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.