title: Reconstitution of Btk signaling by the atypical tec family tyrosine kinases Bmx and Txk.
abstract: Bruton's tyrosine kinase (Btk) is mutated in X-linked agammaglobulinemia patients and plays an essential role in B cell receptor signal transduction. Btk is a member of the Tec family of nonreceptor protein-tyrosine kinases that includes Bmx, Itk, Tec, and Txk. Cell lines deficient for Btk are impaired in phospholipase C-gamma2 (PLCgamma2)-dependent signaling. Itk and Tec have recently been shown to reconstitute PLCgamma2-dependent signaling in Btk-deficient human cells, but it is not known whether the atypical Tec family members, Bmx and Txk, can reconstitute function. Here we reconstitute Btk-deficient DT40 B cells with Bmx and Txk to compare their function with other Tec kinases. We show that in common with Itk and Tec, Bmx reconstituted PLCgamma2-dependent responses including calcium mobilization, extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) activation, and apoptosis. Txk also restored PLCgamma2/calcium signaling but, unlike other Tec kinases, functioned in a phosphatidylinositol 3-kinase-independent manner and failed to reconstitute apoptosis. These results are consistent with a common role for Tec kinases as amplifiers of PLCgamma2-dependent signal transduction, but suggest that the pleckstrin homology domain of Tec kinases, absent in Txk, is essential for apoptosis.
authors.affiliation: Department of Cell Signaling, DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 94304, USA. tomlinson@dnax.org
authors.forename: M G
authors.initials: MG
authors.lastname: Tomlinson
authors.forename: T
authors.initials: T
authors.lastname: Kurosaki
authors.forename: A E
authors.initials: AE
authors.lastname: Berson
authors.forename: G H
authors.initials: GH
authors.lastname: Fujii
authors.forename: J A
authors.initials: JA
authors.lastname: Johnston
authors.forename: J B
authors.initials: JB
authors.lastname: Bolen
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D011947:Receptors, Antigen, B-Cell; C492367:BMX protein, human; C492366:Bmx protein, mouse; C089848:Tec protein-tyrosine kinase; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C000625951:Btk protein, mouse