In vitro identification of nonalcoholic fatty liver diseaserelated protein hnRNPM

AIM:To study the formation of intracellular glyceraldehyde-derived advanced glycation end products(Glycer-AGEs)in the presence of high concentrations of fructose.METHODS:Cells of the human hepatocyte cell line Hep3B were incubated with or without fructose for five days,and the corresponding cell lysates were separated by two-dimensional gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis.Glycer-AGEs were detected with the anti-Glycer-AGEs antibody.Furthermore,the identification of the proteins that are modified by glyceraldehyde in the presence of high concentrations of fructose was conducted using matrixassisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS).The protein and m RNA levels were determined by Western blotting and realtime reverse transcription PCR,respectively.RESULTS:The results of the two-dimensional gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated a greater amount of GlycerAGEs in the sample exposed to high concentrations of fructose than in the control.The detected GlycerAGEs showed isoelectric points in the range of 8.0-9.0and molecular weights in the range of 60-80 k Da.The heterogeneous nuclear ribonucleoprotein M(hn RNPM),which plays an important role in regulating gene expression by processing heterogeneous nuclear RNAs to form mature m RNAs,was identified as a modified protein using MALDI-TOF-MS.Increasing the concentration of fructose in the medium induced a concentration-dependent increase in the generated Glycer-AGEs.Furthermore,in an experiment using glyceraldehyde,which is a precursor of Glycer-AGEs,hn RNPM was found to be more easily glycated than the other proteins.CONCLUSION:The results suggest that glyceraldehyde-modified hn RNPM alters gene expression.This change may cause adverse effects in hepatocytes and may serve as a target for therapeutic intervention.