Pdx-1 is a key regulator of glucose-stimulated insulin gene transcription in β-cells. The regulation of Pdx-1 in response to glucose has previously been associated with a remarkable shift in electrophoretic mobility on SDS-PAGE from 31 to 45 kDa. This has been attributed to different post-translational modifications including phosphorylation, sumoylation or glycosylation. However, and in contrast with previous studies, we describe in this paper that Pdx-1 produced in Escherichia coli, by in vitro transcription/translation or exogenously expressed in eukaryotic cells, migrates with an apparent molecular mass of 45 kDa despite a calculated mass of 31 kDa. Moreover, we show that the migration of endogenous Pdx-1 obtained from a mouse β-cell line as well as from human primary islets is not dependent on glucose concentration. Taken together, these data, validated by mass spectrometry techniques, establish that anomalous migration of Pdx-1 on SDS-PAGE does not result from post-translational modifications.

Diabetes, Human islets of Langerhans, MALDI-TOF, MIN6, Phosphorylation, Transcription factor
dx.doi.org/10.1016/j.bbrc.2008.03.071, hdl.handle.net/1765/28828
Biochemical and Biophysical Research Communications
Erasmus MC: University Medical Center Rotterdam

Carlotti, F, Zaldumbide, A, Charif, H, de Koning, E.J, Luider, T.M, & Hoeben, R.C. (2008). The 45-kDa form of Pdx-1 does not result from post-translational modifications. Biochemical and Biophysical Research Communications, 370(2), 225–229. doi:10.1016/j.bbrc.2008.03.071