Vn. Bochkov et al., LIGAND SELECTIVITY OF 105-KDA AND 130-KDA LIPOPROTEIN-BINDING PROTEINS IN VASCULAR-SMOOTH-MUSCLE-CELL MEMBRANES IS UNIQUE, Biochemical journal, 317, 1996, pp. 297-304
Using ligand blotting techniques, with low-density lipoprotein (LDL) a
s ligand, we have previously described the existence of atypical lipop
rotein-binding proteins (105 kDa and 130 kDa) in membranes from human
aortic medial tissue. The present study demonstrates that these protei
ns are also present in membranes from cultured human (aortic and mesen
teric) and rat (aortic) vascular smooth-muscle cells (VSMCs). To asses
s the relationship of 105 and 130 kDa lipoprotein-binding proteins to
known lipoprotein receptors, ligand binding specificity was studied, W
e tested effects of substances known to antagonize ligand binding to e
ither the LDL [apolipoprotein B,E (ape B,E)] receptor (dextran sulphat
e, heparin, pentosan polysulphate, protamine, spermine, histone), the
scavenger receptor (dextran sulphate, fucoidin), the very-low-density-
lipoprotein (VLDL) receptor [receptor-associated protein (RAP)], or LD
L receptor-related protein (RAP, alpha(2)-macroglobulin, lipoprotein l
ipase, exotoxin-A). None of these substances, with the exception of de
xtran sulphate, influenced binding of LDL to either 105 or 130 kDa pro
teins. Sodium oleate or oleic acid, known stimuli for the lipoprotein
binding activity of the lipolysis-stimulated receptor, were also witho
ut effect. LDL binding to 105 and 130 kDa proteins was inhibited by an
ti-LDL (ape B) antibodies. LDL and VLDL bound to 105 and 130 kDa prote
ins with similar affinities (approximate to 50 mu g/ml). The unique li
gand selectivity of 105 and 130 kDa proteins supports the existence of
a novel lipoprotein-binding protein that is distinct from all other c
urrently identified LDL receptor family members. The similar ligand se
lectivity of 105 and 130 kDa proteins suggests that they may represent
variant forms of an atypical lipoprotein-binding protein.