title: Role of the Small GTPase Rho3 in Golgi/Endosome trafficking through functional interaction with adaptin in Fission Yeast.
abstract: BACKGROUND
  We had previously identified the mutant allele of apm1(+) that encodes a homolog of the mammalian µ1A subunit of the clathrin-associated adaptor protein-1 (AP-1) complex, and we demonstrated the role of Apm1 in Golgi/endosome trafficking, secretion, and vacuole fusion in fission yeast.
  
  
  RESULTS
  In the present study, we isolated rho3(+), which encodes a Rho-family small GTPase, an important regulator of exocystosis, as a multicopy-suppressor of the temperature-sensitive growth of the apm1-1 mutant cells. Overexpression of Rho3 suppressed the Cl(-) sensitivity and immunosuppressant sensitivity of the apm1-1 mutant cells. Overexpression of Rho3 also suppressed the fragmentation of vacuoles, and the accumulation of v-SNARE Syb1 in Golgi/endosomes and partially suppressed the defective secretion associated with apm1-deletion cells. Notably, electron microscopic observation of the rho3-deletion cells revealed the accumulation of abnormal Golgi-like structures, vacuole fragmentation, and accumulation of secretory vesicles; these phenotypes were very similar to those of the apm1-deletion cells. Furthermore, the rho3-deletion cells and apm1-deletion cells showed very similar phenotypic characteristics, including the sensitivity to the immunosuppressant FK506, the cell wall-damaging agent micafungin, Cl(-), and valproic acid. Green fluorescent protein (GFP)-Rho3 was localized at Golgi/endosomes as well as the plasma membrane and division site. Finally, Rho3 was shown to form a complex with Apm1 as well as with other subunits of the clathrin-associated AP-1 complex in a GTP- and effector domain-dependent manner.
  
  
  CONCLUSIONS
  Taken together, our findings reveal a novel role of Rho3 in the regulation of Golgi/endosome trafficking and suggest that clathrin-associated adaptor protein-1 and Rho3 co-ordinate in intracellular transport in fission yeast. To the best of our knowledge, this study provides the first evidence of a direct link between the small GTPase Rho and the clathrin-associated adaptor protein-1 in membrane trafficking.
authors.affiliation: Laboratory of Molecular Pharmacogenomics, School of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Kita
authors.forename: Cuifang
authors.initials: C
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
authors.forename: Nanae
authors.initials: N
authors.lastname: Umeda
authors.forename: Akira
authors.initials: A
authors.lastname: Doi
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Yasuda
authors.forename: Shunji
authors.initials: S
authors.lastname: Ishiwata
authors.forename: Atsushi
authors.initials: A
authors.lastname: Taga
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Horiuchi
authors.forename: Reiko
authors.initials: R
authors.lastname: Sugiura
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000235:genetics / Q000378:metabolism*; D033983:Adaptor Protein Complex mu Subunits / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001692:Biological Transport / Q000235:genetics; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D011485:Protein Binding; D012568:Schizosaccharomyces / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*
chemical_list: D033961:Adaptor Protein Complex 1; D033983:Adaptor Protein Complex mu Subunits; D029702:Schizosaccharomyces pombe Proteins; C499066:adaptor protein complex 1, mu 1 subunit; C489566:rho3 protein, S pombe; D020741:rho GTP-Binding Proteins