Interleukin 2 stimulation of p70 S6 kinase activity is inhibited by the immunosuppressant rapamycin.

Abstract

Binding of interleukin 2 (IL-2) to its receptor generates intracellular signals, including the activation of tyrosine and serine/threonine kinases. In this study the activation of the serine/threonine-specific ribosomal protein S6 kinases in response to IL-2 was analyzed in the murine T-cell line CTLL-20, a model system of IL-2-dependent proliferation. Two major classes of S6 kinases have been characterized: the 90-kDa (rsk) family and the 70-kDa family. In response to the addition of recombinant IL-2, total S6 kinase activity was increased. This S6 kinase activity could not be immunoprecipitated by an antiserum specific for S6 kinases of the 90-kDa family, exhibited a chromatographic behavior characteristic of 70-kDa S6 kinases, and was recognized by a 70-kDa S6 kinase-specific antiserum. Thus, IL-2 binding to its receptor induces specific activation of the 70-kDa family of S6 kinases. Rapamycin, a macrolide immunosuppressant that inhibits IL-2-dependent proliferation, inhibited IL-2-stimulated 70-kDa S6 kinase activity subsequent to early increases in tyrosine kinase activity. These findings imply that the targets of rapamycin include molecules involved in the activation of70-kDa S6 kinases. These observations further suggest that S6 kinases of the 70-kDa family participate in signal transmission pathways subsequent to IL-2 binding to its receptor.Interleukin-2 (IL-2) is a critical regulator of cell cycle progression in T lymphocytes (1). IL-2 binds to a specific cell surface receptor comprised of at least two distinct subunits, the IL-2Ra and IL-2Rl3 chains (2-5). The signal transduction events that culminate in the entry of cells into S phase appear to be dependent only on the IL-2RB subunit (6-8). The biochemical mechanisms that couple IL-2 receptor occupancy to subsequent proliferative responses are being actively investigated.A conserved response of many cell types to mitogenic signals is the phosphorylation of the ribosomal protein S6 on multiple serine residues (9). This phosphorylation increases the efficiency of protein synthesis, which appears to be required in several steps of cell cycle progression (9). IL-2 binding has been reported to stimulate S6 phosphorylation and protein synthesis (10). Recently, two families of S6 kinases have been characterized at the enzymatic and molecular levels: the 90-kDa (rsk) S6 kinase family (11) and the 70-kDa S6 kinase family (12,13). The activity of both types of kinases is regulated by serine/threonine phosphorylation (9), and both are serine/threonine kinases themselves. We performed experiments to determine which of these kinases were responsible for the IL-2-triggered increase in S6 phosphorylation. Here we show that IL-2 stimulation up-regulates total S6 kinase activity. However, S6 kinases of the 90-kDa family, as detected by a specific antiserum, do not become activated by IL-2 stimulation, and microtubule-associated protein 2 (MAP) kinase, an upstream activator of the 90-kDa S6 kinases, is only minimally activated. In contrast, anionexchange chrom...

Rapamycin-resistant Proliferation of CD8+ T Cells Correlates with p27 Down-regulation and bcl-xL Induction, and Is Prevented by an Inhibitor of Phosphoinositide 3-Kinase Activity

“…p70 s6k phosphorylation was inhibited by rapamycin, as we and others have shown (6,7,47). The induction of c-Myc expression was inhibited by LY294002, consistent with the involvement of the PI3K pathway in the induction of c-Myc expression in response to stimulation (48 -50).…”

“…The inhibition of the mammalian target of rapamycin (mTOR) by the FKBP12/rapamycin complex halts cell cycle progression at the G 1 -S transition. mTOR activity appears to be upstream of several pathways involved in regulating progression through the cell cycle, including p70 s6k (7), cyclin/cdk activity (8,9), and 4EBP (PHAS) (Refs. 10 -12; reviewed in Ref.…”

Activation of p70 S6 protein kinase is necessary for angiotensin II‐induced hypertrophy in neonatal rat cardiac myocytes

“…The maximum activation was obtained by 10 -6 are necessary for p70 s6K activation are same as those for the activation of MAP kinases and p90 rsk [7][8][9]. The immunosuppressant agents rapamycin and FK506 are structurally related macrolides that have been reported to inhibit proliferation and activation of T cells by binding the same cellular receptor, FK506-binding protein (FKBP) [20,[25][26][27]. It has been demonstrated that these two agents interfere with distinct signaling pathways after binding FKBP [21][22][23].…”

Mechanism of Ribosomal p70S6 Kinase Activation by Granulocyte Macrophage Colony-stimulating Factor in Neutrophils

“…The cytokines IL-3, EPO, and IL-2 induce activation of p70S6K (25)(26)(27), as well as cellular proliferation. Both responses are inhibited with rapamycin, an immunosuppressant drug that complexes with FKBP and binds to mTOR, resulting in the dephosphorylation of p70S6K (3,28).…”