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Membrane signaling and progesterone in female and male osteoblasts. II. Direct involvement of Gαq/11 coupled to PLC‐β1 and PLC‐β3
Author(s) -
Le Mellay Véronique,
Lieberherr Michèle
Publication year - 2000
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/1097-4644(20001101)79:2<173::aid-jcb10>3.0.co;2-3
Subject(s) - pertussis toxin , phospholipase c , heterotrimeric g protein , g protein , signal transduction , receptor , second messenger system , cholera toxin , medicine , gq alpha subunit , inositol trisphosphate , inositol , endocrinology , cytosol , microbiology and biotechnology , biology , chemistry , biochemistry , enzyme
We have shown that progesterone (10 pM–10 nM) and progesterone covalently bound to bovine serum albumin (P‐CMO BSA; 100 pM–1 μM) rapidly increased (within 5 s) the cytosolic free Ca 2+ concentration and inositol 1,4,5 trisphosphate (InsP 3 ) formation in confluent female and male rat osteoblasts via a pertussis toxin‐insensitive G‐protein. The activation of G‐proteins coupled to effectors such as phospholipase C (PLC) is an early event in the signal transduction pathway leading to InsP 3 formation. We used antibodies against the various PLC isoforms to show that only PLC‐β1 and PLC‐β3 were involved in the Ca 2+ mobilization and InsP 3 formation induced by both progestins in female and male osteoblasts, whereas PLC‐β2, PLC‐γ1, andPLC‐γ2 were not. We also used antibodies against the subunits of heterotrimeric G‐proteins to show that the activation of PLC‐β1 and PLC‐β3 by both progestins involved the Gαq/11 subunit, which was insensitive to pertussis toxin, whereas Gαi, Gαs, and Gβγ subunits were not. The membrane effects were independent of the concentration of nuclear progesterone receptor, because the concentration of nuclear progesterone receptors was lower in male than in female osteoblasts. These data suggest that progesterone and P‐CMO BSA, which does not enter the cell, directly activate G‐protein leading to the very rapid formation of second messengers without involving the nuclear receptor. J. Cell. Biochem. 79:173–181, 2000. © 2000 Wiley‐Liss, Inc.