Human endothelial cells selectively express large amounts of pancreatic-type ribonuclease (RNase 1).
Pyrimidine-specific ribonucleases are a superfamily of structurally related enzymes with distinct catalytic and biological properties. We used a combination of enzymatic and non-enzymatic assays to investigate the release of such enzymes by isolated cells in serum-free and serum-containing media. We found that human endothelial cells typically expressed large amounts of a pancreatic-type RNase that is related to, if not identical to, human pancreatic RNase. This enzyme exhibits pyrimidine-specific catalytic activity, with a marked preference for poly(C) substrate over poly(U) substrate. It was potently inhibited by placental RNase inhibitor, the selective pancreatic-type RNase inhibitor Inhibit-Ace, and a polyclonal antibody against human pancreatic RNase. The enzyme isolated from medium conditioned by immortalized umbilical vein endothelial cells (EA.hy926) possesses an amino-terminal sequence identical to that of pancreatic RNase, and shows molecular heterogeneity (molecular weights 18,000-26,000) due to different degrees of N-glycosylation. Endothelial cells from arteries, veins, and capillaries secreted up to 100 ng of this RNase daily per million cells, whereas levels were low or undetectable in media conditioned by other cell types examined. The corresponding messenger RNA was detected by RT-PCR in most cell types tested so far, and level of its expression was in keeping with the amounts of protein. The selective strong release of pancreatic-type RNase by endothelial cells suggests that it is endowed with non-digestive functions and involved in vascular homeostasis.
Landré
Julien B P
JB
INSERM EPI-0113, Université Bordeaux-I, Avenue des Facultés, Talence, France.
Hewett
Peter W
PW
Olivot
Jean-Marc
JM
Friedl
Peter
P
Ko
Yon
Y
Sachinidis
Agapios
A
Moenner
Michel
M
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D002417:Cattle; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000737:chemistry; D016895:Culture Media, Serum-Free; D004727:Endothelium / Q000166:cytology* / Q000201:enzymology*; D005786:Gene Expression Regulation; D006031:Glycosylation; D006801:Humans; D008969:Molecular Sequence Data; D009928:Organ Specificity; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012259:Ribonuclease, Pancreatic / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D014471:Umbilical Veins
D000906:Antibodies; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D012259:Ribonuclease, Pancreatic