At the Department of Cell Biology, we investigate under these two themes to gain insights into the mechanism of the vectorial transport and the mechanism of the pathogenesis of human dementia.

1) Mechanism of cell polarization:
Polarization of the cell is crucial to the proper function of various kinds of cells. Epithelial cells become polarized to have apical and basolateral sides to secrete enzymes or hormones efficiently (Figure 1). Neurons are also polarized to have dendrites and axons which are essential for neurotransmission.
To investigate the mechanism of cell polarization, we are making knockout mice of proteins crucial for this process. We are going to investigate the mutant mice by various cell biological and neurobiological methods (Figure 2). We are also planning to identify novel proteins crucial for cell polarization.


The small GTP-binding protein Rab8 was thought to regulate basolateral transport in polarized kidney epithelial cells through the AP1B-complex-mediated pathway. However, the role of Rab8 in cell polarity in vivo remained unknown.
In our recent work, we showed that Rab8 is responsible for the localization of apical proteins in intestinal epithelial cells (Figure 3). We found that apical peptidases and transporters localized to lysosomes in the small intestine of Rab8-deficient mice. Their mislocalization and degradation in lysosomes led to a marked reduction in the absorption rate of nutrients in the small intestine, and ultimately to death. Ultrastructurally, a shortening of apical microvilli, an increased number of enlarged lysosomes, and microvillus inclusions in the enterocytes were also observed. One microvillus inclusion disease patient who shows an identical phenotype to Rab8-deficient mice expresses a reduced amount of RAB8. Our results demonstrated that Rab8 is necessary for the proper localization of apical proteins and the absorption and digestion of various nutrients in the small intestine.
This work was published in Nature 448, 366-369 (19 July 2007).

3) Generation and analyses of the model mice for human dementia:
In a hereditary neuronal disease called FTDP-17, clinical features (dementia) and pathological features (neurofibrillary tangles and neuronal cell death) similar to Alzheimer's disease are observed. The gene of tau protein, one of microtubule-associated proteins, have missense mutation or splice-donor site mutation in these patients. To make the model mice for human dementia, we are making 'knockin' mice that have a mutated human tau cDNA on the mouse tau locus (Figure 4) and analysing the mutant mice to see whether they have similar phenotype as human patients. If they show such phenotypes, they are useful for investigating the pathogenesis of human dementia and the development of treatment for human dementia.

Kawamura N, Wada S, Aoyama M, Harada A, Takasuga S, Sasaki T, Wada Y.
Delivery of Endosomes to Lysosomes via Microautophagy in the Visceral Endoderm of Mouse Embryos.
Nature Communications, in press, (2012).

Hashimoto Y, Muramatsu K, Kunii M, Yoshimura S, Yamada M, Sato T, Ishida Y, Harada R, Harada A. (The first two authors contributed equally to this paper).
Uncovering genes required for neuronal morphology by morphology-based gene trap screening with a revertible retrovirus vector.
FASEB Journal, doi: 10.1096/fj.12-207530, (2012).

Nakakura T, Mogi C, Tobo M, Tomura H, Sato K, Kobayashi M, Ohnishi H, Tanaka S, Wayama M, Sugiyama T, Kitamura T, Harada A, Okajima F.
Deficiency of proton-sensing ovarian cancer G protein-coupled receptor 1 attenuates glucose-stimulated insulin secretion.
Endocrinology, 153: 4171-4180; doi:10.1210/en.2012-1164, (2012).

Sakamori R, Das S, Yu S, Feng S, Stypulkowski E, Guan Y, Douard V, Tang W, Ferraris RP, Harada A, Brakebusch C, Guo W, Gao N.
Cdc42 and Rab8a are critical for intestinal stem cell division, survival, and differentiation in mice.
Journal of Clinical Investigation, 122: 1052-1065; doi: 10.1172/JCI60282, (2012).

Sato M, Yoshimura S, Hirai R, Goto A, Kunii M, Atik N, Sato T, Sato K, Harada R, Shimada J, Hatabu T, Yorifuji H, Harada A.
The role of VAMP7/TI-VAMP in cell polarity and lysosomal exocytosis in vivo.
Traffic, 12: 1383-1393; doi: 10.1111/j.1600-0854.2011.01247.x, (2011).

Sato M, Saegusa K, Sato K, Hara T, Harada A, Sato K.
Caenorhabditis elegans SNAP-29 is required for organellar integrity of the endomembrane system and general exocytosis in intestinal epithelial cells.
Molecular Biology of the Cell, 22: 2579-2587; doi: 10.1091/mbc.E11-04-0279, (2011).

Yamamoto K, Takahara K, Oyadomari S, Okada T, Sato T, Harada A, Mori K.
Induction of liver steatosis and lipid droplet formation in ATF6alpha-knockout mice burdened with pharmacological endoplasmic reticulum stress.
Molecular Biology of the Cell, 21: 2975-2986; doi: 10.1091/mbc.E09-02-0133, (2010).

Harada A.
Molecular mechanism of polarized transport.
Journal of Biochemistry, 147: 619-624; doi: 10.1093/jb/mvq027, (2010).

Akiyama H, Gotoh A, Shin RW, Koga T, Ohashi T, Sakamoto W, Harada A, Arai H, Sawa A, Uchida C, Uchida T.
A novel role for hGas7b in microtubular maintenance: possible implication in tau-associated pathology in Alzheimer disease.
Journal of Biological Chemistry, 284: 32695-32699; doi: 10.1074/jbc.M109.035998, (2009).

Tanaka S, Kunii M, Harada A, Okabe S.
Generation of cortactin floxed mice and cellular analysis of motility in fibroblasts.
Genesis, 47: 638-646; doi: 10.1002/dvg.20544, (2009).

Uemura T, Sato T, Aoki T, Yamamoto A, Okada T, Hirai R, Harada R, Mori K, Tagaya M, Harada A.
p31 deficiency influences endoplasmic reticulum tubular morphology and cell survival.
Molecular and Cellular Biology, 29: 1869-1881; doi: 10.1128/MCB.01089-08, (2009).

Kato Y, Sugiura T, Nakadera Y, Sugiura M, Kubo Y, Sato T, Harada A, Tsuji A.
Investigation of the role of oligopeptide transporter PEPT1 and sodium/glucose cotransporter SGLT1 in intestinal absorption of their substrates using small GTP-binding protein Rab8-null mice.
Drug Metabolism and Disposition, 37: 602-607; doi: 10.1124/dmd.108.023689, (2009).

Sadakata H, Okazawa H, Sato T, Supriatna Y, Ohnishi H, Kusakari S, Murata Y, Ito T, Nishiyama U, Minegishi T, Harada A, Matozaki T.
SAP-1 is a microvillus-specific protein tyrosine phosphatase that modulates intestinal tumorigenesis.
Genes to Cells, 14: 295-308; doi: 10.1111/j.1365-2443.2008.01270.x, (2009).

Mogi C, Tobo M, Tomura H, Murata N, He XD, Sato K, Kimura T, Ishizuka T, Sasaki T, Sato T, Kihara Y, Ishii S, Harada A, Okajima F.
Involvement of proton-sensing TDAG8 in extracellular acidification-induced inhibition of proinflammatory cytokine production in peritoneal macrophages.
Journal of Immunology, 182: 3243-3251; doi: 10.4049/jimmunol.0803466, (2009).

Sato M, Grant BD, Harada A, Sato K.
Rab11 is required for synchronous secretion of chondroitin proteoglycans after fertilization in Caenorhabditis elegans.
Journal of Cell Science, 121: 3177-3186; doi: 10.1242/jcs.034678, (2008).

Muramatsu K, Hashimoto Y, Uemura T, Kunii M, Harada R, Sato T, Morikawa A, Harada A.
Neuron-specific recombination by Cre recombinase inserted into the murine tau locus.
Biochemical and Biophysical Research Communications, 370: 419-423; doi: 10.1016/j.bbrc.2008.03.103, (2008).

Sato M, Sato K, Liou W, Pant S, Harada A, Grant BD.
Regulation of endocytic recycling by C. elegans Rab35 and its regulator RME-4, a coated-pit protein.
EMBO Journal, 27: 1183-1196; doi: 10.1038/emboj.2008.54, (2008).

Hashimoto Y, Muramatsu K, Uemura T, Harada R, Sato T, Okamoto K, Harada A.
Neuron-specific and inducible recombination by Cre recombinase in the mouse.
Neuroreport, 19: 621-624, (2008).

Adachi Y, Yamamoto K, Okada T, Yoshida H, Harada A, Mori K.
ATF6 is a Transcription Factor Specializing in the Regulation of Quality Control Proteins in the Endoplasmic Reticulum.
Cell Structure and Function, 33: 75-89; doi: 10.1247/csf.07044, (2008).

Sato T, Mushiake S, Kato Y, Sato K, Sato M, Takeda N, Ozono K, Miki K, Kubo Y, Tsuji A, Harada R, Harada A.
The Rab8 GTPase regulates apical protein localization in intestinal cells.
Nature, 448: 366-369; doi: 10.1038/nature05929, (2007).

Yamamoto K, Sato T, Matsui T, Sato M, Okada T, Yoshida H, Harada A, Mori K. (The first two authors contributed equally to this paper).
Transcriptional induction of mammalian ER quality control proteins is mediated by single or combined action of ATF6alpha and XBP1.
Developmental Cell, 13: 365-376, (2007).

Fujio K, Sato M, Uemura T, Sato T, Sato-Harada R, Harada A.
14-3-3 proteins and protein phosphatases are not reduced in tau-deficient mice.
Neuroreport, 18: 1049-1052, (2007).

Hou X, Wei L, Harada A, Tatamoto K.
Activation of bombesin receptor subtype-3 stimulates adhesion of lung cancer cells.
Lung Cancer, 54: 143-148, (2006).

Sohara E, Rai T, Yang SS, Uchida K, Nitta K, Horita S, Ohno M, Harada A, Sasaki S, Uchida S.
Pathogenesis and treatment of autosomal-dominant nephrogenic diabetes insipidus caused by an aquaporin 2 mutation.
Proc Natl Acad Sci USA, 103: 14217-14222, (2006).

Iriuchijima N, Sato-Harada R, Takano M, Fujio K, Sato T, Goto F, Harada A.
Reduced expression of kinase-associated phosphatase in cortical dendrites of MAP2-deficient mice.
Biochemical and Biophysical Research Communications, 338: 1216-1221, (2005).

Wang JQ, Kon J, Mogi C, Tobo M, Damirin A, Sato K, Komachi M, Malchinkhuu E, Murata N, Kimura T, Kuwabara A, Wakamatsu K, Koizumi H, Uede T, Tsujimoto G, Kurose H, Sato T, Harada A, Misawa N, Tomura H, Okajima F.
TDAG8 is a proton-sensing and psychosine-sensitive G-protein-coupled receptor.
Journal of Biological Chemistry, 279: 45626-45633, (2004).

Nakatsu F, Okada M, Mori F, Kumazawa N, Iwasa H, Zhu G, Kasagi Y, Kamiya H, Harada A, Nishimura K, Takeuchi A, Miyazaki T, Watanabe M, Yuasa S, Manabe T, Wakabayashi K, Kaneko S, Saito S, Ohno H.
Defective function of GABA-containing synaptic vesicles in mice lacking the AP-3B clathrin adaptor.
Journal of Cell Biology, 167: 293-302, (2004).

Oyama F, Kotliarova S, Harada A, Ito M, Miyazaki H, Ueyama Y, Hirokawa N, Nukina N, Ihara Y.
Gem GTPase and tau: morphological changes induced by gem GTPase in cho cells are antagonized by tau.
Journal of Biological Chemistry, 279: 27272-27277, (2004).

Hayashi K, Kawai-Hirai R, Harada A, Takata K.
Inhibitory neurons from fetal rat cerebral cortex exert delayed axon formation and active migration in vitro.
Journal of Cell Science, 116: 4419-4428, (2003).

Harada A, Teng J, Takei Y, Oguchi K, Hirokawa N.
MAP2 is required for dendrite elongation, PKA anchoring in dendrites, and proper PKA signal transduction.
Journal of Cell Biology, 158: 541-549, (2002).

Sato T, Sato-Harada R, Takano M, Kato S, Saburi S, and Harada A.
Localization of cAMP-dependent protein kinase in the actin and microtubule cytoskeletons in mouse hippocampal neurons.
Neuroscience Letters, 325: 83-86, (2002).

Teng J, Takei Y, Harada A, Nakata T, Chen J, Hirokawa N.
Synergistic effects of MAP2 and MAP1B knockout in neuronal migration, dendritic outgrowth, and microtubule organization.
J Cell Biol, 155: 65-76, (2001).

Takei Y, Teng J, Harada A, Hirokawa N.
Defects in axonal elongation and neuronal migration in mice with disrupted tau and map1b genes.
Journal of Cell Biology, 150: 989-1000, (2000).

Kanai Y, Okada Y, Tanaka Y, Harada A, Terada S, Hirokawa N.
KIF5C, a novel neuronal kinesin enriched in motor neurons.
Journal of Neuroscience, 20: 6374-6384, (2000).

Ikegami S, Harada A, Hirokawa, N. (The first two authors contributed equally to this paper).
Muscle weakness, hyperactivity, and impairment in fear conditioning in tau-deficient mice.
Neuroscience Letters, 279: 129-132, (2000).

Nonaka S, Tanaka Y, Okada Y, Takeda S, Harada A, Kanai Y, Kido M, Hirokawa N.
Randomization of Left-Right Asymmetry due to Loss of Nodal Cilia Generating Leftward Flow of Extraembryonic Fluid in Mice Lacking KIF3B Motor Protein.
Cell, 95: 829-837, (1998).

Tanaka Y, Kanai Y, Okada Y, Nonaka S, Takeda S, Harada A, Hirokawa N.
Targeted disruption of mouse conventional kinesin heavy chain, kif5B, results in abnormal perinuclear clustering of mitochondria.
Cell, 93: 1147-1158, (1998).

Yonekawa Y, Harada A, Okada Y, Funakoshi T, Kanai Y, Takei Y, Terada S, Noda T, Hirokawa N.
Defect in synaptic vesicle precursor transport and neuronal cell death in KIF1A motor protein-deficient mice.
J Cell Biol, 141: 431-441, (1998).

Harada A, Takei Y, Kanai Y, Tanaka Y, Nonaka S, Hirokawa N.
Golgi vesiculation and lysosome dispersion in cells lacking cytoplasmic dynein.
Journal of Cell Biology, 141: 51-59, (1998).

Takei Y, Kondo S, Harada A, Inomata S, Noda T, Hirokawa N.
Delayed development of nervous system in mice homozygous for disrupted microtubule-associated protein 1B (MAP1B) gene.
Journal of Cell Biology, 137: 1615-1626, (1997).

Takei Y, Harada A, Takeda S, Kobayashi K, Terada S, Noda T, Takahashi T, Hirokawa N.
Synapsin I deficiency results in the structural change in the presynaptic terminals in the murine nervous system.
Journal of Cell Biology, 131: 1789-1800, (1995).

Harada A, Oguchi K, Okabe S, Kuno J, Terada S, Ohshima T, Sato-Yoshitake R, Takei Y, Noda T, Hirokawa N.
Altered microtubule organization in small-calibre axons of mice lacking tau protein.
Nature, 369: 488-491, (1994).

Harada A, Sobue K, Hirokawa N.
Developmental changes of synapsin I subcellular localization in rat cerebellar neurons.
Cell Structure and Function, 15: 329-342, (1990).

Hirokawa N, Sobue K, Kanda K, Harada A, Yorifuji H.
The cytoskeletal architecture of the presynaptic terminal and molecular structure of synapsin1.
Journal of Cell Biology, 108: 111-126, (1989).