title: ASPP2 Is a Novel Pan-Ras Nanocluster Scaffold.
abstract: Ras-induced senescence mediated through ASPP2 represents a barrier to tumour formation. It is initiated by ASPP2's interaction with Ras at the plasma membrane, which stimulates the Raf/MEK/ERK signaling cascade. Ras to Raf signalling requires Ras to be organized in nanoscale signalling complexes, called nanocluster. We therefore wanted to investigate whether ASPP2 affects Ras nanoclustering. Here we show that ASPP2 increases the nanoscale clustering of all oncogenic Ras isoforms, H-ras, K-ras and N-ras. Structure-function analysis with ASPP2 truncation mutants suggests that the nanocluster scaffolding activity of ASPP2 converges on its α-helical domain. While ASPP2 increased effector recruitment and stimulated ERK and AKT phosphorylation, it did not increase colony formation of RasG12V transformed NIH/3T3 cells. By contrast, ASPP2 was able to suppress the transformation enhancing ability of the nanocluster scaffold Gal-1, by competing with the specific effect of Gal-1 on H-rasG12V- and K-rasG12V-nanoclustering, thus imposing ASPP2's ERK and AKT signalling signature. Similarly, ASPP2 robustly induced senescence and strongly abrogated mammosphere formation irrespective of whether it was expressed alone or together with Gal-1, which by itself showed the opposite effect in Ras wt or H-ras mutant breast cancer cells. Our results suggest that Gal-1 and ASPP2 functionally compete in nanocluster for active Ras on the plasma membrane. ASPP2 dominates the biological outcome, thus switching from a Gal-1 supported growth-promoting setting to a senescence inducing and stemness suppressive program in cancer cells. Our results support Ras nanocluster as major integrators of tumour fate decision events.
authors.affiliation: Turku Centre for Biotechnology, Åbo Akademi University, Tykistökatu 6B, 20520, Turku, Finland.
authors.forename: Itziar M D
authors.initials: IM
authors.lastname: Posada
authors.affiliation: Turku Centre for Biotechnology, Åbo Akademi University, Tykistökatu 6B, 20520, Turku, Finland.
authors.forename: Marc
authors.initials: M
authors.lastname: Serulla
authors.affiliation: University of Texas Health Science Center at Houston, Medical School, Houston, Texas, United States of America.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Turku Centre for Biotechnology, Åbo Akademi University, Tykistökatu 6B, 20520, Turku, Finland.
authors.forename: Christina
authors.initials: C
authors.lastname: Oetken-Lindholm
authors.affiliation: Turku Centre for Biotechnology, Åbo Akademi University, Tykistökatu 6B, 20520, Turku, Finland.
authors.forename: Daniel
authors.identifier: http://orcid.org/0000-0003-2769-0745
authors.initials: D
authors.lastname: Abankwa
authors.affiliation: Turku Centre for Biotechnology, Åbo Akademi University, Tykistökatu 6B, 20520, Turku, Finland.
authors.forename: Benoît
authors.initials: B
authors.lastname: Lectez
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D063646:Carcinogenesis / Q000235:genetics; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020935:MAP Kinase Signaling System / Q000235:genetics; D061986:MCF-7 Cells; D051379:Mice; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism; D051058:Oncogene Protein v-akt / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000378:metabolism; D054457:Tissue Scaffolds; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics*; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C511437:Trp53bp2 protein, mouse; D025521:Tumor Suppressor Proteins; D051058:Oncogene Protein v-akt; D048490:raf Kinases; C495971:Hras protein, mouse; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins