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Li X, Kirkpatrick RB, Wang X, Tucker CJ, Shukla A, Jessen HJ, Wang H, Shears SB, Gu C. Homeostatic coordination of cellular phosphate uptake and efflux requires an organelle-based receptor for the inositol pyrophosphate IP8. Cell Rep 2024; 43:114316. [PMID: 38833370 DOI: 10.1016/j.celrep.2024.114316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 04/16/2024] [Accepted: 05/17/2024] [Indexed: 06/06/2024] Open
Abstract
Phosphate (Pi) serves countless metabolic pathways and is involved in macromolecule synthesis, energy storage, cellular signaling, and bone maintenance. Herein, we describe the coordination of Pi uptake and efflux pathways to maintain mammalian cell Pi homeostasis. We discover that XPR1, the presumed Pi efflux transporter, separately supervises rates of Pi uptake. This direct, regulatory interplay arises from XPR1 being a binding partner for the Pi uptake transporter PiT1, involving a predicted transmembrane helix/extramembrane loop in XPR1, and its hitherto unknown localization in a subset of intracellular LAMP1-positive puncta (named "XLPVs"). A pharmacological mimic of Pi homeostatic challenge is sensed by the inositol pyrophosphate IP8, which functionalizes XPR1 to respond in a temporally hierarchal manner, initially adjusting the rate of Pi efflux, followed subsequently by independent modulation of PiT1 turnover to reset the rate of Pi uptake. These observations generate a unifying model of mammalian cellular Pi homeostasis, expanding opportunities for therapeutic intervention.
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Affiliation(s)
- Xingyao Li
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA
| | - Regan B Kirkpatrick
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA
| | - Xiaodong Wang
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Charles J Tucker
- Fluorescence Microscopy and Imaging Center, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Anuj Shukla
- Institute of Organic Chemistry, and CIBSS - the Center for Integrative Biological Signaling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Henning J Jessen
- Institute of Organic Chemistry, and CIBSS - the Center for Integrative Biological Signaling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Huanchen Wang
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA; Nucleolar Integrity Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA
| | - Stephen B Shears
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA
| | - Chunfang Gu
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA; Synaptic & Developmental Plasticity Group, Neurobiology Laboratory, National Institute of Environmental, Health Sciences, Research Triangle Park, NC 27709, USA.
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Bali A, Schaefer SP, Trier I, Zhang AL, Kabeche L, Paulsen CE. Molecular mechanism of hyperactivation conferred by a truncation of TRPA1. Nat Commun 2023; 14:2867. [PMID: 37208332 PMCID: PMC10199097 DOI: 10.1038/s41467-023-38542-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 05/08/2023] [Indexed: 05/21/2023] Open
Abstract
A drastic TRPA1 mutant (R919*) identified in CRAMPT syndrome patients has not been mechanistically characterized. Here, we show that the R919* mutant confers hyperactivity when co-expressed with wild type (WT) TRPA1. Using functional and biochemical assays, we reveal that the R919* mutant co-assembles with WT TRPA1 subunits into heteromeric channels in heterologous cells that are functional at the plasma membrane. The R919* mutant hyperactivates channels by enhancing agonist sensitivity and calcium permeability, which could account for the observed neuronal hypersensitivity-hyperexcitability symptoms. We postulate that R919* TRPA1 subunits contribute to heteromeric channel sensitization by altering pore architecture and lowering energetic barriers to channel activation contributed by the missing regions. Our results expand the physiological impact of nonsense mutations, reveal a genetically tractable mechanism for selective channel sensitization, uncover insights into the process of TRPA1 gating, and provide an impetus for genetic analysis of patients with CRAMPT or other stochastic pain syndromes.
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Affiliation(s)
- Avnika Bali
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Samantha P Schaefer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Isabelle Trier
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Cancer Biology Institute, Yale University, West Haven, CT, USA
| | - Alice L Zhang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Lilian Kabeche
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
- Cancer Biology Institute, Yale University, West Haven, CT, USA
| | - Candice E Paulsen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
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Stick R, Peter A. CaaX-less lamins: Lophotrochozoa provide a glance at the playground of evolution. PROTOPLASMA 2023; 260:741-756. [PMID: 36102949 PMCID: PMC10125929 DOI: 10.1007/s00709-022-01809-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Accepted: 09/01/2022] [Indexed: 05/05/2023]
Abstract
Nuclear lamins are the main components of the nuclear lamina in many eukaryotes. They are members of the intermediate filament (IF) protein family. Lamins differ from cytoplasmic IF proteins by the presence of a nuclear localisation sequence (NLS) and a C-terminal tetrapeptide, the CaaX motif. The CaaX motif is target of post-translational modifications including isoprenylation, proteolytic processing, and carboxyl-methylation. These modifications, in conjunction with the NLS, direct lamins to the inner nuclear membrane where they assemble into filaments. Lamins lacking a CaaX motif are unable to associate independently with nuclear membranes and remain in the nucleoplasm. So far, three species have been reported to exclusively express CaaX-less lamins. All three belong to the lophotrochozoan lineage. To find out whether they represent rare exceptions, we analysed lamins of representatives of 17 lophotrochozoan phyla. Here we report that all four clades of Rotifera as well as individual taxa of Mollusca and Annelida lack CaaX-lamins, but express lamins with alternative C-termini. Of note, the respective mollusc and annelid groups occupy very different phylogenetic ranks. Most of these alternative C-termini are rich in aromatic residues. A possible function of these residues in membrane association is discussed. Alternative splicing of terebellid lamin transcripts gives rise to two lamin variants, one with a CaaX motif and one with an alternative C-terminus. A similar situation is found in Arenicolidae, Opheliidae, Capitellidae, and Echiura. This points a way, how the switch from lamins carrying a CaaX motif to lamins with alternative C-termini may have occurred.
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Affiliation(s)
- Reimer Stick
- Department of Cell Biology, University of Bremen, P.O. Box 330440, 28334, Bremen, Germany.
| | - Annette Peter
- Department of Cell Biology, University of Bremen, P.O. Box 330440, 28334, Bremen, Germany
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Pietraszewska-Bogiel A, Joosen L, Chertkova AO, Goedhart J. Not So Dry After All: DRY Mutants of the AT1 A Receptor and H1 Receptor Can Induce G-Protein-Dependent Signaling. ACS OMEGA 2020; 5:2648-2659. [PMID: 32095688 PMCID: PMC7033670 DOI: 10.1021/acsomega.9b03146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
G-protein-coupled receptors (GPCRs) are seven transmembrane spanning receptors that regulate a wide array of intracellular signaling cascades in response to various stimuli. To do so, they couple to different heterotrimeric G proteins and adaptor proteins, including arrestins. Importantly, arrestins were shown to regulate GPCR signaling through G proteins, as well as promote G protein-independent signaling events. Several research groups have reported successful isolation of exclusively G protein-dependent and arrestin-dependent signaling downstream of GPCR activation using biased agonists or receptor mutants incapable of coupling to either arrestins or G proteins. In the latter category, the DRY mutant of the angiotensin II type 1 receptor was extensively used to characterize the functional selectivity downstream of AT1AR. In an attempt to understand histamine 1 receptor signaling, we characterized the signaling capacity of the H1R DRY mutant in a panel of dynamic, live cell biosensor assays, including arrestin recruitment, heterotrimeric G protein activation, Ca2+ signaling, protein kinase C activity, GTP binding of RhoA, and activation of ERK1/2. Here, we show that both H1R DRY mutant and the AT1AR DRY mutant are capable of efficient activation of G protein-mediated signaling. Therefore, contrary to the common belief, they do not constitute suitable tools for the dissection of the arrestin-mediated, G protein-independent signaling downstream of these receptors.
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Bandekar SJ, Arang N, Tully ES, Tang BA, Barton BL, Li S, Gutkind JS, Tesmer JJG. Structure of the C-terminal guanine nucleotide exchange factor module of Trio in an autoinhibited conformation reveals its oncogenic potential. Sci Signal 2019; 12:12/569/eaav2449. [PMID: 30783010 DOI: 10.1126/scisignal.aav2449] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The C-terminal guanine nucleotide exchange factor (GEF) module of Trio (TrioC) transfers signals from the Gαq/11 subfamily of heterotrimeric G proteins to the small guanosine triphosphatase (GTPase) RhoA, enabling Gαq/11-coupled G protein-coupled receptors (GPCRs) to control downstream events, such as cell motility and gene transcription. This conserved signal transduction axis is crucial for tumor growth in uveal melanoma. Previous studies indicate that the GEF activity of the TrioC module is autoinhibited, with release of autoinhibition upon Gαq/11 binding. Here, we determined the crystal structure of TrioC in its basal state and found that the pleckstrin homology (PH) domain interacts with the Dbl homology (DH) domain in a manner that occludes the Rho GTPase binding site, thereby suggesting the molecular basis of TrioC autoinhibition. Biochemical and biophysical assays revealed that disruption of the autoinhibited conformation destabilized and activated the TrioC module in vitro. Last, mutations in the DH-PH interface found in patients with cancer activated TrioC and, in the context of full-length Trio, led to increased abundance of guanosine triphosphate-bound RhoA (RhoA·GTP) in human cells. These mutations increase mitogenic signaling through the RhoA axis and, therefore, may represent cancer drivers operating in a Gαq/11-independent manner.
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Affiliation(s)
- Sumit J Bandekar
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nadia Arang
- Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA.,Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Ena S Tully
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Brittany A Tang
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Brenna L Barton
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sheng Li
- Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA
| | - J Silvio Gutkind
- Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA.,Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
| | - John J G Tesmer
- Departments of Biological Sciences and of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA.
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