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Deregulation of cellular polarity proteins and their associated complexes leads to changes in cell migration and proliferation. The nitric oxide synthase 1 adaptor protein (NOS1AP) associates with the tumor suppressor protein Scribble to control cell migration and oncogenic transformation. However, how NOS1AP is linked to the cell signaling events that curb oncogenic progression has remained elusive. Here we identify several novel NOS1AP isoforms, NOS1APd, NOS1APe, and NOS1APf, with distinct cellular localizations. We show that isoforms with a membrane-interacting phosphotyrosine binding (PTB) domain can associate with Scribble and recognize acidic phospholipids. In a screen to identify novel binding proteins, we have discovered a complex consisting of NOS1AP and the transcriptional coactivator YAP linking NOS1AP to the Hippo signaling pathway. Silencing of NOS1AP reduces the phosphorylation of YAP and of the upstream kinase Lats1. Conversely, expression of NOS1AP promotes YAP and Lats1 phosphorylation, which correlates with reduced TEAD activity and restricted cell proliferation. Together, these data implicate a role for NOS1AP in the regulation of core Hippo signaling and are consistent with the idea that NOS1AP functions as a tumor suppressor. C ellular polarity is important for establishing and maintaining the shape and function of a cell. Loss of cellular polarity is associated with an epithelial-to-mesenchymal transition (EMT), where cells lose cell-cell adhesion and gain migratory and invasive properties that contribute to tumor progression. The Hippo signaling cascade, first identified in Drosophila melanogaster (1, 2), is highly conserved in mammals and is an important intracellular signaling pathway that controls tissue growth by modulating cell proliferation and cell differentiation (3). Deregulation of the Hippo signaling pathway connects the EMT to increased invasion, which has been associated with a number of different cancers (4). At the core of the Hippo complex are the serine threonine kinases MST1/2 and LATS1/2, which form a kinase cascade that controls the phosphorylation of the transcriptional coactivators YAP and TAZ (3, 5). Phosphorylation of YAP/TAZ on conserved serine residues restricts them to the cytosol, where they can associate with 14-3-3 proteins, be targeted for proteasomal degradation, or localize to regions of cell-cell contact, all of which prevent the nuclear localization and transcriptional activation of YAP/TAZ target genes (6). Recently, both genetic (7-9) and biochemical (9, 10) studies have revealed an association between the Hippo pathway and the polarity protein Scribble. Scribble is a large scaffolding protein that contains leucine-rich repeats (LRRs) at its N terminus and four PDZ domains that connect YAP/TAZ with MST1/2 and LATS1/2 (10), downstream of LKB1 and PAR-1 kinases (10). Together, these data suggest that Scribble regulates Hippo signaling and that the loss of Scribble is an important trigger to modify intracellular events leading to tumor development in a Hip...

Wigerius et al. identify the polarity protein AMOT-130 as vital for dendritic spine morphogenesis. They show that reduced Lats1 kinase activity in the neonatal brain is required for the recruitment of AMOT-130 to postsynaptic compartments to stabilize dendritic spines.

BackgroundHPV infection causes cervical cancer, mediated in part by the degradation of Scribble via the HPV E6 oncoprotein. Recently, Scribble has been shown to be an important regulator of the Hippo signaling cascade. Deregulation of the Hippo pathway induces an abnormal cellular transformation, epithelial to mesenchymal transition, which promotes oncogenic progression. Given the recent rise in oropharyngeal HPV squamous cell carcinoma we sought to determine if Hippo signaling components are implicated in oropharyngeal squamous cell carcinoma.MethodsMolecular and cellular techniques including immunoprecipiations, Western blotting and immunocytochemistry were used to identify the key Hippo pathway effector Yes-Associated Protein (YAP)1. Oropharyngeal tissue was collected from CO2 laser resections, and probed with YAP1 antibody in tumor and pre-malignant regions of HPV positive OPSCC tissue.ResultsThis study reveals that the Scribble binding protein Nitric Oxide Synthase 1 Adaptor Protein (NOS1AP) forms a complex with YAP. Further, the NOS1APa and NOS1APc isoforms show differential association with activated and non-activated YAP, and impact cellular proliferation. Consistent with deregulated Hippo signaling in OPSCC HPV tumors, we see a delocalization of Scribble and increased nuclear accumulation of YAP1 in an HPV-positive OPSCC.ConclusionOur preliminary data indicates that NOS1AP isoforms differentially associate with YAP1, which, together with our previous findings, predicts that loss of YAP1 enhances cellular transformation. Moreover, YAP1 is highly accumulated in the nucleus of HPV-positive OPSCC, implying that Hippo signaling and possibly NOS1AP expression are de-regulated in OPSCC. Further studies will help determine if NOS1AP isoforms, Scribble and Hippo components will be useful biomarkers in OPSCC tumor biology.