Activation of Bruton's tyrosine kinase (BTK) by a point mutation in its pleckstrin homology (PH) domain

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Agammaglobulinaemia Tyrosine Kinase
  • Animals
  • B-Lymphocytes / enzymology
  • Base Sequence
  • Cell Transformation, Neoplastic
  • Enzyme Activation
  • Gene Expression
  • Mice
  • Molecular Sequence Data
  • Phosphotyrosine
  • Point Mutation
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • RNA, Messenger / genetics
  • Signal Transduction
  • Tumor Cells, Cultured
  • Tyrosine / analogs & derivatives
  • Tyrosine / metabolism


  • RNA, Messenger
  • Phosphotyrosine
  • Tyrosine
  • Protein-Tyrosine Kinases
  • Agammaglobulinaemia Tyrosine Kinase
  • BTK protein, human
  • Btk protein, mouse