Browsing by Subject "Pathologic bone demineralization"

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    A SNP in Steroid Receptor Coactivator-1 Disrupts a GSK3β Phosphorylation Site and Is Associated with Altered Tamoxifen Response in Bone
    (Oxford University Press, 2012-02) Hartmaier, R.J.; Richter, A.S.; Gillihan, R.M.; Sallit, J.Z.; McGuire, S.E.; Wang, J.; Lee, A.V.; Osborne, C.K.; O'Malley, B.W.; Brown, P.H.; Xu, J.; Skaar, Todd C.; Philips, S.; Rae, J.M.; Azzouz, F.; Li, L.; Hayden, J.; Henry, N.L.; Nguyen, A.T.; Stearns, V.; Hayes, D.F.; Flockhart, D.A.; Oesterreich, S.
    The coregulator steroid receptor coactivator (SRC)-1 increases transcriptional activity of the estrogen receptor (ER) in a number of tissues including bone. Mice deficient in SRC-1 are osteopenic and display skeletal resistance to estrogen treatment. SRC-1 is also known to modulate effects of selective ER modulators like tamoxifen. We hypothesized that single nucleotide polymorphisms (SNP) in SRC-1 may impact estrogen and/or tamoxifen action. Because the only nonsynonymous SNP in SRC-1 (rs1804645; P1272S) is located in an activation domain, it was examined for effects on estrogen and tamoxifen action. SRC-1 P1272S showed a decreased ability to coactivate ER compared with wild-type SRC-1 in multiple cell lines. Paradoxically, SRC-1 P1272S had an increased protein half-life. The Pro to Ser change disrupts a putative glycogen synthase 3 (GSK3)β phosphorylation site that was confirmed by in vitro kinase assays. Finally, knockdown of GSK3β increased SRC-1 protein levels, mimicking the loss of phosphorylation at P1272S. These findings are similar to the GSK3β-mediated phospho-ubiquitin clock previously described for the related coregulator SRC-3. To assess the potential clinical significance of this SNP, we examined whether there was an association between SRC-1 P1272S and selective ER modulators response in bone. SRC-1 P1272S was associated with a decrease in hip and lumbar bone mineral density in women receiving tamoxifen treatment, supporting our in vitro findings for decreased ER coactivation. In summary, we have identified a functional genetic variant of SRC-1 with decreased activity, resulting, at least in part, from the loss of a GSK3β phosphorylation site, which was also associated with decreased bone mineral density in tamoxifen-treated women.