Showing papers by "Michael Karin published in 2003"
TL;DR: The results show the dual function of the NF-κB system, which is responsible for both tissue protection and systemic inflammation, and underscore the caution that should be exerted in using NF-β and IKK inhibitors.
Abstract: We studied the role of NF-kappaB in acute inflammation caused by gut ischemia-reperfusion through selective ablation of IkappaB kinase (IKK)-beta, the catalytic subunit of IKK that is essential for NF-kappaB activation. Ablation of IKK-beta in enterocytes prevented the systemic inflammatory response, which culminates in multiple organ dysfunction syndrome (MODS) that is normally triggered by gut ischemia-reperfusion. IKK-beta removal from enterocytes, however, also resulted in severe apoptotic damage to the reperfused intestinal mucosa. These results show the dual function of the NF-kappaB system, which is responsible for both tissue protection and systemic inflammation, and underscore the caution that should be exerted in using NF-kappaB and IKK inhibitors.
496 citations
TL;DR: It is found that a member of the c-Jun NH(2)-terminal protein kinase (JNK) subgroup of MAP kinases, JNK1, is involved in regulation of MT dynamics in neuronal cells.
381 citations
TL;DR: Evidence is presented that endogenous ROS produced through Rac/NADPH oxidase do not mediate NF‐κB signaling, but instead lower the magnitude of its activation, and this hypothesis is mainly based on the findings that N‐acetyl‐L‐cysteine and pyrrolidine dithiocarbamate, compounds recognized as potential antioxidants, can inhibit NF-κB activation in a wide variety of cell types.
Abstract: It has been postulated that reactive oxygen species (ROS) may act as second messengers leading to nuclear factor (NF)-kappaB activation. This hypothesis is mainly based on the findings that N-acetyl-L-cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), compounds recognized as potential antioxidants, can inhibit NF-kappaB activation in a wide variety of cell types. Here we reveal that both NAC and PDTC inhibit NF-kappaB activation independently of antioxidative function. NAC selectively blocks tumor necrosis factor (TNF)-induced signaling by lowering the affinity of receptor to TNF. PDTC inhibits the IkappaB-ubiquitin ligase activity in the cell-free system where extracellular stimuli-regulated ROS production does not occur. Furthermore, we present evidence that endogenous ROS produced through Rac/NADPH oxidase do not mediate NF-kappaB signaling, but instead lower the magnitude of its activation.
375 citations
TL;DR: The transcription factor NF-kappaB is a key regulator in oncogenesis by promoting proliferation and inhibiting apoptosis, which tips the balance between proliferation and apoptosis toward malignant growth in tumor cells.
348 citations
TL;DR: It is shown that UV-induced NF-κB activation depends on phosphorylation of IκBα at a cluster of C-terminal sites that are recognized by CK2 (formerly casein kinase II), which is an important component of the mammalian UV response.
311 citations
TL;DR: Using JNK-deficient mice, it is shown that JNK is required for ConA-induced liver damage and the antiapoptotic function of IKKβ, which is most critical in situations that involve cell-bound TNFα, is mediated partially through attenuation of JNK activity.
288 citations
TL;DR: A specific role is established for the MEKK1–JNK cascade in transmission of TGF‐β and activin signals that control epithelial cell movement, providing the mechanistic basis for the regulation of eyelid closure by MEK1.
Abstract: MEKK1-deficient mice show an eye open at birth phenotype caused by impairment in embryonic eyelid closure. MEK kinase 1 (MEKK1) is highly expressed in the growing tip of the eyelid epithelium, which displays loose cell–cell contacts and prominent F-actin fibers in wild-type mice, but compact cell contacts, lack of polymerized actin and a concomitant impairment in c-Jun N-terminal phosphorylation in MEKK1-deficient mice. In cultured keratinocytes, MEKK1 is essential for JNK activation by TGF-β and activin, but not by TGF-α. MEKK1-driven JNK activation is required for actin stress fiber formation, c-Jun phosphorylation and cell migration. However, MEKK1 ablation does not impair other TGF-β/activin functions, such as nuclear translocation of Smad4. These results establish a specific role for the MEKK1–JNK cascade in transmission of TGF-β and activin signals that control epithelial cell movement, providing the mechanistic basis for the regulation of eyelid closure by MEKK1. This study also suggests that the signaling mechanisms that control eyelid closure in mammals and dorsal closure in Drosophila are evolutionarily conserved.
179 citations
TL;DR: It is found that the loss of IKKβ results in a dramatic reduction in all peripheral B cell subsets due to associated defects in cell survival, consistent with a failure to mount effective Ab responses to T cell-dependent and independent Ags.
Abstract: NF-κB activity in mammalian cells is regulated through the IκB kinase (IKK) complex, consisting of two catalytic subunits (IKKα and IKKβ) and a regulatory subunit (IKKγ). Targeted deletion of Ikkβ results in early embryonic lethality, thus complicating the examination of IKKβ function in adult tissues. Here we describe the role of IKKβ in B lymphocytes made possible by generation of a mouse strain that expresses a conditional Ikkβ allele. We find that the loss of IKKβ results in a dramatic reduction in all peripheral B cell subsets due to associated defects in cell survival. IKKβ-deficient B cells are also impaired in mitogenic responses to LPS, anti-CD40, and anti-IgM, indicating a general defect in the ability to activate the canonical NF-κB signaling pathway. These findings are consistent with a failure to mount effective Ab responses to T cell-dependent and independent Ags. Thus, IKKβ provides a requisite role in B cell activation and maintenance and thus is a key determinant of humoral immunity.
168 citations
TL;DR: The NAK-NAP1 complex may protect cells from TNF-α-induced apoptosis by promoting NF-κB activation and NAP1 is defined as an activator of IKK-related kinases.
Abstract: The IkappaB kinase (IKK)-related kinase NAK (also known as TBK or T2K) contributes to the activation of NF-kappaB-dependent gene expression Here we identify NAP1 (for NAK-associated protein 1), a protein that interacts with NAK and its relative IKK epsilon (also known as IKKi) NAP1 activates NAK and facilitates its oligomerization Interestingly, the NAK-NAP1 complex itself effectively phosphorylated serine 536 of the p65/RelA subunit of NF-kappaB, and this activity was stimulated by tumor necrosis factor alpha (TNF-alpha) Overexpression of NAP1 specifically enhanced cytokine induction of an NF-kappaB-dependent, but not an AP-1-dependent, reporter Depletion of NAP1 reduced NF-kappaB-dependent reporter gene expression and sensitized cells to TNF-alpha-induced apoptosis These results define NAP1 as an activator of IKK-related kinases and suggest that the NAK-NAP1 complex may protect cells from TNF-alpha-induced apoptosis by promoting NF-kappaB activation
164 citations
TL;DR: This article showed that NF-kappaB DNA-binding activity is detected in both mammary carcinoma cell lines and primary human breast cancer tissues and there are strong suggestions that NF plays an important role in the etiology of breast cancer.
Abstract: Nuclear factor of kappaB (NF-kappaB) is a group of sequence-specific transcription factors that is best known as a key regulator of the inflammatory and innate immune responses. Recent studies of genetically engineered mice have clearly indicated that NF-kappaB is also required for proper organogenesis of several epithelial tissues, including the mammary gland. Mice have shown severe lactation deficiency when NF-kappaB activation is specifically blocked in the mammary gland. In addition, there are strong suggestions that NF-kappaB may play an important role in the etiology of breast cancer. Elevated NF-kappaB DNA-binding activity is detected in both mammary carcinoma cell lines and primary human breast cancer tissues.
153 citations
TL;DR: Results confirm that the Ah receptor plays a critical role in B[a]P-7,8-dihydrodiol-induced apoptosis while p38 MAP kinase links the actions of an electrophilic metabolite like BPDE-2 to the regulation of programmed cell death.
Journal Article•
TL;DR: Increased CYP1B1 expression is central to and seems to be responsible for sensitizing Ikkbeta(-/-) cells to stress-induced JNK activation, which was largely associated with an oxidative stress response.
Abstract: Stress signals activate both inhibitor of nuclear factor-kappaB kinase (IKKbeta) and c-Jun NH(2)-terminal kinase (JNK). It was shown recently that IKK-dependent nuclear factor kappaB activation results in attenuation of tumor necrosis factor alpha-induced JNK activation. How that negative cross-talk between nuclear factor kappaB and JNK occurs is not well-understood. By using wild-type and Ikkbeta gene knockout (Ikkbeta(-/-)) mouse embryo fibroblasts, we found that IKKbeta deficiency results in prolongation of arsenic-induced JNK activation, which was not due to the decreased expression of GADD45beta or X-linked Inhibitor of Apoptosis (XIAP), as suggested previously for RelA(-/-) cells treated with tumor necrosis factor alpha. This enhanced JNK activation was largely associated with an oxidative stress response as indicated by elevated expression of heme oxygenase-1 and the accumulation of H(2)O(2) in Ikkbeta(-/-) cells. Expression profiling experiments revealed an increased expression of p450 family CYP1B1 mRNA in Ikkbeta(-/-) cells compared with wild-type cells. Inhibition of CYP1B1 reduced both oxidative stress and arsenic-stimulated JNK activation. Thus, increased CYP1B1 expression is central to and seems to be responsible for sensitizing Ikkbeta(-/-) cells to stress-induced JNK activation.
TL;DR: It is found that retinoid antagonist MX781 inhibited the activation of NF-κB-dependent transcriptional activity in different tumor cell lines and induction of apoptosis by the Retinoid-related molecules that inhibited IKK was dependent on caspase activity but independent of the retinoids receptors.
Abstract: The transcription factor NF-kappaB is overexpressed or constitutively activated in many cancer cells, where it induces expression of antiapoptotic genes correlating with resistance to anticancer therapies. Small molecules that inhibit the NF-kappaB signaling pathway could therefore be used to induce apoptosis in NF-kappaB-overexpressing tumors and potentially serve as anticancer agents. We found that retinoid antagonist MX781 inhibited the activation of NF-kappaB-dependent transcriptional activity in different tumor cell lines. MX781 was able to completely inhibit tumor necrosis factor alpha-mediated activation of IkappaB kinase (IKK), the upstream regulator of NF-kappaB. Inhibition of IKK activity resulted from direct binding of MX781 to the kinase, as demonstrated by in vitro inhibition studies. Two other molecules, MX3350-1 and CD2325, which are retinoic acid receptor gamma-selective agonists, were capable of inhibiting IKK in vitro, although they exerted variable inhibition of IKK and NF-kappaB activities in intact cells in a cell type-specific manner. However, N-(4-hydroxyphenyl)-retinamide, another apoptosis-inducing retinoid, and retinoic acid as well as other nonapoptotic retinoids did not inhibit IKK. Inhibition of IKK by the retinoid-related compounds and other small molecules correlated with reduced cell proliferation and increased apoptosis. Reduced cell viability was also observed after overexpression of an IKKbeta kinase-dead mutant or the IkappaBalpha superrepressor. The induction of apoptosis by the retinoid-related molecules that inhibited IKK was dependent on caspase activity but independent of the retinoid receptors. Thus, the presence of an excess of retinoic acid or a retinoid antagonist did not prevent the inhibition of IKK activation by MX781 and CD2325, indicating a retinoid receptor-independent mechanism of action.
TL;DR: It is proposed that the technique of proteotyping will have wide applications in the analyses of defects in other mouse models and its use in the elucidation of specific developmental lesions is proposed.
Abstract: Through the use of transgenic and gene knockout mice, several studies have identified specific genes required for the functional development of mammary epithelium. Although histological and milk pr...
TL;DR: Evidence is provided that c-Jun expression is critical for induction of liver cancer by a classical protocol of tumor initiation—tumor promotion by Eferl et al.
Patent•
28 Feb 2003TL;DR: In this paper, the authors provide methods and compositions for inhibiting IKK and COX2, as well as identifying compounds with activity as inhibitors of IKK, and for the treatment of diseases and conditions wherein IKK is implicated and inhibition of its activity is desired.
Abstract: The present invention provides methods and compositions for inhibiting IKK, as well as methods and compositions for identifying compounds with activity as inhibitors of IKK, and methods and compositions for the treatment of diseases and/or conditions wherein IKK is implicated and inhibition of its activity is desired. In addition, the present invention provides methods and compositions for the improving the therapeutic activity of COX2 inhibitors, comprising administering the COX2 to a subject in combination with a compound that inhibits IKK activity. The present invention further provides compositions that comprise compounds that inhibit IKK and COX2.
Patent•
17 Dec 2003TL;DR: In this paper, isolated nucleic acid molecules encoding IκB kinase (IKK) catalytic subunit polypeptides were associated with an IKK serine protein kinase that phosphorylates a protein (IκB) that inhibits the activity of the NF-κB transcription factor.
Abstract: The present invention provides an isolated nucleic acid molecules encoding IκB kinase (IKK) catalytic subunit polypeptides, which are associated with an IKK serine protein kinase that phosphorylates a protein (IκB) that inhibits the activity of the NF-κB transcription factor, vectors comprising such nucleic acid molecules and host cells containing such vectors. In addition, the invention provides nucleotide sequences that can bind to a nucleic acid molecule of the invention, such nucleotide sequences being useful as probes or as antisense molecules. The invention also provides isolated IKK catalytic subunits, which can phosphorylate an IκB protein, and peptide portions of such IKK subunit. In addition, the invention provides anti-IKK antibodies, which specifically bind to an IKK complex or an IKK catalytic subunit, and IKK-binding fragments of such antibodies. The invention further provides methods of substantially purifying an IKK complex, methods of identifying an agent that can alter the association of an IKK complex or an IKK catalytic subunit with a second protein, and methods of identifying proteins that can interact with an IKK complex or an IKK catalytic subunit.