Membrane-associated PGE synthase-1 (mPGES-1) is coexpressed with both COX-1 and COX-2 in the kidney.
BACKGROUND
Prostaglandin E2 (PGE2) plays an important role in many physiologic and pathophysiologic processes in the kidney. Multiple enzymes are involved in PGE2 biosynthesis, including phospholipases, cyclooxygenases (COX), and the PGE2 synthases (PGES). The present studies were aimed at determining the intrarenal localization of mPGES-1 and whether it is coexpressed with COX-1 or COX-2.


METHODS
Rabbit mPGES-1 and COX-1 cDNAs were cloned using reverse transcription-polymerase chain reaction (RT-PCR) and screening a cDNA library. RNase protection assay and immunoblotting were used to examine mPGES-1 expression levels. In situ hybridization and immunostaining were used to determine the intrarenal localization of mPGES-1 and cyclooxygenases.


RESULTS
Rabbit mPGES-1 shares high sequence similarity to the human homolog. Nuclease protection studies showed that the kidney expresses among the highest level of mPGES-1 of any rabbit tissue. In situ hybridization showed COX-1 and mPGES-1 mRNA was highly expressed in renal medullary collecting ducts (MCD), and to a lesser extent in cortical collecting ducts (CCD). Fainter mPGES-1 expression was also observed in macula densa (MD) and medullary interstitial cells (RMICs), where COX-2 is highly expressed. Double-labeling studies (immunostaining plus in situ hybridization) and immunohistochemistry of mouse tissues confirmed that mPGES-1 predominantly colocalizes with COX-1 in distal convoluted tubule (DCT), CCD, and MCD, and is coexpressed with COX-2 at lower levels in MD and RMICs.


CONCLUSIONS
Together, these studies suggest mPGES-1 colocalizes with both COX-1 and COX-2 to mediate the biosynthesis of PGE2 in the kidney.
Schneider
André
A
Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Zhang
YaHua
Y
Zhang
Mingzhi
M
Lu
Wendell J
WJ
Rao
Reena
R
Fan
Xuefeng
X
Redha
Reyadh
R
Davis
Linda
L
Breyer
Richard M
RM
Harris
Raymond
R
Guan
YouFei
Y
Breyer
Matthew D
MD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000201:enzymology*; D003001:Cloning, Molecular; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D018076:DNA, Complementary; D005260:Female; D019746:Intramolecular Oxidoreductases; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology*; D007679:Kidney Medulla / Q000166:cytology / Q000201:enzymology; D007685:Kidney Tubules, Collecting / Q000201:enzymology; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D014018:Tissue Distribution
D018076:DNA, Complementary; D007527:Isoenzymes; D008565:Membrane Proteins; D012333:RNA, Messenger; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496512:Ptgs1 protein, mouse; D019746:Intramolecular Oxidoreductases; C492485:membrane-associated PGE synthase-1, rabbit