Elsevier

Biochemical Pharmacology

Volume 55, Issue 4, 15 February 1998, Pages 489-497
Biochemical Pharmacology

Research paper
Prolonged depletion of AH receptor without alteration of receptor mRNA levels after treatment of cells in culture with 2,3,7,8-tetrachlorodibenzo-p-dioxin,☆☆

https://doi.org/10.1016/S0006-2952(97)00493-0Get rights and content

Abstract

Previous experiments have shown that the total cellular content of the AH receptor (AHR) drops rapidly after exposure of mouse hepatoma cells (Hepa-1) to the potent AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); within 6 hr after treatment, less than 20% of the original cell content of AHR can be detected by radioligand binding or by immunoblotting. The goals of our current study were to determine the duration of receptor depletion following treatment with ligand and to determine if depletion is due to decreased expression of the Ahr gene that encodes the AHR. We found that depletion of AHR persisted for at least 72 hr after exposure to TCDD. Treatment with 3-methylcholanthrene caused a transient drop in total cell AHR, but the AHR levels returned to near pretreatment levels within 72 hr after the first exposure. TCDD treatment did not alter the levels of AHR mRNA as assessed by reverse transcription-polymerase chain reaction or slot blot assays. Thus, the decrease in AHR protein cannot be attributed to depression of transcription of the Ahr gene by TCDD. TCDD treatment did not alter the levels of the dimerization partner of the AHR, the AH receptor nuclear translocator protein (ARNT), or ARNT mRNA. In the presence of TCDD, both the AHR and the ARNT protein can be maintained at high levels in the nucleus if transcription is inhibited with actinomycin-D. In the absence of actinomycin-D, the AHR protein was lost rapidly, but the ARNT protein level in the cell was maintained. Together, these results suggest that the AHR protein is degraded through a selective mechanism that spares the ARNT protein and that the degradation pathway involves a protein that itself has a short half-life.

References (28)

  • R. Pohjanvirta et al.

    Short-term toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in laboratory animals: Effects, mechanisms, and animal models

    Pharmacol Rev

    (1994)
  • D.W. Nebert et al.

    Role of the Ah receptor and the dioxin-inducible [Ah] gene battery in toxicity, cancer, and signal transduction

    Ann NY Acad Sci

    (1993)
  • K.W. Bock

    Aryl hydrocarbon or dioxin receptor: Biologic and toxic responses

    Rev Physiol Biochem Pharmacol

    (1993)
  • J.V. Schmidt et al.

    AH receptor signaling pathways

    Annu Rev Cell Dev Biol

    (1996)
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    A preliminary report of portions of this research was presented at the 8th International Conference on Cytochrome P450, Lisbon, Portugal, 1994.

    ☆☆

    This work was supported by a grant to A.B.O. from the Medical Research Council of Canada and grant CA28868 from the National Cancer Institute, U.S.A. to O. Hankinson (in whose laboratory part of the work of this study was performed by M.P.).

    M.P. was supported by a fellowship from the Swiss National Science Foundation.

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