Dataset Information

ER??4, an ER? splice variant missing exon4, interacts with caveolin-3 and mGluR2/3.

ABSTRACT: The two isoforms of the nuclear estrogen receptor, ER? and ER? are widely expressed in the central nervous system. Although they were first described as nuclear receptors, both isoforms have also been found at the cell membrane where they mediate cell signaling. Surface biotinylation studies using neuronal and glial primary cultures label an alternatively spliced form of ER?. The 52 kDa protein, ER??4, is missing exon 4 and is highly expressed in membrane fractions derived from cultured cells. In vivo, both full-length (66 kDa) ER? and ER??4 are present in membrane fractions. In response to estradiol, full-length ER? and ER??4 are initially trafficked to the membrane, and then internalized in parallel. Previous studies determined that only the full-length ER? associates with metabotropic glutamate receptor-1a (mGluR1a), initiating cellular signaling. The role of ER??4, remained to be elucidated. Here, we report ER??4 trafficking, association with mGluR2/3, and downstream signaling in female rat arcuate nucleus (ARH). Caveolin (CAV) proteins are needed for ER transport to the cell membrane, and using co-immunoprecipitation CAV-3 was shown to associate with ER??4. CAV-3 was necessary for ER??4 trafficking to the membrane: in the ARH, microinjection of CAV-3 siRNA reduced CAV-3 and ER??4a in membrane fractions by 50%, and 60%, respectively. Moreover, co-immunoprecipitation revealed that ER??4 associated with inhibitory mGluRs, mGluR2/3. Estrogen benzoate (EB) treatment (5 ?g; s.c.; every 4 days; three cycles) reduced levels of cAMP, an effect attenuated by antagonizing mGluR2/3. Following EB treatment, membrane levels of ER??4 and mGluR2/3 were reduced implying ligand-induced internalization. These results implicate ER??4 in an estradiol-induced inhibitory cell signaling in the ARH.

SUBMITTER: Wong AM

PROVIDER: S-EPMC6591055 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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ERαΔ4, an ERα splice variant missing exon4, interacts with caveolin-3 and mGluR2/3.

Wong Angela M AM Scott Alexandra K AK Johnson Caroline S CS Mohr Margaret A MA Mittelman-Smith Melinda M Micevych Paul E PE

Journal of neuroendocrinology 20190523 6

The two isoforms of the nuclear estrogen receptor, ERα and ERβ are widely expressed in the central nervous system. Although they were first described as nuclear receptors, both isoforms have also been found at the cell membrane where they mediate cell signaling. Surface biotinylation studies using neuronal and glial primary cultures label an alternatively spliced form of ERα. The 52 kDa protein, ERαΔ4, is missing exon 4 and is highly expressed in membrane fractions derived from cultured cells. I ...[more]

PMID: 31050077

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Project description:Viral interleukin-6 (vIL-6) specified by human herpesvirus 8 is, unlike its cellular counterpart, secreted very inefficiently and can signal via vIL-6(2):gp130(2) signaling complexes from the endoplasmic reticulum (ER) compartment. Intracellular, autocrine activities of vIL-6 are important for proproliferative and prosurvival activities of the viral cytokine in latently infected primary effusion lymphoma (PEL) cells. However, the molecular determinants of vIL-6 ER localization and function are unclear. Using yeast two-hybrid analysis, we identified the database-documented but uncharacterized splice variant of vitamin K epoxide reductase complex subunit 1 (VKORC1), termed VKORC1 variant 2 (VKORC1v2), as a potential interaction partner of vIL-6. In transfected cells, epitope-tagged VKORC1v2 was found to localize to the ER, to adopt a single-transmembrane (TM) topology placing the C tail in the ER lumen, and to bind vIL-6 via these sequences. Deletion mutagenesis and coprecipitation assays mapped the vIL-6-binding domain (vBD) of VKORC1v2 to TM-proximal residues 31 to 39. However, while sufficient to confer vIL-6 binding to a heterologous protein, vBD was unable to induce vIL-6 secretion when fused to (secreted) hIL-6, suggesting a VKORC1v2-independent mechanism of vIL-6 ER retention. In functional assays, overexpression of ER-directed vBD led to suppression of PEL cell proliferation and viability, effects also mediated by VKORC1v2 depletion and, as reported previously, by vIL-6 suppression. The growth-inhibitory and proapoptotic effects of VKORC1v2 depletion could be rescued by transduced wild-type VKORC1v2 but not by a vIL-6-refractory vBD-altered variant, indicating the functional relevance of the vIL-6-VKORC1v2 interaction. Notably, gp130 signaling was unaffected by VKORC1v2 or vBD overexpression or by VKORC1v2 depletion, suggesting an alternative pathway of vIL-6 activity via VKORC1v2. Combined, our data identify a novel and functionally significant interaction partner of vIL-6 that could potentially be targeted for therapeutic benefit.

Dataset Information

ER??4, an ER? splice variant missing exon4, interacts with caveolin-3 and mGluR2/3.

Publications

ERαΔ4, an ERα splice variant missing exon4, interacts with caveolin-3 and mGluR2/3.

Similar Datasets

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