Location of NLS-RARα protein in peripheral blood tumor cells of patients with acute promyeolic leukemia / 第二军医大学学报

Objective To verify the presence and location of the NLS-RARex protein in the peripheral blood tumor cells of patients with acute promyeolic leukemia (APL). Methods Western blotting analysis was used to identify the NE enzyme in the peripheral blood tumor cells of APL patients. The nucleoprotein in tumor cells was prepared and NLS-RARex protein was detected by Western blotting analysis. The expression and location of NLS-RARex protein in peripheral blood tumor cells of APL patients were examined by FITC/DAPI double immunofluorescence staining and FITC/PI double staining laser confocal microscopy. The expression and location of NLS-RARex protein in NB4 cells infected with recombinant adenovirus Ad-NE was used as positive control and those of wildtype RARex in the neutrophils of healthy controls were taken as negative control. Results Positive control was successfully established. NE enzyme and NLS-RARex protein were expressed in peripheral blood tumor cells of APL patients. Immunofluorescence and laser confocal findings indicated that NL&RARex protein was mainly located at the nuclei of peripheral blood tumors cells in APL patients. Conclusion NLS-RARex protein has been successfully detected by 3 different methods in the peripheral blood tumor cells of APL patients and its intracellular location has also been proposed, which can contribute to the early diagnosis and recurrence monitoring of APL.

The hydrophobic amino acids involved in the interdomain association of phospholipase D1 regulate the shuttling of phospholipase D1 from vesicular organelles into the nucleus

Phospholipase D (PLD) catalyzes the hydrolysis of phosphatidylcholine to generate the lipid second messenger, phosphatidic acid. PLD is localized in most cellular organelles, where it is likely to play different roles in signal transduction. PLD1 is primarily localized in vesicular structures such as endosomes, lysosomes and autophagosomes. However, the factors defining its localization are less clear. In this study, we found that four hydrophobic residues present in the N-terminal HKD catalytic motif of PLD1, which is involved in intramolecular association, are responsible for vesicular localization. Site-directed mutagenesis of the residues dramatically disrupted vesicular localization of PLD1. Interestingly, the hydrophobic residues of PLD1 are also involved in the interruption of its nuclear localization. Mutation of the residues increased the association of PLD1 with importin-beta, which is known to mediate nuclear importation, and induced the localization of PLD1 from vesicles into the nucleus. Taken together, these data suggest that the hydrophobic amino acids involved in the interdomain association of PLD1 are required for vesicular localization and disturbance of its nuclear localization.

Verification of interaction between glutamate-ammonia ligase and nuclear localization signal-retinoic acid receptor α protein inside and outside cells / 第二军医大学学报

Objective: To verify the interaction between glutamate-ammonia ligase (GLUL) and nuclear localization signal-retinoic acid receptor α (NLS-RARα) protein by yeast two-hybrid and co-immunoprecipitation method. Methods: The two plasmids expressing NLS-RARα bait-protein and GLUL protein were co-transformed into yeast AH109 to investigate the interaction in vivo. Tagged fusion protein eukaryotic expression vectors were constructed and co-transfected into HEK 293 cells. Co-immunoprecipitation was used to investigate the interaction between NLS-RARα and GLUL in vitro. Results: Positive blue clones were found in the QDO/X-α-gal plate. Eukaryotic expression vectors were co-transfected into HEK 293 cells, then HA-NLS-RARα protein was immunoprecipitated by anti-HA polyclonal antibody, and GLUL-cMyc protein expression was confirmed by Western blotting analysis using anti c-Myc monoclonal antibody. Conclusion: The interaction between NLS-RARα and GLUL has been verified by both yeast two-hybrid and co-immunoprecipitation.

Nuclear localization and the heat shock proteins.

The highly conserved heat shock proteins (HSP) belong to a subset of cellular proteins that localize to the nucleus. HSPs are atypical nuclear proteins in that they localize to the nucleus selectively, rather than invariably. Nuclear localization of HSPs is associated with cell stress and cell growth. This aspect of HSPs is highly conserved with nuclear localization occurring in response to a wide variety of cell stresses. Nuclear localization is likely important for at least some of the heat shock proteins' protective functions; little is known about the function of the heat shock proteins in the nucleus. Nuclear localization is signalled by the presence of a basic nuclear localization sequence (NLS) within a protein. Though most is known about HSP 72’s nuclear localization, the NLS(s) has not been definitively identified for any of the heat shock proteins. Likely more is involved than presence of a NLS; since the heat shock proteins only localize to the nucleus under selective conditions, nuclear localization must be regulated. HSPs also function as chaperons of nuclear transport, facilitating the movement of other macromolecules across the nuclear membrane. The mechanisms involved in chaperoning of proteins by HSPs into the nucleus are still being identified.