Two Distinct Pathways for Cyclooxygenase-2 Protein Degradation

Mbonye, Uri; Yuan, Chong; Harris, Clair; Sidhu, Ranjinder S.; Song, In‐Seok; Arakawa, Toshiya; Smith, William L.

doi:10.1074/jbc.m710137200

Cited by 105 publications

(141 citation statements)

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“…Absent key residues important in Asn 594 glycosylation, ⌬18 COX-2 cannot undergo degradation via the ERAD pathway. However, ⌬18 COX-2 is kinetically and pharmacologically indistinguishable from native COX-2 (17), and like native COX-2 it undergoes a substrate-dependent disappearance (18). Here, we provide evidence that both inactivation processes function in vivo in normal and endotoxin-treated mice but that the contribution of each process to COX-2 protein degradation is different in different tissues.…”

mentioning

confidence: 59%

“…4). In contrast, COX-2 levels in macrophages from WT mice increase in a predictable manner following treatments with LPS, LPS and flurbiprofen, and LPS plus KIF (18) (Fig. 5C); the lower band of the protein doublet seen when KIF is included is COX-2 with three asparagine residues glycosylated, whereas glycosylation at a fourth asparagine, primarily Asn 594 , results in formation of the band with slower electrophoretic mobility (18).…”

Section: Animalmentioning

confidence: 94%

“…In part because of the association of COX-2 expression with pathologies such as inflammation and colon cancer (13)(14)(15), many studies have been performed to elucidate the mechanisms of transcriptional regulation of COX-2 as reviewed recently (6,7). It is now also clear that COX-2 is regulated post-transcriptionally at the level of both mRNA degradation (16) and protein degradation (17,18).…”

mentioning

confidence: 99%

“…Sequences both upstream and downstream of Asn 594 modulate the rate of Asn 594 glycosylacorrelates with COX-2 suicide inactivation, and is independent of N-glycosylation at Asn 594 . In vitro, this pathway can be attenuated or blocked by various nonspecific and nonsteroidal anti-inflammatory drugs and COX-2 inhibitors (3,18). The biochemical mechanism underlying the disappearance of immunoreactive COX-2 associated with substrate-dependent inactivation is unresolved.…”

mentioning

confidence: 99%

“…In vitro studies with cultured murine NIH 3T3 fibroblasts and with HEK293 cells heterologously expressing various forms of COX-2 have suggested that there are two independent pathways of COX-2 protein degradation (17,18) dubbed "endoplasmic reticulum-associated degradation" (ERAD) and "substratedependent degradation" pathways. N-Glycosylation of Asn 594 , which appears to occur post-translationally, leads to entry of COX-2 into the ERAD pathway.…”

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confidence: 99%

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Two Pathways for Cyclooxygenase-2 Protein Degradation in Vivo

Wada

Saunders

Morrow

et al. 2009

Journal of Biological Chemistry

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COX-2, formally known as prostaglandin endoperoxide H synthase-2 (PGHS-2), catalyzes the committed step in prostaglandin biosynthesis. COX-2 is induced during inflammation and is overexpressed in colon cancer. In vitro, an 18-amino acid segment, residues 595-612, immediately upstream of the C-terminal endoplasmic reticulum targeting sequence is required for N-glycosylation of Asn 594 , which permits COX-2 protein to enter the endoplasmic reticulum-associated protein degradation system. To determine the importance of this COX-2 degradation pathway in vivo, we engineered a del595-612 PGHS-2 (⌬18 COX-2) knock-in mouse lacking this 18-amino acid segment. ⌬18 COX-2 knock-in mice do not exhibit the renal or reproductive abnormalities of COX-2 null mice. ⌬18 COX-2 mice do have elevated urinary prostaglandin E 2 metabolite levels and display a more pronounced and prolonged bacterial endotoxin-induced febrile response than wild type (WT) mice. Normal brain tissue, cultured resident peritoneal macrophages, and cultured skin fibroblasts from ⌬18 COX-2 mice overexpress ⌬18 COX-2 relative to WT COX-2 expression in control mice. These results indicate that COX-2 can be degraded via the endoplasmic reticulum-associated protein degradation pathway in vivo. Treatment of cultured cells from WT or ⌬18 COX-2 mice with flurbiprofen, which blocks substrate-dependent degradation, attenuates COX-2 degradation, and treatment of normal mice with ibuprofen increases the levels of COX-2 in brain tissue. Thus, substrate turnover-dependent COX-2 degradation appears to contribute to COX-2 degradation in vivo. Curiously, WT and ⌬18 COX-2 protein levels are similar in kidneys and spleens from WT and ⌬18 COX-2 mice. There must be compensatory mechanisms to maintain constant COX-2 levels in these tissues.

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confidence: 59%

Section: Animalmentioning

confidence: 94%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Two Pathways for Cyclooxygenase-2 Protein Degradation in Vivo

Wada

Saunders

Morrow

et al. 2009

Journal of Biological Chemistry

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Cyclooxygenase Pathway of the Arachidonate Cascade

Seta

Bachschmid

2012

Encyclopedia of Life Sciences

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Prostanoids are potent lipid mediators produced from arachidonic acid by the action of prostaglandin endoperoxide H 2 synthases (PGHS‐1 and ‐2), also known as cyclooxygenases (COX‐1 and ‐2). PGHS‐1, by virtue of its constitutive expression, is associated with homeostatic functions, such as platelet aggregation and gastric cytoprotection, whereas PGHS‐2, induced by a variety of inflammatory and mitogenic stimuli, is important in inflammation and cancer. However, this paradigm has been reevaluated over the years thanks to sophisticated genetic and pharmacological tools that have expanded tremendously our knowledge about the COX cascade. Despite identical structure and catalytic activities, subtle biochemical and metabolic differences account for a functional segregation of the two isoforms. Interestingly, in some biological processes, they seem not functionally interchangeable. Nonsteroidal anti‐inflammatory drugs are popular anti‐inflammatory, analgesic and antipyretic medications that block the formation of prostanoids. The search for specific inhibitors of the COX cascade, devoid of unwanted side effects, is still the subject of ongoing research. Key Concepts: Arachidonic acid (AA, 5,8,11,14‐eicosatetraenoic acid), a 20‐carbon, polyunsaturated fatty acid esterified into membrane phospholipids, can be metabolised via lipoxygenases, to produce leukotrienes; CYP450 monooxygenases to produce epoxyeicosatrienoic and hydroxyeicosatetraenoic acids (EETs and HETEs), and prostaglandin endoperoxide H 2 synthase (PGHS) to produce prostanoids. Prostanoids are a group of lipid autacoids including prostaglandins (PGD 2 , PGE 2 and PGF 2 α ), prostacyclin (PGI 2 ) and thromboxanes (TXA 2 ), that act through specific receptors (DP 1−2 , EP 1−4 , FP A−B , IP and TP) and, in some cases, nuclear receptors (PPAR), to elicit a variety of physiological and pathophysiological effects. Prostaglandin H 2 synthase (PGHS), commonly known as cyclooxygenase (COX), exists in two isoforms: PGHS‐1 and ‐2, or COX‐1 and ‐2 that catalyses the bis‐oxygenation of AA into PGH 2 , further reduced by cell‐specific downstream PGH 2 reductases and isomerases (prostanoid synthases) into prostanoids. PGHS‐1 and PGHS‐2 have identical catalytic activity that is best explained by a branched‐chain reaction between the peroxidase site (POX) and the cyclooxygenase site (COX), both present in the catalytic active site of the enzyme. PGHS‐1 and PGHS‐2 differ in peroxide requirement, substrate utilisation, subcellular localisation and translational and post‐translational regulation, suggesting a segregated activity of the two isoforms when both are present. PGHS‐1, constitutively expressed in many cell types is associated with homeostatic functions, such as platelet aggregation and gastric cytoprotection and PGHS‐2, mainly induced by inflammatory and mitogenic stimuli, is linked to inflammation and cancer. However, it is now clear that both isoforms are important for cardiovascular, renal and reproductive function and both play a role in inflammation and pain sensitisation. PGHS‐2, by virtue of a larger side pocket in the substrate‐binding site, can metabolise polyunsaturated fatty acids other than AA with higher efficiency than PGHS‐1, yielding lipid mediators different from prostanoids, such as glycerol‐prostaglandins and aspirin‐triggered lipoxins. Nonsteroidal anti‐inflammatory drugs (NSAIDs), such as aspirin, diclofenac and coxibs, are anti‐inflammatory, analgesic and antipyretic drugs that block the formation of prostanoids by competitive or irreversible inhibition of AA binding to COX. NSAIDs are a heterogeneous class of organic acids that differ considerably in pharmacokinetics and pharmacodynamics, including the selectivity for PGHS‐1 and PGHS‐2. Individual isoform selectivity attained in vivo is crucial for therapeutic and side effects, and this can vary among individuals and the drug used.

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The Cyclooxygenases

Malkowski

2017

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Cyclooxygenases (COX‐1 and COX‐2) are membrane‐associated, heme‐containing enzymes that oxygenate arachidonic acid to generate prostaglandin H 2 in the committed step of prostanoid biosynthesis. The resulting prostanoids play a key role in the maintenance of numerous physiological processes within the body. Abnormal changes in COX‐mediated prostanoid production are associated with various disease pathologies, including inflammation, cardiovascular disease, and cancer. Aspirin, nonselective nonsterroidal anti‐inflammatory drugs, and COX‐2‐selective drugs target COX‐1 and COX‐2 to reduce acute and chronic inflammation. As such, the crystal structures of COX‐1 and COX‐2 have been extensively characterized in the presence of substrates and inhibitors in order to gain a deeper understanding at the molecular level of the mechanistic nuances that underlie catalysis and inhibition. This review serves to summarize the recent advances in COX structural biology.

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Two Distinct Pathways for Cyclooxygenase-2 Protein Degradation

Cited by 105 publications

References 69 publications

Two Pathways for Cyclooxygenase-2 Protein Degradation in Vivo

Two Pathways for Cyclooxygenase-2 Protein Degradation in Vivo

Cyclooxygenase Pathway of the Arachidonate Cascade

The Cyclooxygenases

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