Anti-apoptotic Signaling of Pleiotrophin through Its Receptor, Anaplastic Lymphoma Kinase

The secreted growth factor pleiotrophin (PTN) can induce mitogenesis in cells that express the receptor for this growth factor, anaplastic lymphoma kinase (ALK). Here we examine the ability of PTN to produce anti-apoptotic signals. We demonstrate that PTN is a survival factor for SW-13 epithelial cells and show that ribozyme-mediated depletion of ALK from SW-13 cells abolishes this effect of PTN. Furthermore, in serum-starved NIH3T3 fibroblasts PTN prevents apoptosis (measured by annexin V staining) with an EC50 of 0.2 ng/ml and induces cell growth at higher concentrations of PTN. A polyclonal antibody against the PTN ligand-binding domain of the ALK receptor (α-LBD) was a partial agonist for ALK in NIH3T3 cells. This α-LBD antibody showed high agonist activity for anti-apoptosis (56 ± 9% relative to PTN), low agonist activity for cell growth (21 ± 1% relative to PTN), and was an antagonist of PTN-induced cell growth (61 ± 2% inhibition). Both MAP kinase and phosphatidylinositol (PI) 3-kinase cascades in NIH3T3 cells were activated by PTN, and this effect persisted for up to 3 h. Surprisingly, the anti-apoptotic effect of PTN was completely blocked by the MAP kinase inhibitor UO126, but was not affected by the PI 3-kinase inhibitor LY294002. In contrast, PTN-dependent cell growth required both MAPK and PI 3-kinase activity. We conclude that anti-apoptotic signaling of PTN through ALK in NIH3T3 fibroblasts is via the MAP kinase pathway. The secreted growth factor pleiotrophin (PTN) can induce mitogenesis in cells that express the receptor for this growth factor, anaplastic lymphoma kinase (ALK). Here we examine the ability of PTN to produce anti-apoptotic signals. We demonstrate that PTN is a survival factor for SW-13 epithelial cells and show that ribozyme-mediated depletion of ALK from SW-13 cells abolishes this effect of PTN. Furthermore, in serum-starved NIH3T3 fibroblasts PTN prevents apoptosis (measured by annexin V staining) with an EC50 of 0.2 ng/ml and induces cell growth at higher concentrations of PTN. A polyclonal antibody against the PTN ligand-binding domain of the ALK receptor (α-LBD) was a partial agonist for ALK in NIH3T3 cells. This α-LBD antibody showed high agonist activity for anti-apoptosis (56 ± 9% relative to PTN), low agonist activity for cell growth (21 ± 1% relative to PTN), and was an antagonist of PTN-induced cell growth (61 ± 2% inhibition). Both MAP kinase and phosphatidylinositol (PI) 3-kinase cascades in NIH3T3 cells were activated by PTN, and this effect persisted for up to 3 h. Surprisingly, the anti-apoptotic effect of PTN was completely blocked by the MAP kinase inhibitor UO126, but was not affected by the PI 3-kinase inhibitor LY294002. In contrast, PTN-dependent cell growth required both MAPK and PI 3-kinase activity. We conclude that anti-apoptotic signaling of PTN through ALK in NIH3T3 fibroblasts is via the MAP kinase pathway. phosphatidylinositol anaplastic lymphoma kinase ligand binding domain mitogen-activated protein kinase pleiotrophin nucleophosmin phosphate-buffered saline epidermal growth factor EGF receptor bovine epithelial lens The ability of multicellular organisms to maintain homeostasis is dependent upon a delicate balance between cell survival and programmed cell death or apoptosis. One of the key elements regulating this balance is growth factor signaling. Growth factors and cytokines have been shown to regulate a wide variety of cellular effects, including cell survival. Growth factor-mediated effects occur through the stimulation of specific intracellular signaling cascades via the intrinsic tyrosine kinase activities of their receptors. For tyrosine kinase receptors, ligand-dependent activation results in autophosphorylation of tyrosine residues within the cytosolic domain of the receptor creating specific binding sites for intracellular signal transduction molecules. A number of growth factors, including insulin-like growth factor I, epidermal growth factor, basic fibroblast growth factor, platelet-derived growth factor, nerve growth factor, and cytokines such as interleukin-3 promote cell survival through pathways requiring the activation of PI1 3-kinase (for review, see Ref. 1Datta S.R. Brunet A. Greenberg M.E. Genes Dev. 1999; 13: 2905-2927Crossref PubMed Scopus (3721) Google Scholar). The lipid products of PI 3-kinase act as second messengers to stimulate the activity of the serine/threonine kinase Akt (for review, see Ref. 2Rameh L.E. Cantley L.C. J. Biol. Chem. 1999; 274: 8347-8350Abstract Full Text Full Text PDF PubMed Scopus (852) Google Scholar). Activated Akt has been shown to phosphorylate the pro-apoptotic Bad protein on serine 136, resulting in its dissociation from a complex with Bcl-xl (3Datta S.R. Dudek H. Tao X. Masters S., Fu, H. Gotoh Y. Greenberg M.E. Cell. 1997; 91: 231-241Abstract Full Text Full Text PDF PubMed Scopus (4946) Google Scholar). The uncomplexed Bcl-xl can suppress cell death responses by blocking the release of mitochondrial cytochrome c, a critical step in the activation of the downstream caspase cascade, required for apoptosis (4Zha J. Harada H. Yang E. Jockel J. Korsmeyer S.J. Cell. 1996; 87: 619-628Abstract Full Text Full Text PDF PubMed Scopus (2254) Google Scholar). Recent reports suggest that Bad can also be phosphorylated in a MAPK-dependent manner at serine 112 (5Scheid M.P. Schubert K.M. Duronio V. J. Biol. Chem. 1999; 274: 31108-31113Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar). This event also will disrupt the association of Bad with the Bcl-2·Bcl-xl complex and inhibit apoptotic signaling (5Scheid M.P. Schubert K.M. Duronio V. J. Biol. Chem. 1999; 274: 31108-31113Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar). Therefore, activation of either PI 3-kinase or Ras/Raf/MAPK can lead to the inhibition of apoptosis in response to growth factor stimuli. Pleiotrophin (PTN) is an 18-kDa heparin-binding growth factor named for its pleiotrophic effects (for review, see Ref. 6Schulte A.M. Wellstein A. Bicknell R. Lewis C.E. Ferrara N. Tumour Angiogenesis. Oxford University Press, Oxford1997: 273-289Google Scholar). The described biological consequences for PTN-mediated signaling include neurite outgrowth, angiogenesis, and mitogenesis of fibroblast, endothelial, epithelial, and some tumor cell lines. We have previously reported that PTN can induce the activation of both the MAPK and PI 3-kinase pathways in bovine epithelial lens (BEL) cells, and we have also demonstrated a direct role for PTN in mitogenesis (7Souttou B. Ahmad S. Wellstein A. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). In of the on PTN has described the role of this growth factor within the of cell growth and R. H. J. 1997; PubMed Scopus Google N. R. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Wellstein A. H. Google Wellstein A. 1997; PubMed Scopus Google N. Wellstein A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). Here we will the role of PTN in a cellular the of survival and apoptosis. a tyrosine kinase receptor for PTN, the anaplastic lymphoma kinase A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). on the tyrosine kinase of this receptor was from a in the of the tyrosine kinase domain of ALK with a nucleophosmin PubMed Scopus Google X. 1997; PubMed Scopus Google Scholar). This protein resulting in activation of tyrosine kinase activity Cell. Biol. 1997; PubMed Scopus Google Scholar). This is in of the anaplastic cell a of and is PubMed Scopus Google Scholar). In the we examine PTN-dependent signal transduction via the tyrosine kinase growth factor receptor We show a inhibition of apoptosis for NIH3T3 fibroblasts in response to PTN, and we demonstrate that this response is by the receptor for PTN. This effect is to activation of the MAPK and is of the PI 3-kinase pathway. at in NIH3T3 cells, stimulation of PI 3-kinase is in that both of pathways in response to ALK signaling The polyclonal ligand-binding domain antibody was described A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). In was in against a protein between and the of pleiotrophin in the ALK receptor This was and the resulting antibody was shown to binding of PTN to the ALK receptor in cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). were from for the polyclonal The and were was from was from PTN was as described previously (7Souttou B. Ahmad S. Wellstein A. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). NIH3T3 fibroblast and SW-13 cell were from the and from the were in and NIH3T3 cells were in with and SW-13 cells were in with cell were from were in the of and to were and to be for the of SW-13 cells were of an ALK specific in to ALK at either or relative to the were with a at both the and and were described Wellstein A. J. Biol. Chem. Full Text PDF PubMed Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and the were the SW-13 cells were with the or to the were to for of with For SW-13 and SW-13 cells were and cells were in in was a a described previously N. Wellstein A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). growth was the the cells were a the cells were serum-starved for the of PTN or to the For inhibitor cells were with inhibitor for to the of PTN. growth was h. were at of a and to and were with and was Pleiotrophin was to the at the were for up to survival the of this was at and h. was a with an and as a For at were and the cells to the were was a to the of in the a of apoptosis. This was the annexin V binding from and the were cells were in a and to and were with and to to induce apoptosis. PTN or the antibody was to the For inhibitor cells were with inhibitor for to the of PTN. cells were with and in to the demonstrated that this effect on the of apoptosis. were in and cells were to the annexin binding for in the was in the to the of cells in apoptosis. was a For protein NIH3T3 cells were at in were to and with was and the cells were serum-starved for h. were with of PTN for the and cells were with of 1% with a inhibitor was to a at cell were the were and cell by at for at The protein of was the For and of was of a were to sites were blocked with bovine in and were For of was with a of protein for at this of a polyclonal antibody and a of protein were with the for at were in and from the by in were by on and by as The was for were for and of for were We have previously described the cell growth effects of PTN for a number of and cell lines. In we have demonstrated that PTN and of SW-13 cells N. Wellstein A. J. Biol. Chem. Full Text PDF PubMed Google and of the PTN receptor ALK the effect of the growth factor on of cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). SW-13 cells not express PTN or the growth factor A.M. Wellstein A. Bicknell R. Lewis C.E. Ferrara N. Tumour Angiogenesis. Oxford University Press, Oxford1997: 273-289Google but express and ALK is phosphorylated in response to PTN A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). We this cell as a to the of PTN signaling through ALK to cell growth and survival. the of ALK for the PTN we the ALK from cells as described for cells A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and the response of the cells to PTN. PTN of SW-13 cells in see also Ref. A. Y. J. M.E. J. Biol. Chem. Full Text PDF PubMed Google and of SW-13 cells to to PTN is that in response to was not in the ALK cells in with cells not the of the This PTN-induced of SW-13 cells that showed a between PTN signal transduction and ALK in cells ALK depletion by A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, the of a growth response of cells to PTN the of ALK as the receptor for growth signal transduction of PTN. cell apoptosis upon we this from a growth to examine to the to cell survival of SW-13 cells. We cell survival of and ALK cells and of cells was In the of both cell showed a in the of cells, and PTN at ng/ml was to the but not the ALK cells and show that PTN the cell survival of SW-13 cells via signaling through its the cell growth effects of PTN have been described for a variety of cell including endothelial, and tumor cell N. Wellstein A. J. Biol. Chem. Full Text PDF PubMed Google we an NIH3T3 to the survival effects of PTN and the signaling showed that NIH3T3 cells to PTN-induced and of PTN in cells has been shown to induce a including and tumor in S. A. PubMed Scopus Google Scholar). We reported that NIH3T3 cells express ALK A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and we that a of the signaling and anti-apoptotic responses of cells to PTN the we that apoptosis. We that of an from of cells to of cells in and from a shown in of PTN apoptosis and we this effect as We that the response was at a PTN of ng/ml with an 0.2 ng/ml as a and from cells as a and In with the anti-apoptotic response of NIH3T3 cells to PTN, we also the growth response the EC50 of PTN for anti-apoptotic effects was this was on and and we a in the of cellular survival and to PTN. a step in the we a polyclonal antibody against the of ALK (α-LBD) to the of ALK to the PTN This antibody was shown to the binding of PTN to the ALK receptor in cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and we this antibody for its activity in the cell growth has been shown that the binding of to the domain of tyrosine kinase can induce partial agonist activity J. 1997; PubMed Scopus Google the of the receptor the antibody E. Scopus Google has of the to the of the antibody in the of B. S. H. V. A. J. J. N. J. PubMed Scopus Google Scholar). Furthermore, intrinsic activities for cellular responses have been reported for a antibody a specific receptor the growth factor receptor S. J. PubMed Google or the receptor J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). we a low partial agonist activity of the α-LBD for effects (21 1% relative to PTN the of the α-LBD with a of PTN that the intrinsic activity of the α-LBD the PTN response by 2% to a from that by the α-LBD c, with the partial agonist activity of the α-LBD antibody and a of the α-LBD for PTN ALK receptor binding reported A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, direct that ALK is a receptor for PTN not in and cells, as we have but is also the receptor for PTN in NIH3T3 cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). be that the concentrations of α-LBD antibody the of that was from and at the concentrations effect and c, described and we a higher of the anti-apoptotic growth effect of PTN. We that this also be in a higher agonist activity of the α-LBD antibody effect on apoptosis. the α-LBD antibody showed a inhibition of apoptosis of serum-starved NIH3T3 cells with a activity of 9% relative to PTN, the agonist This is higher the 1% intrinsic activity for the growth effect the EC50 of the antibody for the effects is receptor of the insulin-like growth factor receptor and of PI 3-kinase have that PI 3-kinase is a factor for the transduction of cell survival signals. the serine/threonine kinase Akt as a downstream of PI 3-kinase that in will phosphorylate and the pro-apoptotic caspase and We demonstrated previously that PTN signaling will activation of both MAPK and PI 3-kinase in cells (7Souttou B. Ahmad S. Wellstein A. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google but PI 3-kinase in cells to a activation of MAPK in cells A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). we to the activation of pathways in the NIH3T3 We cell from NIH3T3 cells with PTN and a to examine activation of both the MAPK and PI 3-kinase MAPK activation was and the showed that MAPK was activated by of to ng/ml PTN and that this activation was for up to 3 examine PI 3-kinase activation we of both Akt and the of PI that Akt was activated in with PI phosphorylated were and was by Both and Akt were phosphorylated by of to PTN, and this activation was also the 3 This of PTN activation of PI 3-kinase was to that in cells A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). We also for ligand-dependent of ALK in the NIH3T3 cells but were to a signal to the low of receptor in cells. This was to an of ALK by PTN in SW-13 cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and by the growth factor in E. A. and A. J. Biol. that PTN both the MAPK and PI 3-kinase pathways in NIH3T3 cells, we to examine the anti-apoptotic response of PTN. is an and is a specific PI 3-kinase were to the cells to PTN and that the concentrations of the were to MAPK or Akt by PTN. MAPK was completely at of PTN by MAPK activity was by the PI 3-kinase In contrast, effect on Akt completely this event not The of apoptosis were of We that the anti-apoptotic effect in response to PTN the PI we that completely blocked the PTN-mediated anti-apoptotic response This that the PTN-mediated inhibition of apoptosis was via MAPK and not PI 3-kinase as In we the effect of on PTN-mediated cell described we a PTN-dependent in growth the anti-apoptotic inhibition of either PI 3-kinase or MAPK pathways blocked the growth the of the and the that MAPK the anti-apoptotic PTN Furthermore, suggest that activation of the PI 3-kinase and MAPK cascades occur in and of In this we demonstrate that PTN signaling through its receptor ALK can a survival signal for epithelial and fibroblast cells. that PTN has growth effects on a variety of both cell and tumor cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google is to suggest that PTN signaling also a anti-apoptotic as a tyrosine kinase growth factor be to both and anti-apoptotic signaling ALK has been as the receptor for PTN and as an receptor was on the of the tyrosine kinase domain of ALK to as the of a N. B. M.P. PubMed Scopus Google Scholar). This results in a protein with J. Cell. Biol. PubMed Google to produce an anti-apoptotic signal via PI 3-kinase activation J. PubMed Google Scholar). the of this protein have a number of signaling cascades that activation to the of this In the and in association with and PI have been shown as activated in response to signaling. on PTN signaling via ALK in with this A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and we that the of PTN to cells induces the of both ALK and the downstream and PI 3-kinase A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). responses in lead to the activation of MAPK and Akt activation of downstream signaling cascades (7Souttou B. Ahmad S. Wellstein A. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). A an that the MAPK is in response to an activation of the ALK tyrosine kinase R. S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). This be to the that this receptor is not activated in response to a showed that the MAPK is critical to of the cell and that by the of MAPK B. N. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). We have shown the association of and and the of MAPK in a number of cell in response to PTN A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, a of the of ALK this receptor as a critical tyrosine kinase in the activation of MAPK in the C.E. A. J. Genes PubMed Scopus Google Scholar). We ALK as the tyrosine kinase receptor for PTN. In this we also demonstrated that ALK is phosphorylated in response to PTN as as of the ligand A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, we showed of ALK receptor binding by α-LBD by protein or by and we demonstrated that receptor and downstream signaling is by as as by the We were to demonstrate a direct of ALK in NIH3T3 cells to low of receptor in cells but have demonstrated ALK in response to PTN in SW-13 cells A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and in response to in In the we the α-LBD antibody as a to PTN with the ALK receptor in NIH3T3 cells. This polyclonal antibody as a partial agonist and and apoptosis relative to PTN This of partial agonist activity for cellular responses was also reported previously for with S. J. PubMed Google or the receptor J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and is to a of of the downstream to the activation by the receptor J. 1997; PubMed Scopus Google Scholar). The and EC50 of PTN for the effect a higher and of the receptor to the downstream and the intrinsic activity of the antibody is that the α-LBD antibody stimulation of by PTN that ALK is the receptor for PTN in NIH3T3 cells. we the downstream signaling and anti-apoptotic effects in this we that MAP kinase and not the PI 3-kinase activation was the survival signal of PTN in cells. have that MAPK stimulation can an anti-apoptotic effect of the PI X. S. R. Y. J. PubMed Scopus Google M.P. Duronio V. S. A. PubMed Scopus Google Scholar). demonstrated that growth factors, the pathways in the cell in of their ability to induce and anti-apoptotic both interleukin-3 and factor can stimulate PI 3-kinase and Akt the anti-apoptotic effect of factor on cells was completely dependent upon the MAPK a growth response required activation of both MAPK and PI 3-kinase M.P. Duronio V. S. A. PubMed Scopus Google Scholar). X. S. R. Y. J. PubMed Scopus Google demonstrated that stimulation of fibroblast cell including in stimulation of both the PI 3-kinase and MAPK In that to for PTN, anti-apoptotic were through activation of both cascades was for cell also suggest that the of was required for a Furthermore, suggest that the survival of can be from its activity. We that this is also for PTN signaling via the role of MAPK as an anti-apoptotic is dependent not on the cell but also is specific to the receptor that the In this is the for an anti-apoptotic signal via a tyrosine kinase receptor by the MAPK pathway. the of this apoptosis is with that the anti-apoptotic of PI is activated is not for cell survival. The role of Akt activation in NIH3T3 cells with PTN to be In a we in cells that inhibition of MAPK completely responses to PTN (7Souttou B. Ahmad S. Wellstein A. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). of PI 3-kinase with blocked we the effects of on and in cells, we that inhibition of either MAPK or PI 3-kinase produce a partial inhibition of demonstrate that growth factors within the cell can the MAPK and PI 3-kinase pathways for the of cell In the inhibition of either the MAPK or the PI 3-kinase in a of We that this is not to the cell but also the growth has been that signal regulate signal X. S. R. Y. J. PubMed Scopus Google Scholar). in we a stimulation of both PI 3-kinase stimulation and Akt In in a we that PI 3-kinase activation is critical for PTN-induced and the stimulation of We that effects of MAPK activation and to the anti-apoptotic pathway. and A. In to for PTN have been the receptor tyrosine A. S. A. PubMed Scopus Google and the E. R. H. J. Biol. Chem. Full Text PDF PubMed Google Scholar). In can to their receptor and a role for PTN, this ligand is also a heparin-binding growth factor A.M. Wellstein A. Bicknell R. Lewis C.E. Ferrara N. Tumour Angiogenesis. Oxford University Press, Oxford1997: 273-289Google Scholar). The receptor tyrosine a role as a or downstream signal transduction of PTN through we have not been to to that showed that receptor binding and signal transduction of PTN completely by the of the ALK protein A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, depletion of ALK abolishes signaling of PTN in cells as shown A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and in SW-13 cells as demonstrated in the the inhibition of by the antibody to the ALK c, the of the role of ALK as the signal receptor for PTN. is of that receptor binding of PTN in cells was completely by the α-LBD antibody A. A. B. A. Wellstein A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). we the that ALK is the tyrosine kinase receptor that is for PTN signal act as a of signaling and act as a for the in to the growth factors that promote cell survival through pathways requiring the activation of PI 3-kinase and Akt S.R. Brunet A. Greenberg M.E. Genes Dev. 1999; 13: 2905-2927Crossref PubMed Scopus (3721) Google 2Rameh L.E. Cantley L.C. J. Biol. Chem. 1999; 274: 8347-8350Abstract Full Text Full Text PDF PubMed Scopus (852) Google Scholar). Activated Akt has been shown to phosphorylate Bad on serine 136, resulting in its dissociation from a complex with Bcl-xl (3Datta S.R. Dudek H. Tao X. Masters S., Fu, H. Gotoh Y. Greenberg M.E. Cell. 1997; 91: 231-241Abstract Full Text Full Text PDF PubMed Scopus (4946) Google Scholar). The uncomplexed Bcl-xl can suppress cell death responses by blocking the release of mitochondrial cytochrome (4Zha J. Harada H. Yang E. Jockel J. Korsmeyer S.J. Cell. 1996; 87: 619-628Abstract Full Text Full Text PDF PubMed Scopus (2254) Google Scholar). reports suggest that Bad can also be phosphorylated in a MAPK-dependent manner at serine 112 (5Scheid M.P. Schubert K.M. Duronio V. J. Biol. Chem. 1999; 274: 31108-31113Abstract Full Text Full Text PDF PubMed Scopus (350) Google Scholar). has been demonstrated that serine at either of will lead to dissociation of from either the MAPK or the PI 3-kinase cascades have the to inhibit an apoptotic response via the molecules. In we show that PTN both SW-13 and NIH3T3 cells from and we that this effect is via the ALK receptor in cells. We show in NIH3T3 cells that PTN induces MAPK as as PI 3-kinase activity and that PTN-induced growth both anti-apoptotic effects of the growth factor dependent on MAPK and not on the PI We and for with the The the for the apoptosis