (RalGEFs), RalGDS (49Wolthuis R. Bauer B. van't Veer L. de Vries-Smits A. Cool R. Spaargaren M. Wittinghofer A. Burgering B. Bos J. Oncogene. 1996; 13: 353-362PubMed Google Scholar, 50Herrmann C. Horn G. Spaargaren M. Wittinghofer A. J. Biol. Chem. 1996; 271: 6794-6800Abstract Full Text PDF PubMed Scopus (299) Google Scholar). Moreover, NGF stimulated Rap1 activity via the exchange factor Crk/C3G and was also shown to activate this pathway through a cAMP-dependent mechanism, involving (51Yao H. York R. Misra-Press A. Carr D. Stork P. J. Biol. Chem. 1998; 273: 8240-8247Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar) or not involving protein kinase A (52de Rooij J. Zwartkruis F.J. Verheijen M.H. Cool R.H. Nijman S.M. Wittinghofer A. Bos J.L. Nature. 1998; 396: 474-477Crossref PubMed Scopus (1602) Google Scholar). Similar mechanisms could also be considered for NG108-15 cells because chronic treatment with cAMP analogs is a well known differentiating factor for these cells (42Beaman-Hall C.M. Vallano M.L. J. Neurobiol. 1993; 24: 1500-1516Crossref PubMed Scopus (13) Google Scholar, 43Hamprecht B. Glaser T. Reiser G. Bayer E. Propst F. Methods Enzymol. 1985; 109: 316-341Crossref PubMed Scopus (144) Google Scholar). The aim of the present study was to investigate whether the Rap1/B-Raf pathway could be involved in the Ang II-induced sustained increase in p42/p44 mapk activity participating in the morphological differentiation of the NG108-15 cells and to verify whether cAMP could be involved in the signaling pathway of the AT2 receptor.DISCUSSIONIn the present study, we have demonstrated that the binding of Ang II to the AT2 receptor, in NG108-15 cells, increased Rap1/B-Raf activities, two events accompanied by a concomitant decrease in p21 ras and a sustained increase in p42/p44 mapk activities. However, in contrast to many G protein-coupled receptors that activate the Rap1/B-Raf cascade, the action of Ang II is independent of cAMP or PKA, again confirming the atypical nature of this seven-transmembrane domain receptor.Application of Ang II, on NG108-15 cells, led to a transient stimulation of B-Raf kinase activity, as measured by an in vitro kinase assay using MEK1 as a substrate, but it did not affect the basal level of Raf-1 activity. One of the better described activators of B-Raf is the small G protein Rap1 (62Zwartkruis F.J. Bos J.L. Exp. Cell Res. 1999; 253: 157-165Crossref PubMed Scopus (149) Google Scholar). Using RalGDS as affinity probe, we found that Ang II treatment of NG108-15 cells significantly increased the active, GTP-bound form, of Rap1 within 1 min and B-Raf within 5 min, whereas Raf-1 activity was not modified.Members of the Raf family of proteins include Raf-1, A-Raf, and B-Raf. Neurons are known to express the ubiquitous isoform Raf-1 and the specific neuronal isoform B-Raf (63Dugan L. Kim J. Zhang Y. Bart R. Sun Y. Holtzman D. Gutmann D. J. Biol. Chem. 1999; 274: 25842-25848Abstract Full Text Full Text PDF PubMed Scopus (195) Google Scholar). In neurons stimulated with NGF, B-Raf is the major isoform activated, with only 5% of the total activity attributed to Raf-1 (64Zheng J. Felder M. Connor J. Poo M. Nature. 1994; 368: 140-144Crossref PubMed Scopus (510) Google Scholar, 65Kao S. Jaiswal R.K. Kolch W. Landreth G.E. J. Biol. Chem. 2001; 276: 18169-18177Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar). The findings that both proteins, Rap1 and B-Raf, are activated after Ang II treatment are thus compatible with the observation that activation of p42/p44 mapk is stimulated in a p21 ras -independent mechanism by the AT2 receptor (41Gendron L. Laflamme L. Rivard N. Asselin C. Payet M. Gallo-Payet N. Mol. Endocrinol. 1999; 13: 1615-1626Crossref PubMed Google Scholar). Moreover, our results demonstrated that Rap1 activation is responsible for the AT2-induced p42/p44 mapk phosphorylation as well as for the Ang II-induced neurite outgrowth in NG108-15 cells. In fact, we find that in cells transfected with RapN17 or Rap1GAP constructs (in which the endogenous Rap1 activity is substantially decreased), Ang II-induced p42/p44 mapk activation is abolished. In addition, these transfected cells exposed to Ang II have the same morphology as the native, untreated NG108-15 cells. As we have shown previously that a sustained activation of the p42/p44 mapk pathway was an essential event to promote neurite outgrowth in NG108-15 cells treated with Ang II (41Gendron L. Laflamme L. Rivard N. Asselin C. Payet M. Gallo-Payet N. Mol. Endocrinol. 1999; 13: 1615-1626Crossref PubMed Google Scholar), these results indicate that Rap1 activation is necessary for Ang II to induce p42/p44 mapk activation and that Rap1 is required for the Ang II-induced neurite outgrowth.How Rap1 could be activated in our model remain unknown. In several models, cAMP and cAMP-activated proteins appeared to be of great importance, and many studies have reported the requirement of PKA for NGF activation of Rap1 as well as for p42/p44 mapk (47York R. Yao H. Dillon T. Ellig C. Eckert S. McCleskey E. Stork P. Nature. 1998; 392: 622-626Crossref PubMed Scopus (757) Google Scholar). Indeed, several studies indicate that treatment of cells with cAMP or analogs induced neurite outgrowth, both in PC12 (44Cowley S. Paterson H. Kemp P. Marshall C.J. Cell. 1994; 77: 841-852Abstract Full Text PDF PubMed Scopus (1845) Google Scholar) and in NG108-15 cells (24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar, 42Beaman-Hall C.M. Vallano M.L. J. Neurobiol. 1993; 24: 1500-1516Crossref PubMed Scopus (13) Google Scholar, 43Hamprecht B. Glaser T. Reiser G. Bayer E. Propst F. Methods Enzymol. 1985; 109: 316-341Crossref PubMed Scopus (144) Google Scholar). Activation of Rap1 by cAMP favored its association with Raf-1, consequently inhibiting the transient p21 ras -dependent activation of p42/p44 mapk (66Schmitt J.M. Stork P.J. Mol. Cell. Biol. 2001; 21: 3671-3683Crossref PubMed Scopus (125) Google Scholar). In parallel, the action of Rap1 on B-Raf accounted for the sustained stimulatory effect on p42/p44 mapk activity (51Yao H. York R. Misra-Press A. Carr D. Stork P. J. Biol. Chem. 1998; 273: 8240-8247Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar, 55Vossler M. Yao H. York R. Pan M. Rim C. Stork P. Cell. 1997; 89: 73-82Abstract Full Text Full Text PDF PubMed Scopus (942) Google Scholar, 66Schmitt J.M. Stork P.J. Mol. Cell. Biol. 2001; 21: 3671-3683Crossref PubMed Scopus (125) Google Scholar). In PC12 cells stimulated with NGF, cAMP is required for a sustained increase of p42/p44 mapk activity (51Yao H. York R. Misra-Press A. Carr D. Stork P. J. Biol. Chem. 1998; 273: 8240-8247Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar), even if in these cells, the NGF TrkA receptor is coupled directly to Rap1 through the adaptor protein CrkII (47York R. Yao H. Dillon T. Ellig C. Eckert S. McCleskey E. Stork P. Nature. 1998; 392: 622-626Crossref PubMed Scopus (757) Google Scholar).However, in the NG108-15 cells stimulated with Ang II, the present results indicate that cAMP (or analogs) and PKA are not involved in the increased activities of Rap1 and B-Raf. We report that the PKA inhibitor H-89 or an inactive cAMP analog, Rp-8-Br-cAMP-S, neither impaired the ability of Ang II to induce p42/p44 mapk activation nor did either affect morphological differentiation. Furthermore, forskolin-induced cAMP production in NG108-15 cells inhibited p42/p44 mapk phosphorylation but did not modify Rap1 activity. These results corroborate our previous observations that coincubation of Ang II with dibutyryl cAMP inhibits differentiation induced by each stimulus alone (24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar). Furthermore, Ang II did not stimulate cAMP production or accumulation, demonstrating that the cAMP/PKA pathway is not involved in the AT2 receptor signaling mechanisms leading to p42/p44 mapk activation and neuronal differentiation of NG108-15 cells. Those results corroborate the observations of Sanchez et al. (67Sanchez S. Sayas C. Lim F. Diaz-Nido J. Avila J. Wandosell F. J. Neurochem. 2001; 78: 468-481Crossref PubMed Scopus (74) Google Scholar) which indicate that in the human neuroblastoma cell line SH-SY5Y, cAMP-induced neurite outgrowth was independent of p42/p44 mapk activation.Fig. 11 shows, in the same time scale, the sequential activation of Rap1/B-Raf and p42/p44 mapk . The delay between B-Raf and p42/p44 mapk could be explained by the presence of an intermediate type of reaction, such as activation of MEK. In NGF-stimulated cells, York et al. (56York R. Molliver D. Grewal S. Stenberg P. McCleskey E. Stork P. Mol. Cell. Biol. 2000; 20: 8069-8083Crossref PubMed Scopus (203) Google Scholar) have shown a sustained Rap1 activation mediated by TrkA internalization and phosphoinositide 3-kinase activation. In this system, the authors proposed that phosphoinositide 3-kinase favors clathrin-dependent TrkA internalization into the endocytotic compartment where Rap1 is localized. However, such a mechanism is incompatible with the known behavior of the AT2 receptor. Indeed, in contrast to many G protein-coupled receptors, including the AT1 receptor, the AT2receptor does not internalize (68Ouali R. Berthelon M.-C. Bégeot M. Saez J. Endocrinology. 1997; 138: 725-733Crossref PubMed Scopus (72) Google Scholar, 69Hein L. Meinel L. Pratt R. Dzau V. Kobilka B. Mol. Endocrinol. 1997; 11: 1266-1277Crossref PubMed Scopus (215) Google Scholar). In addition, the differences in activation kinetics could be also the result of variations in the molecular composition and the stability of protein complexes recruited by the different receptors (65Kao S. Jaiswal R.K. Kolch W. Landreth G.E. J. Biol. Chem. 2001; 276: 18169-18177Abstract Full Text Full Text PDF PubMed Scopus (315) Google Scholar).Our recent observations on the AT2 receptor signaling mechanisms in NG108-15 cells are summarized in Fig. 12. After binding of Ang II, the activated AT2 receptor rapidly inactivates p21 ras (5–120 min) (41Gendron L. Laflamme L. Rivard N. Asselin C. Payet M. Gallo-Payet N. Mol. Endocrinol. 1999; 13: 1615-1626Crossref PubMed Google Scholar) and enhances the level of the GTP-bound form of Rap1 (1–5 min). Activated Rap1 then enhances the activity of B-Raf (5–15 min) which in turn stimulates p42/p44 mapk phosphorylation (30–60 min). Finally, the return of p42/p44 mapk phosphorylation to basal level, occurring much later (seen after 120 min of Ang II treatment), may be under a phosphotyrosine phosphatase activity such as SHP-1, shown to be activated after the AT2receptor stimulation (39Bedecs K. Elbaz N. Sutren M. Masson M. Susini C. Strosberg A.D. Nahmias C. Biochem. J. 1997; 325: 449-454Crossref PubMed Scopus (199) Google Scholar).Figure 12Schematic representation of the AT2 receptor signaling mechanisms in the NG108-15 cells. The Ang II AT2 receptor induction of neurite outgrowth and elongation involves at least two distinct, independent, but complementary pathways. First, after binding of Ang II, the activated AT2 receptor rapidly inactivates p21 ras and activates the Rap1/B-Raf pathway, leading to a delayed p42/p44 mapk phosphorylation. Another pathway involving the nitric oxide/soluble guanylyl cyclase/cGMP cascade of signaling is also necessary to observe neurite outgrowth. Stimulation of these two parallel pathways could modulate gene expression and the phosphorylation state of different microtubule-associated proteins (MAPs) to control microtubules stability/dynamic responsible for neurite elongation.NOS, nitric-oxide synthase; NO, nitric oxide;sGC, soluble guanylyl cyclase; unP-MAPs, unphosphorylated MAPs; P-MAPs, phosphorylated MAPs.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Ang II also stimulates the nitric oxide/soluble guanylyl cyclase/cGMP cascade of signaling (33Gendron L. Côté F. Payet M.D. Gallo-Payet N. Neuroendocrinology. 2002; 75: 70-81Crossref PubMed Scopus (53) Google Scholar). Our studies have shown that this cascade, together with MAPK activation, is involved in neurite outgrowth, through a mechanism independent of Ras activation. All of these pathways may have as final targets regulation of gene expression and modulation of the phosphorylation states of different microtubule-associated proteins such as MAP2, tau, and MAP1b, as we have shown previously in NG108-15 cells (24Laflamme L., De Gasparo M. Gallo J.-M. Payet M.D. Gallo-Payet N. J. Biol. Chem. 1996; 271: 22729-22735Abstract Full Text Full Text PDF PubMed Scopus (172) Google Scholar) as well as in granule cells from rat cerebellum (25Côté F., Do, T. Laflamme L. Gallo J. Gallo-Payet N. J. Biol. Chem. 1999; 274: 31686-31692Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar).Three important conclusions can be drawn from the present work. First, Ang II, in NG108-15 cells, induced a rapid activation of Rap1 and B-Raf, two proteins that account for the sustained activation of p42/p44 mapk induced by the AT2receptor. Second, AT2 signaling mechanisms leading to Rap1/B-Raf-dependent p42/p44 mapk activation and neurite elongation are clearly cAMP-independent. Third, the capability of cAMP to induce neurite outgrowth and neuronal differentiation in the NG108-15 cells occurs independently of the sustained increase in p42/p44 mapk activity. Altogether, these observations suggest that when present in the cell type studied, such as neurons, the Rap1/B-Raf signaling cascade could play a pivotal role in transduction (63Dugan L. Kim J. Zhang Y. Bart R. Sun Y. Holtzman D. Gutmann D. J. Biol. Chem. 1999; 274: 25842-25848Abstract Full Text Full Text PDF PubMed Scopus (195) Google Scholar). Thus, the presence of Rap1/B-Raf may explain the controver" @default.
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• W2023220022 title "Cyclic AMP-independent Involvement of Rap1/B-Raf in the Angiotensin II AT2 Receptor Signaling Pathway in NG108-15 Cells" @default.
• W2023220022 cites W1515062278 @default.
• W2023220022 cites W1527240164 @default.
• W2023220022 cites W1563716772 @default.
• W2023220022 cites W1667204010 @default.
• W2023220022 cites W1761458604 @default.
• W2023220022 cites W1851770675 @default.
• W2023220022 cites W1885709862 @default.
• W2023220022 cites W1886908195 @default.
• W2023220022 cites W1969771018 @default.
• W2023220022 cites W1975889812 @default.
• W2023220022 cites W1976849281 @default.
• W2023220022 cites W1981747438 @default.
• W2023220022 cites W1982803842 @default.
• W2023220022 cites W1983561419 @default.
• W2023220022 cites W1983566138 @default.
• W2023220022 cites W1984415485 @default.
• W2023220022 cites W1985948341 @default.
• W2023220022 cites W1989480480 @default.
• W2023220022 cites W1990257506 @default.
• W2023220022 cites W1990761820 @default.
• W2023220022 cites W1991475526 @default.
• W2023220022 cites W1991930853 @default.
• W2023220022 cites W2000579941 @default.
• W2023220022 cites W2002501384 @default.
• W2023220022 cites W2013690237 @default.
• W2023220022 cites W2016955301 @default.
• W2023220022 cites W2017235854 @default.
• W2023220022 cites W2023849708 @default.
• W2023220022 cites W2029424515 @default.
• W2023220022 cites W2038063954 @default.
• W2023220022 cites W2043932843 @default.
• W2023220022 cites W2046806062 @default.
• W2023220022 cites W2046906382 @default.
• W2023220022 cites W2050062150 @default.
• W2023220022 cites W2050584514 @default.
• W2023220022 cites W2050836208 @default.
• W2023220022 cites W2056002519 @default.
• W2023220022 cites W2060681074 @default.
• W2023220022 cites W2063640709 @default.
• W2023220022 cites W2067640500 @default.
• W2023220022 cites W2070564840 @default.
• W2023220022 cites W2076261991 @default.
• W2023220022 cites W2078047724 @default.
• W2023220022 cites W2079940904 @default.
• W2023220022 cites W2080697422 @default.
• W2023220022 cites W2082542825 @default.
• W2023220022 cites W2082776443 @default.
• W2023220022 cites W2084488354 @default.
• W2023220022 cites W2085673586 @default.
• W2023220022 cites W2096682768 @default.
• W2023220022 cites W2099019879 @default.
• W2023220022 cites W2103411175 @default.
• W2023220022 cites W2111175065 @default.
• W2023220022 cites W2114938192 @default.
• W2023220022 cites W2117506103 @default.
• W2023220022 cites W2118399632 @default.
• W2023220022 cites W2124603060 @default.
• W2023220022 cites W2125954573 @default.
• W2023220022 cites W2131033837 @default.
• W2023220022 cites W2143118993 @default.
• W2023220022 cites W2150388314 @default.
• W2023220022 cites W2157776145 @default.
• W2023220022 cites W2157840083 @default.
• W2023220022 cites W2164354034 @default.
• W2023220022 cites W2280767401 @default.
• W2023220022 cites W2416418622 @default.
• W2023220022 cites W3205595473 @default.
• W2023220022 cites W4246371881 @default.
• W2023220022 cites W4383479573 @default.
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