Txk

Txk/Rlk is a Tec-family nonreceptor tyrosine kinase that supports T-cell activation and Th1 effector function by increasing IFN-γ transcription in human T lymphocytes^[1]. Mechanistically, activated Txk moves from cytoplasm to nucleus, where it regulates the IFN-γ promoter through a complex with PARP1 and EF-1α^[2]. In TCR signaling, Txk augments PLC-γ1-mediated calcium signaling and affects thymocyte selection, linking Txk to T-cell development and activation models^[3]. In disease models, excessive Txk expression associates with Th1-skewed cytokine production in Behçet’s disease, including elevated IFN-γ, IL-12, and lesion-infiltrating Txk-positive lymphocytes^[4]. Compared with related Tec isoforms, Txk is atypical because it lacks the pleckstrin homology domain, restores PLCγ2/calcium signaling in Btk-deficient cells, but does not restore apoptosis^[5]. In T cells, Itk is expressed at higher levels and plays the major TCR-signaling role, while Rlk/Txk contributes to cytokine-producing effector T-cell regulation^[6]. For experimental applications, Txk plasmid administration increased antigen-specific IFN-γ and reduced serum IgE in an ovalbumin-sensitized mouse model^[7]. PJ34, a PARP1 inhibitor, suppressed IFN-γ but not IL-4 production, supporting pathway-level interrogation of Txk-associated transcriptional machinery^[2].