title: Associations of saposin C, Src, and androgen receptor upregulate the expression and function of androgen receptor in human prostate cancer cells.
abstract: We previously demonstrated that ectopic expression of neurotrophic peptide (NP) derived from saposin C promotes androgen receptor (AR) expression and transactivation in human prostate cancer cells. This prompted us to investigate how NP or saposin C can function in cells. We constructed plasmids expressing saposin C or a chimeric peptide of a viral TAT transduction domain and saposin C (TAT-saposin C) with His-tag. Intracellular localization of saposin C and NP was predominantly shown in transfected cells, while TAT-saposin C was detected around membrane and in cytosol by immunofluorescence staining. Furthermore, induction of the AR expression and activation of the AR transcriptional function were observed in cells transfected with saposin C or TAT-saposin C, compared to control cells transfected with an empty plasmid. The effects of saposin C and TAT-saposin C on AR activity were examined in the presence of inhibitors of GPCR, MAPK1/2, and PI3K/Akt. Interestingly, we found that these inhibitors only affect AR activities in cells with TAT-saposin C expression but not with saposin C expression. Immunostaining images showed that co-localization of saposin C, Src, and the AR occurred in transfected cells. Physical interactions of saposin C/NP, Src, and the AR were then demonstrated by co-immunoprecipitation assays. Blockage of Src activity by specific inhibitor led to a decrease in the saposin C-mediated enhancement of AR transactivity, suggesting that intracellular expression of saposin C caused stimulation of AR expression and activity by associations with Src in LNCaP cells. This effect may not be mediated by GPCR.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, Shandong University, Jinan 250012, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Ding
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Wang
authors.forename: Aihui
authors.initials: A
authors.lastname: Xu
authors.forename: Xia
authors.initials: X
authors.lastname: Xu
authors.forename: Keli
authors.initials: K
authors.lastname: Tian
authors.forename: Charles Y F
authors.initials: CY
authors.lastname: Young
authors.forename: Huiqing
authors.initials: H
authors.lastname: Yuan
mesh_terms: D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008297:Male; D011401:Promoter Regions, Genetic; D017430:Prostate-Specific Antigen / Q000235:genetics; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis*; D049231:Saposins / Q000096:biosynthesis*; D015533:Transcriptional Activation; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D011944:Receptors, Androgen; D011994:Recombinant Proteins; D049231:Saposins; D019061:src-Family Kinases; D017430:Prostate-Specific Antigen