title: The GNA13-RhoA signaling axis suppresses expression of tumor protective Kallikreins.
abstract: Gα13 (encoded by GNA13 gene) is the alpha subunit of a heterotrimeric G-protein that mediates signaling through specific G-protein-coupled receptors (GPCRs). Increased GNA13 expression has been observed in metastatic breast cancer cells. Recently, we have shown that enhanced GNA13 signaling in MCF-10a cells, a benign breast cancer cell line increased its invasiveness. Previous studies have reported that Kallikrein-related peptidases (KLKs 1-15) are down-regulated in breast tumors and may have a tumor protective function. However, the mechanisms that lead to the down-regulation of KLK genes in breast cancer are yet to be elucidated. We found that enhanced GNA13 signaling represses KLK gene expression in breast cancer, and undertook examination of the mechanisms involved. A microarray analysis revealed down-regulation of several members of the Kallikrein-related peptidases (KLK) gene family, namely KLK5, KLK6, KLK7, KLK8 and KLK10, in MCF-10a lines with enhanced GNA13 protein expression. Using real-time PCR and promoter analysis, we identified that the mRNA expression and promoter activities of these KLKs are suppressed upon enforced expression of GNA13 in MCF-10a cells. Using Rhotekin pull-down assays, we identified that GNA13 suppressed Rho-A activation and protein levels in MCF-10a cells. Blocking Rho-A activation using C3-toxin or by inhibiting its down-stream effector, Rho-associated kinase (ROCK), reduced the above-mentioned KLK mRNAs in MCF-10A cells. Importantly, in a metastatic breast cancer cell line MDA-MB-157, knock down of GNA13 alone was sufficient to induce the expression KLK mRNAs. Taken together, our findings suggested that enhanced GNA13 signaling down-regulates KLK gene transcription. The ability of enhanced GNA13 signaling to suppress KLK gene expression appears at least in part due to the ability of enhanced GNA13 signaling to negatively impact Rho/ROCK-signaling.
authors.affiliation: Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road, 169857, Singapore. Electronic address: cuirong.teo@duke-nus.edu.sg.
authors.forename: Cui Rong
authors.initials: CR
authors.lastname: Teo
authors.affiliation: Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road, 169857, Singapore; Dept. of Pharmacology and Cancer Biology, Duke Univ. Medical Center, Durham, NC 27710, USA. Electronic address: patrick.casey@duke-nus.edu.sg.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Casey
authors.affiliation: Program in Cancer and Stem Cell Biology, Duke-NUS Graduate Medical School, 8 College Road, 169857, Singapore. Electronic address: kabeer.rasheed@duke-nus.edu.sg.
authors.forename: Suhail Ahmed Kabeer
authors.initials: SA
authors.lastname: Rasheed
mesh_terms: D001427:Bacterial Toxins / Q000494:pharmacology; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005260:Female; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D007610:Kallikreins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015203:Reproducibility of Results; D015398:Signal Transduction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D054460:rho-Associated Kinases; D007610:Kallikreins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020742:rhoA GTP-Binding Protein
keywords: Breast cancer; Gα13; Invasion; Kallikreins; ROCK; RhoA; Transcriptional regulation