Phosphorylation of sterol regulatory element binding protein-1a by protein kinase A (PKA) regulates transcriptional activity.
Phosphorylation of sterol regulatory element binding protein-1a by protein kinase A (PKA) regulates transcriptional activity.
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DOI：
10.1016/j.bbrc.2014.05.046
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发表时间：
2014-07-11
影响因子：
3.1
通讯作者：
Elam MB
中科院分区：
文献类型：
--
作者：
Dong Q;Giorgianni F;Deng X;Beranova-Giorgianni S;Bridges D;Park EA;Raghow R;Elam MB
反调节激素胰高血糖素通过下调固醇调节元件结合蛋白1（SREBP-1）来抑制脂肪生成。胰高血糖素的作用通过蛋白激酶A（PKA）介导。为了确定SREBP-1是否是PKA的直接磷酸化靶标，我们在体外PKA处理后对重组N-末端SREBP-1a进行了质谱分析。该分析将丝氨酸331/332鉴定为PKA的真正磷酸化靶标。为了确定这些位点磷酸化的功能后果，我们构建了nSREBP-1a和1c亚型的哺乳动物表达载体，其中候选PKA磷酸化位点突变为活性磷酸模拟物或不可磷酸化的氨基酸。野生型SREBP和突变型的转录活性被nSREBP-1a的S332和nSREBP-1c的相应丝氨酸（S308）的磷酸化模拟突变降低。该位点是介导胰高血糖素对SREBP-1和脂肪生成的负调节作用的强有力的候选者。
The counter-regulatory hormone glucagon inhibits lipogenesis via downregulation of sterol regulatory element binding protein 1 (SREBP-1). The effect of glucagon is mediated via protein kinase A (PKA). To determine if SREBP-1 is a direct phosphorylation target of PKA, we conducted mass spectrometry analysis of recombinant n-terminal SREBP-1a following PKA treatment in vitro. This analysis identified serines 331/332 as bona-fide phosphorylation targets of PKA. To determine the functional consequences of phosphorylation at these sites, we constructed mammalian expression vector for both nSREBP-1a and 1c isoforms in which the candidate PKA phosphorylation sites were mutated to active phosphomimetic or non-phosphorylatable amino acids. The transcriptional activity of WT SREBP and mutant forms was reduced by the phosphomimetic mutation of S332 of nSREBP-1a and the corresponding serine (S308) of nSREBP-1c. This site is a strong candidate for mediating the negative regulatory effect of glucagon on SREBP-1 and lipogenesis.