Regulation of Bcr-Abl-induced SAP kinase activity and ... - Nature

Oncogene (1998) 17, 1889 ± 1892  1998 Stockton Press All rights reserved 0950 ± 9232/98 $12.00 http://www.stockton-press.co.uk/onc

Regulation of Bcr-Abl-induced SAP kinase activity and transformation by the SHPTP1 protein tyrosine phosphatase Michaela Liedtke, Pramod Pandey, Shailendra Kumar, Surender Kharbanda and Donald Kufe Cancer Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA

The oncogenic Bcr-Abl variant of the c-Abl tyrosine kinase transforms cells by a mechanism dependent on activation of the stress-activated protein kinase (SAPK). Other work has shown that c-Abl interacts with the SHPTP1 protein tyrosine phosphatase in induction of SAPK activity by genotoxic stress. The present studies demonstrate that Bcr-Abl binds constitutively to SHPTP1. We show that Bcr-Abl phosphorylates SHPTP1 on C-terminal Y536 and Y564 sites. The functional signi®cance of the Bcr-Abl/SHPTP1 interaction is supported by the ®nding that SHPTP1 regulates Bcr-Abl-induced SAPK activity. Importantly, SHPTP1 also decreases Bcr-Abl-dependent transformation of ®broblasts. These ®ndings indicate that SHPTP1 functions as a tumor suppressor in cells transformed by Bcr-Abl. Keywords: Bcr-Abl; SHPTP1; SAP kinase; transformation

Introduction The c-Abl protein tyrosine kinase is transiently activated by ionizing radiation and certain other DNA-damaging agents (Kharbanda et al., 1995a,b; Liu et al., 1996). DNA damage-induced activation of cAbl is mediated in part by the DNA-dependent protein kinase (DNA-PK) and the product of the ataxia telangiectasia gene (ATM), both sensors of DNA damage (Baskaran et al., 1997; Kharbanda et al., 1997; Shafman et al., 1997). c-Abl interacts with the p53 tumor suppressor and contributes to p53dependent Gl phase growth arrest and induction of apoptosis (Goga et al., 1995a; Sawyers et al., 1994; Yuan et al., 1996a,b, 1997). Activation of c-Abl also contributes to transient induction of the stressactivated protein kinase (SAPK, Jun N-terminal kinase) in the response to genotoxic stress (Kharbanda et al., 1995b). The protein tyrosine phosphatase SHPTP1 (Pei et al., 1993, 1994) interacts with c-Abl and functions as a negative regulator of the cAbl?SAPK cascade (Kharbanda et al., 1996). In the absence of DNA damage, the tyrosine kinase activity of c-Abl is low in comparison to oncogenic variants, such as Bcr-Abl, that induce transformation (Pendergast et al., 1991). Fusion to Bcr results in constitutive activation of the Abl kinase by a mechanism that may involve interference with the

Correspondence: M Liedtke Received 22 January 1998; revised 7 May 1998; accepted 8 May 1998

negative regulatory function of the Abl SH3 domain (Pendergast et al., 1991). Whereas Bcr-Abl interacts with diverse proteins (Raitano et al., 1997), Bcr-Ablinduced transformation is dependent on Ras activation (Goga et al., 1995b; Sawyers et al., 1995) and induction of SAPK activity (Raitano et al., 1995). Activation of Ras by Bcr-Abl is conferred by multiple pathways involving the adaptor proteins Grb2, Shc and CRKL (Pendergast et al., 1993; Senechal et al., 1996). Bcr-Abl also activates SAPK (Raitano et al., 1995). Significantly, both the JIP-1 inhibitor of SAPK and a dominant negative mutant of c-Jun block transforming activity of Bcr-Abl (Dickens et al., 1997; Raitano et al., 1995).These ®ndings have suggested that Bcr-Abl induces Jun-responsive promoters through a Ras- and SAPK-dependent pathway. The present ®ndings demonstrate that Bcr-Abl binds constitutively to SHPTP1 and phosphorylates Cterminal Y536 and Y564 sites. We also show that SHPTP1 down-regulates Bcr-Abl-induced SAPK activity and cellular transformation. Results and discussion To determine whether Bcr-Abl associates with SHPTP1, lysates from 32D/Bcr-Abl cells were subjected to immunoprecipitation with anti-Bcr antibody. Immunoblot analysis of the precipitate with anti-SHPTP1 demonstrated reactivity at 70 kDa (Figure 1a). By contrast, there was no detectable SHPTP1 in immunoprecipitates prepared with preimmune rabbit serum (Figure 1a). Similar ®ndings were obtained in 3T3 cells that overexpress the p210BcrAbl protein and were transiently transfected with SHPTP1 (Figure 1b). In reciprocal experiments, analysis of anti-SHPTP1 immunoprecipitates with anti-Bcr demonstrated an association of SHPTP1 with p210Bcr-Abl (Figure 1c). Taken together, these results provide evidence for a constitutive interaction between Bcr-Abl and SHPTP1. To determine whether the interaction between BcrAbl and SHPTP1 involves tyrosine phosphorylation of SHPTP1, we transfected 3T3/Bcr-Abl cells with Flagtag SHPTP1. Analysis of anti-Flag immunoprecipitates with anti-P-Tyr demonstrated tyrosine phosphorylation of SHPTP1 (Figure 2a). As a control, 3T3 cells were also transfected with the Flag-SHPTP1 (Figure 2a). Whereas similar amounts of SHPTP1 protein were immunoprecipitated with anti-Flag, tyrosine phosphorylation of SHPTPI was increased in 3T3/Bcr-Abl transformed cells compared to that in 3T3 cells (Figure 2a). In concert with these ®ndings, analysis of anti-P-Tyr immunoprecipitates by immunoblotting with anti-SHPTP1 demonstrated reactivity in immuno-

SHPTP1 regulates Bcr-Abl-mediated transformation M Liedtke et al

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complexes from 3T3/Bcr-Abl, but not 3T3, cells (Figure 2b). To de®ne whether and where Bcr-Abl phosphorylates SHPTP1, we incubated anti-Bcr immunoprecipitates with recombinant SHPTP1 protein (residues 1 ± 595) (Pei et al., 1994) and [g-32P]ATP. Autoradiography of the reaction products demonstrated tyrosine phosphorylation of SHPTP1 (Figure 2c, left). Two dimensional phosphoamino acid analysis con®rmed phosphorylation of SHPTP1 on tyrosine (Figure 2c, right). The C-terminal region of SHPTP1 contains potential tyrosine phosphorylation sites at positions 536, 541 and 564. Mutation of Y536 to F failed to block phosphorylation by Bcr-Abl (Figure 2d). Similar results were obtained with Y541F and Y564F mutants (Figure 2d). By contrast, there was no detectable phosphorylation of the Y536F/Y564F double mutant (Figure 2d). These ®ndings indicate that Bcr-Abl phosphorylates the Y536 and Y564 sites in SHPTP1 and suggest that Bcr-Abl contributes, at least in part, to tyrosine phosphorylation of SHPTP1 in cells. Previous studies have demonstrated that Bcr-Abl activates SAPK in DAGM cells (Raitano et al., 1995). Whereas the present ®ndings indicate that Bcr-Abl interacts with SHPTP1, we asked whether SHPTP1 is involved in regulation of Bcr-Abl-mediated activation of SAPK. To address this issue, we transfected 3T3/ Bcr-Abl cells with pEBG-SAPK (Sanchez et al., 1994) and then assayed glutathione-Sepharose protein precipitates for phosphorylation of GST-Jun. Importantly, cotransfection of wildtype SHPTP1 decreased activation of SAPK by over 50% as compared to that

Figure 1 In vivo association of SHPTP1 with Bcr-Abl. (a) Lysates of 32D/Bcr-Abl cells were subjected to immunoprecipitation with anti-Bcr or preimmune rabbit serum (PIRS). The immunoprecipitated proteins were separated by SDS ± PAGE and analysed by immunoblotting with anti-SHPTP1. (b) 3T3/Bcr-Abl ®broblasts were transiently transfected with SHPTP1. Proteins were immunoprecipitated with anti-Bcr or PIRS and analysed by immunoblotting with anti-SHPTP1. (c) 3T3/Bcr-Abl cell lysates were immunoprecipitated with anti-SHPTP1 or PIRS and analysed by immunoblotting with anti-Bcr

obtained with the vector pcDNA3. These ®ndings indicate that Bcr-Abl-mediated activation of SAPK is regulated by SHPTP1 (Figure 3). Whereas SHPTP1 regulates SAPK activation and Bcr-Abl-induced transformation is mediated through a SAPK-dependent pathway (Raitano et al., 1995), we asked whether SHPTP1 regulates Bcr-Abl transforming activity. Transfection of vectors expressing wild-type SHPTP1 or the pcDNA3 vector into 3T3 cells had little if any eect on growth (data not shown). In the ®broblast transformation assay, transient expression of SHPTP1 inhibited the formation of colonies by 3T3 cells expressing Bcr-Abl by *50% as compared to that obtained with the pcDNA3 vector (Figure 4). These ®ndings indicate that, like activation of SAPK,

Figure 2 Tyrosine phosphorylation of SHPTP1 by Bcr-Abl. (a) 3T3 and 3T3/Bcr-Abl cells were transfected with Flag-tagged SHPTP1. Equal amounts of protein from whole cell lysates were subjected to immunoprecipitation with anti-Flag. Immunoprecipitated proteins were resolved and analysed by immunoblotting with anti-P-Tyr. (b) Cell lysates were subjected to immunoprecipitation with anti-P-Tyr and analysed by immunoblotting with anti-SHPTP1. (c) 3T3/Bcr-Abl cell lysates were subjected to immunoprecipitation with anti-Bcr. Immune complex kinase assays were performed by incubating the resulting immunoprecipitates in kinase buer with 3 mg of puri®ed SHPTP1 protein and 2 ± 5 mCi of [g-32P]ATP. The reaction products were resolved by SDS ± PAGE (left) and two dimensional phosphoamino acid analysis (right), and visualized by autoradiography. (d). Immune complex kinase assays were performed by incubating anti-Bcr immunoprecipitates from 3T3/Bcr-Abl cell lysates with puri®ed wildtype or mutant Y536F, Y541F, Y564F and Y536F/Y564F SHPTP1 proteins (3 mg each) in kinase buer containing 2 ± 5 mCi of [g-32P]ATP. Reaction products were analysed by SDS ± PAGE and autoradiography


®broblast transformation by Bcr-Abl is inhibited by SHPTP1. Activation of the c-Abl kinase by DNA damage has been shown to be an upstream signal to the transient induction of SAPK activity (Kharbanda et al., 1995b). By contrast, Bcr-Abl and other activated forms of Abl constitutively stimulate the SAPK pathway (Kharbanda et al., 1995a; Raitano et al., 1995; Renshaw et al., 1996; Sanchez et al., 1994). Whereas the transforming activity of Bcr-Abl is dependent on SAPK activation (Raitano et al., 1995), Bcr-Ablinduced transformation has been attributed to dysregulation of SAPK activity. The present studies demonstrate that Bcr-Abl interacts with SHPTP1. Signi®cantly, the results also support a role for SHPTP1 as a negative regulator of Bcr-Abl-induced SAPK activity and transformation. The SAPK path-

way is comprised of the MEKK-1 serine/threonine kinase, the SEK-1 dual speci®city kinase and SAPK (Sanchez et al., 1994; Yan et al., 1994). The ®nding that a dominant-negative mutant of MEKK-1 blocks Bcr-Abl-induced activation of Jun has suggested that Bcr-Abl functions upstream to MEKK-1 (Raitano et al., 1995). Thus, SHPTP1 may regulate Bcr-Ablinduced activation of SAPK by controlling MEKK-1 activity. Alternatively, SEK-1-induced tyrosine phosphorylation and thereby activation of SAPK could be a target for SHPTP1 activity.

Materials and methods Cell culture NIH3T3 and 3T3/Bcr-Abl transformed ®broblasts (Renshaw et al., 1995) were grown in Dulbecco's modi®ed Eagle's medium supplemented with 10% heat-inactivated fetal bovine serum. 32D cells were maintained in Isocove's modi®ed Dulbecco's medium supplemented with 10% heatinactivated fetal bovine serum and 10% WEH1-conditioned medium. Preparation of cell lysates Cells were incubated in 600 ml of ice cold lysis buer (50 mM Tris-HCl, pH 7.6, 150 mM NaCl, 1 M sodium orthovanadate, 1 mM phenylmethylsulfonyl ¯uoride, 1 mM dithiothreitol, 10 mg each of leupeptin and aprotinin per ml, 10 mM sodium ¯uoride and 1% Brij 97) for 30 min and then centrifuged at 140 00 r.p.m. for 20 min. Immunoprecipitation and immunoblot analysis

Figure 3 Regulation of Bcr-Abl-induced SAPK activity by SHPTP1. 3T3/Bcr-Abl cells were transiently cotransfected with pEBG-SAPK and wildtype SHPTP1 or the pcDNA3 vector. After 48 h, cell lysates were incubated with glutathione-Sepharose. Immune complex kinase assays were performed with the resulting adsorbates using GST-Jun (2 ± 100) as a substrate. The proteins were resolved by SDS ± PAGE and analysed by autoradiography (a). The data represent the mean+s.d. of three independent transfections and are expressed as percentage SAPK activity of that obtained with the pcDNA3 vector. The intensity of the bands was quantitated by laser densitometry (b)

Immunoprecipitation was performed as described (Kharbanda et al., 1995a). In brief, lysates were incubated with anti-SHPTP1 (Upstate Biotechnology), anti-Bcr (Calbiochem), anti-Flag (Kodak) or anti-P-Tyr (Upstate Biotechnology) for 1 h and precipitated with protein A-Sepharose for an additional 1 h. Rabbit anti-mouse antibody (Calbiochem) was added to the immunoprecipitations to enhance binding of monoclonal antibodies to protein ASepharose. The resulting immune complexes were washed three times with lysis buer, separated by electrophoresis in SDS/polyacrylamide gels, and then transferred to nitrocellulose paper. The residual binding sites were blocked by incubating the ®lters with 5% dry milk in phosphate-buered saline and 0.1% Tween 20 for 1 h at room temperature. The ®lters were then incubated with anti-Abl, anti-Bcr, anti-SHPTP1 or anti-P-Tyr for 1 h followed by incubation with anti-rabbit or anti-mouse IgG peroxidase conjugate (Amersham). The antigen-antibody complexes were visualized by enhanced chemiluminescence (ECL, Amersham). Immune complex kinase assays

Figure 4 Regulation of Bcr-Abl-induced transformation by SHPTP1. 3T3/Bcr-Abl cells were cotransfected with GFP and wildtype SHPTP1 or the pcDNA3 vector. After 48 h, cells were sorted for GFP expression by FACS and assayed for colony formation in soft agar (a). The data represent the mean+s.d. of three independent transfections and are expressed as percentage colony formation of that obtained with the pcDNA3 vector (b)

Lysates were incubated with anti-Bcr for 1 h at 408C and then for an additional 2 h after the addition of rabbit antimouse IgG and protein-A-Sepharose. The protein complexes were washed two times with lysis buer and once with kinase buer (20 mM HEPES, 10 mM MgC12, 0.1 mM sodium orthovanadate, 2 mM dithiothreitol) and resuspended in kinase buer containing 25 mM ATP, 2 ± 5 mCi of [g-32P]ATP per ml (6000 Ci/mmol; DuPont/NEN) and SHPTP1. The reaction mixture was incubated for 15 min at 308C and terminated by the addition of SDS sample buer. The proteins were analysed by SDS ± PAGE and autoradiography.

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Transient transfections Cells (1 ± 2610 ) were transfected with 1 mg of pEBGSAPK (Sanchez et al., 1994) and 4 mg of (i) pcDNA3SHPTP1 (wildtype) or (ii) pcDNA3-vector (Pei et al., 1994) in serum-free media with lipofectamine (GIBCO/ BRL). After incubation for 6 h, the cells were grown in media with serum for 42 h. Cell lysates were incubated with glutathione-Sepharose and immune complex kinase assays were performed with GST-Jun (2-100) as substrate. 6

Soft agar transformation assays 3T3/Bcr-Abl ®broblasts were transfected with 2 mg of GFP and (i) pcDNA3-SHPTP1 (wildtype) or (ii) pcDNA3-

vector. After 48 h, cells were sorted for GFP expression by FACS analysis and plated in soft agar in duplicate plates. Colonies 40.5 mm in diameter after 2 weeks were scored as positive.

Acknowledgements The authors thank Dr Charles Sawyers for providing the 32D/Bcr-Abl cells. The investigation was supported by PHS Grant CA66996 awarded by the National Cancer Institute, DHSS.

References Baskaran R, Wood LD, Whitaker LL, Xu Y, Barlow C, Canman CE, Morgan SE, Baltimore D, Wynshaw-Boris A, Kastan MB and Wang JYJ. (1997). Nature, 387, 516 ± 519. Dickens M, Rogers JS, Cavanagh J, Raitano A, Xia Z, Halpern JR, Greenberg ME, Sawyers CL and Davis, RJ. (1997). Science, 277, 693 ± 696. Goga A, Liu X, Hambuch TM, Senechal K, Major E, Berk AJ, Witte ON and Sawyers CL. (1995a). Oncogene, 11, 791 ± 799. Goga A, McLaughlin J, Afar DEH, Saran DC and Witte ON. (1995b). Cell, 82, 981 ± 988. Kharbanda S, Bharti A, Pei D, Wang J, Pandey P, Ren R, Weichselbaum R, Walsh CT and Kufe D. (1996). Proc. Natl. Acad. Sci. USA, 93, 6898 ± 6901. Kharbanda S, Pandey P, Jin S, Inoue S, Bharti A, Yuan Z-M, Weichselbaum R, Weaver D and Kufe, D. (1997). Nature, 386, 732 ± 735. Kharbanda S, Pandey P, Ren R, Feller S, Mayer B, Zon L and Kufe D. (1995a). J. Biol. Chem., 270, 30278 ± 30281. Kharbanda S, Ren R, Pandey P, Shafman TD, Feller SM, Weichselbaum RR and Kufe DW. (1995b). Nature, 376, 785 ± 788. Liu Z-G, Baskaran R, Lea-Chou ET, Wood L, Chen Y, Karin M and Wang JYJ. (1996). Nature, 384, 273 ± 276. Pei D, Lorenz U, KlingmuÈller U, Neel BG and Walsh CT (1994). Biochemistry, 33, 15483 ± 15493. Pei D, Neel BG and Walsh CT. (1993). Proc. Natl. Acad. Sci. USA, 90, 1092 ± 1096. Pendergast, AM, Muller AJ, Havlik MH, Clark R, McCormick H and Witte ON. (1991). Proc. Natl. Acad. Sci. USA, 88, 5927 ± 2931. Pendergast AM, Quilliam LA, Cripe LD, Bassing CH, Dai Z, Li N, Batzer K, Rabun M, Der CJ, Schlessinger J. and Gishizky ML. (1993). Cell, 75, 175 ± 185.

Raitano AB, Halpern JR, Hambuch TM and Sawyers CL. (1995) Proc. Natl. Acad. Sci. USA, 92, 11746 ± 11750. Raitano AB, Whang YE and Sawyers CL. (1997). Biochem. Biophys. Acta, 1333, F201 ± F216. Renshaw MW, Lea-Chou E and Wang JYJ. (1996). Curr. Biol., 6, 76 ± 83. Renshaw MW, McWhirter JR and Wang JYJ. (1995). Mol. Cell. Biol., 15, 1286 ± 1293. Sanchez I, Hughes RT, Mayer BJ, Yee K, Woodgett JR, Avruch J, Kyriakis JM and Zon LI. (1994). Nature, 372, 794 ± 798. Sawyers CL, McLaughlin J, Goga A, Havilik M and Witte O. (1994). Cell, 77, 121 ± 131. Sawyers CL, McLaughlin J and Witte ON. (1995). J. Exp. Med., 181, 307 ± 313. Senechal K, Halpern J and Sawyers, CL. (1996). J. Biol. Chem., 271, 23255 ± 23261. Shafman T, Khanna KK, Kedar P, Yen T, Spring K, Kozlov S, Gatei M, Zhang N, Watters D, Egerton M, Shiloh Y, Kharbanda S, Kufe D and Lavin MF. (1997). Nature, 387, 520 ± 523. Yan, M, Dai T, Deak JC, Kyriakis JM, Zon LI, Woodgett JR and Templeton DJ. (1994). Nature, 372, 798 ± 800. Yuan ZM, Huang Y, Fan MM, Sawyers C, Kharbanda S and Kufe D. (1996a). J. Biol. Chem., 271, 26457 ± 26460. Yuan ZM, Huang Y, Ishiko T, Kharbanda S, Weichselbaum R and Kufe D. (1997). Proc. Natl. Acad. Sci. USA, 94, 1437 ± 1440. Yuan ZM, Huang Y, Whang Y, Sawyers C, Weichselbaum R, Kharbanda S and Kufe D. (1996b). Nature, 382, 272 ± 274