title: Spectrin rearrangement early in erythrocyte ghost endocytosis.
abstract: The endocytic vacuoles induced in white ghosts were found to be depleted of spectrin and therefore it was proposed that they arose from spectrin-free areas in the erythrocyte membrane. To follow changes in spectrin distribution during endocytosis, affinity-purified rabbit antispectrin antibodies were produced. Quantitative techniques were developed for the use of a highly specific 125I-F(ab')2 antispectrin, and these showed that before the appearance of vacuoles, as assessed by phase microscopy, there was a reproducible decrease in immunoreactive spectrin. To determine whether this spectrin decrease represented a local or diffuse spectrin loss or a spectrin rearrangement, morphologic studies were undertaken using transmission electron microscopy on samples treated with rabbit antispectrin and ferritin-conjugated goat anti-rabbit immunoglobulin. These studies showed that endocytosis was preceded by the creation of extensive spectrin-free areas separated by discrete spectrin-containing zones. Pretreatment of ghosts with alkaline phosphatase blocked all forms of endocytosis and prevented the creation of spectrin-free areas. Therefore, it is proposed that under the impetus of endocytosis inducers, phosphorylated spectrin is redistributed so that spectrin-free zones are created, and that endocytic vacuoles form and fuse in spectrin-free areas.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000494:pharmacology; D001666:Binding Sites, Antibody; D004492:Edetic Acid / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D013049:Spectrin / Q000276:immunology / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology; D014617:Vacuoles / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D013049:Spectrin; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D000469:Alkaline Phosphatase; D014357:Trypsin