Receptor-mediated pinocytosis of mannose glycoconjugates by macrophages: Characterization and evidence for receptor recycling

摘要: 125I-Mannose--BSA is taken up by alveolar macrophages receptor-mediated endocytosis. Uptake macrophage-specific and does not occur in polymorphonuclear leukocytes. Binding (4 degrees C) uptake (37 of 125I--Man--BSA are time- ligand concentration-dependent [Kuptake = 40 nM; Kd 10 nM]. When adjusted for degradation, linear with time. saturates at 60 min requires Ca++. Following binding, remains on the cell surface where it can be released EGTA trypsin. Internalization prebound occurs very rapidly (t 1/2 less than 5 min) when cells warmed to 37 C. internalization ligand, binding activity recovered min). Trypsin treatment substantially reduces (greater 70% per 30 However, treated trypsin 4 C warming absence added ligand. destroys uptake. On contrary, produces only a modest reduction subsequent These results, together observation that cycloheximide has no effect uptake, suggest receptors must spared from degradation reutilization probably occurs.