Macrophage Recognition of Cells with Elevated Calcium Is Mediated by Carbohydrate Chains of CD43

Abstract

ABSTRACT. Macrophages remove deteriorating cells (those undergoing apoptosis and oxidation) via poly-Nacetyllactosaminyl chains on CD43 caps, a major cell-surface glycoprotein. Unusually high intracellular calcium levels are also deteriorating for cells and tissue. Here we artificially elevated calcium levels in cells and examined the mechanism by which this elevation was resolved by macrophages. Results showed that treatment with the calcium ionophore A23187 and ionomycin induces capping of CD43 on Jurkat cells, which are subsequently recognized and phagocytosed by macrophages, indicating that macrophages regard cells with elevated calcium as targets for removal. Further tests showed that A23187-and ionomycin-treated Jurkat cells did not induce apoptotic changes such as DNA fragmentation or phosphatidylserine expression, indicating that these cells were removed despite still being viable. Jurkat cells pretreated with anti-CD43 antibody or those with poly-Nacetyllactosaminyl chains containing oligosaccharides inhibited macrophage binding, indicating that macrophages recognize the poly-N-acetyllactosaminyl chains on CD43. Binding was also inhibited by treating macrophages with anti-nucleolin antibody, indicating that recognition occurs through nucleolin, a cell-surface receptor. Further, nucleolin-transfected HEK293 cells bound A23187-treated cells, and this binding was inhibited by in the presence of oligosaccharides. Taken together, these results show that elevated calcium levels induce CD43 capping, and macrophages remove the cells if their nucleolin receptors can bind to the poly-Nacetyllactosaminyl chains of capped CD43.

Shuttling Protein Nucleolin Is a Microglia Receptor for Amyloid Beta Peptide 1-42

“…[12][13][14][15][16][17][18][19][20][21][22][23]35) This study showed that Aβ42 is also a ligand for nucleolin. These observations support the idea that nucleolin on the surface of phagocytes has a general scavenger-like ability.…”

“…12,13) Previous studies have shown that macrophages utilize nucleolin to recognize and phagocytose apoptotic and oxidized cells 14,15) as well as living cells that have been treated with cytochalasin B and A23187. 16,17) Nucleolin-mediated recognition is therefore simple and powerful, as indicated by the indiscriminant removal of cells. Nucleolin is also a receptor for lipoproteins, 18) coxsackie B virus, 19) human immunodeficiency virus, 20) human parainfluenza virus type 3, 21) and enterohemorrhagic Escherichia coli O157 : H7.…”

Calcyclin

“…Unusual high intracellular calcium levels, observed in pathological conditions such as systemic lupus erythematosus (SLE), Alzheimer's disease, and brain trauma, result in capping of CD43. Similar to what happens with apoptotic cells, capped CD43 interacts with the macrophage receptor nucleolin, leading to recognition and phagocytosis of viable cells with elevated intracellular calcium levels by macrophages (Miki et al 2013).…”

Syncytium calcium signaling and macrophage function in the heart

“…The immune effectiveness can be improved with elevation of extracellular Ca concentrations in the range of physiologic levels of Ca signaling [ 46 , 47 ]. In vitro studies with macrophage-like cell lines U937 and MH-S [ 48 ] demonstrated that macrophage recognition to elevated Ca involves a sensor zone on the carbohydrate chains of CD43 [ 49 ].…”