Soichiro Kakuta

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During the process of autophagy, cytoplasmic materials are sequestered by double-membrane structures, the autophagosomes, and then transported to a lytic compartment to be degraded. One of the most fundamental questions about autophagy involves the origin of the autophagosomal membranes. In this study, we focus on the intracellular dynamics of Atg9, a(More)
In autophagy, a cup-shaped membrane called the isolation membrane is formed, expanded, and sealed to complete a double membrane-bound vesicle called the autophagosome that encapsulates cellular constituents to be transported to and degraded in the lysosome/vacuole. The formation of the autophagosome requires autophagy-related (Atg) proteins. Atg8 is a(More)
Podocytes present a unique 3D architecture specialized for glomerular filtration. However, several 3D morphological aspects on podocyte development remain partially understood because they are difficult to reveal using conventional scanning electron microscopy (SEM). Here, we adopted serial block-face SEM imaging, a powerful tool for analyzing the 3D(More)
Phosphatidylinositol 3-kinase is indispensable for autophagy but it is not well understood how its product, phosphatidylinositol 3-phosphate (PtdIns(3)P), participates in the biogenesis of autophagic membranes. Here, by using quick-freezing and freeze-fracture replica labelling, which enables determination of the nanoscale distributions of membrane lipids,(More)
Atg9 is a transmembrane protein that is essential for autophagy. In the budding yeast Saccharomyces cerevisiae, it has recently been revealed that Atg9 exists on cytoplasmic small vesicles termed Atg9 vesicles. To identify the components of Atg9 vesicles, we purified the Atg9 vesicles and subjected them to mass spectrometry. We found that their protein(More)
The hypotrichous ciliated protozoan Euplotes aediculatus possesses a characteristic C-shaped somatic nucleus (macronucleus) within the cytoplasm, which shows dynamic shape change during the cell cycle. It is shown that isolated macronuclei possess Ca(2+)-dependent contractility. Macronuclei were isolated, stuck fast on the glass surface, and subjected to(More)
A colorless euglenoid flagellate Peranema trichophorum shows unique unidirectional gliding cell locomotion on the substratum at velocities up to 30 micro m/s by an as yet unexplained mechanism. In this study, we found that (1) treatment with NiCl(2) inhibited flagellar beating without any effect on gliding movement; (2) water currents applied to a gliding(More)
Ca2+-dependent contractility was found to exist in the nucleus of the heliozoon protozoan Actinophrys sol. Upon addition of Ca2+ ([Ca2+]free = 2.0 x 10(-3) M), diameters of isolated and detergent-extracted nuclei became reduced from 16.5+/-1.7 microm to 11.0+/-1.3 microm. The threshold level of [Ca2+]free for the nuclear contraction was 2.9 x 10(-7) M. The(More)
Retromer is a complex of proteins that functions in the endosome-to-Golgi retrieval cargo transport pathway. VPS35 works as the central subunit of retromer to recognize the cargos and binds with VPS29 and VPS26 via distinct domains. We show that deficiency of VPS35 or VPS29 accompanies degradation of other subunits, whereas VPS26 deficiency had no effect on(More)
Exocytosis of extrusomes, secretory granules found in protozoa, is involved in prey capture by the heliozoon Actinophrys sol. Here, we show that extracellular Ca(2+) is necessary for exocytosis and prey capture in A. sol. We found that A. sol could not capture prey cells in a Ca(2+)-free solution. L-type Ca(2+) channel blockers and a calmodulin antagonist(More)