External surface membrane proteins in normal and neoplastic murine erythroid cells

The development pattern of one class of plasma membrane proteins, the external surface proteins, was examined in neoplastic and nonneoplastic differentiating murine erythroid cells. Neoplastic erythroid precusor cells were obtained from spleens of CD-1 mice after infection with Friend erythroleukemia virus while the nonneoplastic ellls were obtained from spleens of mice with phenylhydrazine-stimulated erythroid hyperplasia. Erythroid precursors at different stages of development were isolated from these erythroid cell populations by sedimentation at unit gravity. The surface proteins were labeled by lactoperoxidase-catalyzed iodination, solubilized in sodium dodecyl sulfate, and separated by sodium dodecyl sulfate gradient gel electrophoresis. Multiple labeled bands were found at all stages of neoplastic and nonneoplastic erythroid differentiation examined. The pattern of external membrane proteins labeled in nonneoplastic erythrocytes and in reticulocytes from peripheral blood were qualitatively similar and not altered by infection with Friend virus. The nucleated precursor cells from noninfected mice exhibited distinct differences from erythrocytes, and with increaseing differentiation an evolutionary pattern of several minor proteins was seen. Clear-cut differences in lactoperoxidast-reactive proteins were also observed between neoplastic and nonneoplastic precursors. The most marked differences were observed between the most immature cells. The youngest neoplastic cells from CD-1 mice possessed a protein with a molecular weight of 8000 not seen in normal erythroid cells. Additionally, there was an absence of a normally occurring protein with a molecular weight of 13,000 and increased amounts of a protein with a molecular weight of 140,000. With increasing maturation of the neoplastic cells, labeling of the protein with a molecular weight of 8,000 decreased while the protein with a molecular weight of 13,000 became apparent, so that a labeling pattern similar to that of nonneoplastic cells was obtained. These studies deomnstrate both distinct alterations of lactoperoxidase-reactive surface membrane proteins in nonneoplastic erythroid cells druring cell maturation in neoplastic erythroid cells as compared with nonneoplastic erythroid cells at similar stages of development.