A Gαs protein-coupled membrane receptor, distinct from the classical oestrogen receptor, transduces rapid effects of oestradiol on [Ca 2+] i in female rat distal colon

• Published in: Molecular and cellular endocrinology 2003, Vol.199 (1), p.87-103
• Main Authors: Doolan, Christina M., Harvey, Brian J.
• Format: Article
• Language: English
• Subjects: Ca 2; Distal colon; G protein coupled receptors; Oestradiol; PKC; Rapid non-genomic
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/S0303-7207(02)00303-9

We examined the hypothesis whether rapid non-genomic effects of oestradiol (E2) on [Ca 2+] i are mediated via a membrane-located oestrogen receptor (ER) and further elucidated the signalling pathways involved in rapid non-genomic effects of E2 on [Ca 2+] i in distal colonic crypts. Basal [Ca 2+] i was significantly increased, within minutes, in response to physiological concentrations of E2. Oestradiol linked to bovine serum albumin (E2–BSA), which renders the E2 membrane impermeable, rapidly increased [Ca 2+] i suggesting mediation by a membrane surface receptor. A classical ER is not involved however, as no inhibition of either the E2 or E2–BSA [Ca 2+] i response was seen in the presence of the classical ER antagonist ICI 182,780. Treatment with the Gαs inhibitor cholera toxin abolished both E2 and E2–BSA induced Ca 2+ increases. In contrast, treatment with pertussis toxin, an inhibitor of Gαi and Gαo, had no inhibitory effect. Following subsequent additions of E2 and E2–BSA, no further increases in [Ca 2+] i were observed, indicating receptor desensitisation. The E2-induced increase in [Ca 2+] i was completely abolished by the PKCδ-specific inhibitor rottlerin, whereas Go6976, an inhibitor of Ca 2+-sensitive PKC isoforms, was without inhibitory effect. The phospholipase A2 antagonist, quinacrine, and the COX1 inhibitor, indomethacin, abolished the E2-induced increase in [Ca 2+] i. MAP kinase activation is not involved in rapid stimulatory effects of E2 on [Ca 2+] i as the specific inhibitor PD98059 did not inhibit the E2 response. These results demonstrate that rapid E2-induced stimulation of [Ca 2+] i, in femal rat distal colonic crypts, occurs via a CTx-sensitive Gαs-coupled membrane receptor distinct from the classical ER. PKCδ and fatty acids are involved in the E2 signalling pathway. In contrast, PKCα and MAP kinase are not required.