Organization of lymphocyte plasma membrane. Surface protein-membrane matrix interactions in B-cell lines of different stages of differentiation.
Composition of surface proteins and their interactions with cytoskeleton or membrane matrix were compared in tumor B-cell lines of different stages of B-lymphocyte maturation. All studied B-cell lines were found to share a similar set of cell surface proteins, which are tightly associated with the cytoskeleton. The increase in amount of detergent-unextractable cell surface proteins with B-cell maturation suggested that differentiation of B lymphocytes was accompanied by development of specific interactions between surface proteins and elements of the cytoskeleton or membrane matrix. Using a recently developed procedure for lymphocyte plasma membrane fractionation we demonstrate changes in distribution of cell surface proteins in membrane matrix-rich and membrane matrix-poor plasma membrane fractions during B-lymphocyte maturation. Thus, cell surface proteins of the mature B-cell line MOPC-315 were predominantly found in the plasma membrane vesicles of a high buoyant density. These vesicles mostly contained plasma membrane proteins tightly associated with elements of the membrane matrix. In immature B cells (line 70Z3) virtually all surface proteins were detected in both low and high buoyant density membrane vesicles. The tendency to increased associations between surface proteins and cytoskeleton/membrane matrix with maturation of B cells could not be explained by increased amounts of filamentous actin, since no correlation was found between the amount of globular or filamentous actin and the degree of surface protein-cytoskeleton (membrane matrix) interactions.
Trenn
G
G
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892.
Takayama
H
H
Davidson
W F
WF
Morse
H C
HC
Sitkovsky
M V
MV
D000199:Actins / Q000502:physiology; D000818:Animals; D001402:B-Lymphocytes / Q000648:ultrastructure*; D002454:Cell Differentiation; D002460:Cell Line; D002462:Cell Membrane / Q000648:ultrastructure; D005591:Chemical Fractionation; D003599:Cytoskeleton / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology*
D000199:Actins; D008565:Membrane Proteins