Translation-linked mRNA destabilization accompanying serum-induced Nox4 expression in human endothelial cells.
NADPH oxidase is involved in cell signaling, regulating proliferation of vascular cells, especially in endothelium. The Nox4 catalytic subunit has a major role in endothelial cells, but growth arrest of cultured endothelial cells following serum deprivation paradoxically increases mRNA for Nox4. We investigated the relationships between Nox4 mRNA stability and protein expression in human microvascular endothelial cells. Serum starvation increased the steady-state level of Nox4 mRNA but paradoxically diminished Nox4 protein expression. mRNA transcription in the absence of serum is maintained by the p38MAP kinase pathway, for inhibition of p38MAP kinase reduced both Nox4 mRNA and Nox4 promoter activity. In serum-starved cells, reintroduction of serum increased Nox4 protein levels within 30 min and up to 24 h. In contrast, the mRNA decreased equally rapidly after serum stimulation. Inhibition of Nox4 translation by cycloheximide blocked serum-induced mRNA degradation and Nox4 protein synthesis, and actinomycin-D also delayed Nox4 mRNA decay. Therefore, Nox4 mRNA level falls after serum stimulation because of a translation-initiated mRNA destabilization program. Clearly Nox4 mRNA is regulated at both transcriptional and post-transcriptional levels, and the steady state level of Nox4 mRNA does not accurately reflect Nox4 protein abundance and functions, with implications for regulation of cell proliferation and survival.
Peshavariya
Hitesh
H
Bernard O'Brien Institute of Microsurgery, University of Melbourne, Victoria 3065, Australia.
Jiang
Fan
F
Taylor
Caroline J
CJ
Selemidis
Stavros
S
Chang
Catherine W T
CW
Dusting
Gregory J
GJ
D000818:Animals; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; D014176:Protein Biosynthesis; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D048051:p38 Mitogen-Activated Protein Kinases