Biomedical Engineering Reference
In-Depth Information
LDL binds to LDL receptors and LDL receptor-related protein 1. As mentioned
earlier, MM-LDL also binds to LDL receptors instead of scavenger receptors.
Ox-LDL/immunoglobulin G complexes can be mediated via Fcγ receptors, and
Ox-LDL bound by immunoglobulin M or C-reactive protein can in turn bind
complement and undergo enhanced binding via complement receptors. Ox-LDL
can bind to epidermal growth factor receptor and platelet-derived growth factor
receptor. Ox-LDL can also bind to lysophosphatidic acid receptors.
Ox-LDL RECEPTOR STRUCTURES SUGGESTING SIGNAL
TRANSDUCTION
h e endothelial scavenger receptors CD36 and SREC may induce tyrosine kinase-
related signaling in the presence of Ox-LDL stimulation. CD36 tightly associates
with the Fyn, Lyn, and Yes tyrosine kinases of the Src family, and these kinases
display an autophosphorylation activity
in vitro
. h e carboxyl terminal domain
of CD36 contains a sulh ydryl sequence (CXCX
5
K) that may be involved in
tyrosine kinase binding and may play a role in receptor-kinase-mediated signal
transduction. SREC has a tyrosine residue (Tyr
822
) i tting the consensus sequence
(R
XX
-E
XX
Y) for a site phosphorylated by tyrosine kinases, thus suggesting that
this residue may play a role in some signal transduction processes. Ox-LDL also
triggers the tyrosine phosphorylation of receptor tyrosine kinases including
epidermal growth factor receptor and platelet-derived growth factor receptor.
Growth hormone-releasing peptides are a class of small synthetic peptides
that are known to stimulate growth hormone release through the binding of a
G-protein-coupled receptor. Hexarelin, a hexapeptide member of the growth
hormone-releasing peptide family, binds to the amino acid residues 132-177 of
CD36. h e chemical cleavage of the hexarelin binding site results in the release of
free ligands, and Met
169
is the contact point for the ligands within the receptor-
binding pocket. h e binding domain on CD36 for Ox-LDL overlaps with that for
hexarelin (the amino acid residues 155-183). In addition, Ox-LDL can bind to
lysophosphatidic acid receptors, which are a type of G-protein-coupled receptor.
ADHESION MOLECULE EXPRESSION
h is section shows a dif erent pattern of adhesion molecule expression depending
on the oxidation process of LDL, the responsible molecules of Ox-LDL, and the
organ specii city of endothelial cells
(Table 2)
.
Selectins
Cu-LDL treatment upregulates the expression of E- and P-selectins via LOX-1 on
human coronary artery endothelial cells (HCAECs; Li
et al
. 2002). Both human
