Decreased Ras-mitogen-activated protein kinase signaling may cause DNA hypomethylation in T lymphocytes from lupus patients.
OBJECTIVE
Previous studies have shown that inhibiting T cell DNA methylation causes a lupus-like disease by modifying gene expression. T cells from patients with lupus exhibit diminished levels of DNA methyltransferase (MTase) enzyme activity, hypomethylated DNA, and changes in gene expression similar to those exhibited by T cells treated with methylation inhibitors, suggesting that DNA hypomethylation may contribute to human lupus. Since it is known that DNA MTase levels are regulated by the ras-mitogen-activated protein kinase (MAPK) pathway, this study sought to determine whether decreased ras-MAPK signaling could account for the DNA hypomethylation in lupus T cells.


METHODS
DNA MTase messenger RNA (mRNA) from lupus patients and from healthy controls was quantitated by Northern analysis, and ras-MAPK signaling was determined by immunoblotting with antibodies to the activated forms of extracellular receptor-associated kinase (ERK). Results were compared with those in T cells in which ras-MAPK signaling was inhibited with a soluble inhibitor of MAPK ERK I (MEK1).


RESULTS
T cells from patients with active lupus had diminished DNA MTase mRNA levels and decreased signaling through the ras-MAPK pathway. Inhibiting signaling through the ras-MAPK pathway with the MEK1 inhibitor decreased DNA MTase mRNA and enzyme activity to the levels seen in lupus T cells, and resulted in DNA hypomethylation resembling that seen in lupus T cells.


CONCLUSIONS
These results suggest that a decrease in signaling through the ras-MAPK pathway may be responsible for the decreased MTase activity and DNA hypomethylation in patients with lupus.
Deng
C
C
University of Michigan and the Ann Arbor VA Hospital, USA.
Kaplan
M J
MJ
Yang
J
J
Ray
D
D
Zhang
Z
Z
McCune
W J
WJ
Hanash
S M
SM
Richardson
B C
BC
D000293:Adolescent; D000328:Adult; D000368:Aged; D019175:DNA Methylation; D005260:Female; D011905:Genes, ras; D006801:Humans; D008177:Lupus Vulgaris / Q000235:genetics* / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D013601:T-Lymphocytes / Q000378:metabolism*