Regulation of hamster α1B-adrenoceptors expressed in Chinese hamster ovary cells

Si Jia Zhu, D. Roselyn Cerutis, Jodi L. Anderson, Myron L. Toews

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Chinese hamster ovary (CHO) cells were stably transfected to express the hamster α1B-adrenoeceptor, and the function and agonist-induced regulation of the binding properties of these receptors were characterized. The cells expressed approximately 230 000 receptors per cell, with a KD for [3H]prazosin of 140 pM. In assays of competition by epinephrine for [3H]prazosin binding to receptors on intact cells, 88% of the receptors were in a low affinity form. The protein kinase C activator phorbol 12-myristate, 13-acetate (PMA) did not further increase the fraction in the low affinity form, but the protein kinase C inhibitor staurosporine reduced the low affinity fraction to 51%. In sucrose density gradient centrifugation assays of receptor internalization, the percentage of receptors in the light vesicle fraction was 25% for control cells, 53% for epinephrine-pretreated cells, 44% for PMA-pretreated cells, and 53% for cells pretreated with epinephrine plus PMA. Staurosporine completely blocked PMA-induced internalization, but only partially inhibited epinephrine-induced internalization. These results suggest a relationship between low affinity binding and internalization for α1B-adrenoceptors and the involvement of protein kinase C in both processes. Longer-term (24 h) exposure of cells to epinephrine induced an unexpected up-regulation of receptor density of approximately 2-fold that was accompanied by an increase in maximal agonist-stimulated phosphoinositide turnover. These studies document several regulatory differences between α1B-adrenoceptors expressed in transfected CHO cells and those natively expressed in DDT1 MF-2 hamster smooth muscle cells, and they provide additional information on the molecular mechanisms involved in agonist-induced regulation of α1B-adrenoceptors.

Original languageEnglish (US)
Pages (from-to)205-212
Number of pages8
JournalEuropean Journal of Pharmacology
Volume299
Issue number1-3
DOIs
StatePublished - Mar 28 1996

Keywords

  • Adrenoceptor
  • Desensitization
  • Intact cell binding
  • Internalization
  • Up-regulation

ASJC Scopus subject areas

  • Pharmacology

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