title: Sphingosylphosphorylcholine regulates the Hippo signaling pathway in a dual manner.
abstract: Sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid which regulates many cancer-related processes, including cellular proliferation. The Hippo signaling pathway consists of a cascade of tumor suppressive kinases Mst1/2 and Lats1/2 and their downstream targets YAP and TAZ which are generally pro-proliferative transcriptional regulators. Direct phosphorylation by Lats1/2 causes inhibition or degradation of YAP/TAZ and down-regulation of their target genes. We found SPC treatment of MDA-MB-435S breast cancer cells to strongly inhibit their proliferation and to induce a sustained Lats2 protein expression (6-24h). Therefore, we hypothesized that Hippo signaling might mediate the anti-proliferative SPC response. We also saw a cell density-dependent increase in S127-phosphorylated YAP (pS127-YAP) and a decrease in mRNA levels of YAP target genes (CTGF, Cyr61) in response to long (9h) SPC treatment. Knockdown of S1P receptor 2 (S1P2) prevented the SPC-induced up-regulation of Lats2 and attenuated the anti-proliferative effect of SPC. However, while knockdown of Lats2 alone or in combination with Lats1 expectedly increased basal proliferation it did not attenuate the SPC-induced inhibition of proliferation. Exogenous expression of wild-type or kinase-dead Lats2 and knockdown of YAP/TAZ also had no effect on the anti-proliferative SPC response. It has been previously shown that activation of S1P2-G12/13by sphingosine-1-phosphate (S1P) leads to rapid de-phosphorylation and up-regulation of YAP. Similarly, we saw a decrease in pS127-YAP and an increase in total YAP levels with short (1h) SPC treatment as well as a subsequent transient increase in YAP target gene expression. Inhibition of S1P2prevented the SPC-induced YAP de-phosphorylation. The rapid YAP activation and subsequent up-regulation of Lats2 mRNA does not constitute a negative feedback loop as knockdown of YAP/TAZ did not inhibit SPC-induced Lats2 expression. In conclusion, in this study we show that SPC is able to regulate Hippo signaling in a dual and opposite manner, causing an initial activation of YAP followed by an inhibition. However, even the strong SPC-induced effects seen in Lats2 and YAP did not mediate the anti-proliferative SPC response.
authors.affiliation: Department of Biosciences, Åbo Akademi University; Tykistökatu 6, 20520 Turku, Finland.
authors.forename: Kati
authors.initials: K
authors.lastname: Kemppainen
authors.affiliation: Department of Biosciences, Åbo Akademi University; Tykistökatu 6, 20520 Turku, Finland.
authors.forename: Nina
authors.initials: N
authors.lastname: Wentus
authors.affiliation: Department of Biosciences, Åbo Akademi University; Tykistökatu 6, 20520 Turku, Finland.
authors.forename: Taru
authors.initials: T
authors.lastname: Lassila
authors.affiliation: Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Tykistökatu 6, 20520 Turku, Finland.
authors.forename: Asta
authors.initials: A
authors.lastname: Laiho
authors.affiliation: Department of Biosciences, Åbo Akademi University; Tykistökatu 6, 20520 Turku, Finland; Minerva Foundation Institute for Medical Research, Biomedicum Helsinki, Tukholmankatu 8, 00290 Helsinki, Finland. Electronic address: ktornqvi@abo.fi.
authors.forename: Kid
authors.initials: K
authors.lastname: Törnquist
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D002452:Cell Count; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D000090683:Hippo Signaling Pathway; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008246:Lysophospholipids / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D015534:Trans-Activators; D014157:Transcription Factors; D000091364:Transcriptional Coactivator with PDZ-Binding Motif Proteins; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D000091102:YAP-Signaling Proteins; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; D010750:Phosphoproteins; D015534:Trans-Activators; D014157:Transcription Factors; D000091364:Transcriptional Coactivator with PDZ-Binding Motif Proteins; D025521:Tumor Suppressor Proteins; C551991:WWTR1 protein, human; D000091102:YAP-Signaling Proteins; C088374:YAP1 protein, human; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; C060506:sphingosine 1-phosphate; C406449:LATS2 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins; D013110:Sphingosine
keywords: Lats2; Proliferation; S1P(2); Sphingosylphosphorylcholine; Yap