title: Prostaglandin receptor EP₁-mediated differential degradation of cyclooxygenases involves a specific lysine residue.
abstract: The cyclooxygenase (COX) enzyme isoforms COX-1 and COX-2 catalyze the main step in the generation of prostanoids that mediate major physiological functions. Whereas COX-1 is a ubiquitously expressed stable protein, COX-2 is transiently upregulated in many pathologies and is often associated with a poor prognostic outcome. We have recently shown that an interaction of COX-2 with the prostaglandin EP₁ receptor accelerates its degradation via a mechanism that augments its level of ubiquitination. Here we show that the sensitivity of both COX-1 and COX-2 to EP₁ is altered upon modification of one lysine residue. A point mutation of lysine to-arginine in position 432 of COX-2 (K432R) yields an enzyme with decreased sensitivity to EP₁ -mediated degradation. In contrast, insertion of a putative ubiquitination site into the corresponding position of COX-1 (H446K') yields an enzyme with higher levels of ubiquitination and reduced expression. Furthermore, compared to wild type COX-1, H446K' is significantly more sensitive to downregulation by EP₁ . Together these data suggest that distinctive ubiquitination of COX-1 and COX-2 may be responsible for their different sensitivity to EP₁ -mediated degradation.
authors: Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa 31905, Israel.
authors: Almog
authors: A
authors: Spector-Chotiner
authors: Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa 31905, Israel.
authors: Niva
authors: N
authors: Shraga-Heled
authors: Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa 31905, Israel.
authors: Rapita
authors: R
authors: Sood
authors: Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Be'er-Sheva 84105, Israel.
authors: Gilad
authors: G
authors: Rimon
authors: Department of Human Biology, Faculty of Natural Sciences, University of Haifa, Mt. Carmel, Haifa 31905, Israel. Electronic address: lbarki@psy.haifa.ac.il.
authors: Liza
authors: L
authors: Barki-Harrington
mesh_terms: D051545:Cyclooxygenase 1 / Q000737:chemistry* / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000737:chemistry* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008239:Lysine / Q000737:chemistry*; D011485:Protein Binding; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D058306:Receptors, Prostaglandin E, EP1 Subtype; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D008239:Lysine
keywords: COX-1; COX-2; Cyclooxygenase; Degradation; EP(1); Ubiquitination