SURFACE FUNCTIONS DURING MITOSIS

在有丝分裂过程中膜功能的深刻变化现在已知

Profound changes in membrane function during mitosis are now known to occur. Endocytosis virtually stops. Con A-receptor complexes appear immobile, without patching or cap formation, until they move rapidly into the cleavage (Berlin et al., Cell, 1978, 15:327; J. Cell Biol., 1980, 85:660). A series of experiments is proposed: 1) to determine the mechanism of ligant-receptor movement into the cleavage furrow and in particular to test the possibility that it occurs according to a new model of wave motion; 2) to analyze the mechanism of altered binding of C3b (complement) coated particles to mitotic cells; 3) to determine the coordination of membrane function with the chromosome cycle and cytokinesis; 4) to determine if additional membrane functions are altered during mitosis; and 5) to examine the role of membrane changes during mitosis for the subsequent organization of the membrane of interphase cells. The experimental approach relies on single cell techniques and the development of a methodology for precise identification of stages of mitosis, temporal analysis of the progression of mitosis, and pinocytosis. Lateral diffusion will be measured by fluorescence recovery after photo-bleaching. A new approach for the analysis of wave motion is proposed using quantitative video image processing. Electrophysiological recordings from mitotic myocardial cells will be made using standard techniques. The macrophage cell line J774 will be employed for mobility studies using fluorescent lectins and the F(ab)2' fo an anti-C3b receptor. Chick embryonic myocardial cells will be used for electrophysiological studies of beat frequency, action potential and responses to beta-adrenergic drugs. The use of a fluorescent beta-adrenergic analogue (9AAP) will be reexamined and its distribution and binding determined. A fluorescent alpha-MSH analogue will be used to study the binding mobility and distribution of the alpha-MSH receptor. We aim overall to obtain unique information on the mechanism of ligand-receptor movement and control of endocytosis. We hope to learn whether cells in mitosis are altered at the membrane level in their response to external signals, and whether the membrane changes in mitosis are critical in the further differentiation of cells. The results should have significance for all biological systems in which cell division or surface functions are important.