Resumen del póster presentado al 6th Symposium on Biomedical Research: Advances and Perspectives in Molecular Endocrinology "In Homage to Gabriella Morreale", celebrado en el Instituto de Investigaciones Biomédicas Alberto Sols (IIBM-CSIC) el 31 de mayo de 2019., Serotonin receptor 6 (Htr6) is a neuronal G protein-coupled receptor (GPCR) involved in multiple aspects of brain pathophysiology. Htr6 localizes to primary cilia, microtubule-based plasma membrane protrusions that act as signaling platforms. Htr6 contains a ciliary targeting sequence (CTS) in its third intracellular loop. This CTS (CTS1) is sufficient to confer cilia localization to non-ciliary proteins such as Htr7, a non-ciliary GPCR, or CD8?, a single pass transmembrane protein. Surprisingly, however, CTS1 is not required for Htr6 itself to localize to cilia, suggesting that Htr6 contains another CTS. Here, we have identified a second CTS (CTS2) in the C-terminal tail of Htr6. Like CTS1, the novel CTS2 is sufficient but not necessary for cilia localization. When both CTS1 and CTS2 are mutated, Htr6 no longer accumulates in cilia. Thus, CTS1 and CTS2 act redundantly and are, in combination, both necessary and sufficient for Htr6 ciliary targeting. Furthermore, we have found that the same pattern applies to another ciliary GPCR, namely, Somatostatin receptor 3 (Sstr3). We are now elucidating the mechanisms of action of these novel CTSs., This work was funded by MINECO/FEDER (SAF2015-66568-R) and Ramón y Cajal (RYC2013-14887) grants from the Spanish Ministry of Economy and Competitiveness to F.R.G.G, Peer reviewed

© The Author(s) 2019., The transcription factor NRF2 is a master regulator of cellular antioxidant and detoxification responses, but it also regulates other processes such as autophagy and pluripotency. In human embryonic stem cells (hESCs), NRF2 antagonizes neuroectoderm differentiation, which only occurs after NRF2 is repressed via a Primary Cilia-Autophagy-NRF2 (PAN) axis. However, the functional connections between NRF2 and primary cilia, microtubule-based plasma membrane protrusions that function as cellular antennae, remain poorly understood. For instance, nothing is known about whether NRF2 affects cilia, or whether cilia regulation of NRF2 extends beyond hESCs. Here, we show that NRF2 and primary cilia reciprocally regulate each other. First, we demonstrate that fibroblasts lacking primary cilia have higher NRF2 activity, which is rescued by autophagy-activating mTOR inhibitors, indicating that the PAN axis also operates in differentiated cells. Furthermore, NRF2 controls cilia formation and function. NRF2-null cells grow fewer and shorter cilia and display impaired Hedgehog signaling, a cilia-dependent pathway. These defects are not due to increased oxidative stress or ciliophagy, but rather to NRF2 promoting expression of multiple ciliogenic and Hedgehog pathway genes. Among these, we focused on GLI2 and GLI3, the transcription factors controlling Hh pathway output. Both their mRNA and protein levels are reduced in NRF2-null cells, consistent with their gene promoters containing consensus ARE sequences predicted to bind NRF2. Moreover, GLI2 and GLI3 fail to accumulate at the ciliary tip of NRF2-null cells upon Hh pathway activation. Given the importance of NRF2 and ciliary signaling in human disease, our data may have important biomedical implications., Tis work was supported by European Regional Development Fund (ERDF)-cofunded grants from the Spanish Ministry of Economy and Competitiveness (MINECO) to FRGG (SAF2015-66568-R and RYC2013-14887) and to A.C. and I.L.B. (SAF2016-76520-R). AMH was supported by an ERDF-cofunded predoctoral contract from the Community of Madrid government. RMM, NRA and RB were supported by predoctoral grants from MINECO.

This article belongs to the Special Issue Keap1/Nrf2 Signaling Pathway., When not dividing, many cell types target their centrosome to the plasma membrane, where it nucleates assembly of a primary cilium, an antenna-like signaling structure consisting of nine concentric microtubule pairs surrounded by membrane. Primary cilia play important pathophysiological roles in many tissues, their dysfunction being associated with cancer and ciliopathies, a diverse group of congenital human diseases. Several recent studies have unveiled functional connections between primary cilia and NRF2 (nuclear factor erythroid 2-related factor 2), the master transcription factor orchestrating cytoprotective responses to oxidative and other cellular stresses. These NRF2-cilia relationships are reciprocal: primary cilia, by promoting autophagy, downregulate NRF2 activity. In turn, NRF2 transcriptionally regulates genes involved in ciliogenesis and Hedgehog (Hh) signaling, a cilia-dependent pathway with major roles in embryogenesis, stem cell function and tumorigenesis. Nevertheless, while we found that NRF2 stimulates ciliogenesis and Hh signaling, a more recent study reported that NRF2 negatively affects these processes. Herein, we review the available evidence linking NRF2 to primary cilia, suggest possible explanations to reconcile seemingly contradictory data, and discuss what the emerging interplay between primary cilia and NRF2 may mean for human health and disease., This work was funded by European Regional Development Fund (ERDF/FEDER)-cofunded grants from the Spanish Ministry of Economy and Competitiveness (MINECO) to F.R.G.G. (SAF2015-66568-R and RYC2013-14887). A.M.H. was supported by a FEDER-cofunded predoctoral contract from the Community of Madrid government., Peer reviewed

© 2021 The Author(s)., Primary cilia are hair-like projections of the cell membrane supported by an inner microtubule scaffold, the axoneme, which polymerizes out of a membrane-docked centriole at the ciliary base. By working as specialized signaling compartments, primary cilia provide an optimal environment for many G protein-coupled receptors (GPCRs) and their effectors to efficiently transmit their signals to the rest of the cell. For this to occur, however, all necessary receptors and signal transducers must first accumulate at the ciliary membrane. Serotonin receptor 6 (HTR6) and Somatostatin receptor 3 (SSTR3) are two GPCRs whose signaling in brain neuronal cilia affects cognition and is implicated in psychiatric, neurodegenerative, and oncologic diseases. Over a decade ago, the third intracellular loops (IC3s) of HTR6 and SSTR3 were shown to contain ciliary localization sequences (CLSs) that, when grafted onto non-ciliary GPCRs, could drive their ciliary accumulation. Nevertheless, these CLSs were dispensable for ciliary targeting of HTR6 and SSTR3, suggesting the presence of additional CLSs, which we have recently identified in their C-terminal tails. Herein, we review the discovery and mapping of these CLSs, as well as the state of the art regarding how these CLSs may orchestrate ciliary accumulation of these GPCRs by controlling when and where they interact with the ciliary entry and exit machinery via adaptors such as TULP3, RABL2 and the BBSome., This work was supported by grants from the Spanish Ministry of Science and Innovation (MICINN) to FRGG [PID2019-104941RB-I00, SAF2015-66568-R and RYC2013-14887, the last two cofunded by the European Regional Development Fund (ERDF/FEDER)].