Taxol normalizes the impaired agonist-induced β2-adrenoceptor internalization in splenocytes from GRK2+/- mice

Anne Vroon, Maria Stella Lombardi, Annemieke Kavelaars, Cobi J. Heijnen

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

G protein-coupled receptor kinase 2 (GRK2) is involved in the agonist-induced desensitization of β2-adrenoceptors. In addition, GRK2 is capable of binding and phosphorylating tubulin. Interestingly, microtubule dynamics profoundly affect agonist-induced internalization of β2-adrenoceptors. Here, we analyzed agonist-induced β2-adrenoceptor internalization and signaling in splenocytes from GRK2+/- mice that have a ∼ 50% lower level of GRK2 protein compared to wild type (WT) mice. In addition, we investigated the role of microtubule stability in these processes. Splenocytes from GRK2+/- mice express ∼ 50% less β2-adrenoceptors on the cell surface and show impaired agonist-induced β2-adrenoceptor internalization. Disruption of microtubules using colchicine reduces agonist-induced β2-adrenoceptor internalization in cells from WT, but not in cells from GRK2+/- mice. Importantly, increasing tubulin stability by taxol almost completely restores the defective agonist-induced β2-adrenoceptor internalization in cells from GRK2+/- animals, without affecting WT cells. Despite lower surface receptor numbers, cells of GRK2+/- mice show normal β2-adrenoceptor agonist-induced cAMP responses. Although interfering with microtubule stability has major effects on agonist-induced receptor internalization in GRK2+/- cells, microtubule dynamics do not influence cAMP responses. Our data suggest that cells with low GRK2 adapt to the lower GRK2 level by decreasing the number of β2-adrenoceptors on the cell surface. In addition, the cellular GRK2 level determines the extent of agonist-induced β2-adrenoceptor internalization via a mechanism involving microtubule stability. Importantly, however, normalization of agonist-induced receptor internalization by taxol is not sufficient to alter receptor signaling.

Original languageEnglish (US)
Pages (from-to)9-16
Number of pages8
JournalEuropean Journal of Pharmacology
Volume560
Issue number1
DOIs
StatePublished - Mar 29 2007

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G-Protein-Coupled Receptor Kinase 2
Paclitaxel
Adrenergic Receptors
Microtubules
Tubulin
Mouse Adrbk1 protein
Colchicine
Cell Surface Receptors

Keywords

  • G protein-coupled receptor kinase 2
  • Microtubules
  • Receptor internalization
  • Tubulin
  • cAMP
  • β-adrenoceptor

ASJC Scopus subject areas

  • Pharmacology

Cite this

Taxol normalizes the impaired agonist-induced β2-adrenoceptor internalization in splenocytes from GRK2+/- mice. / Vroon, Anne; Lombardi, Maria Stella; Kavelaars, Annemieke; Heijnen, Cobi J.

In: European Journal of Pharmacology, Vol. 560, No. 1, 29.03.2007, p. 9-16.

Research output: Contribution to journalArticle

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abstract = "G protein-coupled receptor kinase 2 (GRK2) is involved in the agonist-induced desensitization of β2-adrenoceptors. In addition, GRK2 is capable of binding and phosphorylating tubulin. Interestingly, microtubule dynamics profoundly affect agonist-induced internalization of β2-adrenoceptors. Here, we analyzed agonist-induced β2-adrenoceptor internalization and signaling in splenocytes from GRK2+/- mice that have a ∼ 50{\%} lower level of GRK2 protein compared to wild type (WT) mice. In addition, we investigated the role of microtubule stability in these processes. Splenocytes from GRK2+/- mice express ∼ 50{\%} less β2-adrenoceptors on the cell surface and show impaired agonist-induced β2-adrenoceptor internalization. Disruption of microtubules using colchicine reduces agonist-induced β2-adrenoceptor internalization in cells from WT, but not in cells from GRK2+/- mice. Importantly, increasing tubulin stability by taxol almost completely restores the defective agonist-induced β2-adrenoceptor internalization in cells from GRK2+/- animals, without affecting WT cells. Despite lower surface receptor numbers, cells of GRK2+/- mice show normal β2-adrenoceptor agonist-induced cAMP responses. Although interfering with microtubule stability has major effects on agonist-induced receptor internalization in GRK2+/- cells, microtubule dynamics do not influence cAMP responses. Our data suggest that cells with low GRK2 adapt to the lower GRK2 level by decreasing the number of β2-adrenoceptors on the cell surface. In addition, the cellular GRK2 level determines the extent of agonist-induced β2-adrenoceptor internalization via a mechanism involving microtubule stability. Importantly, however, normalization of agonist-induced receptor internalization by taxol is not sufficient to alter receptor signaling.",
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