Intracellular calcium signalling after binding of low-density lipoprotein to confluent and nonconfluent cultures of an endothelial cell line, EA.hy 926.
The effect of lipoproteins on cellular calcium ion concentration ([Ca2+]i) in EA.hy 926 endothelial cells was investigated, particularly with respect to the difference in response on [Ca2+]i between native low-density lipoprotein (LDL) which binds to the apo B/E receptor, and acetylated LDL (AcLDL) which binds to the scavenger receptor. The scavenger receptor recognizes chemically or cell-induced modified LDL. LDL as well as AcLDL caused a transient increase of [Ca2+]i lasting 1-2 min. On a protein basis, LDL was more effective that AcLDL in raising [Ca2+]i. Preincubation of confluent cultures in growth medium with a reduced fetal bovine serum content (2% FBS instead of 10%) increased the potency of LDL to increase [Ca2+]i. The LDL-induced peak [Ca2+]i was dependent on cell density. The effect of AcLDL on [Ca2+]i did not differ between confluent and nonconfluent cultures. Also, preincubation with 2% FBS did not modify the AcLDL-induced calcium response. We conclude that binding of lipoproteins to membrane lipoprotein receptors is responsible for the transient rise of [Ca2+]i although the characteristics of the calcium response are dependent on the receptor involved, i.e. the apo B/E (LDL) receptor or the scavenger receptor. We suggest that Ca2+ acts as a second messenger, and that the LDL-induced calcium response is controlled by the proliferative state of the cells.
Schaefer
H I
HI
Department of Cardiology, University Hospital, Leiden, The Netherlands.
Höld
K M
KM
Egas-Kenniphaas
J M
JM
van der Laarse
A
A
D002118:Calcium / Q000502:physiology*; D002461:Cell Line, Transformed; D002788:Cholesterol Esters / Q000378:metabolism; D003260:Contact Inhibition; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006822:Hybrid Cells; D007424:Intracellular Fluid / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008175:Lung Neoplasms / Q000473:pathology; D008565:Membrane Proteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D011973:Receptors, LDL / Q000145:classification / Q000378:metabolism*; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D015398:Signal Transduction / Q000502:physiology*; D014471:Umbilical Veins; D014700:Verapamil / Q000494:pharmacology
D002788:Cholesterol Esters; D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C032629:acetyl-LDL; C032531:apolipoprotein B,E receptor; D014700:Verapamil; D002118:Calcium