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要旨:
Glucose and cAMP-inducing agents such as 3-isobutyl-1-
methylxanthine (IBMX) rapidly change the expression profile
of insulin-producing pancreatic !-cells mostly through
post-transcriptional mechanisms. A thorough analysis of
these changes, however, has not yet been performed. By
combining two-dimensional differential gel electrophoresis
and mass spectrometry, we identified 165 spots, corresponding
to 78 proteins, whose levels significantly change
after stimulation of the !-cell model INS-1 cells with 25 mM
glucose " 1 mM IBMX for 2 h. Changes in the expression of
selected proteins were verified by one- and two-dimensional
immunoblotting. Most of the identified proteins are novel targets
of rapid regulation in !-cells. The transcription inhibitor
actinomycin D failed to block changes in two-thirds of the
spots, supporting their post-transcriptional regulation. More
spots changed in response to IBMX than to glucose alone
conceivably because of phosphorylation. Fourteen mRNAbinding
proteins responded to stimulation, thus representing
themost prominent class of rapidly regulated proteins. Bioinformatics
analysis indicated that the mRNA 5"- and 3"-untranslated
regions of 22 regulated proteins contain potential
binding sites for polypyrimidine tract-binding protein 1,
which promotes mRNA stability and translation in stimulated
!-cells. Overall our findings support the idea that
mRNA-binding proteins play a major role in rapid adaptive
changes in insulin-producing cells following their stimulation
with glucose and cAMP-elevating agents.
