Astrocyte beta(1)-adrenergic receptor immunoreactivity and agonist inducedincreases in [Ca2+](i) - Differential results indicative of a modified membrane receptor
T. Thorlin et al., Astrocyte beta(1)-adrenergic receptor immunoreactivity and agonist inducedincreases in [Ca2+](i) - Differential results indicative of a modified membrane receptor, LIFE SCI, 67(11), 2000, pp. 1285-1296
Antibodies against the C-terminus of the beta(1)-adrenergic receptor were u
sed for staining cultured astrocytes from the rat cerebral cortex. Immunore
activity was found to be localized exclusively to an intracellular organell
e structure similar to the Golgi complex, with no staining of the plasma me
mbrane. The astrocytes stained positive with BODIPY CGP 12177, a FITC-conju
gated beta-adrenergic receptor agonist, and this staining was blocked by th
e beta(1)-adrenergic antagonist atenolol, indicating that these receptors a
re expressed on the surface of the astrocytes. The presence of functional p
lasma membrane beta(1)-adrenergic receptors was further verified using micr
ospectrofluorometry for measurements of intracellular calcium changes upon
beta-adrenergic agonist stimulation. Intracellular immunoreactivity confine
d to the organelles was also found in astrocytes from mixed astroglial-neur
onal cultures. In contrast, the neurons in these cultures showed a strong l
abeling of the cell bodies by the beta(1)-adrenergic receptor antibodies. T
hus, the beta(1)-adrenergic receptor antibody, which stains the cell bodies
of the neurons, recognizes the astroglial receptors only intracellularly,
although functional beta(1)-adrenergic receptors are present on the astrogl
ial surface. Taken together, these data suggest that the beta(1)-adrenergic
receptors observed intracellularly might be processed on their passage to
the surface to a modified form of the final plasma membrane receptor, which
is not recognized by the antibodies. (C) 2000 Elsevier Science Inc. All ri
ghts reserved.