Colorectal cancer (CRC) remains a significant public health challenge, with an urgent need of novel prognostic biomarkers and therapeutic targets. PTK7, a membrane tyrosine pseudokinase and Wnt receptor, is overexpressed in CRC and linked to poor prognosis. In CRC, PTK7 expression correlates with metastatic progression and decreased survival in non-metastatic patients, positioning PTK7 as both a potential biomarker and a promising drug target. Notably, a targeted antibody-drug conjugate (ADC) against PTK7 has recently shown efficacy in inducing tumor regression in patient-derived xenograft (PDX) models of solid tumors and has progressed to a Phase I clinical trial with promising results. Other PTK7-targeting ADCs and anti-PTK7 CAR-T cells recently entered into preclinical development. At the plasma membrane, PTK7 can interact with a range of membrane receptors, including VEGFR, EGFR, ROR2, and Plexins, enhancing their signaling capabilities. Using biotin proximity labeling in HCT116 CRC cells, we identified a novel network of PTK7-associated membrane proteins. Among these, we focused on EPHA2, an active tyrosine kinase receptor also implicated in cancer. Our findings indicate that PTK7 and EPHA2 interact via their extracellular domains (ECDs), and that PTK7 depletion significantly upregulates EPHA2 expression and signaling in response to its ligand EFNA-1 in HCT116 cells. Additionally, PTK7 regulates EPHA2’s endosomal sorting through a Rab11-dependent mechanism, as well as its K63-linked ubiquitination and subsequent lysosomal degradation. Mechanistically, PTK7 does not appear to participate directly in EFNA-1 binding but instead promotes multimerization of active EPHA2, a crucial step in amplifying EPHA2 signaling. This study aims to elucidate the functional role of the interaction between PTK7 and EPHA2 in colorectal cancer progression. By mapping the PTK7:EPHA2 interface using AlphaFold3 predictions and introducing targeted deletions and mutations within the ECDs of both receptors, we seek to understand how disrupting this interaction influences tumorigenic and metastatic processes. Our findings indicate that PTK7 depletion triggers cell rounding and detachment, with a marked increase in total and activated EPHA2 levels, which may drive pro-metastatic activity in vivo. Outcomes may significantly impact the use of anti-PTK7-ADCs or CAR-T cells and orient new therapeutic strategies to design agents interfering with PTK7 and EPHA2 interaction and function. Charlotte Dessaux, Constantin Semenchenko, Luc Camoin, Stéphane Audebert, Emilie Baudelet, Avais Daulat, Flavio Maina, Jean-Paul Borg. Exploring a novel crosstalk between PTK7 and EPHA2 tyrosine kinase receptors in metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2006.

Abstract Colorectal cancer (CRC) remains the second cause of death by cancer worldwide and its survival is currently estimated at 60%1. There is therefore a crucial need to identify biomarkers and new targets for therapy. In 90% of CRC, the Wnt/β-catenin pathway is constitutively activated due to mutations of β-catenin, APC (Adenomatous Polyposis Coli) or axin-12. These alterations cause an accumulation of β-catenin and lead to an over-transcription of target genes involved in tumorigenesis3-4. Studies of our team pointed out an overexpression of the Protein Tyrosine Kinase 7 (PTK7) in CRC, an event associated with metastatic development, reduced metastases-free survival, and resistance to chemotherapy. In CRC cells, the pseudokinase PTK7 has pro-metastatic and pro-migratory functions, and thus appears to be a promising new therapeutic target5-6. The role of PTK7 in the Wnt/β-catenin pathway has been demonstrated in several studies7-8. Our group identified β-catenin as a partner of PTK7. We selected a first series of small molecules inhibitors targeting PTK7/β-catenin interaction9. This strategy could represent, in the future, a new therapeutic strategy to inhibit CRC cell growth dependent on the Wnt signaling pathway. However, the compounds identified had weak activity, with an IC50 of around 10-25 mM. We have set up a new method with SYNSIGHT to select more potent chemical inhibitors targeting PTK7/β-catenin in CRC in order to counteract the Wnt/β-catenin signaling pathway deregulation. References: 1Colorectal cancer (Source : Globocan 2020); 2Cancer Genome Atlas Network. Nature. 2012; 3He, T. C. et al. Science. 1998; 4Tetsu, O. & McCormick, F. Nature. 1999; 5Lhoumeau, A.-C. et al. PLOS ONE. 2015; 6Lhoumeau, A.-C. et al. J. Immunol. 2016; 7Puppo, F. et al. EMBO Rep. 2011; 8Peradziryi, H. et al. EMBO J. 2011; 9Ganier, L. et al. ACS Chem. Biol. 2022; 10Daulat, A. M. & Borg, J.-P. Trends Cancer. 2017; 11Stamos, J. L. & Weis, W. I. Cold Spring Harb. Perspect. Biol. 2013. Citation Format: Jean-Paul Borg, Manon Pierre, Laetitia Ganier, Avais Daulat, Amandine Molliex, Julien Duez, Maxime Sanchez, Etienne Lallemand, Anthony Goncalves, Guillaume Bollot. New strategies to target the pseudokinase receptor PTK7 in the Wnt pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1807.

Abstract Colorectal cancer (CRC) remains a major public health issue. Identification of biomarkers predicting high risk of recurrence and discovery of novel targets for therapy are urgently needed1. The cell surface receptor PTK7 is a poorly described evolutionary conserved member of the receptor tyrosine kinase superfamily that was first identified in human colon carcinoma and melanoma2-3. Accumulated data highlighted the implication of PTK7 in diverse cancer-related signaling pathways4-6 and, despite the lack of kinase activity, anti-PTK7 inhibitors are currently in development at preclinical and clinical stages7-9. The dual aim of this project is to increase the basic knowledge about PTK7 and to evaluate its role in CRC in order to propose in the future novel therapeutics directed against PTK7. With the aim to discover novel PTK7 associated pathways, we used a proximity biotinylation strategy coupled to mass spectrometry in CRC cells. Among the partners identified, we found that the pseudokinase PTK7 interacts with the active receptor tyrosine kinase EphrinA2 (EPHA2). Similarly to PTK7, EPHA2 expression correlates with poor prognosis in CRC10. In this work, we also demonstrate that PTK7 acts as a negative regulator of EPHA2 activation through the promotion of distinct oligomeric protein complexes and the modulation of EPHA2 phosphorylation. We also shed in light on the role of PTK7 in EPHA2 K63-linked ubiquitination and its subsequent endosomal sorting and lysosomal degradation. References 1 Punt CJ et al, Nat. Rev. Clin. Oncol., 2016; 2 Lhoumeau AC et al, Cell Cycle, 2011; 3 Lhoumeau AC et al, PLoS One, 2015; 4 Puppo F et al, EMBO reports, 2011; 5 Martinez S et al, J. Biol. Chem., 2015; 6 Daulat AM and Borg JP, Trends in Cancer, 2017; 7 Damelin M et al, Sci. Transl. Med., 2017; 8 Jie Y et al, Front. Immunol., 2021; 9 Maitland ML et al, Clin. Cancer. Res., 2021; 10 Dunne P et al, Clin. Cancer. Res., 2016; 11 Cioce M and Fazio VM, Cancers, 2021. Citation Format: Jean-Paul Borg, Charlotte Dessaux, Luc Camoin, Stéphane Audebert, Emilie Baudelet, Avais Daulat. The pseudokinase PTK7 is a negative regulator of EPHA2 in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4376.

The rapid identification of early hits by fragment-based approaches and subsequent hit-to-lead optimization represents a challenge for drug discovery. To address this challenge, we created a strategy called "DOTS" that combines molecular dynamic simulations, computer-based library design (chemoDOTS) with encoded medicinal chemistry reactions, constrained docking, and automated compound evaluation. To validate its utility, we applied our DOTS strategy to the challenging target syntenin, a PDZ domain containing protein and oncology target. Herein, we describe the creation of a "best-in-class" sub-micromolar small molecule inhibitor for the second PDZ domain of syntenin validated in cancer cell assays. Key to the success of our DOTS approach was the integration of protein conformational sampling during hit identification stage and the synthetic feasibility ranking of the designed compounds throughout the optimization process. This approach can be broadly applied to other protein targets with known 3D structures to rapidly identify and optimize compounds as chemical probes and therapeutic candidates.

Abstract The developmental Wnt/planar cell polarity (PCP) pathway is the most recently described branch of the Wnt signaling pathways and is strongly implicated in cancer development at early and late stages (PMID: 28718442 and PMID: 30952630). Upregulation of the Wnt/PCP components is observed in many cancers and is associated with cancer progression. However, how their molecular functions are regulated remains an open question. Recent data from our laboratory showed that Prickle1 and Vangl2, two core Wnt/PCP components, are overexpressed in Triple Negative Breast Cancers (TNBC) and associated with poor prognosis (PMID: 27184734 and 26754771). Prickle1 is a cytoplasmic protein phosphorylated by the serine/threonine kinase Mink1, which triggers Prickle1 localization at the plasma membrane and regulates its activity (PMID: 22037766). Activation of this axis contributes to breast cancer cell motility and metastatic spreading in vitro and in vivo (PMID: 27184734). To extend our knowledge of the Mink1 substrates, we carried out a phosphoproteomic strategy and identified LL5β. LL5β is a membrane scaffold molecule that anchors microtubules (MTs) at the cell cortex through its association with CLASP, a plus-end MT protein, to trigger focal adhesion disassembly. We found that LL5β is a prominent member of the Prickle1-associated protein complex and harbors a consensus motif for Mink1 phosphorylation. At the molecular level, we demonstrated a two-step phosphorylation cascade carried out by Mink1 that phosphorylates sequentially Prickle1 to mediate its association with LL5β, then LL5β to promote its interaction with CLASP. Finally, analysis of gene expression data suggests that the concomitant up-regulation of Prickle1 and LL5β mRNA levels is associated with a poor metastasis-free survival for TNBC patients. In an effort to counteract the Mink1-Prickle1-LL5β prometastatic pathway, we selected a Mink1 inhibitor that recapitulates all the phenotypes observed following the knockdown of Mink1 expression. This chemical compound is currently under investigation in preclinical assays using xenografted TNBC cell lines and patient-derived xenografts in nude mice. Citation Format: Avais Daulat, Monica Silveira Wagner, Malgorzata Kowalczewska, Pascal Finetti, Rémy Castellano, Stéphane Audebert, François Bertucci, Luc Camoin, Jean-Paul Borg. The serine-threonine kinase Mink1 as a potential therapeutic target in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2290.

Identification of protein networks becomes indispensable for determining the function of a given protein of interest. Some proteins harbor a PDZ binding motif (PDZBM) located at the carboxy-terminus end. This motif is necessary to recruit PDZ domain proteins which are involved in signaling, trafficking, and maintenance of cell architecture. In the present chapter, we present two complementary approaches (immunopurification and peptide-based purification procedures) followed by mass spectrometry analysis to identify PDZ domain proteins associated to a given protein of interest. As proof of example, we focus our attention on TANC1 which is a scaffold protein harboring a PDZBM at its carboxy-terminus. Using these two approaches, we identified several PDZ domain containing proteins. Some of them were found with both approaches, and some were specifically identified using peptide-based purification procedure. This exemplifies advantages and differences of both strategies to identify PDZ interactions.

Upregulation of the developmental Wnt/planar cell polarity pathway is observed in many cancers and is associated with cancer development at early and late stages. We recently showed that PRICKLE1 and VANGL2, two core Wnt/PCP components, are overexpressed in triple negative breast cancer and associated with poor prognosis. PRICKLE1 is a cytoplasmic protein phosphorylated by the poorly described serine/threonine kinase MINK1 which triggers its localization at the plasma membrane, a key step for its function. Knockdown experiments have demonstrated that MINK1 and PRICKLE1 contribute to TNBC cell motility and spreading in vitro and in vivo . However, the identity of MINK1 substrates and the role of MINK1 enzymatic activity in this process have not yet been addressed issues. We carried out a phosphoproteomic strategy and identified novel MINK1 substrates including LL5β. LL5β is a membrane scaffold molecule that anchors microtubules at the cell cortex through its association with the plus-end MT proteins CLASPs to trigger focal adhesion disassembly. LL5β is a prominent member of the MINK1-PRICKLE1 protein complex and is directly phosphorylated by MINK1 that promotes its interaction with CLASP. Using a kinase inhibitor, we demonstrate that the enzymatic activity of MINK1 is involved in the protein complex assembly and localization, and cell migration. Analysis of gene expression data show that the concomitant up-regulation of PRICKLE1 and LL5 β mRNA levels encoding MINK1 substrates is associated with a poor metastasis-free survival for TNBC patients. Altogether, our results suggest that MINK1 may represent a potential target in TNBC.

Transmission of extracellular signals by G protein-coupled receptors typically relies on a cascade of intracellular events initiated by the activation of heterotrimeric G proteins or β-arrestins followed by effector activation/inhibition. Here, we report an alternative signal transduction mode used by the orphan GPR50 that relies on the nuclear translocation of its carboxyl-terminal domain (CTD). Activation of the calcium-dependent calpain protease cleaves off the CTD from the transmembrane-bound GPR50 core domain between Phe-408 and Ser-409 as determined by MALDI-TOF-mass spectrometry. The cytosolic CTD then translocates into the nucleus assisted by its 'DPD' motif, where it interacts with the general transcription factor TFII-I to regulate c-fos gene transcription. RNA-Seq analysis indicates a broad role of the CTD in modulating gene transcription with ~ 8000 differentially expressed genes. Our study describes a non-canonical, direct signaling mode of GPCRs to the nucleus with similarities to other receptor families such as the NOTCH receptor.

SCRIB is a scaffold protein containing leucine‐rich repeats (LRR) and PSD‐95/Dlg‐A/ZO‐1 domains (PDZ) that localizes at the basolateral membranes of polarized epithelial cells. Deregulation of its expression or localization leads to epithelial defects and tumorigenesis in part as a consequence of its repressive role on several signaling pathways including AKT, ERK, and HIPPO. In the present work, a proteomic approach is used to characterize the protein complexes associated to SCRIB and its paralogue LANO. Common and specific sets of proteins associated to SCRIB and LANO by MS are identified and an extensive landscape of their associated networks and the first comparative analysis of their respective interactomes are provided. Under proteasome inhibition, it is further found that SCRIB is associated to the β‐catenin destruction complex that is central in Wnt/β‐catenin signaling, a conserved pathway regulating embryonic development and cancer progression. It is shown that the SCRIB/β‐catenin interaction is potentiated upon Wnt3a stimulation and that SCRIB plays a repressing role on Wnt signaling. The data thus provide evidence for the importance of SCRIB in the regulation of the Wnt/β‐catenin pathway.

BACKGROUND: Triple-negative breast cancers (TNBC) are poor-prognosis tumours candidate to chemotherapy as only systemic treatment. We previously found that PRICKLE1, a prometastatic protein involved in planar cell polarity, is upregulated in TNBC. We investigated the protein complex associated with PRICKLE1 in TNBC to identify proteins possibly involved in metastatic dissemination, which might provide new prognostic and/or therapeutic targets. METHODS: We used a proteomic approach to identify protein complexes associated with PRICKLE1. The mRNA expression levels of the corresponding genes were assessed in 8982 patients with invasive primary breast cancer. We then characterised the molecular interaction between PRICKLE1 and the guanine nucleotide exchange factor ECT2. Finally, experiments in Xenopus were carried out to determine their evolutionarily conserved interaction. RESULTS: Among the PRICKLE1 proteins network, we identified several small G-protein regulators. Combined analysis of the expression of PRICKLE1 and small G-protein regulators had a strong prognostic value in TNBC. Notably, the combined expression of ECT2 and PRICKLE1 provided a worst prognosis than PRICKLE1 expression alone in TNBC. PRICKLE1 regulated ECT2 activity and this interaction was evolutionary conserved. CONCLUSIONS: This work supports the idea that an evolutionarily conserved signalling pathway required for embryogenesis and activated in cancer may represent a suitable therapeutic target.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. ECT2 associated to PRICKLE1 are poor-prognosis markers in triple-negative breast cancer Luc Camoin, Jean-Paul Borg, Avais Daulat, Pascal Finetti, Diego Revinski, Mônica Silveira Wagner, Stéphane Audebert, Daniel Birnbaum, Laurent Kodjabachian, François Bertucci

Cell polarity is a vital biological process involved in the building, maintenance and normal functioning of tissues in invertebrates and vertebrates. Unsurprisingly, molecular defects affecting polarity organization and functions have a strong impact on tissue homeostasis, embryonic development and adult life, and may directly or indirectly lead to diseases. Genetic studies have demonstrated the causative effect of several polarity genes in diseases; however, much remains to be clarified before a comprehensive view of the molecular organization and regulation of the protein networks associated with polarity proteins is obtained. This challenge can be approached head-on using proteomics to identify protein complexes involved in cell polarity and their modifications in a spatio-temporal manner. We review the fundamental basics of mass spectrometry techniques and provide an in-depth analysis of how mass spectrometry has been instrumental in understanding the complex and dynamic nature of some cell polarity networks at the tissue (apico-basal and planar cell polarities) and cellular (cell migration, ciliogenesis) levels, with the fine dissection of the interconnections between prototypic cell polarity proteins and signal transduction cascades in normal and pathological situations. This review primarily focuses on epithelial structures which are the fundamental building blocks for most metazoan tissues, used as the archetypal model to study cellular polarity. This field offers broad perspectives thanks to the ever-increasing sensitivity of mass spectrometry and its use in combination with recently developed molecular strategies able to probe in situ proteomic networks.

Transforming growth factor-β (TGFβ) signaling is initiated by the type I, II TGFβ receptor (TβRI/TβRII) complex. Here we report the formation of an alternative complex between TβRI and the orphan GPR50, belonging to the G protein-coupled receptor super-family. The interaction of GPR50 with TβRI induces spontaneous TβRI-dependent Smad and non-Smad signaling by stabilizing the active TβRI conformation and competing for the binding of the negative regulator FKBP12 to TβRI. GPR50 overexpression in MDA-MB-231 cells mimics the anti-proliferative effect of TβRI and decreases tumor growth in a xenograft mouse model. Inversely, targeted deletion of GPR50 in the MMTV/Neu spontaneous mammary cancer model shows decreased survival after tumor onset and increased tumor growth. Low GPR50 expression is associated with poor survival prognosis in human breast cancer irrespective of the breast cancer subtype. This describes a previously unappreciated spontaneous TGFβ-independent activation mode of TβRI and identifies GPR50 as a TβRI co-receptor with potential impact on cancer development.

Background Triple-negative breast cancers are poor-prognosis tumors characterized by absence of molecular signature and are chemotherapy is still the only systemic treatment. Currently, research focus to identify biomarkers that may be usable for prognosis and/or for treatment, notably among the proteins involved in cell migration and metastatic capacity. Methods We used proteomic approach to identify protein complexes associated to PRICKLE1 and the mRNA expression level of the corresponding genes in a retrospective series of 8,982 clinically annotated patients with invasive primary breast cancer were assessed. Then, we characterize molecularly the interaction between PRICKLE1 and the guanine nucleotide exchange factor ECT2. Finally, experiments in Xenopus have been carrying out to determine their evolutionary conserved interaction. Results We have identified a network of proteins interacting with the prometastatic scaffold protein PRICKLE1 that includes several small G-protein regulators involved in cell migration and metastasis. Combined analysis expression of PRICKLE1 and small G-protein regulators expression has a strong prognostic value in TNBC. We show that PRICKLE1 controls the activity of ECT2 on RAC1 signaling, a pathway required for cancer cell dissemination. Conclusions This work supports the idea that promigratory proteins, which are overexpressed in cancerous epithelium, are suitable pharmaceutical targets.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. PRICKLE1 contributes to cancer cell dissemination through its interaction with mTORC2 Avais M Daulat, François Bertucci, Stéphane Audebert, Arnauld Sergé, Pascal Finetti, Emmanuelle Josselin, Rémy Castellano, Daniel Birnbaum, Stéphane Angers, Jean-Paul Borg

Cancer cells are addicted to a large spectrum of extracellular cues implicated in initiation, stem cell renewal, tumor growth, dissemination in the body, and resistance to treatment. Wingless/Int-1 (Wnt) ligands and their associated signaling cascades contribute to most of these processes, paving the way for opportunities in therapeutic development. The developmental Wnt/planar cell polarity (PCP) pathway is the most recently described branch of Wnt signaling strongly implicated in cancer development at early and late stages. We describe here some of the latest knowledge accumulated on this pathway and the pending questions, present the most convincing findings about its role in cancer, and review the most promising strategies currently designed to target its components.

Components of the evolutionarily conserved developmental planar cell polarity (PCP) pathway were recently described to play a prominent role in cancer cell dissemination. However, the molecular mechanisms by which PCP molecules drive the spread of cancer cells remain largely unknown. PRICKLE1 encodes a PCP protein bound to the promigratory serine/threonine kinase MINK1. We identify RICTOR, a member of the mTORC2 complex, as a PRICKLE1-binding partner and show that the integrity of the PRICKLE1-MINK1-RICTOR complex is required for activation of AKT, regulation of focal adhesions, and cancer cell migration. Disruption of the PRICKLE1-RICTOR interaction results in a strong impairment of breast cancer cell dissemination in xenograft assays. Finally, we show that upregulation of PRICKLE1 in basal breast cancers, a subtype characterized by high metastatic potential, is associated with poor metastasis-free survival.

Control of cell-division orientation is integral to epithelial morphogenesis and asymmetric cell division. Proper spatiotemporal localization of the evolutionarily conserved Gαi-LGN-NuMA protein complex is critical for mitotic spindle orientation, but how this is achieved remains unclear. Here we identify Suppressor APC domain containing 2 (SAPCD2) as a previously unreported LGN-interacting protein. We show that SAPCD2 is essential to instruct planar mitotic spindle orientation in both epithelial cell cultures and mouse retinal progenitor cells in vivo. Loss of SAPCD2 randomizes spindle orientation, which in turn disrupts cyst morphogenesis in three-dimensional cultures, and triples the number of terminal asymmetric cell divisions in the developing retina. Mechanistically, we show that SAPCD2 negatively regulates the localization of LGN at the cell cortex, likely by competing with NuMA for its binding. These results uncover SAPCD2 as a key regulator of the ternary complex controlling spindle orientation during morphogenesis and asymmetric cell divisions.

Hyperactivation of the mTOR-AKT pathway frequently contributes to the spread of cancer cells, especially in aggressive breast cancer, to distant organs, promoting the lethal metastatic program. Despite advances in the understanding of this signaling pathway and the development of inhibitors, efforts are still needed to dissect its complexity. This is particularly the case for mTORC2, which constitutes one of the two major branches of the mTOR pathway and whose mode of regulation is poorly defined. The mTORC2 complex consists of RICTOR, an evolutionarily conserved protein associated to mTOR, LST8 and SIN1, which is responsible for the phosphorylation of AGC protein kinases (AKT, SGK1 and PKCα). In a recent report1, we reveal that, in breast cancer cells, the mTORC2 complex, through the RICTOR subunit, can associate with PRICKLE1, a core member of planar cell polarity (PCP) which normally shapes organs during embryogenesis of Metazoans (Figure 1).