Identification of Interleukin 1 Receptor-associated Kinase as a Conserved Component in the p75-Neurotrophin Receptor Activation of Nuclear Factor-κB

Abstract

The neurotrophin nerve growth factor (NGF) supports neuronal survival by activating the transcription factor nuclear factor-B (NF-B). We report here, for the first time, the identification of p75-associated kinase that mediates NGF-driven NF-B activation. Using coimmunoprecipitation, we demonstrate an NGF-dependent association of interleukin 1 receptor-associated kinase (IRAK) with the p75 neurotrophin receptor in PC12 cells. Our results reveal that IRAK is recruited to the p75-NGF receptor leading to formation of a complex between IRAK, atypical protein kinase C interacting protein, p62, and TRAF6. Activation of NF-B occurs predominantly through the p75 receptor, and TrkA activity suppresses NF-B activation and retards IB␤ degradation. In addition, we observe a requirement for the kinase activity of IRAK in mediating NGF-induced NF-B activation, recruitment of the adapter protein p62 to the p75 receptor, and cell survival. Moreover, p75-IRAK-mediated B activation and the recruitment of IKK␤, but not IKK␣, to the receptor require p62. Altogether, our data provide novel information regarding the proximal components involved in p75 receptor signaling and underscore the importance of the atypical PKC interacting protein p62 in this process. The transcription factor, nuclear factor-B (NF-B)1 regulates the expression of a wide variety of genes involved in immunity, inflammation, apoptosis, and other cellular processes (1-3). NF-B resides in the cytoplasm in an inactive form bound to an inhibitory protein of the IB family. Activation of NF-B by an external stimulus involves phosphorylation and rapid degradation of IB proteins by the IB kinase (IKK) complex, leading to nuclear translocation of NF-B. The proinflammatory cytokines IL-1␤ and TNF␣ are the most well characterized stimuli that lead to the activation of NF-B.Binding of interleukin-1 (IL-1) to its receptor promotes the association of IL-1 receptor-associated kinase (IRAK) with the receptor (4), through the adapter protein MyD88 (5). IRAK then gets highly phosphorylated and leaves the receptor complex to interact with TRAF6, a member of the TNF receptor associated factor family (6). The IRAK⅐TRAF6 interaction triggers kinase cascades that lead to the activation of NF-B (6 -8).IRAK is a serine/threonine-specific protein kinase that shares 25% sequence identity with human mixed-lineage kinase, 30 -33% sequence identity with a protein kinase that is a product of the pto gene of tomato plant, and 32% identity to the kinase domain of Drosophila pelle, which is involved in the activation of Dorsal, the Drosophila equivalent of NF-B (4). These kinases define a subgroup of cytoplasmic kinases called the serine/threonine innate immunity kinases (SIIK) group (9). IRAK is a multidomain protein containing an N-terminal death domain of 120 amino acids, a central 300-amino acid kinase domain, and an undetermined C-terminal domain that is absent in pelle (10). Two other IRAK-related proteins IRAK-2 and IRAK-M (for its higher levels of expression in cells of monocytic lineage)...

Association of the Atypical Protein Kinase C-interacting Protein p62/ZIP with Nerve Growth Factor Receptor TrkA Regulates Receptor Trafficking and Erk5 Signaling

“…When both receptors, p75 and TrkA, are coexpressed, NGF-activated B signal is attenuated (37); inhibition of TrkA by K252a enhances survival signaling, impairs TrkA internalization, and promotes activation of NF-B. Alternatively, overexpression of p62 can enhance survival signaling and activation of NF-B (37,12). Thus, our data support a model whereby survival signaling occurs predominantly from NGF bound at the cell surface (11).…”

“…Given the similarities between p62 and Pincher in their ability to modulate Erk5 and TrkA internalization, it is possible that p62 may connect with the Pinchermediated internalization pathway. Altogether, these findings underscore the role of p62 as a critical regulator of not only NGF survival signaling (12,37) but also in intracellular signaling of activated TrkA. We propose that p62 is a component of a targeting pathway leading to delivery of TrkA and subsequently degradation of TrkA in the lysosomes.…”

Regulation of Interleukin-1α Expression by Integrins and Epidermal Growth Factor Receptor in Keratinocytes from a Mouse Model of Inflammatory Skin Disease

“…In the past, the kinase activity of IRAK has not been regarded as important for its ability to signal to downstream pathways in response to IL-1 (55,57,60). However, a number of recent reports do demonstrate kinase-dependent functions (81)(82)(83)(84). The kinase that phosphorylates kd IRAK1 in mouse keratinocytes is unknown, but possibilities include endogenous IRAK1 and a recently identified IRAK family member, IRAK4, which is critical in IL-1-and lipopolysaccharide-dependent responses (85) and acts upstream of IRAK1 (86).…”

p62/SQSTM1 at the interface of aging, autophagy, and disease

“…These receptors signal downstream by recruiting the ubiquitin-ligase TRAF6, which subsequently binds to p62/SQSTM1 on the TB domain and to interleukin-1 receptor-associated kinase (IRAK). This complex then recruits PKC λ/ι via the PB1 domain of p62/SQSTM1 and activates it through phosphorylation by IRAK (Sanz et al 2000;Mamidipudi et al 2002). p62/SQSTM1 plays additional roles in IL-1β and NGF signaling: the UBA and PB1 domain are necessary to allow TRAF6 to oligomerize in the receptor complex and poly-ubiquitylate itself in response to NGF .…”