Li T, Tsukada S, Satterthwaite A, Havlik M H, Park H, Takatsu K, Witte O N
Molecular Biology Institute, University of California, Los Angeles 90095, USA.
Immunity. 1995 May;2(5):451-60. doi: 10.1016/1074-7613(95)90026-8.
Bruton's tyrosine kinase (BTK) is a nonreceptor tyrosine kinase critical for B cell development and function. Mutations in BTK result in X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (xid) in mice. Using a random mutagenesis scheme, we isolated a gain-of-function mutant called BTK* whose expression drives growth of NIH 3T3 cells in soft agar. BTK* results from a single point mutation in the pleckstrin homology (PH) domain, where a Glu is replaced by Lys at residue 41. BTK* shows an increase in phosphorylation on tyrosine residues and an increase in membrane targeting. Transforming activity requires kinase activity, a putative autophosphorylation site, and a functional PH domain. Mutation of the SH2 or SH3 domains did not affect the activity of BTK*. Expression of BTK* could also relieve IL-5 dependence of a B lineage cell line. These results show that transformation activation and regulation of BTK are critically dependent on the PH domain.
布鲁顿酪氨酸激酶（BTK）是一种对B细胞发育和功能至关重要的非受体酪氨酸激酶。BTK突变会导致人类的X连锁无丙种球蛋白血症（XLA）和小鼠的X连锁免疫缺陷（xid）。我们采用随机诱变方案，分离出了一个名为BTK的功能获得性突变体，其表达可驱动NIH 3T3细胞在软琼脂中生长。BTK是由pleckstrin同源（PH）结构域中的一个单点突变导致的，在第41位残基处，一个谷氨酸被赖氨酸取代。BTK显示酪氨酸残基磷酸化增加以及膜靶向性增强。转化活性需要激酶活性、一个假定的自磷酸化位点和一个功能性PH结构域。SH2或SH3结构域的突变不影响BTK的活性。BTK*的表达还可缓解一个B系细胞系对IL-5的依赖性。这些结果表明，BTK的转化激活和调控严重依赖于PH结构域。
