Cooling evokes redistribution of α2C-adrenoceptors from Golgi to plasma membrane in transfected human embryonic kidney 293 cells

S. C. Jeyaraj, M. A. Chotani, S. Mitra, H. E. Gregg, N. A. Flavahan, K. J. Morrison

Research output: Contribution to journalArticlepeer-review

Abstract

Cold-induced vasoconstriction in cutaneous blood vessels is mediated by increased constrictor activity of vascular α2-adrenoceptors (α2-ARs). In mouse cutaneous arteries, α2-AR constriction at 37°C is mediated by α2A-ARs, whereas after cold exposure (28°C), α2C-ARs are no longer silent and mediate the remarkable cold-induced augmentation of α2-AR responsiveness. The goals of the present study were to develop a cell model of cutaneous thermoregulation and to determine the mechanisms underlying the thermosensitivity of α2C-ARs. Human embryonic kidney 293 cells were transiently transfected with the mouse α2A- or α2C-AR. In cells expressing α2A-ARs, UK-14,304 (5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine), an α2-AR agonist, inhibited (10 pM) and stimulated (1-10 nM) the accumulation of cAMP evoked by forskolin. Similar responses were obtained at 37°C and 28°C. In contrast, in cells expressing α2C-ARs, UK-14,304 did not affect forskolin-stimulated cAMP accumulation at 37°C but did cause a concentration-dependent inhibitory effect at 28°C. Subcellular fractionation revealed that at 37°C α2C-ARs were localized predominantly to Golgi compartments, whereas α2A-ARs localized predominantly to the plasma membrane. After cooling (28°C), α2C-ARs relocated from Golgi compartments to the plasma membrane, whereas the α2A-AR remained at the plasma membrane. Immunofluorescence microscopy confirmed that, at 37°C, α2A-ARs were localized to the cell surface, whereas α2C-ARs colocalized with a trans-Golgi marker. Cooling did not affect localization of α2A-ARs, but shifted α2C-ARs to the cell surface. Moderate cooling, therefore, caused a selective redistribution of α2C-ARs from the Golgi compartments to the cell surface, allowing the rescue of the α2C-adrenergic functional response. This mechanism may explain the role of α2-ARs in thermoregulation of the cutaneous circulation.

Original languageEnglish (US)
Pages (from-to)1195-1200
Number of pages6
JournalMolecular Pharmacology
Volume60
Issue number6
DOIs
StatePublished - 2001
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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