The RanBP2/RanGAP1-SUMO complex gates β-arrestin2 nuclear entry to regulate the Mdm2-p53 signalling axis

Mdm2 antagonizes the tumor suppressor p53. Targeting the Mdm2-p53 interaction represents an attractive approach for the treatment of cancers with functional p53. Investigating mechanisms underlying Mdm2-p53 regulation is therefore important. The scaffold protein β-arrestin2 (β-arr2) regulates tumor suppressor p53 by counteracting Mdm2. β-arr2 nucleocytoplasmic shuttling displaces Mdm2 from the nucleus to the cytoplasm resulting in enhanced p53 signaling. β-arr2 is constitutively exported from the nucleus, via a nuclear export signal, but mechanisms regulating its nuclear entry are not completely elucidated. β-arr2 can be SUMOylated, but no information is available on how SUMO may regulate β-arr2 nucleocytoplasmic shuttling. While we found β-arr2 SUMOylation to be dispensable for nuclear import, we identified a non-covalent interaction between SUMO and β-arr2, via a SUMO interaction motif (SIM), that is required for β-arr2 cytonuclear trafficking. This SIM promotes association of β-arr2 with the multimolecular RanBP2/RanGAP1-SUMO nucleocytoplasmic transport hub that resides on the cytoplasmic filaments of the nuclear pore complex. Depletion of RanBP2/RanGAP1-SUMO levels result in defective β-arr2 nuclear entry. Mutation of the SIM inhibits β-arr2 nuclear import, its ability to delocalize Mdm2 from the nucleus to the cytoplasm and enhanced p53 signaling in lung and breast tumor cell lines. Thus, a β-arr2 SIM nuclear entry checkpoint, coupled with active β-arr2 nuclear export, regulates its cytonuclear trafficking function to control the Mdm2-p53 signaling axis

Post-translational control of Beta-arrestin 2 cytonuclear shuttling

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Control of the Mdm2-p53 signal loop by β-arrestin 2: the ins and outs

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Data from: PTEN controls glandular morphogenesis through a juxtamembrane β-Arrestin1/ARHGAP21 scaffolding complex

PTEN controls three-dimensional (3D) glandular morphogenesis by coupling juxtamembrane signalling to mitotic spindle machinery. While molecular mechanisms remain unclear, PTEN interacts through its C2 membrane-binding domain with the scaffold protein β-Arrestin1. Because β-Arrestin1 binds and suppresses the Cdc42 GTPase-activating protein ARHGAP21, we hypothesize that PTEN controls Cdc42-dependent morphogenic processes through a β-Arrestin1-ARHGAP21 complex. Here we show that PTEN knockdown (KD) impairs β-Arrestin1 membrane localization, β-Arrestin1-ARHGAP21 interactions, Cdc42 activation, mitotic spindle orientation and 3D glandular morphogenesis. Effects of PTEN-deficiency were phenocopied by β-Arrestin1 KD or inhibition of β-Arrestin1-ARHGAP21 interactions. Conversely, silencing of ARHGAP21 enhanced Cdc42 activation and rescued aberrant morphogenic processes of PTEN-deficient cultures. Expression of the PTEN C2 domain mimicked effects of full-length PTEN but a membrane-binding defective mutant of the C2 domain abrogated these properties. Our results show that PTEN controls multicellular assembly through a membrane-associated regulatory protein complex composed of β-Arrestin1, ARHGAP21 and Cdc42

GLP-1R signaling neighborhoods associate with the susceptibility to adverse drug reactions of incretin mimetics

G protein-coupled receptors are important drug targets that engage and activate signaling transducers in multiple cellular compartments. Delineating therapeutic signaling from signaling associated with adverse events is an important step towards rational drug design. The glucagon-like peptide-1 receptor (GLP-1R) is a validated target for the treatment of diabetes and obesity, but drugs that target this receptor are a frequent cause of adverse events. Using recently developed biosensors, we explored the ability of GLP-1R to activate 15 pathways in 4 cellular compartments and demonstrate that modifications aimed at improving the therapeutic potential of GLP-1R agonists greatly influence compound efficacy, potency, and safety in a pathway- and compartment-selective manner. These findings, together with comparative structure analysis, time-lapse microscopy, and phosphoproteomics, reveal unique signaling signatures for GLP-1R agonists at the level of receptor conformation, functional selectivity, and location bias, thus associating signaling neighborhoods with functionally distinct cellular outcomes and clinical consequences. Agonists of the glucagon-like peptide-1 receptor are used to treat diabetes and obesity. Here, Wright et al. investigate the subcellular location of the receptor's signaling events and uncover associations between signaling profiles and adverse drug reactions

G protein-specific mechanisms in the serotonin 5-HT2A receptor regulate psychosis-related effects and memory deficits

G protein-coupled receptors (GPCRs) are sophisticated signaling machines able to simultaneously elicit multiple intracellular signaling pathways upon activation. Complete (in)activation of all pathways can be counterproductive for specific therapeutic applications. This is the case for the serotonin 2 A receptor (5-HT2AR), a prominent target for the treatment of schizophrenia. In this study, we elucidate the complex 5-HT2AR coupling signature in response to different signaling probes, and its physiological consequences by combining computational modeling, in vitro and in vivo experiments with human postmortem brain studies. We show how chemical modification of the endogenous agonist serotonin dramatically impacts the G protein coupling profile of the 5-HT2AR and the associated behavioral responses. Importantly, among these responses, we demonstrate that memory deficits are regulated by Gαq protein activation, whereas psychosis-related behavior is modulated through Gαi1 stimulation. These findings emphasize the complexity of GPCR pharmacology and physiology and open the path to designing improved therapeutics for the treatment of stchizophrenia.This work was supported by the ERAnet NEURON consortium fund (funding was provided by CIHR NDD-161471 and FRQ-S 278647 for M.B., the German Federal Ministry of Education and Research under grant number 01EW1909 for P.K., as well as the Instituto de Salud Carlos III and Fondo Europeo de Desarrollo Regional number AC18/00030 for J.S. and P.R.). This work was further supported by the Instituto de Salud Carlos III (ISCIII) and co-funded by the European Union (PI18/00094) to J.S. and (PI18/00053) to P.R. We acknowledge grant support from Agencia Estatal de Investigación (PID2020-119428RB-I00; SAF2017-88126R), Basque Government (IT-1211/19, IT-1512/22 and KK-2019/00-49), Xunta de Galicia (ED431C 2022/20 and ED431G 2019/02) and European Regional Development Fund (ERDF). P.K. thanks the German Research Foundation DFG for Heisenberg Professorship KO4095/5-1. S.S.O. and R.S. thank the PTQ-17-09103 (Ayuda Torres Quevedo, Ministerio de Ciencia e Innovación), and BioExcel-2 (Grant Number 823830, Horizon2020). M.B. was in part supported by an operating grant (# PJT 183758) from the Canadian Institute for Health Research. I.M-A. was the recipient of a predoctoral fellowship from the Basque Government. The authors would like to thank the staff members of the Basque Institute of Legal Medicine for their cooperation in the study, especially to Dr. Benito Morentin. R.D-A., T.M.S, D.A.G., I.M.A., A.S., P.K. and J.S. are members of COST Action CA18133 “ERNEST”