Dual Specificity of the Interleukin 1- and Tumor Necrosis Factor-activated β Casein Kinase

Abstract

Tumor necrosis factor (TNF) and interleukin 1 (IL1) activate a protein kinase, TIP kinase, which phosphorylates ␤ casein in vitro. We have now identified its main phosphorylation site on ␤ casein, Ser 124 (K m Ϸ 28 M), and a minor phosphorylation site, Ser 142 (K m Ϸ 0.7 mM). The sequence motif that determined the phosphorylation of Ser 124 by the kinase was studied with synthetic peptides bearing deletions or substitutions of the neighboring residues. This allowed synthesis of improved substrates (K m Ϸ 6 M) and showed that efficient phosphorylation of Ser 124 was favored by the presence of large hydrophobic residues at positions ؉1, ؉9, ؉11, and ؉13 (counted relative to the position of the phosphoacceptor amino acid) and of a cysteine at position ؊2. Peptides in which Ser124 was replaced by tyrosine were also phosphorylated by TIP kinase, showing it to have dual specificity. It is unable to phosphorylate the MAP kinases in vitro and is therefore not directly involved in their activation. Its biochemical characteristics indicate that TIP kinase is a novel dual specificity kinase, perhaps related to the mixed lineage kinases. It copurified with a phosphoprotein of about 95 kDa, which could correspond either to the autophosphorylated kinase or to an associated substrate.

Signal transduction pathways activated by the IL-1 receptor family: ancient signaling machinery in mammals, insects, and plants

“…In addition to these three kinase systems, another kinase has been shown to be activated by IL-1. This has been termed TNF/IL-1-induced protein kinase (TIP kinase) because it is the only kinase so far shown to be exclusively regulated by IL-1 and TNF [49]. It is a cytosolic enzyme of about 100 kDa that may be part of larger aggregates of 200-600 kDa.…”

“…Three MAP kinase cascades are IL-1 responsive and evidence has been presented for the involvement of a lethal toxin-sensitive G protein in the activation of p38 and p42/p44 MAP kinases [52]. In addition, a novel protein kinase, termed TNF/IL-1-activated protein kinase (TIP kinase), has been described [49] that may be related to mixed lineage kinases. It is a 95-kDa protein, but may occur in a complex of 200-600 kDa.…”

“…It is a cytosolic enzyme of about 100 kDa that may be part of larger aggregates of 200-600 kDa. The gene for this protein has yet to be cloned, although the site it phosphorylates has been mapped and indicates that TIP kinase corresponds to a new type of dual-specificity protein kinase, directed toward a novel sequence motif, which may be related to the mixed lineage kinase family [49].…”

Ceramide-binding and activation defines protein kinase c-Raf as a ceramide-activated protein kinase.

“…The nature of the primary signal delivered by IL-1 receptor activation is poorly understood and controversial (1), but it is clear that IL-1 does stimulate protein kinase activities in a wide variety of different cell types. IL-1 and tumor necrosis factor a have been shown to induce rapid mitogen-activated protein kinase (MAPK) activation in fibroblasts, U937 cells, KB cells, and mesangial cells (2)(3)(4)(5)(6). Furthermore, both cytokines employ the sphingomyelin signaling pathway to generate ceramide and to stimulate a putative ceramide-activated serine/threonine protein kinase (7)(8)(9).…”

Tumor Necrosis Factor-α Induces Interleukin-6 Production and Integrin Ligand Expression by Distinct Transduction Pathways

“…However, little definitive data have come forth delineating the post-receptor molecular events. TNF receptors do not contain an intrinsic kinase domain, and recently, the involvement of serine/threonine protein kinases, including the so-called mitogen-activated protein kinases (MAPKs), has been proposed by a number of investigators (13)(14)(15)(16)(17). MAPKs form a large family of serine/threonine protein kinases activated by separate cascades and are important mediators of signal transduction from the cell surface to the nucleus.…”