van Kerkhof Peter, Putters Joyce, Strous Ger J
Department of Cell Biology, University Medical Center Utrecht and Institute of Biomembranes, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
J Biol Chem. 2007 Jul 13;282(28):20475-83. doi: 10.1074/jbc.M702610200. Epub 2007 May 10.
SCF ubiquitin ligases play a pivotal role in the regulation of cell division and various signal transduction pathways, which in turn are involved in cell growth, survival, and transformation. SCF(TrCP) recognizes the double phosphorylated DSGPhiXS destruction motif in beta-catenin and IkappaB. We show that the same ligase drives endocytosis and degradation of the growth hormone receptor (GHR) in a ligand-independent fashion. The F-box protein beta-TrCP binds directly and specifically with its WD40 domain to a novel recognition motif, previously designated as the ubiquitin-dependent endocytosis motif. Receptor degradation requires an active neddylation system, implicating ubiquitin ligase activity. GHR-TrCP binding, but not GHR ubiquitination, is necessary for endocytosis. TrCP2 silencing is more effective on GHR degradation and endocytosis than TrCP1, although overexpression of either isoform restores TrCP function in silenced cells. Together, these findings provide direct evidence for a key role of the SCF(TrCP) in the endocytosis and degradation of an important factor in growth, immunity, and life span regulation.
SCF泛素连接酶在细胞分裂和各种信号转导途径的调控中起关键作用，而这些途径又参与细胞生长、存活和转化。SCF(TrCP)识别β-连环蛋白和IκB中双磷酸化的DSGPhiXS破坏基序。我们发现，同一连接酶以不依赖配体的方式驱动生长激素受体（GHR）的内吞作用和降解。F-box蛋白β-TrCP通过其WD40结构域直接且特异性地与一个新的识别基序结合，该基序先前被称为泛素依赖性内吞基序。受体降解需要一个活跃的NEDD化系统，这暗示了泛素连接酶的活性。内吞作用需要GHR-TrCP结合，但不需要GHR泛素化。TrCP2沉默对GHR降解和内吞作用的影响比TrCP1更有效，尽管任一亚型的过表达都能恢复沉默细胞中的TrCP功能。总之，这些发现为SCF(TrCP)在生长、免疫和寿命调节的一个重要因子的内吞作用和降解中起关键作用提供了直接证据。
