The flowing blood generates shear stress at the endothelial cell surface. T
he endothelial cells modify their phenotype by alterations in gene expressi
on in response to different levels of fluid shear stress. To identify genes
involved in this process, human umbilical vein endothelial cells were expo
sed to laminar shear stress (venous or arterial levels) in a cone-and-plate
apparatus for 24 hours. Using the method of RNA arbitrarily primed polymer
ase chain reaction, we cloned a polymerase chain reaction fragment represen
ting an mRNA species downregulated by arterial compared with venous shear s
tress (shear stress downregulated gene-1, SSD-1). According to Northern blo
t analysis, corresponding SSD-1 cDNA clones revealed a similar, time-depend
ent downregulation after 24 hours of arterial shear stress compared with ve
nous shear stress or static controls. Three SSD-1 mRNA species of 2.8, 4.1,
and 4.6 kb were expressed in a tissue-specific manner. The encoded amino a
cid sequence of the human endothelial SSD-1 isoform (4.1-kb mRNA species) r
evealed 80.4% identity and 90.9% homology to the bovine beta -tubulin foldi
ng cofactor D (tfcD) gene. Downregulation of tfcD mRNA expression by shear
stress was defined at the level of transcription by nuclear run-on assays.
The tfcD protein was downregulated by arterial shear stress. The shear stre
ss-dependent downregulation of tfcD mRNA and protein was attenuated by the
NO synthase inhibitor N omega -nitro-L-arginine methyl ester, Furthermore,
the NO donor DETA-NO downregulated tfcD mRNA. Because tfcD was shown to be
a microtubule-destabilizing protein, our data suggest a shear stress-depend
ent regulation of the microtubular dynamics in human endothelial cells.