Calmodulin activates nuclear protein import: a link between signal transduction and nuclear transport.
In addition to the well-characterized GTP-dependent nuclear transport observed in permeabilized cells, we detected a mode of nuclear transport that was GTP-independent at elevated cytoplasmic calcium concentrations. Nuclear transport under these conditions was blocked by calmodulin inhibitors. Recombinant calmodulin restored ATP-dependent nuclear transport in the absence of cytosol. Calmodulin-dependent transport was inhibited by wheat germ agglutinin consistent with transport proceeding through nuclear pores. We propose that release of intracellular calcium stores upon cell activation inhibits GTP-dependent nuclear transport; the elevated cytosolic calcium then acts through calmodulin to stimulate the novel GTP-independent mode of import.
Sweitzer
T D
TD
Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 26892-0850, USA.
Hanover
J A
JA
D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*
D002147:Calmodulin; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D002118:Calcium