![Sample our Bioscience journals, sign in here to start your access, Latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5925/TOC-Subject-Sample-2021-Bioscience.jpg"})
Abstract
The preprophase band (PPB) of microtubules (MTs) marks the site of the future division plane irrespective of the orientation of the equatorial plane. Because the PPB MTs disappear during prometaphase, some positional information is thought to remain in the cortical cytoplasm after the disappearance of the PPB MTs. Cytoskeletal proteins are known to be excluded from the PPB site during mitosis. These depleted zones of cytoskeletal proteins are potential candidates for a “negative memory” system. However, how these depleted zones of the cytoskeletal proteins are produced remains unknown. In a recent paper, we have quantified the distribution of clathrin-coated pits and vesicles as well as of secretory structures during PPB formation using a combination of high-pressure freezing and electron tomography techniques. Our results demonstrated that the rate of endocytosis is enhanced in PPB regions. We postulate that the removal of membrane proteins by endocytosis plays a role in the creation of PPB "memory" structures.
Acknowledgments
This work was supported by the visiting research associate program of MEXT to IK, JSPS grant 11740454 and 14740454 to IK, JSPS grant 12640651 and 17207006, and MEXT grant 17049019 to YM, NIH grant GM61306 to LAS and Japan-US Cooperative Science Program to Y.M. and L.A.S.
Figures and Tables
Figure 1 Schematic diagrams showing the formation of clathrin-coated pits and vesicles in the region of PPB MT s. (A and B) Longitudinal views of an interphase (A) and a prophase (B) epidermal cell, and the differences in distribution of cortical clathrin molecules inI such cells. Clathrin molecules are distributed evenly over the surface of interphase cells (A), but concentrated around the PPBs of prophase cells (B). (C) A magnified cross sectional view of the PPB. This model postulates that the function of the endocytic activity at the PPB might be the removal of actin-nucleating/binding proteins from these plasma membrane domains, to create the characteristic actin filament-depleted regions of PPBs.
Addendum to: