Chien C T, Wang S, Rothenberg M, Jan L Y, Jan Y N
Howard Hughes Medical Institute and Department of Physiology and Biochemistry, University of California at San Francisco, 94143-0724, USA.
Mol Cell Biol. 1998 Jan;18(1):598-607. doi: 10.1128/MCB.18.1.598.
During asymmetric cell division, the membrane-associated Numb protein localizes to a crescent in the mitotic progenitor and is segregated predominantly to one of the two daughter cells. We have identified a putative serine/threonine kinase, Numb-associated kinase (Nak), which interacts physically with the phosphotyrosine binding (PTB) domain of Numb. The PTB domains of Shc and insulin receptor substrate bind to an NPXY motif which is not present in the region of Nak that interacts with Numb PTB domain. We found that the Numb PTB domain but not the Shc PTB domain interacts with Nak through a peptide of 11 amino acids, implicating a novel and specific protein-protein interaction. Overexpression of Nak in the sensory organs causes both daughters of a normally asymmetric cell division to adopt the same cell fate, a transformation similar to the loss of numb function phenotype and opposite the cell fate transformation caused by overexpression of Numb. The frequency of cell fate transformation is sensitive to the numb gene dosage, as expected from the physical interaction between Nak and Numb. These findings indicate that Nak may play a role in cell fate determination during asymmetric cell divisions.
在不对称细胞分裂过程中，膜相关的Numb蛋白定位于有丝分裂祖细胞中的一个新月形区域，并主要被分配到两个子细胞之一。我们鉴定出一种假定的丝氨酸/苏氨酸激酶，即Numb相关激酶（Nak），它与Numb的磷酸酪氨酸结合（PTB）结构域发生物理相互作用。Shc和胰岛素受体底物的PTB结构域与一个NPXY基序结合，而该基序在与Numb PTB结构域相互作用的Nak区域中不存在。我们发现，Numb PTB结构域而非Shc PTB结构域通过一个11个氨基酸的肽段与Nak相互作用，这意味着一种新的特异性蛋白质-蛋白质相互作用。在感觉器官中过表达Nak会导致正常不对称细胞分裂产生的两个子细胞采用相同的细胞命运，这种转变类似于numb功能缺失表型，并且与Numb过表达引起的细胞命运转变相反。细胞命运转变的频率对numb基因剂量敏感，这正如Nak与Numb之间的物理相互作用所预期的那样。这些发现表明，Nak可能在不对称细胞分裂过程中的细胞命运决定中发挥作用。
