Antipeptide antibodies reveal interrelationships of MBP 200 and MBP 235: unique apoB-specific receptors for triglyceride-rich lipoproteins on human monocyte-macrophages.
Two human monocyte-macrophage (HMM) membrane binding proteins, (MBP) 200 and 235, are receptor candidates that bind to the apolipoprotein (apo)B-48 domain in triglyceride-rich lipoproteins for uptake independent of apoE. Microsequence analysis of the purified reduced MBP 200R characterized tryptic peptides of MBP 200R. A synthetic peptide mimicking a unique, unambiguous 10-residue sequence (AEGLMVTGGR) induced antipeptide antibodies that specifically recognized MBP 200, 235 and 200R, in 1- and 2-dimensional analyses, indicating 1) the ligand binding protein was sequenced and 2) MBP 200 and 235 yielded MBP 200R upon reduction. These antibodies identified the MBPs in human blood-borne, THP-1, U937 MMs, and endothelial cells (EC) but not in human fibroblasts or Chinese hamster ovary (CHO) cells. Fluorescence activated cell sorting (FACS) analysis located the MBPs on the MM surface as necessary for receptor function. The 10-residue, unambiguous MBP 200-derived sequence is unique, with no matches in extant protein databases. Antipeptide antibodies bind to the MBPs in reticuloendothelial cells that have this receptor activity, but not to proteins in cells that lack this receptor activity. These studies provide the first direct protein sequence and immunochemical data that a new, unique apoB receptor for triglyceride-rich lipoproteins exists in human monocytes, macrophages, and endothelial cells.
Bradley
W A
WA
Department of Medicine, Division of Gerontology and Geriatric Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Brown
M L
ML
Ramprasad
M P
MP
Li
R
R
Song
R
R
Gianturco
S H
SH
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000918:Antibody Specificity; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B / Q000378:metabolism; D016466:CHO Cells / Q000737:chemistry; D006224:Cricetinae; D000939:Epitopes / Q000276:immunology; D005347:Fibroblasts / Q000737:chemistry; D005434:Flow Cytometry; D006801:Humans; D008074:Lipoproteins / Q000378:metabolism*; D008264:Macrophages / Q000737:chemistry*; D009000:Monocytes / Q000737:chemistry*; D010455:Peptides / Q000276:immunology; D018110:Receptors, Lipoprotein / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D017421:Sequence Analysis; D014280:Triglycerides / Q000032:analysis*
D000906:Antibodies; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B; D000939:Epitopes; D008074:Lipoproteins; D010455:Peptides; D018110:Receptors, Lipoprotein; D014280:Triglycerides; C072413:apolipoprotein B receptor