Abstract B28: Cep55 regulates YAP/TAZ expression and localization during cell cycle progression

Abstract

Abstract Cell cycle regulation plays a pivotal role in controlling cell proliferation and survival. Aberrant expression of cell cycle-associated genes generally afflicts cells with tumor-prone characteristics and promotes chromosome instability. Cep55 (Centrosome Protein 55kDa; also known as c10orf3 and FLJ10540) was identified as an important regulator of cytokinesis involved in cell growth and proliferation. It is associated with central spindle and midbody during cell cycle progression and cooperates with members of endosomal sorting complex required for transport (ESCRT) machinery to constrict intracellular bridge for cell abscission. In addition to cytokinesis, Cep55 is involved in regulating the PI3K/AKT pathway as well as promoting tumorigenesis. In search of novel Cep55 interplayers that may abrogate their expression upon loss of cep55 expression, we set out experiments with cultured cells exogenously expressed Flag-tagged wild type (wt) Cep 55 versus shRNAs against Cep55 and subjected immunoprecipitates to LC-MS/MS. The Hippo pathway components YAP and its paralogue TAZ were found to be diminished apparently in Cep55 null sample compared with wt counterpart. To confirm if Cep55 knockdown affects expression of Hippo pathway, we transfected 293T cells with Cep55 shRNAs and detected expression of Hippo core components with Western blots. Hippo components such as Merlin, Mst, and Lats are without effect in expression level, with the exception of YAP/TAZ whose expression was decreased extensively. Immunofluorescent microscopy reveals YAP/TAZ colocalized with Cep55 at central spindle and midbody during mitosis; however, depletion of Cep55 results in diffusion of YAP/TAZ at midbody, suggesting cep55 is required for midbody localization of YAP/TAZ. In contrast, knockdown of YAP/TAZ did not significantly alter Cep55 localization to the midbody ring but displays phenotype, such as multinuclear cells and micronuclei, similar to that observed in Cep55-depleted cells. Together our data provide evidence that Cep55-YAP/TAZ interaction plays an important role in cytokinesis and may support a biologic interplay between the Hippo-YAP and PI3K-AKT-mTOR pathways. Note: This abstract was not presented at the conference. Citation Format: Yen-Ming Lin, Chu-Han Wu, Pin Ouyang. Cep55 regulates YAP/TAZ expression and localization during cell cycle progression [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr B28.