PIST [PDZ (PSD-95, Discs-large and ZO-1) protein interacting specifically with TC10] functions as a regulator of membrane trafficking with Rab6A. Recently, the involvement of the fusion of PIST with ROS1 in cancer development has been identified. In this study, the coiled-coil domain of PIST, which is the domain responsible for interaction with Rab6A and fusion with ROS1, corresponding to amino acids 29–133, was overexpressed inEscherichia coliusing engineered C-terminal His tags. The coiled-coil domain of PIST was then purified to homogeneity and crystallized at 293 K. Finally, X-ray diffraction data were collected to a resolution of 4.0 Å from a crystal belonging to the hexagonal space groupP6222 orP6422, with unit-cell parametersa=b= 85.19,c= 240.09 Å, γ = 120.00°.
The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.
AbstractFission yeast adenylate cyclase, like mammalian adenylate cyclases, is regulated by a heterotrimeric G protein. The gpa2 Gα and git5 Gβ are both required for glucose-triggered cAMP signaling. The git5 Gβ is a unique member of the Gβ family in that it lacks an amino-terminal coiled-coil domain shown to be essential for mammalian Gβ folding and interaction with Gγ subunits. Using a git5 bait in a two-hybrid screen, we identified the git11 Gγ gene. Co-immunoprecipitation studies confirm the composition of this Gβγ dimer. Cells deleted for git11 are defective in glucose repression of both fbp1 transcription and sexual development, resembling cells lacking either the gpa2 Gα or the git5 Gβ. Overexpression of the gpa2 Gα partially suppresses loss of either the git5 Gβ or the git11 Gγ, while mutational activation of the Gα fully suppresses loss of either Gβ or Gγ. Deletion of gpa2 (Gα), git5 (Gβ), or git11 (Gγ) confer quantitatively distinct effects on fbp1 repression, indicating that the gpa2 Gα subunit remains partially active in the absence of the Gβγ dimer and that the git5 Gβ subunit remains partially active in the absence of the git11 Gγ subunit. The addition of the CAAX box from the git11 Gγ to the carboxy-terminus of the git5 Gβ partially suppresses the loss of the Gγ. Thus the Gγ in this system is presumably required for localization of the Gβγ dimer but not for folding of the Gβ subunit. In mammalian cells, the essential roles of the Gβ amino-terminal coiled-coil domains and Gγ partners in Gβ folding may therefore reflect a mechanism used by cells that express multiple forms of both Gβ and Gγ subunits to regulate the composition and activity of its G proteins.
The coiled-coil domain of EspA is essential for the assembly of the type III secretion translocon on the surface of enteropathogenic Escherichia coli. Vol. 274 (1999) 35969–35974
