RESUMEN
Large tumor suppressor (LATS)1/2 protein kinases transmit Hippo signaling in response to intercellular contacts and serum levels to limit cell growth via the inhibition of Yes-associated protein (YAP). Here low serum and high LATS1 activity are found to enhance the levels of the 130-kDa isoform of angiomotin (Amot130) through phosphorylation by LATS1/2 at serine 175, which then forms a binding site for 14-3-3. Such phosphorylation, in turn, enables the ubiquitin ligase atrophin-1 interacting protein (AIP)4 to bind, ubiquitinate, and stabilize Amot130. Consistently, the Amot130 (S175A) mutant, which lacks LATS phosphorylation, bound AIP4 poorly under all conditions and showed reduced stability. Amot130 and AIP4 also promoted the ubiquitination and degradation of YAP in response to serum starvation, unlike Amot130 (S175A). Moreover, silencing Amot130 expression blocked LATS1 from inhibiting the expression of connective tissue growth factor, a YAP-regulated gene. Concordant with phosphorylated Amot130 specifically mediating these effects, wild-type Amot130 selectively induced YAP phosphorylation and reduced transcription of connective tissue growth factor in an AIP4-dependent manner versus Amot130 (S175A). Further, Amot130 but not Amot130 (S175A) strongly inhibited the growth of MDA-MB-468 breast cancer cells. The dominant-negative effects of Amot130 (S175A) on YAP signaling also support that phosphorylated Amot130 transduces Hippo signaling. Likewise, Amot130 expression provoked premature growth arrest during mammary cell acini formation, whereas Amot130 (S175A)-expressing cells formed enlarged and poorly differentiated acini. Taken together, the phosphorylation of Amot130 by LATS is found to be a key feature that enables it to inhibit YAP-dependent signaling and cell growth.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proliferación Celular/efectos de los fármacos , Medio de Cultivo Libre de Suero/farmacología , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Proteínas de la Membrana/metabolismo , Fosfoproteínas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Proteínas 14-3-3/genética , Proteínas 14-3-3/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Secuencia de Aminoácidos , Angiomotinas , Animales , Sitios de Unión/genética , Western Blotting , Línea Celular , Línea Celular Tumoral , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intercelular/genética , Células MCF-7 , Proteínas de la Membrana/genética , Proteínas de Microfilamentos , Microscopía Confocal , Mutación , Fosfoproteínas/genética , Fosforilación/efectos de los fármacos , Unión Proteica , Proteínas Serina-Treonina Quinasas/genética , Interferencia de ARN , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Serina/genética , Serina/metabolismo , Factores de Transcripción , Transcripción Genética/efectos de los fármacos , Proteínas Supresoras de Tumor/genética , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Proteínas Señalizadoras YAPRESUMEN
The adaptor protein Amot130 scaffolds components of the Hippo pathway to promote the inhibition of cell growth. This study describes how Amot130 through binding and activating the ubiquitin ligase AIP4/Itch achieves these effects. AIP4 is found to bind and ubiquitinate Amot130 at residue Lys-481. This both stabilizes Amot130 and promotes its residence at the plasma membrane. Furthermore, Amot130 is shown to scaffold a complex containing overexpressed AIP4 and the transcriptional co-activator Yes-associated protein (YAP). Consequently, Amot130 promotes the ubiquitination of YAP by AIP4 and prevents AIP4 from binding to large tumor suppressor 1. Amot130 is found to reduce YAP stability. Importantly, Amot130 inhibition of YAP dependent transcription is reversed by AIP4 silencing, whereas Amot130 and AIP4 expression interdependently suppress cell growth. Thus, Amot130 repurposes AIP4 from its previously described role in degrading large tumor suppressor 1 to the inhibition of YAP and cell growth.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proliferación Celular , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Proteínas de la Membrana/metabolismo , Fosfoproteínas/metabolismo , Proteínas Represoras/metabolismo , Transducción de Señal/fisiología , Ubiquitina-Proteína Ligasas/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Angiomotinas , Regulación de la Expresión Génica/fisiología , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intercelular/genética , Proteínas de la Membrana/genética , Proteínas de Microfilamentos , Fosfoproteínas/genética , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Estabilidad Proteica , Proteolisis , Proteínas Represoras/genética , Factores de Transcripción , Transcripción Genética/fisiología , Ubiquitina-Proteína Ligasas/genética , Proteínas Señalizadoras YAPRESUMEN
The asymmetric organization of epithelial cells is a basic counter to cellular proliferation. However, the mechanisms whereby pro-growth pathways are modulated by intracellular factors that control cell shape are not well understood. This study demonstrates that the adaptor protein Amot, in addition to its established role in regulating cellular asymmetry, also promotes extracellular signal-regulated kinase 1 and 2 (ERK1/2)-dependent proliferation of mammary cells. Specifically, expression of Amot80, but not a mutant lacking its polarity protein interaction domain, enhances ERK1/2-dependent proliferation of MCF7 cells. Further, expression of Amot80 induces nontransformed MCF10A cells to overgrow as disorganized cellular aggregates in Matrigel. Conversely, Amot expression is required for proliferation of breast cancer cells in specific microenvironmental contexts that require ERK1/2 signaling. Thus, Amot is proposed to coordinate the dysregulation of cell polarity with the induction of neoplastic growth in mammary cells.
