An abnormal signal transduction pathway in CD4-CD8- double-negative lymph node cells of MRL lpr/lpr mice.

We describe here a novel 26-kDa posphoprotein (p26), associated to the T cell receptor of CD4-CD8- lymph node cells of lpr/lpr mice, but not present in significant amounts in control mouse cells including polyclonally activated T cells. lpr p26 is constitutively phosphorylated on a tyrosyl residue. It is most likely a member of the G protein family and displays high GTP-binding and GTPase activities both unsensitive to interleukin 2. Bordetella pertussis toxin has no effect on the spontaneously enhanced GTP hydrolysis. The traits associated to p26 could contribute to the distinctive features of lpr/lpr double-negative cells.