Type 1 TNF Receptor Forms a Complex with and Uses Jak2 and c-Src to Selectively Engage Signaling Pathways That Regulate Transcription Factor Activity

Abstract

The type 1 TNFR (TNFR1) contains a death domain through which it interacts with other death-domain proteins to promote cellular responses. However, signaling through death-domain proteins does not explain how TNFR1 induces the tyrosine phosphorylation of intracellular proteins, which are important to cellular responses induced by TNFR1. In this study, we show that TNFR1 associates with Jak2, c-Src, and PI3K in various cell types. Jak2 and c-Src constitutively associate with and are constitutively active in the TNFR1 complex. Stimulation with TNF induces a time-dependent change in the level of Jak2, c-Src, and PI3K associated with TNFR1. The tyrosine kinase activity of the complex varies with the level of tyrosine kinase associated with TNFR1. TNFR1/c-Src plays a role in activating Akt, but not JNK or p38 MAPK, whereas TNFR1/Jak2 plays a role in activating p38 MAPK, JNK, and Akt. TNFR1/c-Src, but not TNFR1/Jak2, plays an obligate role in the activation of NF-κB by TNF, whereas TNFR1/Jak2, but not TNFR1/c-Src, plays an obligate role in the activation of STAT3. Activation of TNFR1 increased the expression of vascular endothelial growth factor, p21WAF1/CIP1, and manganese superoxide dismutase in MCF7 breast cancer cells, and increased the expression of CCl2/MCP-1 and IL-1β in THP-1 macrophages. Inhibitors of Jak2 and c-Src impaired the induction of each of these target proteins. These observations show that TNFR1 associates with and uses nonreceptor tyrosine kinases to engage signaling pathways, activate transcription factors, and modulate gene expression in cells.

The Tyrosine Kinase BMX Is an Essential Mediator of Inflammatory Arthritis in a Kinase-Independent Manner

“…These effects did, however, not reflect a generic inhibition of cellular signaling, as EGF-induced STAT3 phosphorylation was not affected by the siRNA against BMX. Whereas a role for tyrosine phosphorylation in TNF signaling has often been reported (55)(56)(57), direct evidence for a specific kinase is missing. Our report suggests that BMX may be the relevant tyrosine kinase in the tissues that express BMX.…”

Overexpression of HO-1 Protects against TNF-α-Mediated Airway Inflammation by Down-Regulation of TNFR1-Dependent Oxidative Stress

“…22 The elevated levels of TNF-␣ have been detected in the airways, BAL fluid, and nasal lavage from asthmatic and rhinitic patients. Leukocytes and monocytes isolated from BAL fluid of asthmatics were shown to release more TNF-␣ than those of cells from control subjects.…”

“…8 Most of TNF-␣ actions are elicited by TNFR1, which contains a death domain that fosters protein-protein interactions, particularly with other death-domain proteins. 22 The Src family kinases have been shown to regulate ICAM-1 and VCAM-1 expression, NADPH oxidase activation, and ROS generation. [5][6][7]23 In our study, we also established that TNF-␣ induced adhesion molecules expression and ROS generation through TNFR1 and c-Src by pretreatment with an anti-TNFR1 neutralizing Ab or PP1.…”

CYP3A4 Mediates Growth of Estrogen Receptor-positive Breast Cancer Cells in Part by Inducing Nuclear Translocation of Phospho-Stat3 through Biosynthesis of (±)-14,15-Epoxyeicosatrienoic Acid (EET)

“…Although potential redundancies of CYP epoxygenase function and induction of one epoxygenase when another is silenced are therapeutic challenges, a common mechanism of epoxygenase action may be synthesis of (Ϯ)-14,15-EET, which may be rendered less effective by inhibition of Stat3. Novel Stat3 inhibitors are currently being developed for breast cancer therapeutics (38 -40), because other oncoproteins, including c-Src (41), gp130 (42), the type I TNF receptor (43), and the leptin receptor (44), also signal through Stat3. To what extent these other pathways cross-talk with epoxygenase pathways is unknown.…”