BACKGROUND: Secreted protein acidic and rich in cysteine (SPARC) is overexpressed in astrocytomas (World Health Organization grades II-IV). We previously demonstrated that SPARC promotes glioma migration and invasion-in part, by activating the P38 mitogen-activated protein kinase (MAPK)-heat shock protein (HSP)27 signaling pathway. The commonly lost tumor suppressor phosphatase and tensin homolog (PTEN) suppresses SPARC-induced migration, which is accompanied by suppression of Shc-Ras-Raf-MEK-ERK1/2 and Akt signaling. As PTEN completely suppresses SPARC-induced migration, we proposed that PTEN must also interfere with SPARC-induced HSP27 signaling. Therefore, this study determined the effects of PTEN expression on SPARC-induced expression and phosphorylation of HSP27. METHODS: Control and SPARC-expressing clones transfected with control- or PTEN-expression plasmids were plated on fibronectin-coated tissue culture plates for 3, 6, 24, and 48 h and then lysed. Equal amounts of protein were subjected to Western blot and densitometric analyses. RESULTS: The results show that SPARC enhances phosphorylated (p)P38 MAPK, phosphorylated MAPK-activated protein kinase 2 (pMAPKAPK2), and serine (Ser)78 HSP27 phosphorylation relative to total HSP27. PTEN suppresses pAkt and pMAPKAPK2, suggesting that PTEN effects are downstream of pP38 MAPK. PTEN suppressed SPARC-induced sustained phosphorylation at Ser78 HSP27. As the level of total HSP27 differed based on the presence of SPARC or PTEN, the ratios of phosphorylation-specific to total HSP27 were examined. The data demonstrate that SPARC-induced phosphorylation at Ser78 remains elevated despite increasing levels of total HSP27. In contrast, PTEN inhibits SPARC-induced increases in Ser78 HSP27 phosphorylation relative to total HSP27. CONCLUSION: These data describe a novel mechanism whereby PTEN inhibits SPARC-induced migration through suppression and differential regulation of pAkt and the P38 MAPK-MAPKAPK2-HSP27 signaling pathway.
BACKGROUND:Secreted protein acidic and rich in cysteine (SPARC) is overexpressed in astrocytomas (World Health Organization grades II-IV). We previously demonstrated that SPARC promotes glioma migration and invasion-in part, by activating the P38 mitogen-activated protein kinase (MAPK)-heat shock protein (HSP)27 signaling pathway. The commonly lost tumor suppressor phosphatase and tensin homolog (PTEN) suppresses SPARC-induced migration, which is accompanied by suppression of Shc-Ras-Raf-MEK-ERK1/2 and Akt signaling. As PTEN completely suppresses SPARC-induced migration, we proposed that PTEN must also interfere with SPARC-induced HSP27 signaling. Therefore, this study determined the effects of PTEN expression on SPARC-induced expression and phosphorylation of HSP27. METHODS: Control and SPARC-expressing clones transfected with control- or PTEN-expression plasmids were plated on fibronectin-coated tissue culture plates for 3, 6, 24, and 48 h and then lysed. Equal amounts of protein were subjected to Western blot and densitometric analyses. RESULTS: The results show that SPARC enhances phosphorylated (p)P38 MAPK, phosphorylated MAPK-activated protein kinase 2 (pMAPKAPK2), and serine (Ser)78 HSP27 phosphorylation relative to total HSP27. PTEN suppresses pAkt and pMAPKAPK2, suggesting that PTEN effects are downstream of pP38 MAPK. PTEN suppressed SPARC-induced sustained phosphorylation at Ser78HSP27. As the level of total HSP27 differed based on the presence of SPARC or PTEN, the ratios of phosphorylation-specific to total HSP27 were examined. The data demonstrate that SPARC-induced phosphorylation at Ser78 remains elevated despite increasing levels of total HSP27. In contrast, PTEN inhibits SPARC-induced increases in Ser78HSP27 phosphorylation relative to total HSP27. CONCLUSION: These data describe a novel mechanism whereby PTEN inhibits SPARC-induced migration through suppression and differential regulation of pAkt and the P38 MAPK-MAPKAPK2-HSP27 signaling pathway.
Authors: Thomas H Barker; Gretchen Baneyx; Marina Cardó-Vila; Gail A Workman; Matt Weaver; Priya M Menon; Shoukat Dedhar; Sandra A Rempel; Wadih Arap; Renata Pasqualini; Viola Vogel; E Helene Sage Journal: J Biol Chem Date: 2005-08-22 Impact factor: 5.157
Authors: D Williams Parsons; Siân Jones; Xiaosong Zhang; Jimmy Cheng-Ho Lin; Rebecca J Leary; Philipp Angenendt; Parminder Mankoo; Hannah Carter; I-Mei Siu; Gary L Gallia; Alessandro Olivi; Roger McLendon; B Ahmed Rasheed; Stephen Keir; Tatiana Nikolskaya; Yuri Nikolsky; Dana A Busam; Hanna Tekleab; Luis A Diaz; James Hartigan; Doug R Smith; Robert L Strausberg; Suely Kazue Nagahashi Marie; Sueli Mieko Oba Shinjo; Hai Yan; Gregory J Riggins; Darell D Bigner; Rachel Karchin; Nick Papadopoulos; Giovanni Parmigiani; Bert Vogelstein; Victor E Velculescu; Kenneth W Kinzler Journal: Science Date: 2008-09-04 Impact factor: 47.728
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Authors: Chad R Schultz; William A Golembieski; Daniel A King; Stephen L Brown; Chaya Brodie; Sandra A Rempel Journal: Mol Cancer Date: 2012-04-05 Impact factor: 27.401
Authors: Catherine J Libby; Sajina Gc; Gloria A Benavides; Jennifer L Fisher; Sarah E Williford; Sixue Zhang; Anh Nhat Tran; Emily R Gordon; Amber B Jones; Kaysaw Tuy; William Flavahan; Juan Gordillo; Ashlee Long; Sara J Cooper; Brittany N Lasseigne; Corinne E Augelli-Szafran; Victor Darley-Usmar; Anita B Hjelmeland Journal: Cell Adh Migr Date: 2021-12 Impact factor: 3.405