Due to its actin-sequestering properties, thymosin beta-4 (T beta 4) is considered to play a significant role in the cellular metabolism. Several physiological properties of T beta 4 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 T beta 4 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 T beta 4, followed by gold-labeled goat anti-rabbit, stained with uranyl acetate and bismuth subnitrate, observed and photographed in a JEOL 100S transmission electron microscope. Highresolution electron microscopy showed that T beta 4 was mainly restricted to the cytoplasm of HepG2 growing in complete medium. A strong T beta 4 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 T beta 4 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 T beta 4 in both cytoplasmic and nuclear compartments of HepG2 cells. The meaning of T beta 4 presence in the nucleolus is not on the best of our knowledge clarified yet. It could account for the interaction of T beta 4 with nucleolar actin and according with this hypothesis, T beta 4 could contribute together with the other nucleolar acting binding proteins to modulate the transcription activity of the RNA polymerases.
Thymosin Beta 4 May Translocate from the Cytoplasm in to the Nucleus in HepG2 Cells following Serum Starvation. An Ultrastructural Study
Castagnola Massimo
2015
Abstract
Due to its actin-sequestering properties, thymosin beta-4 (T beta 4) is considered to play a significant role in the cellular metabolism. Several physiological properties of T beta 4 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 T beta 4 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 T beta 4, followed by gold-labeled goat anti-rabbit, stained with uranyl acetate and bismuth subnitrate, observed and photographed in a JEOL 100S transmission electron microscope. Highresolution electron microscopy showed that T beta 4 was mainly restricted to the cytoplasm of HepG2 growing in complete medium. A strong T beta 4 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 T beta 4 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 T beta 4 in both cytoplasmic and nuclear compartments of HepG2 cells. The meaning of T beta 4 presence in the nucleolus is not on the best of our knowledge clarified yet. It could account for the interaction of T beta 4 with nucleolar actin and according with this hypothesis, T beta 4 could contribute together with the other nucleolar acting binding proteins to modulate the transcription activity of the RNA polymerases.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
