Selective nuclear transport of mu-calpain.
To study nuclear transport of purified calpains in an in vitro system, A431 cells were permeabilized with digitonin, and fluorescein-labeled calpains were introduced under conditions known to facilitate energy-dependent nuclear transport of proteins. Fluorescein-mu-calpain was transported into nuclei in an ATP-dependent fashion. The calpain-specific inhibitor protein, calpastatin, could not block mu-calpain translocation. Fluorescein-calpastatin and fluorescein-m-calpain were poorly transported at best. In the presence of rat liver cytosolic factors, accumulation of nuclear mu-calpain was maximum at approximately 1 microM Ca2+, and no transport was observed at 0.3 microM Ca2+. Rat erythrocyte and HeLa cell extracts supported transport in the absence of Ca2+.
Department of Pharmacology and Therapeutics, Medical College of Ohio, Toledo 43699-0008.
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D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002154:Calpain / Q000378:metabolism*; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism*; D004072:Digitonin; D019793:Fluorescein; D005452:Fluoresceins; D006801:Humans; D008969:Molecular Sequence Data; D014407:Tumor Cells, Cultured
D002135:Calcium-Binding Proteins; D005452:Fluoresceins; C033668:calpastatin; D002154:Calpain; D004072:Digitonin; D002118:Calcium; D019793:Fluorescein