Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Co-expression of trefoil factor 1 (TFF1) and tyrosine hydroxylase (TH) in the ventral mesencephalon of adult rats.

<p>Double immunofluorescence staining for TFF1 (red) and TH (green) in the ventral mesencephalon of adult rats. Note that nearly all TFF1-immunoreactive (-ir) cells co-localized with TH, while many TH-ir cells did not co-express TFF1. Scale bars: 1 mm (overview); 100 µm (magnification). Abbreviations: SNc, substantia nigra pars compacta; SNl, substantia nigra pars lateralis; VTA, ventral tegmental area.</p

Quantification of trefoil factor 1 (TFF1) and tyrosine hydroxylase (TH) co-expressing cells in adult rats.

<p>Percentage of trefoil factor 1-immunoreactive (TFF1-ir) cells that co-localized with tyrosine hydroxylase (TH) (A) and percentage of TH-ir cells that co-localized with TFF1 (B) in the substantia nigra (SN) and ventral tegmental area (VTA) of adult rats. *: p<0.05 vs. corresponding VTA values, n = 4.</p

Co-expression of trefoil factor 1 (TFF1) and calcium-binding proteins in the ventral mesencephalon of adult rats.

<p>Double immunofluorescence stainings for TFF1 and the calcium-binding proteins calretinin (CR), calbindin (CB) or parvalbumin (PV). Note that many TFF1-immunoreactive (-ir) cells co-expressed CR (arrows), but not all CR-ir cells co-localized with TFF1 (arrowheads). Similarly, co-localization with CB was seen for a few TFF1-ir cells (arrows). As expected from the distribution pattern depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0076592#pone-0076592-g001" target="_blank">Figure 1</a> no co-localization was detected for TFF1-ir cells with PV (arrows). Scale bars middle panel: 50 µm, lower panel: 100 µm.</p

Detection of Trefoil factor 1 (TFF1) in nigrostriatal projection neurons by Fluorogold (FG) labelling.

<p>Representative photomicrographs of double immunofluorescence stainings for TFF1 and the retrograde tracer FG at the level of substantia nigra pars compacta (SNc) 10 days after intrastriatal FG injection. A subpopulation of TFF1-ir cells was found to co-express FG identifying these as projection neurons (arrows). Scale bars upper panel: 100 µm, lower panel: 50 µm.</p

Dynamic Changes in the Protein Localization in the Nuclear Environment in Pancreatic β‑Cell after Brief Glucose Stimulation

Characterization of molecular mechanisms underlying pancreatic β-cell function in relation to glucose-stimulated insulin secretion is incomplete, especially with respect to global response in the nuclear environment. We focus on the characterization of proteins in the nuclear environment of β-cells after brief, high glucose stimulation. We compared purified nuclei derived from β-cells stimulated with 17 mM glucose for 0, 2, and 5 min using quantitative proteomics, a time frame that most likely does not result in translation of new protein in the cell. Among the differentially regulated proteins, we identified 20 components of the nuclear organization processes, including nuclear pore organization, ribonucleoprotein complex, and pre-mRNA transcription. We found alteration of the nuclear pore complex, together with calcium/calmodulin-binding chaperones that facilitate protein and RNA import or export to/from the nucleus to the cytoplasm. Putative insulin mRNA transcription-associated factors were identified among the regulated proteins, and they were cross-validated by Western blotting and confocal immunofluorescence imaging. Collectively, our data suggest that protein translocation between the nucleus and the cytoplasm is an important process, highly involved in the initial molecular mechanism underlying glucose-stimulated insulin secretion in pancreatic β-cells

Loss of trefoil factor 1 (TFF1) expressing cells in a rat model of Parkinson’s disease.

<p>Representative photomicrographs of tyrosine hydroxylase (TH; A) and TFF1 (B) in brain sections from adult rat ventral mesencephalon at 4 weeks after unilateral 6-hydroxydopamine (6-OHDA) lesion. The lesion resulted in a distinct loss of TH-ir neurons in right SN (A2) as compared to the contralateral, unlesioned control side (A1). Similarly, a reduction of TFF1-ir cells was detected on the lesioned side (B2) as compared to the intact control side (B1). This loss of TFF1-ir cells is better recognized on the enlarged images (B2). Scale bars: 1 mm (overview), 500 µm (magnification).</p

Quantification of trefoil factor 1 (TFF1) and tyrosine hydroxylase (TH) co-expressing cells during development.

<p>A) Quantification of trefoil factor 1-immunoreactive (TFF1-ir) cells co-expressing tyrosine hydroxylase (TH) and B) TH-ir cells co-expressing TFF1 in the substantia nigra (SN) of postnatal (P) day 7, 14, 21 and adult rats. The percentage of TH/TFF1 co-expressing cells was significantly higher for P7 and P14 rats compared to P21 rats, whereas there was no significant difference between the percentages of TFF1-ir cells co-expressing TH. Data are expressed as mean ± SEM (*: p<0.05, n = 4-7). C) Representative double immunofluorescence images of TFF1-ir and TH-ir cells in SN of P7, P14 and P21 rats (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0076592#pone-0076592-g002" target="_blank">Figure 2</a> for adult rats). Scale bar: 200 µm.</p

Trefoil factor 1 (TFF1) expression is restricted to neurons.

<p>Representative photomicrographs of double immunofluorescence stainings for TFF1 and astroglial or neuronal markers in the substantia nigra pars compacta (SNc) of adult rats. No co-localization was found of TFF1-positive cells (arrows) with the astroglial marker glial fibrillary acid protein (GFAP) (arrowheads). Notably, a substantial number of the TFF1-ir cells were demonstrated to co-express the pan neuronal marker NeuN (arrows), while some did not (arrowheads). Scale bar: 50 µm.</p