Lin F T, Miller W E, Luttrell L M, Lefkowitz R J
Howard Hughes Medical Institute, Departments of Medicine and Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Biol Chem. 1999 Jun 4;274(23):15971-4. doi: 10.1074/jbc.274.23.15971.
The functions of beta-arrestin1 to facilitate clathrin-mediated endocytosis of the beta2-adrenergic receptor and to promote agonist-induced activation of extracellular signal-regulated kinases (ERK) are regulated by its phosphorylation/dephosphorylation at Ser-412. Cytoplasmic beta-arrestin1 is almost stoichiometrically phosphorylated at Ser-412. Dephosphorylation of beta-arrestin1 at the plasma membrane is required for targeting a signaling complex that includes the agonist-occupied receptors to the clathrin-coated pits. Here we demonstrate that beta-arrestin1 phosphorylation and function are modulated by an ERK-dependent negative feedback mechanism. ERK1 and ERK2 phosphorylate beta-arrestin1 at Ser-412 in vitro. Inhibition of ERK activity by a dominant-negative MEK1 mutant significantly attenuates beta-arrestin1 phosphorylation, thereby increasing the concentration of dephosphorylated beta-arrestin1. Under such conditions, beta-arrestin1-mediated beta2-adrenergic receptor internalization is enhanced as is its ability to bind clathrin. In contrast, if ERK-mediated phosphorylation is increased by transfection of a constitutively active MEK1 mutant, receptor internalization is inhibited. Our results suggest that dephosphorylated beta-arrestin1 mediates endocytosis-dependent ERK activation. Following activation, ERKs phosphorylate beta-arrestin1, thereby exerting an inhibitory feedback control of its function.
β抑制蛋白1促进β2肾上腺素能受体网格蛋白介导的内吞作用以及促进激动剂诱导的细胞外信号调节激酶（ERK）激活的功能，受其Ser-412位点磷酸化/去磷酸化的调控。细胞质中的β抑制蛋白1在Ser-412位点几乎呈化学计量式磷酸化。β抑制蛋白1在质膜上去磷酸化，是将包含激动剂占据受体的信号复合物靶向网格蛋白包被小窝所必需的。在此，我们证明β抑制蛋白1的磷酸化和功能受ERK依赖性负反馈机制的调节。ERK1和ERK2在体外使β抑制蛋白1的Ser-412位点磷酸化。显性负性MEK1突变体抑制ERK活性，可显著减弱β抑制蛋白1的磷酸化，从而增加去磷酸化β抑制蛋白1的浓度。在这种情况下，β抑制蛋白1介导的β2肾上腺素能受体内化增强，其与网格蛋白结合的能力也增强。相反，如果通过转染组成型活性MEK1突变体增加ERK介导的磷酸化，则受体内化受到抑制。我们的结果表明，去磷酸化的β抑制蛋白1介导内吞作用依赖性的ERK激活。激活后，ERK使β抑制蛋白1磷酸化，从而对其功能发挥抑制性反馈控制。
