Analysis of gene expression in homocysteine-injured vascular endothelial cells: Demonstration of GRP78/BiP expression, cloning and characterization of a novel reducing agent tunicamycin regulated gene
T. Miyata et al., Analysis of gene expression in homocysteine-injured vascular endothelial cells: Demonstration of GRP78/BiP expression, cloning and characterization of a novel reducing agent tunicamycin regulated gene, SEM THROMB, 24(3), 1998, pp. 285-291
An elevated plasma level of homocysteine is associated with arteriosclerosi
s and thrombosis. The mechanisms by which homocysteine may promote vascular
diseases have not yet been elucidated. In the present study, we have appli
ed a modified nonradioactive differential display analysis to evaluate chan
ges in gene expression induced by homocysteine treatment of cultured human
umbilical vein endothelial cells (HUVEC). We identified six upregulated and
one downregulated gene. One upregulated gene was GRP78/BiP, a stress prote
in, suggesting that unfolded proteins would accumulate in the endoplasmic r
eticulum because of redox potential changes caused by homocysteine. Another
upregulated gene encoded a bifunctional enzyme with activities of methylen
etetrahydrofolate dehydrogenase and methenyltetrahydrofolate cyclohydrolase
, which is involved in a homocysteine metabolism. A third upregulated gene
encoded activating transcription factor 4. The remaining four were uncharac
terized genes. We isolated a full-length cDNA of one of the upregulated gen
es from a HUVEC library. It encoded a novel protein with 394 amino acids, w
hich was termed reducing-agents and tunicamycin-responsive protein (RTP). N
orthern blot analysis revealed that RTP gene expression was induced in HUVE
C after 4 h of incubation with homocysteine. RTP mRNA was also observed in
unstimulated cells and induced by not only homocysteine but also 2-mercapto
ethanol and tunicamycin. The mRNA was ubiquitously expressed in human tissu
es. These observations indicate that homocysteine can alter the expressivit
y of multiple genes, including a stress protein and several novel genes. Th
ese responses may contribute to atherogenesis.