LRP1B attenuates the migration of smooth muscle cells by reducing membrane localization of urokinase and PDGF receptors.
OBJECTIVE
Studies on the involvement of low-density lipoprotein receptor relatives (LRs) in atherosclerosis have recently gained new focus because of the specific expression of certain of these receptors in the thickened intima. Here, we show that LRP1B, a member of LRs, modulates the migration of smooth muscle cells (SMCs) by increasing the degradation of membrane receptors, urokinase-type plasminogen activator receptor (uPAR), and platelet-derived growth factor receptor (PDGFR) beta.


RESULTS
Immunohistochemistry showed that LRP1B expression in human coronary arteries is localized to the intimal SMCs near the plaque surface as well as to medial SMCs. LRP1B expression levels in cultured SMCs increase at the late phase of proliferation. Cell surface and internalization assays, in combination with coimmunoprecipitation experiments, showed that LRP1B binds and internalizes uPAR. Metabolic labeling analysis demonstrated that anti-LRP1B IgY decreased the catabolism of uPAR. In addition, the anti-LRP1B antibody raised PDGFRbeta protein and PDGFR-mediated phosphorylation levels of ERK1/2. Finally, the anti-LRP1B IgY enhanced the migration and invasion of SMCs in the presence of PDGF-BB.


CONCLUSIONS
LRP1B modulates the catabolism of uPAR and PDGFR, affecting the migration of SMCs. This functional characterization of LRP1B opens novel avenues for elucidating the (patho)physiological significance of SMC migration in atheromatous plaques.
Tanaga
Kousei
K
Department of Clinical Cell Biology, Chiba University Graduate School of Medicine, Chiba, Japan.
Bujo
Hideaki
H
Zhu
Yanjuan
Y
Kanaki
Tatsuro
T
Hirayama
Satoshi
S
Takahashi
Kazuo
K
Inoue
Masahiro
M
Mikami
Keiji
K
Schneider
Wolfgang J
WJ
Saito
Yasushi
Y
D000368:Aged; D000595:Amino Acid Sequence; D000789:Angina, Unstable / Q000473:pathology; D000818:Animals; D000077214:Becaplermin; D002455:Cell Division / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured / Q000166:cytology / Q000378:metabolism; D002645:Chickens; D003331:Coronary Vessels / Q000737:chemistry / Q000473:pathology* / Q000648:ultrastructure; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D009203:Myocardial Infarction / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism / Q000648:ultrastructure; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D020574:Proto-Oncogene Proteins c-sis; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000187:drug effects / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011973:Receptors, LDL / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D055293:Receptors, Urokinase Plasminogen Activator; D011993:Recombinant Fusion Proteins / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D017539:Tunica Intima / Q000473:pathology
C016512:IgY; D007136:Immunoglobulins; C434476:LRP1B protein, human; C524898:PLAUR protein, human; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D055293:Receptors, Urokinase Plasminogen Activator; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000077214:Becaplermin; D020797:Receptor, Platelet-Derived Growth Factor beta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3