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Regulation of liver scavenger receptor class B (SR‐B) isoform expression by estrogen: hormonal potency and estrogen‐mediated alternative splicing
Author(s) -
Moor Andrea Nichole,
Zhang Xiaohui,
Merkler Kathleen,
McLean Mark
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1436-a
Estrogen can enhance plasma HDL levels and promote reverse cholesterol transport. SR‐BI (HDL receptor) is the major determinant of HDL levels. We hypothesize that SR‐BI and SR‐BII, an isoform produced via alternative splicing of the SR‐B gene, protein levels are regulated by estrogen and the mechanism for this regulation resides in specific genomic regions involved in estrogen‐mediated alternative splicing of the SR‐BI pre‐mRNA. Liver SR‐BI/II protein levels were compared in ovariectomized rats exposed to silastic implants containing either ethynylestradiol or E2. Control implants contained no estrogen. Over the course of 0, 3, 7, 10 and 14 days, SR‐BI protein levels were greatly reduced (50%) by ethynylestradiol compared to both control and E2‐treated rat SR‐BI levels. Both N‐glycosylated (84 kDa) and unglycosylated (50–57kDa) forms of SR‐BI were decreased by ethynylestradiol treatment. Alternatively, levels of the unglycosylated SR‐BII isoform increased with ethynylestradiol treatment. To determine the mechanism of SR‐B gene alternative splicing by estrogen compounds, a minigene was constructed with primers designed to obtain an SR‐B genomic fragment from exons 11–13, including introns 11 and 12. Based on analysis for putitive splicing regulatory sequences in this region, areas within introns 11 and 12, in which no essential control elements reside, were removed. A final construct in the pSG5 expression vector contains the 1.5 kb SR‐B minigene insert which can be utilized for in vitro and in vivo studies. Supported by NIH HL078817 , FDOH 04TSP7290, AHA 045533B.