Cytoplasmic localization of LIM-kinase 1 is directed by a short sequence within the PDZ domain.
LIM-containing protein kinase 1 (LIMK1) is a serine/threonine kinase with a structure composed of two LIM domains, a PDZ domain, and a protein kinase domain. We examined the subcellular localization of LIMK1 and its variously deleted mutants in HeLa cells by transfection with these cDNAs. Immunofluorescence analysis revealed that the full-length LIMK1 and its mutants deleted with LIM domain or protein kinase domain preferentially localized in the cytoplasm, while the mutants deleted with the PDZ domain or a 52 amino acid region (B region) within the PDZ domain localized mainly in the nucleus. When the normally nuclear cyclin A was fused with the PDZ domain or the B region of LIMK1, it was localized in the cytoplasm of transfected cells. The corresponding region of the PDZ domain of postsynaptic density protein (PSD)-95 had no such function. Additionally, the PDZ domain of LIMK1 had no potential to bind to the C-terminal S/TXV peptides, to which the PSD-95 PDZ domain can bind. Taken together these results suggest that the PDZ domain, particularly the B region, of LIMK1 has a specific function to localize the protein in the cytoplasm. When glutathione S-transferase (GST) fused with the PDZ domain of LIMK1 (GST-PDZ) or GST-PDZ deleted with the B region (GST-PDZ delta B) was microinjected into the nucleus of COS cells, GST-PDZ was almost completely excluded from the nucleus within 30 min, whereas GST-PDZ delta B remained in the nucleus. These findings suggest that the B region of LIMK1 probably has nuclear export signal activity.
Yang
N
N
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
Higuchi
O
O
Mizuno
K
K
D000595:Amino Acid Sequence / Q000235:genetics*; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D019925:Cyclin A / Q000032:analysis / Q000235:genetics; D003593:Cytoplasm / Q000737:chemistry / Q000201:enzymology*; D000076122:Disks Large Homolog 4 Protein; D051528:Guanylate Kinases; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D054461:Lim Kinases; D008565:Membrane Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000737:chemistry / Q000201:enzymology
D019925:Cyclin A; D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; C033652:postsynaptic density proteins; D011494:Protein Kinases; C515892:LIMK1 protein, human; D054461:Lim Kinases; C515893:Limk1 protein, mouse; D051528:Guanylate Kinases