title: Molecular Characterization and Functional Analysis of Annulate Lamellae Pore Complexes in Nuclear Transport in Mammalian Cells.
abstract: Annulate lamellae are cytoplasmic organelles containing stacked sheets of membranes embedded with pore complexes. These cytoplasmic pore complexes at annulate lamellae are morphologically similar to nuclear pore complexes at the nuclear envelope. Although annulate lamellae has been observed in nearly all types of cells, their biological functions are still largely unknown. Here we show that SUMO1-modification of the Ran GTPase-activating protein RanGAP1 not only target RanGAP1 to its known sites at nuclear pore complexes but also to annulate lamellae pore complexes through interactions with the Ran-binding protein RanBP2 and the SUMO-conjugating enzyme Ubc9 in mammalian cells. Furthermore, upregulation of annulate lamellae, which decreases the number of nuclear pore complexes and concurrently increases that of annulate lamellae pore complexes, causes a redistribution of nuclear transport receptors including importin α/β and the exportin CRM1 from nuclear pore complexes to annulate lamellae pore complexes and also reduces the rates of nuclear import and export. Moreover, our results reveal that importin α/β-mediated import complexes initially accumulate at annulate lamellae pore complexes upon the activation of nuclear import and subsequently disassociate for nuclear import through nuclear pore complexes in cells with upregulation of annulate lamellae. Lastly, CRM1-mediated export complexes are concentrated at both nuclear pore complexes and annulate lamellae pore complexes when the disassembly of these export complexes is inhibited by transient expression of a Ran GTPase mutant arrested in its GTP-bound form, suggesting that RanGAP1/RanBP2-activated RanGTP hydrolysis at these pore complexes is required for the dissociation of the export complexes. Hence, our findings provide a foundation for further investigation of how upregulation of annulate lamellae decreases the rates of nuclear transport and also for elucidation of the biological significance of the interaction between annulate lamellae pore complexes and nuclear transport complexes in mammalian cells.
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America.
authors.forename: Sarita
authors.initials: S
authors.lastname: Raghunayakula
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America.
authors.forename: Divya
authors.initials: D
authors.lastname: Subramonian
authors.affiliation: Laboratory of Gene Regulation and Development, National Institute for Child Health and Human Development, NIH, Bethesda, Maryland, United States of America.
authors.forename: Mary
authors.initials: M
authors.lastname: Dasso
authors.affiliation: Departments of Emergency Medicine and Physiology, Wayne State University, Detroit, Michigan, United States of America.
authors.forename: Rita
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Biological Sciences, Wayne State University, Detroit, Michigan, United States of America.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Zhang
mesh_terms: D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000502:physiology; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D022022:Nuclear Pore / Q000502:physiology*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D025842:SUMO-1 Protein / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D028901:alpha Karyopherins / Q000378:metabolism; D028961:beta Karyopherins / Q000378:metabolism; D000097606:Exportin 1 Protein; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D020690:GTPase-Activating Proteins; D028884:Karyopherins; D018832:Molecular Chaperones; D028861:Nuclear Pore Complex Proteins; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D025842:SUMO-1 Protein; D044763:Ubiquitin-Conjugating Enzymes; D028901:alpha Karyopherins; D028961:beta Karyopherins; D000097606:Exportin 1 Protein; D000098843:Ubiquitin-Conjugating Enzyme UBC9; C000602140:RanGAP1 protein, rat; C087978:karyopherin alpha 2; C094493:ran-binding protein 2