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J Biol Chem. 2015 Feb 27;290(9):5606-20. doi: 10.1074/jbc.M114.632463. Epub 2014 Dec 29.

A cyclooxygenase-2-dependent prostaglandin E2 biosynthetic system in the Golgi apparatus.

Author information

1
From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109.
2
From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109 smithww@med.umich.edu.

Abstract

Cyclooxygenases (COXs) catalyze the committed step in prostaglandin (PG) biosynthesis. COX-1 is constitutively expressed and stable, whereas COX-2 is inducible and short lived. COX-2 is degraded via endoplasmic reticulum (ER)-associated degradation (ERAD) following post-translational glycosylation of Asn-594. COX-1 and COX-2 are found in abundance on the luminal surfaces of the ER and inner membrane of the nuclear envelope. Using confocal immunocytofluorescence, we detected both COX-2 and microsomal PGE synthase-1 (mPGES-1) but not COX-1 in the Golgi apparatus. Inhibition of trafficking between the ER and Golgi retarded COX-2 ERAD. COX-2 has a C-terminal STEL sequence, which is an inefficient ER retention signal. Substituting this sequence with KDEL, a robust ER retention signal, concentrated COX-2 in the ER where it was stable and slowly glycosylated on Asn-594. Native COX-2 and a recombinant COX-2 having a Golgi targeting signal but not native COX-1 exhibited efficient catalytic coupling to mPGES-1. We conclude that N-glycosylation of Asn-594 of COX-2 occurs in the ER, leading to anterograde movement of COX-2 to the Golgi where the Asn-594-linked glycan is trimmed prior to retrograde COX-2 transport to the ER for ERAD. Having an inefficient ER retention signal leads to sluggish Golgi to ER transit of COX-2. This permits significant Golgi residence time during which COX-2 can function catalytically. Cytosolic phospholipase A2α, which mobilizes arachidonic acid for PG synthesis, preferentially translocates to the Golgi in response to physiologic Ca(2+) mobilization. We propose that cytosolic phospholipase A2α, COX-2, and mPGES-1 in the Golgi comprise a dedicated system for COX-2-dependent PGE2 biosynthesis.

KEYWORDS:

Arachidonic Acid (AA) (ARA); Aspirin; COPII; Coxib; Cyclooxygenase (COX); Degron; Endoplasmic Reticulum-associated Protein Degradation (ERAD); Glycoprotein; NSAID; Prostaglandin

PMID:
25548276
PMCID:
PMC4342474
DOI:
10.1074/jbc.M114.632463
[Indexed for MEDLINE]
Free PMC Article

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