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In vivo analysis of importin alpha proteins reveals cellular proliferation inhibition and substrate specificity

Item Type:Article
Title:In vivo analysis of importin alpha proteins reveals cellular proliferation inhibition and substrate specificity
Creators Name:Quensel, C. and Friedrich, B. and Sommer, T. and Hartmann, E. and Koehler, M.
Abstract:The "classical" nuclear import pathway depends on importins {alpha} and {beta}. Humans have only one importin {beta}, while six {alpha} importins have been described. Whether or not distinct {alpha} importins are essential for specific import pathways in living human cells is unclear, We used RNA interference technology to specifically down-regulate the expression of ubiquitously expressed human {alpha} importins in HeLa cells. Down-regulation of importins {alpha}3, {alpha}5, {alpha}7, and {beta} strongly inhibited HeLa cell proliferation, while down-regulation of importins {alpha}1 and {alpha}4 had only a minor effect or no effect. Nucleoplasmin import was not prevented by down-regulation of any {alpha} importin, indicating that the importin {alpha}/{beta} pathway was generally not affected. In contrast, importin {alpha}3 or {alpha}5 down-regulation specifically inhibited the nuclear import of the Ran guanine nucleotide exchange factor, RCC1. Coinjection of recombinant {alpha} importins and RCC1 into down-regulated cells demonstrated that these transport defects were specifically caused by the limited availability of importin {alpha}3 in both cases. Thus, importin {alpha}3 is the only {alpha} importin responsible for the classical nuclear import of RCC1 in living cells.
Keywords:Alpha Karyopherins, Apoptosis, Beta Karyopherins, Cell Cycle Proteins, Cell Nucleus, Cell Proliferation, Cell Separation, Cycloheximide, Cytosol, Down-Regulation, Drug Dose-Response Relationship, Flow Cytometry, Fluorescence Microscopy, Guanine Nucleotide Exchange Factors, Hela Cells, Nuclear Proteins, Protein Synthesis Inhibitors, Recombinant Proteins, RNA Interference, Small Interfering RNA, Substrate Specificity, Time Factors, Transfection, Western Blotting
Source:Molecular and Cellular Biology
Publisher:American Society for Microbiology
Page Range:10246-10255
Date:1 January 2004
Official Publication:https://doi.org/10.1128/MCB.24.23.10246-10255.2004
PubMed:View item in PubMed

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