Purification and Partial Characterization of Membrane-homing Receptors in Two Cloned Murine Hemopoietic Progenitor Cell Lines

Abstract

Selective seeding of bone marrow by intravenously transplanted hemopoietic cells depends on the homing receptors of these cells. The receptors are membrane lectins with galactosyl and mannosyl specificities. To purify these lectins, cell membrane was fractionated from two cloned multipotential (B6STU) and bipotential (FDCP-1) hemopoietic progenitor cells. The membrane was solubilized and its proteins were labeled with 125I. The proteins were subjected to affinity column chromatography using galactosyl and mannosyl groups linked to agarose beads. Elution with D-galactose or D-mannose led to specific elution of a single sharp radioactive peak which constituted a constant fraction of membrane proteins. This peak was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis or by disuccinimidyl suberate cross-linking technique and appeared to have a Mr of 110,000. Under reducing conditions, it consisted of two components with a Mr of 87,000 and 23,000. Treatment with endoglycosidase F indicated about 5% carbohydrate content. Purification of these homing receptors has opened an avenue for the development of immunologic and molecular biologic probes that may help further elucidate the mechanism of homing regulation.