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Thymosin beta 4 may translocate from the cytoplasm in to the nucleus in HepG2 cells following serum starvation. An ultrastructural study.

Piludu M, Piras M, Pichiri G, Coni P, Orrù G, Cabras T, Messana I, Faa G, Castagnola M - PLoS ONE (2015)

Bottom Line: A strong Tβ4 reactivity was detected in the perinuclear region of the cytoplasmic compartment where gold particles appeared strictly associated to the nuclear membrane.The above electron microscopic results confirm and extend previous observations at light microscopic level, highlighting the subcellular distribution of Tβ4 in both cytoplasmic and nuclear compartments of HepG2 cells.The meaning of Tβ4 presence in the nucleolus is not on the best of our knowledge clarified yet.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.

ABSTRACT
Due to its actin-sequestering properties, thymosin beta-4 (Tβ4) is considered to play a significant role in the cellular metabolism. Several physiological properties of Tβ4 have been reported;, however, many questions concerning its cellular function remain to be ascertained. To better understand the role of this small peptide we have analyzed by means of transmission immunoelectron microscopy techniques the ultrastructural localization of Tβ4 in HepG2 cells. Samples of HepG2 cells were fixed in a mixture of 3% formaldehyde and 0.1% glutaraldehyde in 0.1 M cacodylate buffer and processed for standard electron microscopic techniques. The samples were dehydrated in a cold graded methanol series and embedded in LR gold resin. Ultrathin sections were labeled with rabbit antibodies to Tβ4, followed by gold-labeled goat anti-rabbit, stained with uranyl acetate and bismuth subnitrate, observed and photographed in a JEOL 100S transmission electron microscope. High-resolution electron microscopy showed that Tβ4 was mainly restricted to the cytoplasm of HepG2 growing in complete medium. A strong Tβ4 reactivity was detected in the perinuclear region of the cytoplasmic compartment where gold particles appeared strictly associated to the nuclear membrane. In the nucleus specific Tβ4 labeling was observed in the nucleolus. The above electron microscopic results confirm and extend previous observations at light microscopic level, highlighting the subcellular distribution of Tβ4 in both cytoplasmic and nuclear compartments of HepG2 cells. The meaning of Tβ4 presence in the nucleolus is not on the best of our knowledge clarified yet. It could account for the interaction of Tβ4 with nucleolar actin and according with this hypothesis, Tβ4 could contribute together with the other nucleolar acting binding proteins to modulate the transcription activity of the RNA polymerases.

No MeSH data available.


Related in: MedlinePlus

Tβ4 mRNA expression detected by RT-PCR reaction in HepG2 cells growing in normal serum and in starvation conditions.The ratio value Tβ4/β actin detected at 24h in normal condition was assumed as equal to 1 (calibrator sample). In these conditions the Tβ4 expression patterns suggest a moderate Tβ4 mRNA increase expression rate from 24 to 48h in normal conditions and, a more high Tβ4 mRNA expression values, during starvation.(2 folds in difference at 48h). The vertical bars, reppresent the range of standard error (+-SE) of the mean.
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pone.0119642.g002: Tβ4 mRNA expression detected by RT-PCR reaction in HepG2 cells growing in normal serum and in starvation conditions.The ratio value Tβ4/β actin detected at 24h in normal condition was assumed as equal to 1 (calibrator sample). In these conditions the Tβ4 expression patterns suggest a moderate Tβ4 mRNA increase expression rate from 24 to 48h in normal conditions and, a more high Tβ4 mRNA expression values, during starvation.(2 folds in difference at 48h). The vertical bars, reppresent the range of standard error (+-SE) of the mean.

Mentions: In these conditions the Tβ4 expression patterns suggest a moderate increase of the Tβ4 expression rate from 24 to 48h in normal conditions and, a more high Tβ4 expression values, during starvation.(2 folds in difference at 48h). This observation confirm that Tβ4 may be involved in stress processes, not only changing its intracellular localization, but also affecting its gene expression (Fig. 2).


Thymosin beta 4 may translocate from the cytoplasm in to the nucleus in HepG2 cells following serum starvation. An ultrastructural study.

Piludu M, Piras M, Pichiri G, Coni P, Orrù G, Cabras T, Messana I, Faa G, Castagnola M - PLoS ONE (2015)

Tβ4 mRNA expression detected by RT-PCR reaction in HepG2 cells growing in normal serum and in starvation conditions.The ratio value Tβ4/β actin detected at 24h in normal condition was assumed as equal to 1 (calibrator sample). In these conditions the Tβ4 expression patterns suggest a moderate Tβ4 mRNA increase expression rate from 24 to 48h in normal conditions and, a more high Tβ4 mRNA expression values, during starvation.(2 folds in difference at 48h). The vertical bars, reppresent the range of standard error (+-SE) of the mean.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383617&req=5

pone.0119642.g002: Tβ4 mRNA expression detected by RT-PCR reaction in HepG2 cells growing in normal serum and in starvation conditions.The ratio value Tβ4/β actin detected at 24h in normal condition was assumed as equal to 1 (calibrator sample). In these conditions the Tβ4 expression patterns suggest a moderate Tβ4 mRNA increase expression rate from 24 to 48h in normal conditions and, a more high Tβ4 mRNA expression values, during starvation.(2 folds in difference at 48h). The vertical bars, reppresent the range of standard error (+-SE) of the mean.
Mentions: In these conditions the Tβ4 expression patterns suggest a moderate increase of the Tβ4 expression rate from 24 to 48h in normal conditions and, a more high Tβ4 expression values, during starvation.(2 folds in difference at 48h). This observation confirm that Tβ4 may be involved in stress processes, not only changing its intracellular localization, but also affecting its gene expression (Fig. 2).

Bottom Line: A strong Tβ4 reactivity was detected in the perinuclear region of the cytoplasmic compartment where gold particles appeared strictly associated to the nuclear membrane.The above electron microscopic results confirm and extend previous observations at light microscopic level, highlighting the subcellular distribution of Tβ4 in both cytoplasmic and nuclear compartments of HepG2 cells.The meaning of Tβ4 presence in the nucleolus is not on the best of our knowledge clarified yet.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.

ABSTRACT
Due to its actin-sequestering properties, thymosin beta-4 (Tβ4) is considered to play a significant role in the cellular metabolism. Several physiological properties of Tβ4 have been reported;, however, many questions concerning its cellular function remain to be ascertained. To better understand the role of this small peptide we have analyzed by means of transmission immunoelectron microscopy techniques the ultrastructural localization of Tβ4 in HepG2 cells. Samples of HepG2 cells were fixed in a mixture of 3% formaldehyde and 0.1% glutaraldehyde in 0.1 M cacodylate buffer and processed for standard electron microscopic techniques. The samples were dehydrated in a cold graded methanol series and embedded in LR gold resin. Ultrathin sections were labeled with rabbit antibodies to Tβ4, followed by gold-labeled goat anti-rabbit, stained with uranyl acetate and bismuth subnitrate, observed and photographed in a JEOL 100S transmission electron microscope. High-resolution electron microscopy showed that Tβ4 was mainly restricted to the cytoplasm of HepG2 growing in complete medium. A strong Tβ4 reactivity was detected in the perinuclear region of the cytoplasmic compartment where gold particles appeared strictly associated to the nuclear membrane. In the nucleus specific Tβ4 labeling was observed in the nucleolus. The above electron microscopic results confirm and extend previous observations at light microscopic level, highlighting the subcellular distribution of Tβ4 in both cytoplasmic and nuclear compartments of HepG2 cells. The meaning of Tβ4 presence in the nucleolus is not on the best of our knowledge clarified yet. It could account for the interaction of Tβ4 with nucleolar actin and according with this hypothesis, Tβ4 could contribute together with the other nucleolar acting binding proteins to modulate the transcription activity of the RNA polymerases.

No MeSH data available.


Related in: MedlinePlus